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Programming with lcc

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1. We have to differentiate between a NULL string an empty string and a valid or invalid string This is the same as in standard C where we differentiate between NULL and the empty string A pointer can have a NULL value a valid value pointing to an empty string or an invalid value pointing to nowhere We put NULL and empty strings at the start of the lexicographical order so they are always less than non empty strings Note that we compare only as much as the shorter of both strings This is important because we wouldn t want that memcmp continues comparing after the end of the shorter string Since we have the length of the string at hand the operation is very cheap a few machine instructions 2 2 3 3 Dereferencing strings Another operator worth mentioning is the pointer dereference operator In C a table is equivalent to a pointer to the first element With the definitions Chace cer l Zs iis sste 07 The expression str 0 is equivalent to str 0 0 We can mimic this operation with the redef inition of the operator Ghar Operator Strings amp Str struct Exception exc GetAnExceptionStructure PRECONDITION StrvalidA str lt amp str 2count gt 0 gt exc return amp str content 0 This operator must always return a pointer type It returns then a pointer to the first character This allows to support the str a syntax There are several differences
2. We make two passes over the strings first collecting their lengths then joining them We avoid using strcat when joining the strings since that would be very inefficient The standard library strcat needs to find the terminating zero what is more and more expensive as the length of the result string grows Instead we use a roving pointer that adds right at the end of the pre vious string the new one 2 3 3 Accessing The general accessing function for Strings is Int Operator String lt s s1ze T 2ndex This operator returns the character at the given position The operator checks that s is a valid string and that the index is less than the length of the string Dies Gperator TACO Strings String S12 t inder struct Exception exc GetAnExceptionStructure PRECONDITION Strvalad string S index lt String lt count 7 exe return string content index Single byte versions will use StrvalidA and receive StringA strings double byte versions will use StringW and call StrvalidW We will use the generic term String when we mean either StringW or StringA The operation indexed assignment operator is handled by 8 INC Operator ISSI Senin Sire i ndez 1b New Val struct Exception exc GetAnExceptionStructure PRECONDITION C Strvealid string CS Indes lt lt String Count Exa string content index new val return new val 2 3 3 1 Adding and inserting characters Inserting a si
3. else infile fopen argv 1 rb if infile NULL printf File s doesn t exist n argv 1 return infile We pass the arguments of main to our check procedure that writes the corresponding error message if appropriate and returns either an open FILE or NULL if an error was detected The calling function just tests this value and exits if something failed int main int argc char argv i int count 0 FILE infile checkargs argc argv Int Gy if infile NULL return 1 for int 1L 007 axZ bos cree 4 Fregquencies i CharacterValue i s the rest oF marn The details of how the checking of the arguments is done is now away from the main line of the main function The whole function 1s now easier to read and the title of the piece of code that we hid away tells the reader immediately what is going on behind that function call The next step is the initializing of the Frequencies array This is common pattern that we find very often when building software most programs initialize tables and do some setup before actually beginning the computation they want to perform The best is to collect all those ini tializations into a single procedure so that any new initializations aren t scattered all around but concentrated in a single function void Initialize void for int 1 02 2 lt 2567 LFF 4 rrequencies 1 CharacterValue i Top down anal
4. Here 1s a possible implementation of this concept include lt stdio h gt include lt windows h gt include lt direct h gt Here is our callback definition typedef int callback char This function has two phases In the first we scan for normal files and ignore any directories that we find For each file that matches we call the given function pointer The input the char spec argument should be a character string like c or h If several specifications are needed they should be separated by the semi colon char For instance we can use c h asm to find all files that match any of those file types The second argument should be a function that will be called at each file found int ScanFiles char spec callback fn char p q Used to parse the specs char dir MAX PATH Contains the starting directory char fullname MAX PATH will be passed to the function HANDLE hdir HANDLE h WIN32 FIND DATA dirdata WIN32 FIND DATA data Get the current directory so that we can always come back to it after calling recursively this function in another dir memset dir 0 sizeof dir getcwd dir sizeof dir 1 This variable holds the current specification we are using G spec First pass We scan here only normal files looping for each of the specifications separated by do Find the first specification 150 C programming with Icc wi
5. II Vertically center the text y lpdis gt rcItem bottomtlpdis gt rcItem top tm tmHeight 2 Send the text to the screen 6 pixels after the bitmap TextOut lpdis gt hDC XBITMAP 6 y tchBuffer strlen tchBuffer Is the item selected if lpdis gt itemState amp ODS SELECTED Yes Invert the whole rectangle image text to signal the selection BitBLt lpdis gt nDC ipdis gt rcecitem lert Ipdis gt rcltem top lpdis gt rcItem right lpdis gt rcItem left Ipais gt reitem bottom Ipdis gt rcitem top lpdis gt hDC 0 0 PATINVERT break II Do nothing if we gain or lose the focus This is a laxist view but it works case UDA FOCUS break j return TRUE And after all this work here it 1s Building custom controls 291 E Dialog Title X crayon marker 3 15 Building custom controls In many cases it is a good idea to develop a class of windows that can be used in several appli cations with the same interface The idea is to encapsulate into a dll module or just in a static library a specialized window that will do one kind of thing a grid for a database application or for using a simpler example an lcd simulation display The objective is to build a simple display window that simulates a small lcd display that shows a few lines of text To build this application we follow the usual procedure we generate an application with the wizard and we change the display of the wi
6. See S45 Floppy C43 E E Local Disk C34 TE re Local Disk D H acrobat3 E antia H bzip ao controlspy H cpatron i 4 demo SE depends of 0 detours H diff If the call worked 1 e 1f the user interface returns a valid pointer and not NULL we should translate the meaningless stuff we receive into a real path so we call SHGet PathFro mIDList to do exactly that We pass it a pointer to the result character string that we receive as second argument If that function returns OK we verify that the returned path is not empty and if it 1s we set the result of this function to TRUE Now we have to clean up We use the COM interface pointer we received from SHGetMal loc and use its only member IpVtbl to get into the Free function pointer member There are other function pointers in that structure for sure but we do not use them in this application We pass to that Free function a pointer to the interface it gave to us and then the object to free 129 Passing NULL works too Advanced windows techniques 313 When we are done with a COM interface we have to remember to call a function to release it passing it again a pointer to the returned object We are done now we return the result and exit How can this program fail There are only three API calls here and all of them are tested for failure In principle there is no way this can fail although it could fail for other reasons it could provoke a memory l
7. case i1 case 934088 In this case the table could be a very bad idea This is a good technique for very dense switch tables only Using function pointers 153 There are many other uses of function tables for instance in object oriented programming each object has a function table with the methods it supports Since function pointers can be assigned during the run time this allows to change the code to be run dynamically another very useful application We have come up with a decent solution let s see what other might do include lt stdio h gt VOud Print Int T Deke Princ ir 1 ee printi Tan ns in main int argo char argv 4 PEN acota rgy ELS return 0 How does this work By using short circuit evaluation The statement mo Ge Print ial 2 Ee printi aun a y can be read from left to right like this If n is zero do nothing and return The second expression print n 1 1 calls print then yields 1 as its result This means that the third expression is evaluated that prints the number 154 C programming with Icc win32 1 34 Advanced C programming with Icc win32 Lec win32 offers several extensions to the C language described below This extensions are not part of the C standard but they are very much like similar features of the C language so they should be able to run in other environments as well 1 34 1 Operator overloading When you write int a 6 b 8 imme G aTh you ar
8. element to 56 a 23 56 Adds 56 to the 24 element Multidimensional arrays are indexed like this Ime taor Wits 4 taotahi S ae A table of 2 rows and three columns is declared Then we assign 7 to the second row third col umn Remember arrays indexes start with zero Note that when you index a two dimensional array with only one index you obtain a pointer to the start of the indicated row E ps S tabiy Now p contains the address of the start of the second column 1 11 4 Function call syntax sgret hypo 6 07 9510 Jo 77 Calls the function hypo with two arguments and then calls J the Tu nction Sort with Ghe result of hypo An argument may be an expression of any object type In preparing for the call to a function the arguments are evaluated and each parameter is assigned the value of the corresponding argument A function may change the values of its parameters but these changes cannot affect the values of the arguments On the other hand it is possible to pass a pointer to an object and the func tion may change the value of the object pointed to A parameter declared to have array or function type 1s converted to a parameter with a pointer type The order of evaluation of the actual arguments and sub expressions within the actual argu ments is unspecified For instance Pal Gr Os mee we Here the order of the calls to the functions g hO and m is unspecified 1 11 5 Functions with vari
9. return infile We use the library function strrchr That function will return a pointer to the last position where the given character appears in the input string or NULL if the given character doesn t appear at all Using that pointer we replace the backslash with a NULL character Since a zero terminates all strings in C this will effectively cut the string at that position Using that path we call another library function chdir that does what is name indicates changes the current directory to the given one Its prototype 1s in lt direct h gt After changing the current directory we restore the argument argv 1 to its previous value using the same pointer p Note too that when we enter a backslash in a character constant enclosed in single quotes we have to double it This is because the backslash is used as within strings for indicating characters like n or others But this isn t a good solution We change the current directory instead of actually using the path information Changing the current directory could have serious consequences in the working of other functions If our program would be a part of a bigger software this solution would surely provoke more headaches than it solves So let s use our name field that up to now isn t being used at all Instead of passing a name to Fopen we will pass it a STREAM structure and it will be Fopen that will take care of opening the right file
10. 0 9 0 80 See http serc 1isc ernet in ghoshal fpv html nodeliver or the home page of the Siddhartha Kumar Ghoshal Senior Scientific Officer at the Supercomputer Education and Research Centre Indian Insti tute of Science Bangalore 176 C programming with Icc win32 ine he 2 int 1 2 1 ane eo yal nereko Gnt eJl int 1 8 1 To round away from zero you can use FOeEInNe Round x C x gt 02 long xyr0eS 2 Long x 0 5 This will result in nonsense results if there is an overflow A better version would be define Round x x lt LONG MIN 0 5 x gt LONG MAX 0 5 error OE O Cong sc FUS RELONG L CCX 05 The standard library function round does this too To round towards positive infinity you use define RoundUp x int x 0 5 Negative infinity is similar 1 35 3 Numerical stability8 Suppose we have a starting point and a recurrence relation for calculating the numerical value of an integral The starting value is given by Ip 1n x 5 1n 6 In 5 0 182322 The recurrence relation is given by I 1 1 BIY Le S ye es Ly i 1 3 5I ECC We calculate this starting with 0 182322 We use the following program finclude lt stdio h gt include lt math h gt int main void float i 0 182322 for int 2 de Z lt 972FF t 1 0 7 fleat Plime i esa Zo Sa eae 2269 pe a s return QO We use single precision Note
11. 332 C Tutorial Available Used Free while counter 1 Z diskname 0 counter if GetDiskFreeSpaceEx diskname amp BytesAvailable amp capacity amp userFree percent 100 0L long double BytesAvailable long double capacity used capacity BytesAvailable printf formats 6s format string in 6 position left justified negative width 15 lld format 64 bit in 15 positions separating digits in groups 6 2Lf format long double Lf in 6 positions with 2 decimals printf S 6s 15 lld 15 lld 15 lld 6 2Lf 3 n diskname capacity BytesAvailable used percent TotalBytesAvailablet BytesAvailable TotalCapacityt capacity TotalUsed used Countertt l Now print the totals percent 100 0L long double TotalBytesAvailable long double TotalCapacity printi no 6s 215 11d 215 iid 215 1id 26 20te nn Total TotalCapacity TotalBytesAvailable TotalUsed percent return 0 The output of this program can look like this Drive Capacity Available Used Free Ce Op 2o20 peT P ote 7208 3 926 351 504 3759 Da 10 467 1977696 3 563 794 432 6 923 7403 204 33 98 ESY 31 453 4377952 117 499 627 520 1379537010 434 55 643 EFA lo 720 121 264 10p32770380016 S399093 24g G5 GTa H A 509300920 0 569 366 528 0 00 EA Shy T90 6T3r920 27072 530 944 4 118 142 976 87 05 Total 263190 lly 272 Gly 429 4200 345 090 bOr USA Gausec Since it doesn
12. Comments comment on page 49 Slash star introduces a commentary until commentary the sequence star slash is seen see comment Comments on page 49 Replace all appearances of the given identifier by the corresponding expression See Preprocessor commands on page 144 define id text define TAX 6 define max a b a lt b Define a macro with n arguments When define macro a b used the arguments are lexically replaced within the macro See page 145 Hudak id Erase from the pre processor tables the given identifier Insert the contents of the given file from include lt header h gt the standard include directory into the include lt stdio h gt program text at this position X x Insert the contents of the given file from include header h BIV finelude foouh the current directory If the given identifier is defined using ifdef id define include the following lines tifdef TAX Else skip them See page 146 ifndef id The contrary of the above Evaluate expression and if the result is TRUE include the following lines Else if expr if TAX 6 skip all lines until finding an else or endif directive statement defined id If the given identifier is defined return te derned 1 else return 0 token Make a string with a token Only valid E TE E T within macro declarations file foo c Set the file name Frite iro error e
13. Guard vod Return 0 te successtuls else lon mp code int status setjmp ErrorEnvy if status 0 return Status error A7 process return 0 int process void int error Code 44 This wasn t the case in MSDOS for instance NULL pointers were made to point to a special location in memory where the compiler left a special value that was checked when the program exited If the value at the end of the program wasn t what it should be that meant that somewhere in the program a NULL pointer was used in an assignment 66 C programming with Icc win32 if error happened longjmp Errorknvy error code With all respect I have for Harbison and Steele and their excellent book this example shows how NOT to use setjmp longjmp The ErrorEnv global variable is left in an undefined state after the function exits with zero When you use this facility utmost care must be exercised to avoid executing a longjmp to a function that has already exited This will always lead to catastrophic consequences After this function exists with zero the contents of the global ErrorEnv variable are a bomb that will explode your program if used Now the process function 1s entirely tied to that variable and its validity You can t call process from any other place A better way could be include lt setjmp h gt jmp buf ErrorEnv int guard void j Return 0 af successfuls else Longino code
14. Let the driver know the document is done EndDoc hdcPrinter Clean up the objects you created DeleteDC hdcPrinter DeleteDC hdcMemory ReleaseDC hWnd hdcWindow DeleteObject hbm if hPal DeleteObject hPal 3 20 8 Centering a dialog box in the screen Use the following code RECT tG GetWindowRect hDlg amp rc SetWindowPos hDlg NULL GeroystemMetrics oM CXSCREEN FOs Tight rodri GetSystemnMetrics SM CYSCREEN rC bottCom rCwtop O Oy SWP NOSIZE SWP NOACTIVATE MNO 3 20 9 Determining the number of visible items in a list box In a list box if the number of lines is greater than the number of lines in the list box some of them will be hidden In addition it could be that the list box 1s an owner draw list box making the height of each line a variable quantity Here is a code snippet that will handle all cases even when all of the items of the list box are visible and some white space is left at the bot tom The basic idea is to subtract each line height from the total height of the client area box int ntop nCount nRectheight nVisiblelItems RECT rc Lcemrecc First get the index of the first visible item ntop SendMessage hwndList LB GETTOPINDEX 0 0 Then get the number of items in the list box nCount sendMessage hwndlast LB GHTCOUNT 0 0 Get the list box rectangle GetClientRect hwndList amp rc Get the height
15. Multimedia Sound video input devices 300 C Tutorial Network Yes TCP IP Send data through the wire develop your own protocol on top of the basic stuff You have all the tools in here Virtual memory Use those megabytes They are there anyway Build huge tables of data Use virtual memory reserve contiguous address space etc Registry A global database for configuration options Services Run processes in the background without being bothered by a console window or any other visible interface Shell programmin Manage files folders shortcuts and the desktop Terminal services Terminal Services provides functionality similar to a terminal based centralized host or mainframe environment in which multiple terminals connect to a host computer A user can log on at a terminal and then run applications on the host computer accessing files databases network resources and so on Each terminal session is independent with the host operating system managing conflicts between multiple users contending for shared resources Windows Yes Windows is about windows You get a huge variety of graphical objects from the simple check box to sophisticated tree displaying stuff An enormous variety of things that wait for you ready to be used 1 Media Control Interface 3 17 1 Clipboard The data in the clipboard is tagged with a specific format code To initiate the data transfer to or from the clipboard you use OpenCl
16. The translation goes as follows The higher order bits 31 21 are used to index a page of memory called the page directory Each process contains its own page directory filled with 1024 numbers of 32 bits each called page description entry or PDE for short The PDE is used to get the address of another special page called page table The second group of bits 21 12 is used to get the offset in that page table Once the page frame found the remaining 12 bits are used to address an individual byte within the page frame Here is a figure that visualizes the structure Page Directo ry 4K 1024 x 4055 4 MB 1024 x 1024 x 40965 4 Ge We see that a considerable amount of memory is used to manage memory To realize the whole 4GB address space we would use 4MB of RAM But this is not as bad as it looks like since Windows is smart enough to fill these pages as needed And anyway 4MB is not even 0 1 of the total 4GB address space offered by the system Each process has its own page directory This means that processes are protected from stray pointers in other programs A bad pointer can t address anything outside the process address space This is good news compared to the horrible situation under windows 3 1 or even MSDOS where a bad pointer would not only destroy the data of the application where it belonged but destroyed data of other applications making the whole system unstable But this means too that a
17. Wow we are missing 492 466 26 chars Why We read again the specifications of the fopen function It says that we should use it in read mode with r or in binary mode with rb This means that when we open a file in read mode it will translate the sequences of characters r return and n new line into ONE character When we open a file to count all characters in it we should count the return characters too This has historical reasons The C language originated in a system called UNIX actually the whole language was developed to be able to write the UNIX system in a convenient way In that system lines are separated by only ONE character the new line character When the MSDOS system was developed dozens of years later than UNIX people decided to separate the text lines with two characters the carriage return and the new line character This provoked many problems with software that expected only ONE char as line separator To avoid this problem the MSDOS people decided to provide a compatibility option for that case fopen would by default open text files in text mode 1 e would translate sequences of r n into n skipping the r Conclusion C6 66 Instead of opening the file with fopen argv 1 r we use fopen argv 1 rb 1 e we force NO translation We recompile relink and we obtain H lcc examples gt countchars countchars c 493 H lcc examples gt dir countchars c 07 01 00 11 50p 493 c
18. static int files used to count the number of files seen This is the callback function It will print the name of the file and increment a counter int printfile char fname DEIMcsE ss n 4 thame gt files return 1 main expects a specification and possibly a starting directory If no starting directory is given it will default to the current directory Using function pointers 151 Note that many error checks are absent to simplify the code No validation is done to the result of the chdir function for instance int Main int arqc char argv Char spec MAX PATH Char Starctdir MAx PATH if argc 1 printf scan files expects a file spec n return 1 memset startdir 0 sizeof startdir memset spec 0 sizeof spec strncpy spec argv 1 sizeof spec 1 if argo gt 2 4 strcpy Startdir argv 2 Lt etaercaixr oO 0 4 getcwd StartaqLlr Sizeor startdir 1 Chair startdir files 0 ScanFiles spec printfile prince cd files i files return U What is interesting about this solution is that we use no intermediate memory to hold the results If we have a lot of files the size of the resulting list or table would be significant If an application doesn t need this it doesn t have to pay for the extra overhead Using the name of the file the callback function can query any property of the file like the date of creation
19. to know how big our table should be we need to know how many words we have entered This can be done in two ways Either count the number of words in the table when building the report or count the words as we enter them Obviously the second solution is simpler and requires much less effort We just declare a glo bal integer variable that will hold the number of words entered into the table so far int words 0 We increment this counter when we enter a new word 1 e in the function NewWord List i We will need a comparison function for the qsort library function too int comparewords const void wl const void w2 WORDLIST pwl WORDLIST wl pw2 WORDLIST w2 71 Note that we allocate MEM ALLOC SIZE bytes If we want to change to more or less bytes we just change the define line and we are done with the change Counting words 133 1f pwl gt Count pw2 gt Count return strcmp pwl gt Word pw2 gt Word return pwl gt Count pw2 gt Count Note that we have implemented secondary sort key If the counts are the same we sort by alphabetical order within a same count void DoReports char filename Int 1 int idx 0 Index into the resulting table Print file name and number of words printf S s Sd different words n filename words allocate the word list pointer table WORDLIST tab more memory words sizeof WORDLIST Go through the entire hash table
20. 0 result 1 else result 0 1 11 27 Bitwise operators The operators amp bitwise AND bitwise exclusive or and bitwise or perform boolean operations between the bits of their arguments that must be integers long long long int short or char The operation of each of them 1s as follows 1 The amp AND operator yields a 1 bit if both arguments are 1 Otherwise it yields a 0 2 The exclusive or operator yields 1 if one argument is 1 and the other is zero 1 e 1t yields 1 if their arguments are different Otherwise it yields zero 3 The or operator yields 1 if either of its arguments is a 1 Otherwise it yields a zero We can use for those operators the following truth table Note that this operators are normal operators 1 e they evaluate always their operands unlike amp amp or that use short circuit evaluation If we write a 0 amp amp n 67 the function call will never be executed If we write a O amp fn 67 the function call will be executed even if the result is fixed from the start 1 11 28 Address of operator The unary operator amp yields the machine address of its argument that must be obviously an addressable object For instance if you declare a variable as a register variable you can t use this operator to get its address because registers do not live in main memory In a similar way you can t take the address of a constant like amp 45 because the numbe
21. 6227020600 14 871782891532 15 1307674279936 16 ZO9ZZICS4LISITS ITL 355687414628352 18 64023 74067290112 19 121645096004222 930 20 2432902298094158 1600 2L 5109094529921623 1000 22 1 124000724806013e 021 23 2 5852017444594486e 022 24 6 2044383105839766er023 291 Le DOOLL ZUG IZO3247 3067025 26 FeO oZ LST T OO IS 6CTUZLG 27 1 088886923454107e 028 28 30488839051 316128e7029 291 8 84176066146 75607e1 030 30 Ze OOZI2I093 04935 A 7ETUSZ ait 8 2228384475874814e 033 32 Z 63 LSUC30382Z1 990467035 33 8 6833178760213554er036 34 ZxI9Z32303043 7 62167036 Max Lactorial is 34 This measures the range of numbers stored in the float format 1 e the capacity of this format to store big numbers We modify slightly our program by replacing the float numbers by double numbers and we obtain this 1 1 2 2 3 6 4 24 Numerical programming 171 5 120 168 Z DZ OUTS TAAI Tod IGF 169 4 2690680090047056e 304 170 71 29 7415615308004eE 306 Max factorial 1s 170 The range of double precision floats is much greater We can go up to 170 quite a big num ber Even greater as expected is the range of long doubles where we obtain 1751 32674156538 61731951Z2e 49Z20 1752 6 437122255657 5437 1 2et4923 1753 wch2ea2 531416 oe TaZzse14 927 1754 LeOToZols 901 US010059 er4930 Max Factorial 1s 1754 Changing the declarations of the numbers to qfloats and inc
22. An example of its use is the following situation We have a structure of an integer error code and a character field containing the description static struct table unsigned int code unsigned char desc hresultlaby Then we have a lot of error codes defined with the preprocessor E UNEXPECTED E NOTIMPL E INVALIDARG etc We can build a table with hresultTab Table E UNEXPECTED E UNEXPECTED E NOTIMPL E NOTIMPL 5 CEC by This is tedious and there is a big probablity of making a typing mistake A more intelligent way IS define CASE a a ta Now we can build our table like this hresultTab Table CASE E_ UNEXPECTED CASE E_NOTIMPL Le 1 32 2 Things to watch when using the preprocessor 1 One of the most common errors is to add a semi colon after the macro define add a b a b 148 C programming with Icc win32 When expanded this macro will add a semicolon into the text with the consequence of a cascade of syntax errors with apparently no reason 2 Watch for side effects within macros A macro invocation is similar to a function call with the big difference that the arguments of the function call 1s evaluated once but in the macro can be evaluated several times For instance we have the macro square define square a a a If we use it like this b square att After expansion this will be converted into b att att and the variable a will be incremented tw
23. Difference minutes moving westward between UTC and local time short timezone unsigned short pad2 unsigned long lpad2 Nonzero if daylight savings time is currently in effect for the local time zone short Gstilag unsigned unsigned unsigned Fraction of a second in ms unsigned We show here a small program that displays the different time settings lt time h gt lt StO010 h gt lt sys types h gt lt sys timeb h gt lt SUCring h gt n ampm AM SCLUCE Tameb gt Terrucec SCLrUuUcC tm today gmt xmas 1 Oy wy 12 Zo Ly Se I Display operating system style date and time strtime PLeince strdate PLinci tmpbuf NOS Gime E Vn ve vt es ni tmpbuf OS date t t t t s n tmpbuf tmpbuf Get UNIX style time and display as number and string time printf printf amp ltime Time in seconds since UTC 1 1 70 t ld n UNIX time and date t t t s ctime amp ltime 7 ltime Da Display UTC See note 1 in text gmt Printe Convert to time structure and adjust for PM if necessary today at SLrepy Code y tm hour gmtime amp ltime Coordiviated Universal time Ctt o asctime gmt a E localtime amp ltime today gt tm nour gt tz VW pM 23 ampm 136 C programming with Icc win32 16 Coday gt tm hour 0 Adjust 12 Midnugh hour
24. Note that you should add the library PSAPI LIB to the linker command line You should do this in the linker tab in the configuration of wedit AdownloadswindowtreesIoc windowlree ere A more complex example a clone of spy exe 267 And now we are done Each time you click in an item window the program will display the associated information in the status bar E windowtree BAE E File Desktop Help BaseBar tooltips class32 BaseBar tooltips class32 BaseBar BaseBar tooltips class32 Avance Sound Effect Control Panel alcEaxCplClass tooltips class32 tooltips class32 NetDDE Agent WODEAgnt tooltips classse windowtree windowtree WndClass tooltips _class32 Project windowtree Treeviewllass smallTextFopup wedit windowtree d idownloads windowtree Wwindowtree c cMDIFrame E MDIClient ss Margin oe WeditCukput C tutorial doc Microsoft Word Opus4pp Stop Current Jump OFFice Tooltip Edit MsoCommandBarPopup Edit Picture MsoCommandBar L Om einn ai Summary There are many things that could be improved in this small program For instance it could be useful to have a right mouse menu or a dialog box with much more information etc This is just a blueprint to get you started however The whole code for this program is in the appendix 4 268 C Tutorial 3 11 Numerical calculations in C Well we have a beautiful window with nothing in it B
25. Pointer to next element void Data Pointer to the data element k BEOL We can use a fixed anchor as the head of the list for instance a global variable containing a pointer to the list start Lio F ROOT We define the following function to add an element to the list LLST Append hisl pbListRooLr vord daca ELST ryp pPLISCROOC if rvp NULL is the list empty Yes Allocate memory DLLSEROOL vp GC Ma LIOC SEOEL TOTI else find the last element while rvp gt Next EVO EV O FNeExC Add an element at the end of the list tvp Next GC malloc srzeot biol rvp Lryp Next initialize the new element rvp gt Next NULL rvp gt Data data EeCLUE EVO Using structures continued 139 This function receives a pointer to a pointer to the start of the list Why If the list is empty it needs to modify the pointer to the start of the list We would normally call this function with newElement Append amp Root data Note that loop while rvp gt Next EVD Vy p 2 Next This means that as long as the Next pointer is not NULL we position our roving pointer hence the name rvp to the next element and repeat the test We suppose obviously that the last element of the list contains a NULL Next pointer We ensure that this condition is met by initializing the rvp gt Next field to NULL when we initialize the new element To access a list of n elements
26. Set SHFILEOPSTRUCT params for delete operation fT memset amp sh 0 sizeof SHFILEOPSTRUCT sh fFlags FOF SILENT don t report progress sh fFlags FOF NOERRORUI don t report errors sh fFlags FOF NOCONFIRMATION don t confirm delete SM Wwrune FO DELETE REQUIRED delete operation sh pFrom buf REQUIRED which file s sh proe NULL MUST be NULL if bDelete f if delete requested sh fFlags amp FOF ALLOWUNDO don t use Recycle Bin else 4 J7 otherwise sh fFlags FOF ALLOWUNDO send to Recycle Bin return SHFileOperation amp sh 133 This program is based on a similar program published in MSDN magazine 2001 In the comments for that program I found the following If this code works it was written by Paul DiLascia If not I don t know who wrote it FAQ 355 ifdef TEST Test program include lt gc h gt for GC malloc include lt sys stat h gt For stat This list structure holds the names of the files given in the command line typedef struct tagFileList struct tagFileList Next Char Name FILELIST pre declare functions void usage void void help void char GetCurrentDir Char MakeAbsolute char relname BOOL confirm LPCTSTR pFileName LPCTSTR GetErrorMsg int err global command line switches BOOL bPrompt FALSE prompt at each file BOOL bQuiet FALSE don t display messages BOOL bDisplayOnly FALSE d
27. SetFileTime hFile j Secs lastowrite time for file LPFILETIME NULL LPFILETIME NULL amp ft return f 3 20 23 Converting from GMT UTC time to local time The system uses Universal Coordinated Time or UTC based time internally Applications gen erally display the local time or the date and time of day for the current time zone However a developer occasionally may need to programmatically convert from UTC previously referred to as Greenwich Mean time or GMT time to local time This conversion can be done like this FILETIME FileTime LocalFileTime SYSTEMTIME UTCTime LocalTime SystemTimeToFileTime amp UTCTIme amp FileTime FileTimeToLocalFileTime amp FileTime amp LocalFileTime FileTimeToSystemTime amp LocalFileTime amp LocalTime 3 20 24 Displaying the amount of disk space for each drive include lt windows h gt include lt stdio h gt This program will loop through all drives in the system and will print the capacity of each drive the number of bytes free used and the percentage free At the end of the loop it will print the totals int main void long long BytesAvailable TotalBytesAvailable 0 long long capacity TotalCapacity 0 long long userFree TotalUserFree 0 long long used TotalUsed 0 long double percent int counter C Start with C drive ignoring floppies char diskname 512 stropy diskname Cr printf S 6s 15s 15s 15s S6s n Drive Capacity
28. This keyword is a recommendation to the compiler to use a machine register for storing the values of this type The compiler is free to follow or not this directive The type must be either an integer type or a pointer If you use this declaration note that you aren t allowed to use the address of operator since registers do not have addresses Lcc win32 tries to honor your rec ommendations but it is better not to use this declaration and leave the register usage to the compiler Registers are the highest part of your machine memory hierarchy They are the fastest storage available to the program by the circuit and in a PC x86 architecture there are just a few of them available at a time After registers there is the level 1 cache level 2 cache main memory then the disk in order of decreasing access speed 1 11 13 sizeof The result of sizeof is normally a constant integer known when the compiler is running For instance sizeof int will yield under Icc win32 the constant 4 In the case of a variable length array however the compiler can t know its size on advance and it will be forced to gen erate code that will evaluate the size of the array when the program is running 46 C programming with Icc win32 1 11 14 enum An enumeration is a sequence of symbols that are assigned integer values by the compiler The symbols so defined are equivalent to integers and can be used for instance in switch state ments The compiler start
29. char msc os int Counter es sprintf msg i d n i Counter if 1 4 goto label At the point indicated by the arrow the poor Counter identifier has had a busy life e It was bound to an integer object with file scope e Then it had another incarnation within the function prototype scope e Then it was bound to the variables of the function setCounter as a parameter e That definition was again shadowed by a new definition in an inner block as a local variable The value of Counter at the arrow is 78 When that scope is finished its value will be the value of the parameter called Counter within the function function When the function definition finishes the file scope is again the current scope and Counter reverts to its value of 780 The linkage of an identifier refers to the visibility to other modules Basically all identifiers that appear at a global scope file scope and refer to some object are visible from other mod ules unless you explicitly declare otherwise by using the static keyword Problems can appear if you first declare an identifier as static and later on you define it as external For instance static yord Too Gvoid 3 and several hundred lines below you declare yord foo rod 4 Which one should the compiler use static or not static That is the question Lec win32 chooses always non static to the contrary of Microsoft
30. comes from the left hand side of the equals sign of course In the same vein we speak of LHS and RHS as abbreviations for left hand side and right hand side of the equals sign in an assignment 1 11 7 Postfix These expressions increment or decrement the expression at their left side returning the old value For instance array 234 678 a array 234 In this code fragment the variable a will get assigned 678 and the array element 234 will have a value of 679 after the expression is executed In the code fragment array 234 678 a array 234 The integer a and the array element at the 23 50 position will both have the value 679 When applied to pointers these operators increment or decrement the pointer to point to the next or previous element Note that if the size of the object those pointers point to is different than one the pointer will be incremented or decremented by a constant different than one too 1 11 8 Conditional operator The first operand of the conditional expression is evaluated first The second operand is evalu ated only if the first compares unequal to 0 the third operand 1s evaluated only if the first com A closer view 45 pares equal to 0 the result of the whole expression is the value of the second or third operand whichever is evaluated converted to the type described below If both the second and the third operand have an arithmetic type the result of the expression has that t
31. fn and pass it the comma fn args separated argument list args see Function call printf d 5 syntax on page 43 See Functions with variable number of arguments tn acd ssa on page 43 floating constants Access the n dimensional array using the indexes 11 Array il i2 i2 in See Arrays on page 43 in ares Struct cield struct gt field var value expressiontt expression expression expression amp object pointer expression expression expression sizeof expr type expr expr expr expr expr expr expr Sx pE expr expri expr2 expr lt lt exprZ expri gt gt expr expri lt expr2 exprl lt expr2 exprl gt expr2 exprl gt expr2 An overview of the whole language 33 Call the function whose machine address is in the pointer fn Access the member of the structure Customer Name Access the member of the structure through a Customer gt Name pointer Assign to the variable the value of the right hand side of the equals sign See Assignment on page 44 Equivalent to expression expression 1 Increment expression after using its value See Postfix on page 44 Equivalent to expression expression 1 Decrement expression after using its value see Postfix on page 44 Equivalent to expression expression 1 Increment expression before using its
32. include lt shellapi h gt finelude stdavo h gt int IsTaskbarAutoHideOn void APPBARDATA d d cbSize sizeof APPBARDATA return SHAppBarMessage ABM GETSTATE amp ABData amp ABS AUTOHIDE int main void princi Taskbar sautohnide if IsTaskbarAutoHideoOn Plime iON eis 354 C Tutorial else princi OFF printer a 3 21 25 How to erase a file into the recycle bin When you erase a file within a program the deleted file doesn t appear in the recycle bin This can be annoying if you want to undo this operation of course The solution is to use the API SHFileOperation with the flag FOF ALLOWUNDO Here is a small program that does all this for you Compile with DTEST to have a standalone program that will accept command line arguments or without it to have just the Recycle function that will erase a file to the recycle bin include lt windows h gt include lt stdio h gt include lt conio h gt include lt direct h gt include lt shellapi h gt TTT Send a file to the recycle bin Args full pathname of file bDelete if TRUE really delete file no recycle bin II int Recycle LPCTSTR pszPath BOOL bDelete Copy pathname to double NULL terminated string char buf MAX PATH 1 allow one more character SHEP IDEOPSTRUCT xen Strcpy but pszPath copy caller s path name but strien but 4 1 0 need two NULLS at end
33. request dwopenReguesCFrlag INTERNET SCHEME HTIPS urlComp nscheme 7 WINHTTP FLAG SECURE 0 The HTTP Protocol 371 Open a GET request rceContext hRequest WinHttpOpenRequest rcContext hConnect GYGET Sp Urr Comps Ups zurlPrachy NULL WINHTTP NO REFERER WINHTTP DEFAULT ACCEPT TYPES dwOpenRequestFlag if rcContext hRequest 0 goto cleanup Now we are ready to send our request This will open a connection Send the request if WinHttpSendRequest rcContext hRequest WINHTTP NO ADDITIONAL HEADERS 0O WINHTTP NO REQUEST DATA 0 0 0 goto cleanup We wait for the answer if WinHttpReceiveResponse rcContext hRequest 0 goto cleanup We are now ready to query the headers of the resource we are tryingt to obtain The reason is simple if our routine received a request for an inexistent resource many servers will send data anyway containing some HTML that will show the famous page Unable to find server or similar We surely do not want to get that so we have to scan the headers to see if we get a 404 the http error for indicating that the resource is unavailable We do not know how long the headers can be We first query the length of the buffers allocate memory then we make the request to get the actual header data dwSize 0 WinHttpQueryHeaders rcContext hRequest WINHTTP QUERY RAW HEADERS CRLF WINHTTP HEADER NAME BY INDEX NULL amp dwSize WINHTTP NO HEADER INDEX
34. return GetFtpUrl ftp cs virginia edu pub lcc win32 README README To give you an idea when the first FTP protocol implementations under windows 3 0 were monster programs of several thousand lines Of course those thousands of lines are still there in the code of those FtpGetFile primitives The advantage is that you do not have to worry about it To link this program you should use the wininet lib import library 4 5 Querying the network parameters The program ipconfig shows the parameters of the TCPIP configuration We will make here a similar program to give you an idea how you can get those parameters under program control We will use the APIs defined in the IP helper API The header file 1s iphlp h and the library to include is 1phlp lib The interface for our program is very simple There is no parameters and the return value is zero if everything went OK an error code otherwise include lt stdio h gt include lt stdlib h gt include lt string h gt include lt windows h gt FAnclude lt winsock 2 lt A gt include lt iphlpapi h gt int main void PIXED TNEO pr xedi nto IP ADDR_STRING pIPAddr ULONG ulOutBufLen DWORD dwRetVal ire ieee Querying the network parameters 375 We use the GetNetworkParams API to query the host name the domain name and other related information We make two calls in the first one we give an insufficient buffer This call fails obviously returning i
35. s compiler that chooses always static Note that the behavior of the compiler is explicitly left undefined in the stan dard so both behaviors are correct 62 Yes but then all initializations are done out of their respective contexts Some people say this is the wrong way to go and that each data type should initialize in a separate init procedure In this concrete example and in many situations making a global init procedure is a correct way of building software Other contexts may be different of course 100 C programming with Icc win32 1 21 Top down analysis The goal of this introduction is not to show you a lot of code but to tell you how that code is constructed A central point in software construction is learning how you decompose a task in sub tasks so that the whole is more modular and easier to manage and change Let s go back to our frequencies example We see that the main function accomplishes several tasks it checks its arguments opens a file checks the result initializes the Frequency array etc This is an example of a monolithic highly complex function We could decompose it into smaller pieces easily for example by assigning each task to a single procedure One of the first things we could do is to put the checking of the input arguments in a single procedure PLLE eneckargs int aroc char argy EELE Aanta te NULL RE argo lt 21 Aq printf Usage countchars lt file name gt n
36. string content string count while strp lt end if lmememp strp find this comtenty find this count return New SUEI NG Dp String strp 7 else Stroisr return Invalid Stringp We search the first character of the string to search in the string Each time we find it we test if the search pattern 1s there If yes we return a new string pointer otherwise we go on until we reach the end of the string To search a character in a string we use the Strchr function Stringp overloaded Strchr String amp string int element struct Exception exc GetAnExceptionStructure PRECONDITION lt Strvalid string 5 x char p memchr string content element string count LE pi fy ound return New sStringp string ply tetur inva lie stringo 2 3 9 Making a string from a pipe The function Strfrompipe will start a program and capture all its textual output into a String This is useful for many GUI applications that want to show the results of a program in a differ ent way and many others The algorithm used is very simple we start the command indicated in the string argument with the process using a redirected standard output into a temporary file We read then this file into a string a return the result StringA overloaded Strfrompipe String amp Cmdline SIARTUPINEO S6tartvulrnt of char pF int processStarted m string result invalrdstringA HANDLE hWri
37. t grab any more memory than it actually needs 3 Itis portable since it is based in functions required by the C language Drawbacks 1 It is very error prone Any error will provoke obscure and difficult to track bugs that 124 C programming with Icc win32 need advanced programming skills to find And the possibilities of errors are numerous freeing twice a memory block passing a wrong pointer to free forgetting to free a block etc 2 The time used by memory allocation functions can grow to an important percentage of the total run time of the application The complexity of the application increases with all the code needed to keep track and free the memory blocks 3 This strategy suffers from the memory fragmentation problem After many malloc free cycles the memory space can be littered with many small blocks of memory and when a request for a big block of memory arrives the malloc system fails even if there 1s enough free memory to satisfy the request Since it is impossible for the malloc system to move memory blocks around no memory consolidation can be done 4 Another problem is aliasing 1 e when several pointers point to the same object It is the responsibility of the programmer to invalidate all pointers to an object that has been freed but this can be very difficult to do in practice If any pointer to a freed object remains in some data structure the next time it will be used the program can catastrophically fail or retu
38. type meaning some arbitrary type and expr meaning some arbitrary C expression I have forced a page break here so that you can print these pages separately when you are using the system 32 C programming with Icc win32 1 9 1 Statements joes The value associated with that identifier see A identifier ees 1d closer view on page 41 The value defined with this constant see Constants on page 41 Integer constant 45 45L 45LL 45 9 45 98 Fl constant oating constant A5 OL Hello L Hello Define tables or structure data Integer constants long integer constants long long 64 bits integer constant octal constant base 8 introduced with a leading 055 This is 45 in Zero base 8 Ox2d this is 45 in hexa String literal integer constants Hexadecimal constant introduced with 0x Binary constant introduced with 0b This is an lcc 0b101101 this is 45 win32 extension in decimal E 45 9 or l double precision constant 4 5062 45 9f or Float single precision constant 4 59e2f 45 9L or l l ong double constant A 59691 h t o constant string literals enclosed in double quotes a string Access the position index of the given array Indexes start at zero see Within the string the Array index oe 7 Table following abbreviations are recognized on page 42 45 Table 34 23 This access the 35th lane 24 position Of Table Call the function
39. void EnterWord char word int h hash word Get the hash code for this word WORDLIST wl WordTable h Index the list at that slot while wl Go through the list Lf lstromp wl word word 4 wl gt Count Word is already in the table return 74 increment the coant and return wl wl gt Next id GO EO one next icer Im the List Here we have a new word since it wasn t in the table Add it to the table now wl NewWordList word wl gt Next WordTable h WordTable h wl Counting words 131 What would be a good hash function for this application This is a tutorial so we keep things simple Here is a very simple hash function int hash char word IAG D sO while word h word wordt return h amp Oxtrfrt We just add up our characters If we get a hash value of more than 65535 the size of our table we just take the lower 16 bits of the hash value Easy isn t it We declare our word table now like this WORDLIST WordTable Oxffff 1 1 29 2 Memory organization Now we write the constructor for our word list structure It should get more memory from the system to hold the new structure and initialize its fields WORDLIST NewWordList char word int len strlen word WORDLIST result more memory sizeof WORDLIST Llen 1 rFes lt Count 17 ser rCpy res uLt gt Word word return result We allocate more memory to hold
40. yYes f No printf tEnable DNS s n pFixedInfo gt EnableDns Yes No IP ADAPTER INFO pAdaptertInfo pAdapter The same technique as above We pass to the API a buffer of a given length and if it doesn t suffice we allocate the buffer in the returned length Me pAdapteriInf fo IP ADAPTER INFO malloc sizecf IP ADAPIER_INFO uLOUtBuELen sizeot IP ADAPTER INFO 7 rc GetAdaptersInfo pAdapteriInfo amp ulOutBufLen if ro J ERROR SUCCESS 4 free pAdapteriInfo pAdapterInfo IP ADAPTER INFO malloc ulOutBufLen dwRetVal GetAdaptersInfo pAdapteriInfo amp ulOutBufLen if dwRetVal NO ERROR Printt Call to GetAddptersinfo failed nerror d n GetLastkError return 1 376 C Tutorial pAdapter pAdaptertInfo We have now a linked list of adapters Go through that list printing the information while pAdapter printf tAdapter Name t s n pAdapter gt AdapterName printf tAdapter Desc t s n pAdapter gt Description printf tAdapter Addr tt x n pAdapter gt Address printf tIP Address t s n pAdapter gt IpAddressList IpAddress String Printer CIP Mask Ess n pAdapter gt IpAddressList IpMask String printf tGateway t s n pAdapter gt GatewayList IpAddress String if pAdapter gt DhcpEnabled printf tDHCP Enabled Yegin Pranti P eEDHCP Server Le SAn pAdapter gt DhcpServer IpAddress Str
41. 0 statements The printf statement is quite complicated It uses a new directive c meaning character and then a width argument 1 e 3c meaning a width of three output chars We knew the d directive to print a number but now it is augmented with a width directive too Width direc tives are quite handy when building tables to get the items of the table aligned with each other in the output The first thing we do is to build a test file to see 1f our program is working correctly We build a test file containing ABCDEFGHIJK And we call Lee frequencies c lcecink frequencies obj frequencies fexample and we obtain D lcc examples gt frequencies fexample LS ohare I0 Tre 10 1 13 1 A 65 1 B 66 1 C 67 2 D 68 1 E 69 1 E Ops A G 71 1 H 72 1 I 73 1 J 74 1 K Foy We see that the characters r 13 and new line 10 disturb our output We aren t interested in those frequencies anyway so we could just eliminate them when we update our Frequencies table We add the test Lt Ce SS 2 Fregquencies c t 1 e we ignore all characters with value less than space r n or whatever Note that we ignore tabulations too since their value is 8 The output is now more readable H lcc examples gt frequencies fexample 80 C programming with Icc win32 13 chars in file A 65 1 B 66 1 C 67 1 D 68 1 E 69 1 F 70 1
42. 2 and so forth representing each of the physical drives in the system To open a logical drive direct access 1s of the form Ee where X is a hard drive partition letter floppy disk drive or CD ROM drive You can open a physical or logical drive using the CreateFile application programming inter face APD with these device names provided that you have the appropriate access rights to the drive that is you must be an administrator You must use both the CreateFile FILE SHARE READ and FILE SHARE WRITE flags to gain access to the drive Once the logical or physical drive has been opened you can then perform direct I O to the data on the entire drive When performing direct disk I O you must seek read and write in multi ples of sector sizes of the device and on sector boundaries Call DeviceloControl using IOCTL_ DISK GET DRIVE GEOMETRY to get the bytes per sector number of sectors sectors per track and so forth so that you can compute the size of the buffer that you will need Note that a Win32 based application cannot open a file by using internal Windows NT object names for example attempting to open a CD ROM drive by opening Device CdRom0 does not work because this is not a valid Win32 device name You can use the QueryDosDe vice API to get a list of all valid Win32 device names and see the mapping between a par ticular Win32 device name and an internal Windows NT object name An application running Some Coding T
43. 2 No global fragmentation of memory Drawbacks 1 Since the size of the memory that will be needed is not known in advance once an arena is full the strategy fails or needs to be complemented with more sophisticated variations A common solution is to make the arena a linked list of blocks what needs a small processing overhead 2 Determining when the moment has come to release all memory is tricky unless the data processed by the program has a logical structure that adapts itself to this strategy Since there 1s no way of preserving data beyond the frontier where it is released data that is to be preserved must be copied into another location 1 28 4 The malloc free strategy This is the strategy that is most widely used in the C language The standard provides the func tions malloc a function that returns a pointer to an available memory block and free a func tion that returns the block to the memory pool or to the operating system The program allocates memory as needed keeping track of each memory block and freeing it when no longer needed The free function needs a pointer to the same exact location that was returned by malloc If the pointer was incremented or decremented and it is passed to the free function havoc ensues Advantages 1 Itis very flexible since the program can allocate as needed without being imposed any other limit besides the normal limit of available memory 2 It is economic since the program doesn
44. A byte poin The size of pbContent BYTE src content ebContent Src count Get the size of the encoded message BLOB cbEncodedBlob CryptMsgCalculateEn MY ENCODING TYPE es 0 CMSG DATA NULL id NULL cCbCOntent if cbEncodedBlob a return Q0 Allocate memory for the encoded BLOB pbEncodecBlob BYTE allocate p Open a message to encode hMsg CryptMsgOpenToEncode MY ENCODING TYPE oF CMSG DATA NULL NULL NULL if hMsg return Q0 f7 Size of the returned ter to the message message codedLength Message encoding type Flags Message type Pointer to structure Inner content object ID Size of content roper space cbEncodedBlobt1 1 Encoding type Flags Message type Pointer to structure Inner content object ID Update the message with the data fi fl Li 1f CryptMsgUpdate hMsg pbContent cbhConrent TRUE return 0 Get the resulting message if CryptMsgGetParam hMsg CMSG BARE CONTENT PARAM 0 pbEncodedBlob amp cbEncodedBlob return 0 pboEncodedBlob now points to the Close the message if hMsg CrypEeMsgClLose hMsq gt Handle to the message Pointer to the content Size Of the content Last call Ti i Handle to the message Parameter type Index Pointer to the BLOB Size of the BLOB encoded signed content Finding more examples and source code 365 Sr
45. C allows you to define an expression that will be used to initialize a variable 4 We use the variable infile to hold a FILE pointer Note the declaration for a pointer lt type gt identifier the type in this case is a complex structure composite type called FILE and defined in stdio h We do not use any fields of this structure we just assign to it using the functions of the standard library and so we are not concerned about the specific layout of it Note that a pointer is just the machine address of the start of that structure not the structure itself We will discuss pointers extensively later 5 We use an integer to hold the currently read character 6 We start the process of reading characters from a file first by opening it This operation establishes a link between the data area of your hard disk and the FILE variable We pass to the function fopen an argument list separated by commas containing two things the name of the file we wish to open and the mode that we want to open this file in our example in read mode Note that the mode is passed as a character string 1 e enclosed in double quotes 7 Once opened we can use the fgetc function to get a character from a file This function receives as argument the file we want to read from in this case the variable infile and returns an integer containing the character read 8 We use the while statement to loop reading characters from a file This s
46. Explore Open etc To add an entry to this menu you just add your new menu item name to HKEY CLASSES ROOT Directory shell YourltemName The value of this key should be a text string containing the menu item name Then you add a subkey called command that specifies the command to be executed To take a concrete and simple example we want to start a command shell in the directory where the mouse is pointing to We prepare a text file to add this keys using notepad or another text edi tor REGEDIT4 HKEY CLASSES ROOT Directory shell CmdHere CMD amp Prompt Here HKEY CLASSES ROOT Directory shell CmdHere command G WINDOWS System32 cmd exe k cd S1 We call the program regedit with the argument the file we just created and that is all The two new keys will be automatically added to the registry Note the double backward slashes Obviously you should change the path to cmd exe to suit your system configuration laa 3 21 19 How do translate between dialog units and pixels When a application dynamically adds a child window to a dialog box it may be necessary to align the new control with other controls that were defined in the dialog box s resource tem plate in the RC file Because the dialog box template defines the size and position of a control in dialog box units rather than in screen units pixels the application must translate dialog box units to screen units to align the new child win
47. For instance you can declare My Integer I instead of Tit 2 This can be used with structures too For instance if you want to avoid typing at each time you use acoordinate struct coordinate a youcan define typedef struct coordinate COORDINATE and now you can just write COORDINATE a what is shorter and much clearer Structures and unions 93 This new name can be used with the sizeof operator too and we can write GC malloc sizeot COORDINATE k7 instead of the old notation But please keep in mind the following once you have defined a typedef never use the struct keyword in front of the typedef keyword if not the compiler will get really confused 1 18 4 Unions Unions are similar to structures in that they contain fields Contrary to structures unions will store all their fields in the same place They have the size of the biggest field in them Here is an example miom anti loa 4 ie ee double d by This union has two fields an integer and a double precision number The size of an integer is four in lcc win32 and the size of a double is eight The size of this union will be eight bytes with the integer and the double precision number starting at the same memory location The union can contain either an integer or a double precision number but not the two If you store an integer in this union you should access only the integer part if you store a double you should access the double part Field a
48. HANDLE pid char info 4096 pProcessName GetWindowRect hwnd amp rc GetWindowThreadProcessId hwnd amp pid pProcessName PrintProcessNameAndID ULONG pid WSPrintt anio Handle Ox x s left td top Sd right d bottom Sd HELGA Gd Width sdy Process cs hwnd IsWindowVisible hwnd Visible Hidden LC lettr ECs tOr Ose LONE re bot uom EO DOLCON EO TOO LC CiL9gn C26 ere pProcessName UpdatestetusBar into 0 0 The algorithm here is as follows Query the window rectangle in screen coordinates We get the process ID associated with this window We call a subroutine for putting the name of the process executable file given its process ID We format everything into a buffer We call UpdateStatusBar generated by wedit with this character string we have built The procedure for finding the executable name beginning with a process ID 1s quite advanced and here we just give it like that Static char PrintProcessNameAndID DWORD processID 266 C Tutorial static Char szProcessName MAX PATH HMODULE hMod DWORD cbNeeded HANDLE hProcess OpenProcess PROCESS QUERY INFORMATION PROCESS VM READ FALSE processID szProcessName 0 0 if hProcess if EnumProcessModules hProcess amp hMod sizeof hMod amp cCbNeeded GetModuleBaseName hProcess hMod szProcessName Ssizeof szProcessName CloseHandle hProcess return szProcessName
49. Primer LEOTA Cres Writes its output into the standard output sprintf stringy format Writes its output into a string snprintf string size format Writes its output into the given string but never exceeding size chars fprintf filer format sae Writes its output into a file 1 12 5 Scanning values The scanf family of functions fulfills the inverse task of the printf family They scan a charac ter array and transform sequences of characters into values like integers strings or floating point values The general format of this functions are scanf format pl p2 p3 Reads characters from stdin fscantti tle Torma E ply yO reaal SScant String tormat pl pAr Oresi where format 1s a character string like we have seen in printf and p1 p2 p3 are pointers to the locations where scanf will leave the result of the conversion For instance scanf d amp integer and the input line Zo will store the integer 123 at the location of the integer variable Some things to remember when using scanf 1 You have to provide always a format string to direct scanf 2 For each format directive you must supply a corresponding pointer to a suitable sized location 3 Leading blanks are ignored except for the oc character directive 4 The 3 format means float to enter a double you should write S1 5 Scanf ignores new lines and just skips over them However if we put a n in the
50. SIGNATURE Overwrite the signature so that this block can t be freed again ipt 0 S ipi ip int pls Sizeot int if ip MAGIC BrorPrintf Overwritten block size d s return ip 0 AllocatedMemory s free p else The block has been overwritten Complain ErrorPrintf Wrong block passed to release Memory management strategies 127 The allocate function adds to the requested size space for 3 integers 1 The first is a magic number a signature that allows the identification of this block as a block allocated by our allocation system 2 The second is the size of the block After this two numbers the data follows 3 The data is followed by a third number that is placed at the end of the block Any memory overwrite of any block will overwrite probably this number first Since the release function check for this we will be able to detect when a block has been overwritten At any time the user can ask for the size of total allocated memory valid blocks in circula tion by querying the AllocatedMemory variable The release function accepts NULL that is ignored If the pointer passed to it is not NULL it will check that it is a valid block and that the signature is still there 1 e that no memory overwrites have happened during the usage of the block 128 C programming with Icc win32 1 29 Counting words There is no introduction to
51. This avoids name clashes 236 C Tutorial When we start this program from the command line we see Sloc examplessd1alogs lccstestdialog this i amp the string OK Cancel This isn t that bad for a start We have a sophisticated line editor complete with arrow inter face to move around in the text clipboard support built in delete and backspace keys already taken care of etc If we would have to write ourselves an equivalent program it would cost us probably days of development To develop the clipboard interface already is quite a challenge But we are confronted to the problem of resources Our static library idea was a dead end We have to find something else Summary The C language supports the concept of code reuse in the form of libraries The static libraries are combined with the main application at link time statically They can t contain resources Dynamically linked libraries DLLs 237 3 4 Dynamically linked libraries DLLs A dynamically linked library is just like a static library it contains a set of useful functions that can be called from other software As with normal lib libraries there 1s no main function Unlike static libraries however they have several features that make them a very interesting alternative to static libraries e When they are loaded the loader calls a function of the library to allow load time initializations This allows us to register our class for instance
52. To run the program you use the execute option in the Compiler menu or you type Ctrl F5 or you open a command shell and type the program s name Let s do it the hard way first The first thing we need to know is the name of the program we want to start This is easy we ask the IDE Wedit about it using the Executable stats option in the Utils menu We get the following display We see at the first line of the bottom panel that the program executable is called h lcc projects hello exe 18 We open a command shell window and type the command 16 You start wedit by double clicking in its icon or if you haven t an icon for it by going to the Start menu run and then type the whole path to the executable For instance if you installed lcc win32 in c Icc wedit will be in c lcc bin wedit exe Hello 5 Gayest eCc pro7 ecths Vice helo exe Hello Cer Our program displays the character string Hello and then a new line as we wanted If we erase the n of the character string press F9 again to recompile and link the display will be Cear ee pro 7 eces Vleet nel lo exe Hello CENS But how did we know that we have to call printf to display a string Because the documentation of the library told us so The first thing a beginner to C must do is to get an overview of the libraries provided already with the system so that he she doesn t waste time rewriting programs that can
53. allocate proper Space LFL rom count SMALL if result content NULL memset amp result 0 sizeof result 90 The identity function in C 1s int Ldentrty int Ok d returnm c Implementation 203 return result recule Capacitey Ii romscoun int j 0 Torne ay 20s ae Se Om Couns aha 4 for int k 0 k lt setlength k if from content i set k result content J Becik break recultsCOunt x return result We need a valid string and a non null set We allocate space for the string including the termi nating zero with the allocate proper space function That function will raise an exception if no more memory is left and terminate the program In case the user has overridden that behav ior we return an invalid String This is the single byte version and we indicate this to allocate proper space with the SMALL parameter For the wide character set we would replace that with WIDE If the allocation succeeds we set the capacity field and we select the characters to be included in the result At the end we set the count field to the number of chars found that matched the predicate 2 3 5 Conversions To interact easily with other software we need to convert Strings in traditional strings and we have to allow for converting traditional strings into the String structure We use the overloaded cast operator to give the conversions the traditional C meaning SUPILN
54. and can execute it under the control of the user that directs the controlled execution All C development systems offer some debugger and Icc win32 is no exception The debugger is described in more detail in the user s manual and it will not be described here Suffice to note that you start it with F5 or Debugger in the compiler menu you can single step at the same level with F4 and trace with F8 The debugger shows you in yellow the line the program will execute next and marks breakpoints with a special symbol at the left Other debuggers may differ from this of course but the basic operations of all of them are quite similar Note that Icc win32 is binary compatible with the debugger of Microsoft you can debug your programs using that debugger too To be able to use the debugger you need to compile with the g2 flag on That flag is normally set by default It directs the compiler to generate information for the debugger to enable it to show source lines and variable values The compiler generates a whole description of each module and the structures it uses called debug information This information is processed by the linker and written to the executable file If you turn the debugging flag off the debugger will not work The best approach is to leave this flag on at all times Obviously the executable size will be bigger since the information uses up space on disk If you do not want it you can instruct the linker to ignore it at lin
55. and many other advanced features We will just use a tiny part of it the one that implements the FTP protocol suite FTP means File Transfer Protocol and is one of the oldest protocols around It is a 8 bit client server protocol able to handle any type of file any need to encode its contents unlike MIME or UUENCODE The problem with ftp is that it is very slow to start high latency and needs when using manually a lengthy login procedure The current standard for FTP is RFC 959 which obsoleted the previous specification RFC 765 The first FTP specification was RFC 114 written by A Bhushan in the MIT project MAC the 16 April 1971 Yes It is a really old protocol 4 4 1 Implementing the ftp GET We use a simple interface again ignoring all complexities GetFtpUrl needs 3 arguments 1 The name of the host 2 The name of the file to get 3 The name of the local file where the remote file will be written int GStrrpUril char host char infile char outtitle HINTERNET hOpen hConnect int fret 1 The first thing to do is to check that there is an internet connection If the local machine is not connected to the internet a call to this function will bring up a dialog box and a series of wizards to set up the connection i fret InternetAttemptConnect 0 if fret return fret We can assume now that an internet connection exists We initialize the inet library specifying the default proxy sett
56. coday tm hour 12 See note 2 in text Prince 12 hour Times VOL lesss 2a n asctime today 11 ampm J Print additional time information ftime amp tstruct perinti Plus milliseconds CACA iUn tstruct miLlitm J printi Zone difference in seconds from UTC tsuyn tstruct timezone printf Time zone name t t t tes n _tzname 0 printf Daylight savings t t t s n See note 3 in text ctSstructedotilag YES 3 NO J3 Make time for noon on Christmas 1993 if mktime amp xmas t time t 1 printf Christmas t t t tSs n asctime amp xmas Use time structure to build a customized time string today localtime amp ltime Use strftime to build a customized time string Stritime tmoburt 126 Today is tA day d of the month of B in the year Y n today J Printi tmpbur We use this opportunity for introducing new C constructs We see the function call gmtime amp ltime What does this mean The function gmtime requires a pointer to a variable of type time t We do not have a pointer so we make one on the fly by using the address of operator The printf statement uses pointer addition to skip the first 11 characters of the result of asc time That function returns a pointer to a character string To skip characters we just add up a constant 11 to that pointer effectively skipping those characters Since
57. debug setting the inline keyword is ignored You can control this behav ior also by using the command line option fno inline 1 11 26 Logical operators A logical expression consists of two boolean expressions 1 e expressions that are either true or false separated by one of the logical operators amp amp AND or or The AND operator evaluates from left to right If any of the expressions is zero the evaluation stops with a FALSE result and the rest of the expressions 1s not evaluated The result of several AND expressions is true if and only if all the expressions evaluate to TRUE Example w Sl Re Oe Re eee ST Here evaluation stops after the third expression yields false zero The fourth and fifth expres sions are not evaluated The result of all the AND expressions is zero The OR operator evaluates from left to right If any of the expressions yields TRUE evalua tion stops with a TRUE result and the rest of the expressions is not evaluated The result of several OR expressions is true 1f and only if one of the expressions evaluates to TRUE If we have the expression result expri amp amp expr2 this is equivalent to the following C code if expri 0 result Q0 A closer view 51 else if expr2 0 result Uy else result 1 In a similar way we can say that the expression result expri expr2 is equivalent to if exprl L 0 result 1 else if expr2
58. defined the function main above storage for the code generated by the compiler was created and an entry in the program s symbol table was done In the same way when we wrote LA Coun ue above the compiler made space in the local variables area of the function to hold an integer And now the central point You can declare a variable many times in your program but there must be only one place where you define it Note that a definition is also a declaration because when you define some variable automatically the compiler knows what it is of course For instance if you write double balance even if the compiler has never seen the identifier balance before after this definition it knows it is a double precision number 1 51 Variable declaration A variable is declared with lt type gt lt identifier gt like Int a7 double d Long Long My All those are definitions of variables If you just want to declare a variable without allocating any storage because that variable is defined elsewhere you add the keyword extern extern int a extern double d extern long long d Optionally you can define an identifier and assign it a value that is the result of some calcula tion 31 Note that if the function so declared is never used absolutely no storage will be used A declaration doesn t use any space in the compiled program unless what is declared is effectively used If that is the case the compiler emits a
59. frame pointer This has been working for a while now 84 C programming with Icc win32 gsort Frequencies 256 sizeof int compare We pass the Frequencies array its size the size of each element and our comparison function Here is the new version of our program for your convenience New code is in bold include lt stdio h gt Finclude lt stdlib h gt int Frequencies 256 Array of frequencies int compare const void argl const void arg2 Compare both integers return int argl int arg2 int main int a arqe char argy int count 0 FILE intitle Lit CG if argo lt 2 4 infile foopen argy 1 rb gt if infile NULL c fgetc infile while c EOF fclose infile printf 20 chars in filein count qsort Frequencies 256 sizeof int compare ror Count 0 Columr lt 725o Countt 4 if Freguencies count 0 printf S3c 4d Sd n count count Frequencies count return Q0 We compile link and then we write frequencies frequencies c 957 chars in file Pointers and references 85 Well sorting definitely works you read this display line by line but we note with dismay that All the character names are wrong Why Well we have never explicitly stored the name of a character in our integer array it was implicitly stored The sequence of elements in the array corresponded to a
60. hdcObject bmObjectOld DeleteObject SelectObject hdcMem bmMemOl1d DeleteObject SelectObject hdcSave bmSaveOld Delete the memory DCs DeleteDC hdcMem DeleteDC hdcBack DeleteDC hdcObject DeleteDC hdcSave DeleteDC hdcTemp The following is an example of how the DrawTransparentBitmap function might be called DrawTransparentBitmap hdc The destination DC hBitmap The bitmap to be drawn xPos j 7 X Coordinate yPos Ji Y coordinate OxOOFFFFFF The color for transparent pixels white in this example 3 21 5 How do I draw a gradient background DrawBackgroundPattern ji Purpose This function draws a gradient pattern that transitions between blue and black This is similar to the background used in Microsoft setup programs void DrawBackgroundPattern HWND hWnd HDC hDC GetDC hWnd Get the DC for the window RECT rectrill Rectangle for filling band RECT rectClient Rectangle for entire client area float tS cep How large is each band HBRUSH hBrush int iOnBand Loop index 340 C Tutorial How large is the area you need to fill GetClientRect hWnd amp rectClient Determine how large each band should be in order to cover the client with 256 bands one for every color intensity level fStep float rectClient bottom 256 0f Start filling bands for 10nBand 0 gt iOnBand lt 256 iOnBand t Set the loc
61. if rcContext OutputFile NULL WinHttpCloseHandle hSession return 2 gt Now we have everything We have an open file ready to receive the data a correct answer from the server that tells that the file exists so we have just to loop getting the data chunks until there is none left do Check for available data dwSize 0 if WinHttpQueryDataAvailable rcContext hRequest amp dwSize goto cleanup Allocate space for the butter char pszOutBuffer malloc dwSizetl it pszOutBuffer goto cleanup Read the data ZeroMemory pszOutBuffer dwSize 1 if WinHttpReadData rcContext hRegquest LPVOID pszOutBuffer dwSize amp dwDownloaded free pszOutBuffer goto cleanup OK Write the data fwrite pszOutBuffer 1 dwDownloaded reContext OutputFile Free the memory allocated to the buffer free pszOutBuffer while dwSize gt 0 We are finished We fall through to the cleanup section 4 4 The FTP protocol The library winhttp lib that we used for implementing the HTTP GET functionality above is OK for its intended use HTTP There are however several other interesting protocols avail The FTP protocol 373 able to get information from the net like FTP Gopher and others We will turn ourselves to another high level library wininet lib This library with its header file wininet h implements FTP Gopher and HTTP It comes with an embedded caching schema
62. like our dialog function or many other functions under windows is a callback function i e a function that is called by the operating system not directly from our code Because of this fact its interface the arguments it receives and the result it returns is fixed The operating system will always pass the predefined arguments to it and expect a well defined result The arguments that we receive are the following 1 We receive a HANDLE to the instance of the DLL Note that we have to pass to several functions this handle later on so we will store it away in a global variable 2 We receive a DWORD an unsigned long that contains a numerical code telling us the reason why we are being called Each code means a different situation in the life cycle of the DLL We have a code telling us that the we were just loaded DLL PROCESS ATTACH another to inform us that we are going to be unloaded DLL PROCESS DETACH another to inform us that a new thread of execution has been started DLL THREAD ATTACH and another to tell us that a thread has finished DLL THREAD DETACH 3 The third argument is reserved by the system for future use It is always zero The result of LibMain should be either TRUE the DLL has been correctly initialized and loading of the program can continue or zero meaning a fatal error happened and the DLL is unable to load itself Note that we return always TRUE even if our registration failed Why If our registra
63. message effectively canceling the fake quit that you generated 3 21 27 How do I build a Property sheet control For an example of a property sheet control see the Configuration item in Wedit s main menu The property sheet is just a set of dialog boxes that will be displayed by windows in a special way Each dialog box has an associated function that handles the messages to it from the child controls or from the property sheet displaying software The logic of this functions is very similar to the normal dialog box functions BOOL CALLBACK DlgProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam NMHDR pnmhdr Switch msg case WM INITDLG Initialize the dialog box here This is exactly the same as in a normal dialog box procedure NOTE This will only be called if the user selects the page that this dialog box handles Otherwise the whole dialog box procedure is never called break case WM NOTIFY pnmhdr NMHDR 1Param Switch pnmhdr gt code Case PON APPLY Here we should handle things as if the OK button was pressed lf we return PSNRET_NOERROR we inform windows that the changes made are OK We can return PSNRET_INVALID to disallow the closing of the property sheet if any changes are incorrect In that case the focus would be assigned to this page Or we can return PSNRET_INVALID NOCHANGEPAGE to leave the focus where it is AND not discarding the property sheet r
64. mpath 2 0 if mpath strlen mpath 1 Streat mpath ANN bFlag DeleteVolumeMountPoint mpath printf Ss SS in unmounting the volume at s n argv 0O bFlag succeeded failed mpath return bFlag 3 21 FAQ Here are some answer to questions users of Icc win32 have asked or questions that I imagine you will find useful 3 21 1 How do I create a progress report with a Cancel button Here is the answer from the MSDN Knowledge base article Q76415 The following article describes the mechanisms necessary to implement a progress or activity indicator with a Cancel Operation option to be used for lengthy and CPU intensive subtasks of an application Examples of operations using this include copying multiple files directory searches or printing large files The progress dialog box 1s implemented in two steps e Initialize the dialog box before starting lengthy or CPU intensive subtask e After each unit of the subtask is complete call Progress Yield to determine if the user has canceled the operation and to update the progress or activity indicator This is the description of the progress dialog procedure The procedure uses a global variable Cancel to inform the CPU intensive subtask that the user has indicated a desire to terminate the subtask WORD Cancel FALSE This must be global to all modules 7 which call ProgressYield EF BOOL FAR PASCAL ProgressDlgProc hDlg messa
65. or otherwise Avoiding a trap here only means that the trap will appear later probably making error finding more difficult Writing software means making this type of decisions over and over again Obviously this program will fail with any incorrect string 1 e a string that is missing the final zero byte The failure behavior of our program is quite awful in this case this program will start destroying all bytes that happen to be in the range of uppercase characters until it hits a random zero byte This means that if you pass a non zero terminated string to this apparently harmless routine you activate a randomly firing machine gun that will start destroying your program s data in a random fashion The absence of a zero byte in a string is fatal for any C program In a tutorial this can t be too strongly emphasized 1 15 6 paste You have got two text files and you want to merge them in a single file separated by tabula tions For instance if you have a file with this contents line 1 line2 and you got another file2 with this contents line 10 line 11 you want to obtain a file linel line 10 line 2 line 11 Note that both file can be the same A solution for this could be the following program include lt stdio h gt include lt string h gt include lt stdlib h gt i We decide arbitrarily that lines longer than 32767 chars will make this program fail define MAXLINELEN 32767 int Main int arqe
66. our function takes a char pointer size 4 another char pointer and an integer size 4 too we have 12 bytes of procedure arguments hence the 12 Note that all types smaller than an integer will be automatically be promoted to integers when passing them to a function to keep the stack always aligned so that we shouldn t just take the size of the arguments to make the addi tion All of this can become really complicated if we have structures that are pushed by value into the stack or other goodies The best thing would be that our DLL would export GetString 12 as GetString PERIOD Well this is exactly where our dialog def file comes handy Here 1s a dialog def that will solve our problem LIBRARY dialog EXPORTS GerstringelZ Getsorring We have in the first line just the name of the DLL in a LIBRARY statement and in the second line two names The first one is the name as exported by the compiler and the second one is the name as it should be visible from outside By default both are the same but now we can separate them With these instructions the linker will put in the export table of the DLL the character string GetString instead of the compiler generated name Once this technical problems solved we see that our interface 1s much more flexible now We could just return FALSE from our interface function 1f the DLL wasn t there and thus disable some parts of the software but we wouldn t be tied to any DL
67. p 0 This means Fetch the value this pointer is pointing to p and compare it to zero If the comparison is true then we increment the pointer to the next byte We return the number of characters between our pointer p and the saved pointer to the start of the string This pointer arithmetic is quite handy How can this program fail The same problems apply that we discussed in the previous example but in an attenuated form only a wrong answer is returned not an outright wrong pointer The program will only stop at a zero byte 1 15 3 ispowerOfTwo Given a positive number find out 1f it is a power of two Algorithm A power of two has only one bit set in binary representation We count the bits If we find a bit count different than one we return 0 if there is only one bit set we return 1 Implementation We test the rightmost bit and we use the shift operator to shift the bits right shifting out the bit that we have tested For instance if we have the bit pattern 1 0 0 1 shifting it right by one gives 0 1 0 0 the rightmost bit has disappeared and at the left we have a new bit shifted in that 1s always zero int 1spowerOfTwo unsigned int n unsigned int bitcount 0 while m T Q f Pe 0 Ge Lh d Piteoumea ts a a gt gt 1 if bitcount 1 rewur a ay return 0 Our condition here is that n must be different than zero 1 e there must be still some bits to count to go on We
68. sizeof jmp buf Here the contents of global will be either 78 9776 or 23 87 if the longjmp was taken return status int process void int error code 0 global 23 87 Lf error code Long jmp Errorinvyerror code 7 And if you erase a file longymp will not undelete it Do not think that longjmp is a time machine that will go to the past Yet another problem to watch is the fact that if any of the global pointers pointed to an address that was later released after the longjmp their contents will be wrong Any pointers that were allocated with malloc will not be released and setjmp longjmp could be the source of a memory leak Within Icc win32 there is an easy way out since you can use the garbage collector instead of malloc free The garbage collector will detect any unused memory and will released when doing the gc 1 14 2 Register variables and longjmp When you compile with optimizations on the use of setjmp and longjymp can produce quite a few surprises Consider this code include lt setjmp h gt include lt stdio h gt int main void jmp buf jumper int localVariable 1 1 printf 1 d n localVariable if setjmp jumper 0 return from long jmp localVariablett 2 prince 22 sd n LocalVariable longjmp jumper 1 localVariable 3 printf 3 20 n localVariabile return 0 Our local Variable starts with the value 1 Then before ca
69. src string For instance if we have the string pointer that has the characters lccwin32 as above and we call the library function str cat str compiler we will obtain the following sequence Die ee ee E lee i i ase Petals A oc eee den 3 The common operations for strings are defined in the header file lt string h gt Get a system error message strcat Appends strings strerror strerror or prints a user supplied error message _ strerror Find the first occurrence of a strchr l strlen Find the length of a string character in a string Find the last occurrence of a strrchr i strncat Append characters of a string character in a string Copy strings up to a maximum strcmp Compares two strings strncpy ine 85 up re Compare strings up to a maximum Scan strings for characters in strncmp strpbrk l length specified character sets Compare strings up to a maximum length ignoring case Compare strings using locale l strcol a AA strstr Find a substring specific information strcpy Copy a string into another stristr Find a string ignoring case strcspn Find a substring in a string strtok Find the next token in a string Convert string to upper case strdup Duplicate a string Uses malloc Convert string to lower case Reverse characters in a string You will find the details in the online documentation Besides these functions in the standard C library the operating system itself provides quite a few ot
70. statement execution continues with the increment part Remember that the continue statement within a switch statement doesn t mean that execution will continue the switch but continue the next enclosing for while or do statement 1 11 22 Null statements A null statement is just a semicolon This is used in two contexts 1 An empty body of an iterative statement while do or for For instance you can do wiLle p gt f search the end of the string 2 A label should appear just before a closing brace Since labels must be attached to a statement the empty statement does that just fine A closer view 49 1 11 23 Comments Multi line comments are introduced with the characters and and finished with the opposite sequence followed by This commentaries can t be nested Single line com ments are introduced by the sequence and go up to the end of the line Here are some examples a b Four character string literal Single line comment not syntax error f g h Equivalent to f g h 77 fn Part of a comment since the last line ended with a W 1 11 24 Switch statement The purpose of this statement is to dispatch to several code portions according to the value in an integer expression A simple example 1s enum animal CAT DOG MOUSE enum animal pet GetAnimalFromUser switch pet case CAT print Ta ws 1s ca Cat break case DOG
71. that represent an error or NAN and signed infinity positive and negative infinity The representation of NANSs in the IEEE formats is as follows Numerical programming 169 NAN infinity and float TLECVOU00 f800000 ff800000 double ff80000 00000000 FEEVOOOU 00000000 FEFOOOOQO 00000000 long double TLEL ELETETEE TELET 7rerre g0000000 00000000 fFFff 80000000 00000000 We have actually two types of NANs quiet NANs and signalling NANS A Quiet NaN when used as an operand in any floating point operation quietly that is without causing any trap or exception produces another quiet NaN as the result which in turn propa gates A Quiet NaN has a set in the most significant bit position in the mantissa field A Signaling NaN has no business inside an FPU Its very presence means a serious error Sig naling NaNs are intended to set off an alarm the moment they are fetched as an operand of a floating point instruction FPUs are designed to raise a trap signal when they touch a bit pat tern like that Quiet NaNs are produced when you do things like try to divide by zero or you pass incorrect arguments to a standard FPU function for instance taking the square root of 1 Modern FPUs have the ability to either produce a quiet NaN or raise a signal of some sort when they encounter such operands on such instructions They can be initialized to do either of the two options in case the code runs into these situations We wi
72. urn As break case WM CLOSE EndDialog hwndDlg 0 return TRUE return FALSE A dialog box procedure is called by the system It has then a fixed argument interface and should return a predefined value It receives from the system the handle of the dialog box win dow the message and two extra parameters Normally these procedures are a big switch statement that handles the messages the program is interested in The return value should be TRUE if the dialog box procedure has handled the message passed to it FALSE otherwise The general form of a switch statement is very simple you have the switch expression that should evaluate to an integer and then you have several cases that should evaluate to com pile time constants All those names in the switch statement above are just integers that have been given a sym bolic name in windows h using the preprocessor define directive A break keyword sepa rates one case from the next one Note that in C a case statement can finish without a break keyword In that case execution continues with the code of the next case In any case of course a return statement finishes execution of that case since control is immediately passed to the calling function In this procedure we are interested in only three messages hence we have only three cases in our switch 1 WM INITDIALOG This message is sent after the window of the dialog box has be
73. we need in average to access n 2 elements Other functions are surely necessary Let s see how a function that returns the nth member of a list would look like Leo heee Nero liver ae 1 while list amp amp n gt 0 kist rist Next return Lisi Note that this function finds the nth element beginning with the given element which may or may not be equal to the root of the list If there isn t any nth element this function returns NULL If this function is given a negative n it will return the same element that was passed to it Given a NULL list pointer it will return NULL Other functions are necessary Let s look at Insert LIST Insert LIST list LIST element LESE C if list NULL return NULL if list element tetur sec tmp list gt Next list gt Next element if element element gt Next tmp return last We test for different error conditions The first and most obvious is that list is NULL We just return NULL If we are asked to insert the same element to itself 1 e list and element are the same object their addresses are identical we refuse This is an error in most cases but maybe you would need a circular element list of one element In that case just eliminate this test Note that Insert list NULL will effectively cut the list at the given element since all elements after the given one would be inaccessible 140 C prog
74. 0 3 21 8 How do I close an open menu To cancel an active menu send a WM CANCELMODE message to the window that owns it When you send the WM CANCELMODE message to the owner window of an active menu the window exits the menu mode You can use this technique to force the abandonment of active TrackPopupMenu or TrackPopupMenuEx 3 21 9 How do I center a dialog box in the screen To center a dialog box on the screen before it is visible add the following lines to the process ing of the WM_INITDIALOG message RECT rc GetWindowRect hDlg amp rc SetWindowPos hDlg NULL GeCoystenMet11Cs oM CXSCREEN ro right c 1ere GetoystenMetri1cs SM CYSCREEN rc bottom ro top Oy Oy SWP NOSIZE SWP NOACTIVATE ae 2 This code centers the dialog horizontally and vertically 3 21 10 How do I create non rectangular windows In previous versions of Windows and Windows NT it was possible to create only rectangular windows To simulate a non rectangular window required a lot of work on the application developer s part Besides handling all drawing for the window the application was required to perform hit testing and force underlying windows to repaint as necessary to refresh the trans parent portions of the window Windows 95 and Windows NT version 3 51 greatly simplify this by providing the SetWin dowRgn function An application can now create a region with any desired shape and use Set Wi
75. 284 C Tutorial We obtain the following text Wedit Pes Info ifndef windows h include lt windows h gt tendir include winexampleres h BOOL APIENTRY DlgSearch HWND hwnd UINT msg WPARAM wParam LPARAM lParam static WEDITDLGPARAMS WeditDlgParams Switch msg case WM JINITDIALOG SetWindowLong hwnd DWL USER DWORD amp WeditDlgParams DigSearchInit hwnd wParam lParam ee SLOTS The ripae argumento af any 7 SetProp hwnd InputArgument HANDLE lParam break case WM COMMAND Switch LOWORD wParam Case IDOK DlgSearchOnOKSelected hwnd break break return HandleDefaultMessages hwnd msg wParam lParam We have here a normal callback procedure for our dialog It handles two messages WM INITDIALOG and WM COMMAND The callback procedures are in bold type There are two of them The initialization callback called DlgSearchInit and the one we attached to the OK button above DlgSearchOnOkSelected There are more things in there but for the time being we are interested in just those ones because they have to be written by you What you want to do when the dialog box has been created but it 1s not yet visible This is the purpose of the first callback In our text search dialog we could write in the edit field the last searched word for instance to avoid retyping Or we could fill a combo box with all the words the user has search
76. 4 An optional size flag expressed as one of the letters 11 1 L h hh Jj q t or z 5 The type specification a single character from the set a A c d e E f g G 1 n O p S U X X and 43 the quote char is specific to lcc win32 The printf family 57 64 25 7LE comersion Lie starts here width precision Conversion flag size flag 1 12 2 The conversion flags Value will be left justified The pad character is space Use zero as pad character instead of the default space This 1s relevant only if a minimum field width is specified otherwise there is no padding If the data requires it the minimum width is not honored Note that the padding charac ter will be always space when padding is introduced right of the data Always add a sign either or Obviously a minus flag is always written even if this flag is not specified single Separate the digits of the formatted numbers in groups of three For instance quote 123456 becomes 123 456 This is an lcc win32 extension Use either space or minus 1 e the 1s replaced by a space use a variant of the main version algorithm 1 12 2 1 The minimum field width This specifies that if the data doesn t fit the given width the pad character is inserted to increase the field If the data exceeds the field width the field will be bigger than the width set ting Numbers are written in decimal without any leading zeroes that could be misunderstoo
77. 6d 12 7 20 traction 2 023b n rs Aeta ra ee ra Cn al re ey 78 Note that there are as many IEEE754 numbers between 1 0 and 2 0 as there are between 256 and 257 in double format 2 57 2 56 is quite a big number 72 057 594 037 927 936 79 This is an unnamed structure within another structure or union Icc win32 and other compilers like visual C allow to access the members of an unnamed union structure without having to write t u sign t u e etc 174 C programming with Icc win32 int main void number t tofl 178 125 pfloat t return 0 This will produce the output Sign 0 exponent 134 127 7 fraction 01100100010000000000000 To calculate the fraction we do fraction 01100100001 0 1 2 1 1 4 1 8 1 16 1 32 1 64 1 17 1024 This is Odos Toto UL 02D FUs DUU 76062 U 396ULS6Z gt Then we add 1 to 0 3916015625 obtaining 1 3916015625 ooOH This number we multiply it by 2 7 128 Igo PLOULSoZS 120 Tog io 1 35 2 4 Rounding modes When the result of a computation does not hit directly a number in our representation grid we have to decide which number in the grid we should use as the result This is called rounding We have the following rounding modes 1 Round to the nearest grid point This is the default setting when a program compiled with Icc win32 starts executing 2 Round upwards Choose always the next higher grid point in the di
78. Data by This list features two pointers one forward to the following element in the list and one back ward to the previous element of the list A special declaration that can only be used in structures is the bit field declaration You can specify in a structure a field with a certain number of bits That number is given as follows struct flags unsigned HasBeenProcessed 1 58 The usage of the pragma pack construct is explained in lcc win32 user s manual Those explanations will not be repeated here Structures and unions 89 unsigned HasBeenPrinted 1 unsigned Pages 5 by This structure has three fields The first is a bit field of length 1 1 e a Boolean value the sec ond is also a bit field of type Boolean and the third is an integer of 5 bits In that integer you can only store integers from zero to 31 1 e from zero to 2 to the 5th power minus one In this case the programmer decides that the number of pages will never exceed 31 so it can be safely stored in this small amount of memory We access the data stored in a structure with the following notation lt structure name gt field name or lt structure name gt field name We use the second notation when we have a pointer to a structure not the structure itself When we have the structure itself or a reference variable we use the point Here are some examples of this notation void fn void coordinate c Coordinate pc C
79. G 71 1 H 72 1 I 73 1 J 74 1 K 75 1 We test now our program with itself We call frequencies frequencies c 758 chars in file I have organized the data in a table to easy the display What is missing obviously is to print the table in a sorted way so that the most frequent char acters would be printed first This would make inspecting the table for the most frequent char acter easier 1 16 1 How to sort arrays We have in the standard library the function qsort that sorts an array We study its prototype first to see how we should use it VOL GSOLe voLd by S126 DS LZe t Grint E CCOnst VOLT Well this is quite an impressing prototype really But if we want to learn C we will have to read this as it was normal prose So let s begin from left to right 52 The prototype is in the header file stdlib h Using arrays and sorting 81 The function qsort doesn t return an explicit result It is a void function Its argument list 1s the following Argument 1 isa void Void What is that Well in C you have void that means none and void that means this is a pointer that can point to anything 1 e a pointer to an untyped value We still haven t really introduced pointers but for the time being just be happy with this explanation qsort needs the start of the array that will sort This array can be composed of anything integers user defined structures double precision
80. I simulate a key stroke to send it to another window 362 How can I encrypt and decrypt a character string 362 Finding more examples and source code 365 Overview of Icc win32 s documentation 365 Bibliography 366 Chapter 4 Network Programming 367 Introduction 367 What is a network 367 Protocols 368 The HTTP Protocol 368 GetHttpUrl 369 Implementation 369 The FTP protocol 372 Implementing the ftp GET 373 Querying the network parameters 374 Writing ping 378 How does it work 378 Client Server programming using sockets 380 Common steps for server and client 380 Server side 381 Client side 382 Sending and receiving data 382 Simplifying sockets programming with Icc win32 382 Introduction to C This tutorial to the C language supposes you have the Icc win32 compiler system installed You will need a compiler anyway and Icc win32 is free for you to use so please if you haven t done that yet download it and install it before continuing http www q software solutions com What the C language concerns this is not a full fledged introduction to all of C There are other better books that do that see the bibliography at the end of this book Even if I try to explain things from ground up there isn t here a description of all the features of the language Note too that this is not just documentation or a reference manual Functions in the standard library are explained of course but no exhaustive documentation o
81. Live Acree PILLE hE Al lLocUonsole 3 HOr Open osthandle long GetStdHandle STD OUTPUT HANDLE O TEXT E KE fdopen NOCrt w Jy xoCQOuG 7AE setvbuf stdout NULL _IONBF 01 17 princi Helle worlkd Va recur Uy 3 20 16 Enabling or disabling a button or control in a dialog box You should first get the window handle of the control using 328 C Tutorial hwndControl GetDlgItem hwndDlg IDBUTTON Using that window handle call EnableWindow 3 20 17 Making a window class available for all applications in the system Under 32 bit Windows and Windows NT a style of CS GLOBALCLASS indicates that the class is available to every DLL in the process not every application and DLL in the system as it does in Windows 3 1 To have a class registered for every process in the system under Windows NT e Register the class in a DLL e Use a style of CS GLOBALCLASS e List the DLL in the following registry key HKEY LOCAL MACHINE SOFTWARE Microsoft Windows NT CurrentVersion Windows AppInit DLLs This will force the DLL to be loaded into every process in the system thereby registering the class in each and every process NOTE This technique does not work under Windows 95 3 20 18 Accessing the disk drive directly without using a file system To open a physical hard drive for direct disk access raw I O in a Win32 based application use a device name of the form YA Physical Driven where N is 0 1
82. Premier ais 2s a dog 4 break Case MOUSE princi TRS 1 a mouse break default printf Unknown animal break We define an enumeration of symbols and call another function that asks for an animal type to the user and returns its code We dispatch then upon the value of the In this case the integer expression that controls the switch is just an integer but it could be any expression Note that the parentheses around the switch expression are mandatory The compiler generates code that evaluates the expression and a series of jumps gotos to go to the corresponding portions of the switch Each of those portions is introduced with a case keyword that is followed by an integer constant Note that no expressions are allowed in cases only constants that can be evaluated by the compiler during compilation Cases end normally with the keyword break that indicates that this portion of the switch is finished Execution continues after the switch A very important point here is that if you do not explicitly write the break keyword execution will continue into the next case Sometimes this is what you want but most often it 1s not Beware There is a reserved word default that contains the case for all other values that do not appear explicitly in the switch It is a good practice to always add this keyword to all switch state ments and figure out what to do when the input doesn t match any of the expected va
83. Printt tError d getting stats n GetLastHrror return 1 printf tNumber of IP addresses ld n pStats gt dwNumAddr printf tNumber of Interfaces ld n pStats gt dwNumIf printf tReceives Sld n pStats gt dwInReceives printf tOut Requests Sld n pStats gt dwOutRequests printf tRoutes S ld n pStats gt dwNumRoutes printf tTimeout Time ld n pStats gt dwReasmTimeout Printt tIn Delivers lt sld n pStats gt SdwinDelivers Princi tin Discards cld n pStats gt dwinbiscards printi tTotal Ine la n pStats gt dwinDeliverstpStats gt dwinDiscards printf tIn Header Errors ld n pStats gt dwInHdrErrors Get the TCP statistics MIB TCPolATS pICcPotacs PICPStats MIB TCPSTATS malloc sizeor MIB TCPSTAIS 7 378 C Tutorial If COWREL Val Getrcpotatistics PTCP tats NO ERROR printf Error lt d getting TCP Stats n Gethasthrror 4 printf tActive Opens ld n pTCPStats gt dwActiveOpens printf tPassive Opens S ld n pTCPStats gt dwPassiveOpens Printe tSeoments R cv oLan pICPStats Sdwilnsegs Print eS qments mite sld n pIrCrepStats gt dwo0utSegs gt printf tTotal Conxs ld n pTCPStats gt dwNumConns Getting accurate information about the TCP and IP statistics is very important when you want to measure the performance of a network program By getting the count of the pack
84. Procedure multiple 1D 1 Purpose Compiles a multiple regular expression Input Reads input from standard input OULPUL Generates a regexp structure Errors Several errors are displayed using the complain Function void multiple void This comment will be inserted in the interface the next time you ask for the description of the function 30 C programming with Icc win32 1 8 2 Describing a file In the same context menu that appears with a right click you have another menu item that says description of file c where file c is the name of the current file This allows you to describe what the file does The editor will add automatically the name of the currently logged on user most of the time the famous administrator The output of the interface looks like this Module description EI Name Ok d lcc examples regexp try c ok Cancel Identification Author ADMINISTRATOR Project Creation State This module tests the regular expressions package It is self contained and has a maint funetion that will open a file given in the command line that is supposed to conttain several regular expressions to test If any errar are discovered the results are printed to stdout be Module d lcc examples regexp try c Author ADMINISTRATOR Project Stave Creation Date Description This module tests the regular expressions package It is self contained and has a main function that wil
85. Quite a few formats are available for images sound text etc Read and write from COM ports Consoles and text The msdos window improved mode support Debug Help Why not Write a debugger Any one can do it It 1s quite interesting as a program Device I O Manage all kind of cards with DevicelOControl Dynamically linked Yes I know It is hot in DLL Hell But at least you get separate libraries DLLs modules using binary interfaces that can be replaced one by one This can lead to confusion but it is inherent in the method The disk is spinning anyway Use it File Systems Journaling file systems NTFS FAT32 As you like it Graphics Windows are graphical objects The GDI machinery allows you to draw simple objects with lines or regions but you can go to higher dimensions with DirectX or OpenGl Handles and Objects Objects that the system manages windows files threads and many others are described by a numerical identifier A handle to the object Hooks Install yourself in the middle of the message queue and hear what is being passed around you receive the messages before any other window receives them Inter Process Com Client Server and many other forms of organizing applications are munications available You have all the primitives to do any kind of architecture Synchronization pipes mailslots you name it Send receive mail messages using the Messaging API
86. SP W NN f EOL tite 2 SOs a lt MaE a b 4 theta double 1 7 CENTER thetaz2 doubier iI CENTER V 3 14 r scale exp theta2 tan in 9 if r gt cut break x r cos theta CENTER Vy sim theta t CENTER randx double rand double RAND MAX randy double rand double RAND MAX PLOEDGEAD RDC Xfi randx yrf randy RGB 255 7 0 7 0 9 10 We translate both loops into two for statements The exit from those loops before they are fin ished is done with the help of a break statement This avoids the necessity of naming loops when we want to break out from them what could be quite fastidious in the long term I suppose that in the language the author is using loops go until the variable is equal to the number of iterations Maybe this should be replaced by a strictly smaller than but I do not think a point more will do any difference Note the cast of i double i Note too that I always write 50 0 instead of 50 to avoid unnecessary conversions from the integer 50 to the floating point number 50 0 This cast is not necessary at all and is there just for documentation purposes All integers when used in a double precision expression will be automatically converted to double precision by the com piler even if there is no cast The functions exp and tan are declared in math h Note that it is imperative to include math h when you compile this If you don t those functions w
87. Under windows each program should make this event stream pump turn by writing some where while GetMessage ProcessMessage we will describe the exact syntax later This message pump is hidden now from view under the DefDlgProc procedure but it is the source of all the messages passed to the dialog proce dure that we defined A windows program is designed to react to those messages or events It will process them in sequence until it decides to stop the message pump ending the program The general structure is then 110 Application frameworks like MFC introduce an additional simplifying layer between you and the operating system Much has been said and written about them and here I will not discuss this in much more detail Suffice to note that the purpose of Icc win32 is to let you be always in control of what is going on You can do here anything contrary to a framework where you can only do what the framework provides for and nothing else True an application framework can simplify the coding and many people use them It would be feasible to build such a framework with Icc win32 but I will leave this problem as an exercise to the reader 244 C Tutorial e Initialize the application register the window classes etc e Start the message pump e Process events until a predefined event generally the closing of the main window provokes the stop of the message pump e Cleanup This was the s
88. a FILE instead of a stream Let s change it to ProcessStream and change the name of the stream argument to instream to make things clearer int ProcessStream STREAM instream CHARS Frequencies iat COUN a0 int c fgetc instream gt file while c EOF count t if c gt Extending a program 105 Freguencies c Frequencytt c fgetc instream gt file return Count This looks cleaner Now we have to change our main function to make it read all the files that match the given name Our new main procedure looks like this int maimtint argc char argv El int count 0 STREAM infile checkargs argc argv if infile NULL return 1 Initialize dor count ProcessStream infile Frequencies Fe Lose ant wleHst ie gt infile GetNext infile ye alse Cae a ees Pe 20 g printi d chars am TLLA counte gt gsort Frequencies 256 sizeof CHARS compare DisplayOutput Frequencies return U We didn t have to change a lot thanks to the fact that the complexities of reading and handling a stream are now hidden in a function with well defined parameters We build a GetNext function that returns either a valid new stream or NULL 1f it fails It looks like this STREAM GetNext STREAM stream STREAM result Struct Tinddata t fd rong tindnextResult findnext stream handle 41d if findnextResult lt 0 return NUL
89. and the numbers we can represent in it are just a finite approximation to the infinite mathematical continuum The moment we convert a problem from the domain of mathematical analysis to the range of numbers that can be handled in a machine even in a paper and pencil machine we are going to necessarily introduce approximations that can lead to errors truncation errors rounding errors whatever Suppose we want to evaluate exp x by using a series expansion 2 3 4 5 6 7 8 9 eh424242 4 4 41 0 x 2 6 24 120 720 5040 40320 exp x 1 We have to stop somewhere No way out Here we get tired at the 9th term And no matter how much effort we put into this there will be always a truncation error In this case the truncation error can be accurately calculated Analyzing and estimating the error bounds is the art of numerical analysis Computers use bit patterns to represent any object that can be represented in a computer In the section about structures we represented a person by a bit pattern like this structure person Char Name int age by A person is surely not a bit pattern We use the bit pattern to abstract some characteristics of the person we are interested in Numbers aren t different They can be represented by a bit pat tern too We can use 32 bits what allows us to represented almost 4294967296 numbers But obviously there are more numbers infinitely more than that so any representation will alway
90. and the program works It is surely NOT a good practice to do this however since all argument checking is not done for unknown func tions an error in argument passing will pass undetected and will provoke a much harder type of error a run time error In general it is better to get the error as soon as possible The later it is discovered the more difficult it 1s to find it and to track its consequences Do as much as you can to put the C com piler in your side by using always the corresponding header files to allow it to check every function call for correctness 37 You will probably see another display in your computer if you are using a recent version of lcc win32 I improved error handling when I was writing this tutorial 22 C programming with Icc win32 The compiler gives two types of errors classified according to their severity a warning when the error isn t so serious that doesn t allow the compiler to finish its task and the hard errors where the compiler doesn t generate an executable file and returns an error code to the calling environment We should keep in mind however that warnings are errors too and try to get rid from them The compiler uses a two level warning level variable In the default state many warnings aren t displayed to avoid cluttering the output They will be displayed however if you ask explicitly to raise the warning level with the option A This compiler option will make th
91. and then calling the API DialogBox What is it doing We need to register a class in the window system The windows system is object oriented since it is derived from the original model of the window and desktop system developed at Xerox a system based in SmallTalk an object oriented language Note that all windows sys tems now in use maybe with the exception of the X Window system are derived from that original model The Macintosh copied it from Xerox and some people say that Microsoft cop ied it from the Macintosh In any case the concept of a class is central to windows A class of windows is a set of window objects that share a common procedure When some messages or events that concern this window are detected by the system a message is sent to the window procedure of the concerned window For instance when you move the mouse over the surface of a window the system sends a message called WM MOUSEMOVE to the win dows procedure informing it of the event There are quite a lot of messages and it would be horrible to be forced to reply to all of them in all the windows you create Fortunately you do not have to You just treat the messages that interest you and pass all the others to the default windows procedure 95 PLEASE never do this if you use the garbage collector 218 C Tutorial There are several types of default procedures for MDI windows we have MDIDefWindow Proc for normal windows we have DefWindowProc and fo
92. and you press the dir button in the upper right You will see the following display ff WInekample rc You click in the Accelerator tree tab and you will see the following Accelerator keys DT 3 WIRTEEY CONTROL We have here the accelerator called IDM EXIT that has the value of 300 This is just Ctrl Q for quit The key value is 81 the ASCII value of the letter q with a flag indicating that the control key must be pressed to avoid quitting just when the user happens to press the letter q in the keyboard A more advanced window 249 Double clicking in the selected line leads us to yet another dialog Changing an accelerator key Key Modifiers jer M Ctl D Shift D At D No invert Cancel Menu equivalent Type IDM_EXIT Asci f Virtual Key Change key Here you can change the accelerator as you want The flags are explained in the documenta tion for the resource editor But this was just another digression we were speaking about WinMain and that statement LoadAccelerators Well let s go back to that piece of code again After loading the accelerators the status bar is created at the bottom of the window and then at last we show the window Note that the window is initially hidden and it will be shown only when all things have been created and are ready to be shown This avoids screen flicker ing and saves execution time It would be wasteful to redraw the window before we cre
93. are the command line argument Bloc examples dialog lec Bloc examples dialogslec dialog exe E Note the first line Command line arguments to pass to program There we write the string that we want shown in the dialog box When now we press Ctrl F5 we see our dialog box like this these are the command line arguments Nice we can pass our dialog box a prompt string This makes our dialog box more useful as a general input routine Remember that the objective of this series of sections was to introduce you a general routine to input a character string from the user We are getting nearer Still there is one more problem that we haven t solved yet We have a buffer of a limited length i e 1024 characters We would like to limit the text that the user can enter in the dialog box so that we avoid overflowing our buffer We can do this with the message EM SETLIMITTEXT We have to send this message to the control when we start the dialog box so that the limit will be effective before the user has an occasion of overflowing it We add then sendDlgItemMessage hDlg IDENTRYFIELD EM SETLIMITTEXT 512 00 Libraries 231 3 3 Libraries What we would like is a way of using this dialog box in our applications of course How could we do that One way would be to call it as an independent program We could use the facilities for calling a program within the windows system and pass our prompt in the command l
94. argv 1 exit l1 c fgetc infile while c EOF count t Frequencies c c fgetc infile fclose infile printf d chars in file n count for count 0 count lt 256 count if Frequencies count 0 printf 3c 4d d n count count Frequencies count return 0 We declare an array of 256 integers numbered from zero to 255 Note that in C the index ori gin is always zero This array is not enclosed in any scope Its scope then 1s global 1 e this identifier will be associated to the integer array for the current translation unit the current file and its includes from the point of its declaration on Since we haven t specified otherwise this identifier will be exported from the current module and will be visible from other modules In another compilation unit we can then declare extern int Frequencies and we can access this array This can be good it allow us to share data between modules or it can be bad it allows other modules to tamper with private data it depends on the point of view and the application j If we wanted to keep this array local to the current compilation unit we would have written static int Frequencies 256 The static keyword indicates to the compiler that this identifier should not be made visible in another module The first thing our program does is to open the file with the name passed as a paramet
95. calling function char EXPORT operator Stringo amp strp Char result result ula SEL CONTEC result strp count return result result if 0 result NULL return NULL allocate Proper space SLrp cou nttIiy SMALL memcpy result SErPpPr content SCIE Count return result 2 3 6 File operations Files can be read as a whole into a string for later processing This is a similar operation as building a memory mapped file StringA EXPORT overloaded Strfromfile FILE fp StringA result if binarymode fp Topen file name nb y else fp Topen iile name rz if NULL fp Lreturm invalid strings Size needed 0 ine a EV Oy i val PSeek t py U SEEK END IE 0 JS i eve y fclose fp Petur Invalid StringA needed ftell fp i trval fseek Tpr Uy SEEK ond DE Os tS Sera LA fclose fp return invalid Stringa result content if result content NULL Char Tile name 11 banarymode allocate proper space ncededrl sMALL Implementation 205 return invalid scringA result capacity needed 1l cize C U Ivalbl Pread resull content Ty mesded p fclose fp iie U avaL l needed 4 return Invalid StELnNgA result count needed return result According to the binary mode parameter we read the file including the r n sequence into the contents or not We determine the file size then we read the st
96. char argyv 74 C programming with Icc win32 We need two FILE pointers and two line buffers to hold each line from each file We receive in argc the number of arguments passed 1 and in the character array argv the names of the two files T FILE f1 f 2 char bufl MAXLINELEN buf2 MAXLINELEN r We test immediately if the correct number of arguments has been given If not we exit with a clear error message if argc lt 3 forinti stderr Usage paste tilel file2 n 3 exit 1 r We open both files taking care not to open the same file twice We test with strcmp if they are equal fi open argy 1 2 if strcomplargv l1 argy 2 2 fo pen argv 2 r else f2 fl j We read line after line of the first file until we reach the end of the first file T while fgets buf1 MAXLINELEN f1 char o strchr burl n i the fgets function leaves a n in the input We erase it if it is there We use for this the strchr function that returns the first occurrence of a character in a string and returns a pointer to it If it doesn t it returns NULL so we test below before using that pointer if p D Oy i We output the first file line separated from the next with a single tabulation char prance ss t burl J If there are still lines to be read from file 2 we read them and we print them after doing the same treatment as above if f2
97. character value But once we sort the array this ordering is gone and we have lost the correspondence between each array element and the character it was representing C offers us many solutions to this problem but this is taking us too far away from array han dling the subject of this section We will have to wait until we introduce structures and user types before we can solve this problem 1 16 2 Summary of Arrays and sorting e Arrays are declared by indicating their size in square brackets after the identifier declaration lt type gt identifier SIZE e Arrays are equivalent to pointers to their first element e Arrays decay i e are transformed into pointers when passed to other functions e You can sort an array using the qsort function 1 17 Pointers and references Pointers are one of the hard subjects of the C language They are somehow mysterious quite difficult for beginners to grasp and their extensive use within C makes them unavoidable Pointers are machine addresses 1 e they point to data It is important to have clear this distinc tion pointers are NOT the data they point to they contain just a machine address where the data will be found When you declare a pointer like this 86 C programming with Icc win32 FILE intitle you are declaring reserve storage for a machine address and not a FILE structure This machine address will contain the location where that structure starts This
98. could be numbered from zero up but Windows uses a more sophisticated numbering schema called Virtual memory 34 Deep C secrets Peter van der Linden ISBN 0 13 177429 8 Declarations and definitions 19 left and a function prototype at the right Using rule 2 B 1 we continue with the prototype next is a pointer to a function with two arguments We then process the asterisk next is a pointer to a function with two arguments returning a pointer to Finally we add the char const to get next 1s a pointer to a function with two arguments returning a pointer to a constant pointer to char Now let s see this char J 120 7 Again we start with jJ is a pointer to At the right is an expression in brackets so we apply 2 B 2 to get j is a pointer to an array of 20 Yes what We continue at the left and see char Done J is a pointer to an array of 20 chars Note that we use the declaration in the same form without the identifier when making a cast char 20 malloc sizeof j We see in bold and enclosed in parentheses a cast the same as in the declaration but without the identifier J 1 5 2 Function declaration A declaration of a function specifies e The return type of the function 1 e the kind of result value it produces if any e Its name e The types of each argument if any The general form 1s lt type gt lt Name gt lt type of arg 1 gt lt type
99. could have a function this confusing to get a simple error message FormatMessage FORMAT MESSAGE FROM SYSTEM FORMAT MESSAGE IGNORE INSERTS NULL source err error code 0 language ID burt buffer to receive message BUFSIZ Size of but NULL arguments return buf endif 3 21 26 Making a timed message box One of the problems with the MessageBox API 1s that it will stop everything requiring that the user clicks in the OK button There are many situations where this is not desirable since it makes automated program running a problem Here 1s a solution proposed in the knowledge base of MSDN FAQ 359 void CALLBACK MessageBoxTimer HWND hwnd UINT uiMsg UINT idEvent DWORD dwTime PostQuitMessage 0 KK KK KK KK KK KK KKK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KK TimedMessageBox ca The same as the standard MessageBox except it also accepts a timeout If the user does not respond within the a specified timeout then the value 0 is returned instead i of one of the ID values kK KK KK KK KK KK KK KK KK KK KK KK KK KK kK KK KK KK KK KK KK KK KK KK KK KK KK KK KK KKK UINT TimedMessageBox HWND hwndParent LPCTSTR ptszMessage LPCTSTR ptszTitie UINT lags DWORD dwlimeout UINT idTimer UINT uiResult MSG ns jx Set a timer to dismiss the message box ae idTimer SetTimer NULL 0O dwTimeout TIMERPROC MessageBoxTimer
100. definitions file spares us to hard wire that syntax in the source code The definitions file has its drawbacks too however We need yet another file to maintain another small thing that can go wrong For our example we will use the _ declspec dllexport syntax since we have only one function to export We return to our library project and reopen it We go again to the linker configuration tab that now is called librarian since we are building a static library and we check the radio button corresponding to a DLL project We answer yes when Wedit says whether it should rebuild the makefile and there we are Now we have to make the modifications to our small library We have to define a function that will be called when the library is loaded Traditionally the name of this function has been LibMain since the days of Windows 3 0 or even earlier We stick to it and define the following function int WINAPI LibMain HINSTANCE hDLLInst DWORD Reason LPVOID Reserved Switch Reason 107 You can change this by pressing the corresponding button in the linker configuration tab or by giving the argument nounderscores to the linker when building the DLL 238 C Tutorial case DEL PROCESS ATTACH hansk BDLLLINS es DoRegisterClass break case DLL PROCESS DETACH UnregisterClass dialog hDLLInst break Case DEL TAREAD ATTACH break case DEL THREAD DETACH break return TRUE This function
101. documentation for the functions given here 302 C Tutorial One thing you will wonder is how do you get a HANDLE starting with a FILE pointer We Function name Description Geatcrile Opens or creates a penser Cincom le ec open CO cancer conmannicns It can open a COM port serial communica tions or a pipe CloseHandle Use it to close a file ReadFile or ReadFi Reads data from a file starting at the current file pointer Both syn leEx chronous and asynchronous versions exist WriteFile or Write Writes data to a file starting at the current file pointer Both syn FileEx chronous and asynchronous versions exist CopyFile or CopyFi Copy one file to another leEx MoveFile or Move Moves a file FileEx DeleteFile Deletes a file GetFileAttributes or Reads the file attributes like 1f its read only hidden system etc GetFileAttributesEx SetFileAttributes or Sets the file attributes SetFileATtributesEx GetFileSize Returns the size of a file FindFirstFile and Searches for a file matching a certain wildcard FindNextFile discussed above files and used always a FILE structure as specified in lt stdio h gt To obtain a HANDLE that can be used with the windows file functions you write include lt wind ws h gt include lt stdio h gt ELLE pie HANDLE H HANDLE get Osthandle Tilen Iperi 3 17 4 File systems These days files are taken for granted File systems not Moder
102. doesn t open Alloc c Well it seems that the path is not being passed to fopen so that it tries to open the file in the current directory instead of opening it in the directory we specify in the command line One way to solve this would be to change our current directory to the directory specified in the command line and then try to open the file We could do this in checkargs since it 1s there where we open a file for the first time All other files will work 1f we change the current direc tory there How we could do this If the argument contains backslashes it means there is a path component in it We could copy the string up to the last backslash and then change our current directory to that For instance if we find an argument like src77 c the path component would be src77 Here is an updated version of checkargs STREAM checkargs int argc char argv STREAM af ile NULL long Landiirst Result 112 C programming with Icc win32 Struce finddatae 107 char p Lt ergo S 2 E ave ELO Randling eladed 2 4 else Pint PocResult Trt rst argy 1 ipotd s if findfirstResult lt 0 f fprintf stderr PLs 66 dOS Vt exist in arov LIN return NULL infile malloc sizeof STREAM infile gt Name argv 1 DO strrchr argv i lly At if p p 0 chdir argv 1 p N infile gt file fopen fd name rb infile gt handle findfirstResult
103. exception handler block will be executed in case of an exception Provokes an exit to the end of the current _ try block Provokes a jump to the start of the try except block An overview of the whole language 39 1 9 6 Control flow if expression block If the given expression evaluates to something different than zero execute the else statements of the following block Else execute the statements of the block block following the else keyword The else statement is optional Note that a single statement can replace blocks while expression If the given expression evaluates to something different than zero execute the statements statements in the block and return to evaluate the controlling expression again Else continue after the block See while on page 15 do statements Execute the statements in the block and afterwards test if condition is true If y while condition that is the case execute the statements again See do on page 15 TE E Execute unconditionally the expressions in the init statement Then evaluate the for init test incr l i test expression and if evaluates to true execute the statements in the block Statements l l i following the for At the end of each iteration execute the incr statements and evaluate the test code again See for on page 14 switch expression Evaluate the given expression Use the resulting value to test if it matc
104. expr expr exprl Subtract expr1 from expr and store the result in expr a 6 Shift left expr by expr1 bits and store the result in ass oo expr lt lt exprl expr EEE E Shift right expr by expr1 bits and store the result in expr Bitwise and expr with expr1 and store the result in expr amp exprl a amp 32 expr Bitwise xor expr with expr and store the result in A expr exprl a 64 expr Haor e ai nN or expr with expr1 and store the result in a 128 Evaluate expr then exprl and return the result of a 7 b 8 expr y expr evaluating the last expression in this case expr The result oT lt 2 a see page 52 this is 8 asus 1 Variable can be any value that can be assigned to an array element or other constructs like ptr 5 In technical language this is called an lvalue 1 9 2 Declarations An overview of the whole language 35 41 Identifier will have the specified type within this scope In a local scope its value is undetermined In a global scope its initial value is zero at program start type id expr typedef old new register id Identifier will be a pointer to objects of the given type You add an asterisk for each level of indirection A pointer to a pointer needs two asterisks etc Identifier will be an array of expr elements of the given type The expression must evaluate to a compile time constant or to a constant expression that will be evaluated at run time In th
105. f1 amp amp fgets buf2 MAXLINELEN f2 o strehr bur2 n if p p 0 printi so 0 bur jt If we are duplicating the same file just print the same line again i else printi 3s n butt jt End of the while loop When we arrive here the first file has been completely scanned We close and shut down fclose f1 Simple programs 75 if f1 2 TClLOSe EZ return 0 How can this program fail Well there are obvious bugs in this program Before reading the answer try to see if you can see them What is important here is that you learn how to spot bugs and that is a matter of log ical thinking and a bit of effort Solution will be in the next page But just try to find those bugs yourself Before that bug however we see this lines 1n there if f2 1 amp amp fgets buf2 MAXLINELEN f2 else printi s n burl If fl is different from f2 we have two different files and file two is shorter than file one that if statement will fail after n2 lines and the else portion will be executed provoking the dupli cation of the contents of the corresponding line of file one To test this we create two test files file and file2 their contents are Filel File 1 line 1 File 1 line 2 File 1 line 3 File i line 4 File 1 line 5 File 1 line 6 File 1 line 7 File il Line 8 File2 File 2 line 1 File 22 line 2 File 2 lane 3 File 2 line 4 We call our paste prog
106. feature but that doesn t mean that you are exempted from thinking before you write your code Please OK For instance even it is very tempting to do bYPeGeT SELUCE dave int year month day hour sec DATE DATE Operacorr DALE dl DATE d2 ft ss F DATE Operator ADATE ak DATE G27 To x 75 See http www qmw ac uk cgaa260 BUILDING INTR _F90 PRG UNTS OPOLOAD HTM Opera tor overloading in Fortran90 Advanced C programming with Icc win32 155 The operator can t be used for dates There is nothing that can be assigned to 16 July 1970 23 December 1980 The operation has no sense for dates The same applies to multipli cation and division Subtraction is a legal operation for dates but the result type is not a date but a dimensionless number that represents a time interval in days hours etc The only overloaded operator that makes sense then is int Operator DATE dl DATE d2Z T sp J Operator overloading is best done for numbers and similar objects This facility allows you to implement any kind of numbers you would like to design it is fully general Just look at qfloat h and see what would happen with qfloat being any other number type you want Note too that nothing has changed about C There are no classes or any other underlying con text and you are free to build the context you wish as always C has been 1 34 2 References References are a special kind of pointers that are al
107. for i 0 i lt sizeof WordTable sizeof WordTable 0 i WORDLIST wl WordTable i while wl look at the list at this slot tab idx wl wl wl gt Next Lax if idx gt words amp amp wl fprintf stderr program err orn exit 1 Sort the table gsort tab words sizeof WORDLIST comparewords Print the results for 1i 0 ix words it t printi es 2530an tabli Nord tabi Count We start by printing the name of the file and the number of different words found Then we go through our hash table adding a pointer to the word list structure at each non empty slot Note that we test for overflow of the allocated table Since we increment the counter each time that we add a word it would be very surprising that the count didn t match with the number of items in the table But it is better to verify this After filling our table for the qsort call we call it and then we just print the results 72 Global variables like this should be used with care Overuse of global variables leads to problems when the application grows for instance in multi threaded applications When you got a lot of global variables accessed from many points of the program it becomes impossible to use threads because the danger that two threads access the same global variable at a time Another problem is that our global is not static but visible through the whole program If somewhere else somebody
108. fullname name sizeof fullname 1 result fopen fullname mode if result NULL fprintf stderr Impossible to open ss n fullname gt exit 1 return result Never forget to initialize a variable in BOTH cases of an if statement Bugs such as this are very difficult to catch later on What will happen if the name of the file is bigger than our buffer This function will fail The fopen call will return NULL since the file name has been truncated and we will show an error telling that a truncated file name doesn t exist Is this a good behavior It depends For a technical user a long and truncated file name could be an indicator that the file name is just too long Better error reporting would be appropriate 1f required for instance at the start of the function a test could produce a clear message like Name too long 1 26 1 A buffer overflow in the C standard document Examples of sloppy programming abound but it was for me a surprise to discover that the C standard itself propagates this same kind of who cares attitude In the official C standard of 1999 we find the specifications of the asctime function page 341 char asctime const struct tm timeptr Static Const char wday name 7 iol woun Mone Mie Neath raw ae Sac be Statice Const char mon Tomera si 4 Molen Seb Mar mor Mays MJUN y TIL Aug Sep NOC Nov Dec be Statue char result 26
109. gt include netutils h ine Malin argc char argy Session session Char bur 6192 memset amp Ssession 0 sizeof session session port 25876 Session Host I2Z7 0 0 1 if ServerConnect amp session return 0F printi C Conmmiected lt 2 n y memset buf 0 sizeof buf if Receive amp session sizeof buf 1 buf return OF printf received request n prm data 263 ssn but if Send amp session 5 data return OF CloseSession amp Session Basically those procedures implement all the steps described above for client and server sides They are the building blocks for implementing the FTP or HTTP protocols we saw above To use this functions include netutils lib in the linker command line and include netutils h to get the prototypes and structure declarations 384 C Tutorial
110. hbmpOld int y state HDC hdcMem TEATMETRIC tm RECT rcBitmap COLORREF oldcolor Char tchBuffer 200 If there are no list box items skip this message if lpdis gt itemID 1 return 290 C Tutorial Switch lpdis gt itemAction case ODA SELECT case ODA DRAWENTIRE II Windows DOES NOT erase the background of owner draw list boxes Erase the background to start with a coherent state FiliRect lpdis hDC amp lpdis gt rciltem GetStockObject WHITE BRUSH We get the handle of the bitmap to draw from the item data slot in each list box line The initialization procedure sets this hbmpPicture HBITMAP SendMessage lpdis gt hwnditem LB GETITEMDATA lpdis gt itemID LPARAM 0 II We select the image in a memory DC then we select it This is a standard technique for copying a bitmap into the screen hdcMem CreateCompatibleDC lpdis gt hDC hbmpOld SelectObject hdcMem hbmpPicture BitBlt 1pdis gt hnDC Ipdis gt rcItem left Lpdre reltem top ipdus gt rcltem rightl Lodis gt rcitem ert Ipgis rcitem bottom Lpdis gt rcitem top hademMem Us 0 SRCCOPY gt We are done with our memory DC Clean up SelectObject hdcMem hbmpOld DeleteDC hdcMem Now we retrieve the text for this line SendMessage lpdis gt hwndiItem LB GETTEXT lpdis gt itemID LPARAM tchBuffer How big is the text of this item GetTextMetrics lpdis gt hDC amp tm
111. is fully evaluated first and if it produces any value that value will be discarded Then the right operand is evaluated and its result is the result of the expression For instance p En 2 3 s60 7 The p variable will always receive the value 6 and the result of the function call will be dis carded Do not confuse this usage of the comma with other usages for example within a function call The expression fn c d 6 78 is always treated as a function call with three arguments and not as a function call with a comma expression Note too that in the case of a function call the order of evaluation of the different expressions separated by the comma is undefined but with the comma operator it is well defined always from left to right 1 11 30 Casts A cast expression is the transformation of an object from one type to another For instance a common need is to transform double precision numbers into integers This is specified like this dot Le ce int d In this case the cast needs to invoke run time code to make the actual transformation In other cases there is no code emitted at all For instance in vold 0 Char p7 Transforming one type of pointer into another needs no code at all at run time You can use a cast expression in another context to indicate the type of a composite constant literal For instance A closer view 53 typedef struct tagPerson char Name 7 5 int age Person
112. jmp buf pushed env memcpy push env Erroren sizeof jmp buf int status setyjmp ErrorEnvy if status 0 process memcpy Brrorknyv pushed env sizeof jmp DUIN recur Status int process void int error code U uf error code Jong jmp Brrorenv error code j This way the contents ErrorEnv are left as they were before and if you setup in the first lines of the main function int main void if See mp BErorEny Do not pass any other code return ERROR FAILURE Just a general failure code This way the ErrorEnv can be always used without fearing a crash Note that I used memcpy and not just the assignment pushed env ErrorEnv wrong since jmp buf is declared as an array as the standard states Arrays can only be copied with memcpy or a loop assigning each member individually Note that this style of programming is sensitive to global variables Globals will not be restored to their former values and if any of the procedures in the process function modified global variables their contents will be unchanged after the longymp include lt setjmp h gt jmp buf ErrorEnv double global setjmp and longjmp 67 int Guard vold j Return 0 if successtul else long mp code jmp buf pushed env memcpy push env ErrorEnv Sizeor jmp but int status setyjmp ErrorEnvy Global 7o 9776 if status 0 process memcpy ErrorEnv pushed env
113. know that there is no possibility of memory fragmentation or other memory space costs associated with dynamic allocation Drawbacks 1 Since the amount of memory allocated to the program is fixed it is not possible to adapt memory consumption to the actual needs of the program The static buffers could be either over dimensioned wasting memory space or not enough to hold the data needed Since the static buffers must be patterned after the biggest possible input they will be over dimensioned for the average case 2 Unless programming is adapted to this strategy it 1s difficult to reuse memory being used in different buffers to make space for a temporary surge in the space needs of the program 1 28 2 Stack based allocation The C standard allows for this when you write ine Pm ne a char workspace 10000 In this case the compiler generates code that allocates 10000 bytes of storage from the stack This is a refinement of the static buffers strategy The stack is IMB in normal programs but this can be increased with a special linker option A variant of this strategy allows for dynamic allocation Instead of allocating a memory block of size siz with malloc we can write char workspace siz and the compiler will generate code that allocates siz bytes from the program stack Advantages 1 Very fast allocation and deallocation To allocate a memory block only a few assembly instructions are needed Deallocati
114. look roughly like this Advanced styles Text Search An edit field and two push button for OK and Cancel The edit field should receive the ID LD TET Now comes the interesting part How to connect all this We have to first handle the WM COMMAND message so that our main window handles the menu message when this menu item is pressed We go to our window procedure MainWnd Proc Here it is 276 C Tutorial LRESULT CALLBACK MainWndProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam Switch msg case WM SIZE SendMessage hWndStatusbar msg wParam lParam InitializeStatusBar hWndStatusbar 1 break case WM MENUSELECT return MsgMenuSelect hwnd msg wParam lParam case WM COMMAND HANDLE WM COMMAND hwnd wParam 1Param MainWndProc OnCommand break case WM DESTROY PostQuitMessage 0 break default return DefWindowProc hwnd msg wParam lParam return 0 We can see that it handles already quite a few messages In order We see that when the main window is resized it resizes its status bar automatically When the user is going through the items of our menu this window receives the WM MENUSELECT message from the system We show the appropriate text with the explana tions of the actions the menu item in the status bar When a command from the menu or from a child window is received the parameters are passed to a macro defined in windowsx h that breaks up the wParam and lParam par
115. main that is where the execution of the program begins In C the organization of code in files has semantic meaning The main source file given as an argument to the com piler defines a compilation unit A unit can import common definitions using the include preprocessor directive or just by declaring some identifier as extern C supports the separate compilation model 1 e you can split the program in several indepen dent units that are compiled separately and then linked with the link editor to build the final program Normally each module is written in a separate text file that contains functions or data declarations Interfaces between modules are written in header files that describe types or functions visible to several modules of the program Those files have a h extension and they come in two flavours system wide furnished with Icc win32 and private specific to the application you are building A function has a parameter list a body and possibly a return value The body can contain declarations for local variables 1 e variables activated when execution reaches the function body 5 Lisp and scheme two list oriented languages featured automatic garbage collection since several decades APL and other interpreters offered this feature too Lcc win32 offers you the garbage collector developed by Hans Boehm 6 And today the linux kernel is written entirely in C as most operating systems 7 There i
116. many applications where mathematical symbols drawings and icons increase the size of the available alphabet beyond the 256 limit of a byte We classify then strings in multi_byte sequences of characters alphabet is smaller than 256 or wide character strings where the alphabet can go up to 65535 characters The library treates both character types as equivalent The definition of a string looks like this typedet struct String 4 size t Count unsigned char data Size C Capacity r Deeley The count field indicates how many characters are stored in the String Follows the data pointer the allocated size and the type of the string either one or two bytes characters We store a pointer to the data instead of storing the data right behind the descriptor We waste then sizeof void for each string but this buys an increased flexibility Strings are now resiz able since we can change the pointer and reallocate it with a different size without having to allocate a new string This is important since 1f there are any pointers to this string they will still be valid after the resize operation what would not be the case if we had stored the charac ters themselves in the data structure Text is stored either coded in one byte characters or in UNICODE multi byte numbers of two bytes For each type of string there are two functions For instance for copying a string there is the Strcpy function that has two flavors StrepyA for copyin
117. must supply a handle to another key in the registry that 1s already open The system defines predefined keys that are always open Those keys help you navigate in the registry and make it possible to develop tools that allow a system administrator to manipulate categories of data Applications that add data to the registry should always work within the framework of predefined keys so administrative tools can find and use the new data 3 16 2 Enumerating registry subkeys The following example demonstrates the use of the RegQueryInfoKey RegEnumKeyEx and RegEnumValue functions The hKey parameter passed to each function is a handle to an open key This key must be opened before the function call and closed afterward QueryKey Enumerates the subkeys of key and the associated _ values then copies the information about the keys and values into a pair of edit controls and list boxes hDIg Dialog box that contains the edit controls and list boxes hKey Key whose subkeys and values are to be enumerated void QueryKey HWND hDlg HANDLE hKey CHAR achKey MAX PATH CHAR achClass MAX PATH buffer for class name DWORD cchClassName MAX PATH size of class string DWORD cSubKeys number of subkeys DWORD coMaxSubKey longest subkey size DWORD cchMaxClass longest class string DWORD cValues number of values for key DWORD cchMaxValue longest value name DWORD cobMaxValueData longest value data
118. n return 0 How do we write BrowseDir in windows Here it 1s include lt shlobj h gt finclude lt std1o n gt int BrowseDir unsigned char Title char result LPMALLOC pMalloc 1 BROWSEINFO browselInfo 2 EPLTEMIDGIST FremibDhusty 3 Advanced windows techniques 311 int e 3 4 if 9 OK I SHGetMalloe amp pMalroc 5 recur U7 memset amp browseInfo 0 sizeof BROWSEINFO 6 browseInfo hwndOwner GetActiveWindow 7 browseInfo pszDisplayName result 8 browselInfo lpszTitle Title 9 browseInfo ulFlags BIF NEWDIALOGSTYLE 10 ItemIDList SHBrowseForFolder amp browselInfo 11 if ItemIDList NULL SESW Ye if SHGetPathFromiIDList ItemIDList result 12 it resulel o 2 13 pMalloc gt lpVtbl gt Free pMalloc ItemIDList 14 pMalloc gt lpVtbl gt Release pMalloc 15 return r Small isn t it Let s see the gory details We need a local variable that will hold a pointer to a shell defined function that will allocate and release memory The shell returns us a result that needs memory to exist We need to free that memory and we have to take care of using the same function that the shell uses to allocate memory This pointer to an interface the malloc interface will be in our local variable pMal loc The shell needs information about the environment and some pointers to put the results of the interaction with the user We w
119. number of characters in a file e A first working version of the specification is developed Essential parts like error checking are missing but the program works for its essential function e Error checking is added and test cases are built e The program is examined for correctness and the possibility of memory leaks unclosed files etc is reviewed Comments are added to make the purpose of the program clear and to allow other people know what it does without being forced to read the program text 1 8 Commentaries The writing of commentaries apparently simple is when you want to do it right quite a diffi cult task Let s start with the basics Commentaries are introduced in two forms 28 C programming with Icc win32 Two slashes introduce a commentary that will last until the end of the line No space should be present between the first slash and the second one A slash and an asterisk introduce a commentary that can span several lines and is only ter minated by an asterisk and a slash The same rule as above is valid here too no space should appear between the slash and the asterisk and between the asterisk and the slash to be valid comment delimiters Examples This is a one line commentary Here are ignored anyway This is a commentary that can span several lines Note that here the two slashes are ignored too This is very simple but the difficulty is not in the syntax of comme
120. numbers whatever This whatever is precisely the void Argument 2 is a size_t This isn t a known type so it must be a type defined before in stdlib h By looking at the headers and following the embedded include directives we find stdlib h includes stddef h that defines a typedef like this typedef unsigned int size t This means that we define here a new type called size_t that will be actually an unsigned integer Typedefs allow us to augment the basic type system with our own types Mmmm interesting We will keep this for later use In this example it means that the size t n is the number of elements that will be in the array Argument 3 is also a size _ t This argument contains the size of each element of the array i e the number of bytes that each element has This tells qsort the number of bytes to skip at each increment or decrement of a position If we pass to qsort an array of 56 double preci sion numbers this argument will be 8 1 e the size of a double precision number and the preceding argument will be 56 1 e the number of elements in the array Argument 4 is a function int f const void Well this is quite hard really We are in the first pages of this introduction and we already have to cope with gibberish like this We have to use recursion now We have again to start reading this from left to right more or less We have a function pointer f that points to a f
121. of our program would notice this style of programming and give us a file name that when overflowing in the copy to the temporary buffer would form a correct return address that would pass then control to some other routine that the malicious user prepared for us This kinds of exploits can be avoided if we use other functions of the standard library else strncpy fullname stream gt Name sizeof fullname strncat fullname sizeof fullname ep a tN strncat fullname name sizeof fullname Those functions test for overflow conditions and are safer in case of unforeseen input patterns There 1s a problem with strncpy though It does NOT terminate the resulting string with a zero If we get a Name field with exactly sizeof fullname chars the string will be missing the trailing zero since strncpy doesn t add it One way to cover this possibility is to do else ae QO fullname sizeof fullname 1 0 Buffer overflows 115 strncpy fullname stream gt Name sizeof fullname 1 strncat fullname sizeof fullname 1 hp a Te strncat fullname name sizeof fullname 1 We finish fullname with a zero and we copy only up to sizeof fullname 1 chars leaving our terminating zero intact But you should have noted that there is something wrong here We do initialize the terminating zero within an else statement What happens if the execution of the function takes the other pat
122. of your program loose all the data he she was working with I would be delighted to tell you how to avoid those bugs but after more than 10 years working with the C language I must confess to you that memory management bugs still plague my pro grams as they plague all other C programmers The basic problem is that the human mind doesn t work like a machine and here we are ask ing people 1 e programmers to be like machines and keep book exactly of all the many small pieces of RAM a program uses during its lifetime without ever making a mistake But there is a solution that I have implemented in Icc win32 Lec win32 comes with an auto matic memory manager also called garbage collector in the literature written by Hans Boehm This automatic memory manager will do what you should do but do not want to do take care of all the pieces of RAM for you Using the automatic memory manager you just allocate memory with GC_malloc instead of allocating it with malloc The signature 1 e the result type and type of arguments is the same as malloc so by just replacing all malloc by GC_malloc in your program you can benefit of the automatic memory manager without writing any new line of code The memory manager works by inspecting regularly your whole heap and stack address space and checking if there is anywhere a reference to the memory it manages If it doesn t find any references to a piece of memory it will mark that memory as free
123. or other measures to take depending on your applica tion Message Meaning WM MOVE Sent after a window has been moved WM MOVING Sent to a window when the user is moving it By pro cessing this message you can monitor the position of the drag rectangle and if needed change its position 254 C Tutorial Message Meaning WM SIZE Sent after a window has been resized WM SIZING Sent to a window that the user is resizing By process ing this message an application can monitor the size and position of the drag rectangle and if needed change its size or position WM WINDOWPOSCHANGED Sent to a window whose size position or place in the Z order has changed as a result of a call to the SetWin dowPos function or another window management function WM WINDOWPOSCHANGING Same as above message but sent before the changes WM GETMINMAXINFO Sent to a window when the size or position of the win dow is about to change You can use this message to override the window s default maximized size and position or its default minimum or maximum tracking SIZe WM ENTERSIZEMOVE Sent one time to a window after it enters the moving or sizing modal loop The window enters the moving or sizing modal loop when the user clicks the window s title bar or sizing border or when the window passes the WM SYSCOMMAND message to the DefWin dowProc function and the wParam parameter of the message specifies the SC_ MOVE or SC_SIZE value The operation is
124. procedure Do some processing after the original procedure returns Do not call the original procedure at all and replace it entirely We will show a concrete example of this when we speak about windows sub classing later Sub classing allows you to implement dynamic inheritance This is just an example of the many ways you can program in C But is that flexibility really needed Won t just bool UpdateBalance struct customer pCustomer double newBalance do it too Well it depends Actions of the general procedure could be easy if the algorithm is simple and not too many special cases are in there But if not the former method even 1f more compli cated at first sight is essentially simpler because it allows you greater flexibility in small man ageable chunks instead of a monolithic procedure of several hundred lines full of special case code Mixed strategies are possible You leave for most customers the UpdateBalance field empty filled with a NULL pointer and the global UpdateBalance procedure will use that field to calculate its results only if there is a procedure there to call True this wastes 4 bytes per cus tomer in most cases since the field is mostly empty but this is a small price to pay the struc ture is probably much bigger anyway 1 18 2 Structure size In principle the size of a structure is the sum of the size of its members This is however just a very general rule since it depends a lot on the compi
125. r scale exp theta tan in if r gt cut then leave loopl Xx r cos theta 50 yor sin theta 50 call rand randx call rand randy PLOCDOCAT X bir rand YTE Srandy end LOGDZ gt Do r 0 TO Maxit 120 The resource editor has several editors specialized for each kind of resource You get a dialog box editor a menu editor a string table editor an accelerators editor and an image editor Each one is called automatically when clicking in a resource from the menu obtained with the dir button Numerical calculations in C 269 theta Loe 4 5 Oy theta Celoae a 750 S344 r scale exp theta2 tan in if r gt cut then leave loop2 x r cos theta 50 y 1X sin theta 507 call rand randx call rand randy PLOCDOLAG XE randy YEE randy end This are quite clear specs Much clearer than other specs you will find in your future career as programmer So let s translate this into C We can start with the following function void DrawGalaxy HDC hDC double in int maxit double scale double C t double T double theta theta2 r X y randx randy FOr Gine I Oe d Ae nE ey A 1 theta double i CENTER r scale exp theta tan in if r gt cut break x r cos theta CENTER y lt r sSan theta CENTER randx double rand double RAND MAX randy double rand double RAND MAX PIOEDOLAL NDC lt hr randx yre randy ROR 0040 I ono oO
126. remot gt I else x 0 This will provoke a syntax error To avoid this problem you can use the do while statement that consumes the semicolon define s2 x y do int temp x xty y x tempty tempt 6 X 144 C programming with Icc win32 while 0 Note the that continues this long line and the absence of a semicolon at the end of the macro An undef statement can undo the definition of a symbol For instance undef PI will erase from the pre processor tables the PI definition above After that statement the iden tifier PI will be ignored by the preprocessor and passed through to the compiler The second form of pre processor instructions that is important to know is the if expression w DLOGLaM CEE x else Program TEx endif or the pair ifdef symbol else endif When the preprocessor encounters this kind of directives it evaluates the expression or looks up in its tables to see if the symbol is defined If it is the if part evaluates to true and the text until the else or the endif is copied to the output being prepared to the compiler If it is NOT true then the preprocessor ignores all text until it finds the else or the endif This allows you to disable big portions of your program just with a simple expression like if 0 fandis This is useful for allowing disabling portions of your program according to compile time parameters For instance lcc win32 defines the m
127. saver is enabled use this SystemParametersInfo SPI GETSCREENSAVEACTIVE 0 pvParam 0 7 On return the parameter pvParam will point to TRUE if the screen saver setting is enabled in the system control panel applet and FALSE 1f the screen saver setting is not enabled 322 C Tutorial To disable the screen saver setting call SystemParametersInfo with this oystemParametersiInfo SPI SETSCREENSAVEACTIVE FALSE 0 SPIF SENDWININICHANGE 3 20 6 Drawing a gradient background You can draw a smooth gradient background using the following code void DrawBackgroundPattern HWND hWnd HDC hDC GetDC hWnd Get the DC for the window RECT rectriil Rectangle for filling band RECT eceClient Rectangle for entire client area float Step How large is each band HBRUSH HBrush int iOnBand Loop index How large is the area you need to fill GetClientRect hWnd amp rectClient Determine how large each band should be in order to cover the client with 256 bands one for every color intensity level fStep float rectClient bottom 256 0f Start filling bands for 10OnBand 0 iOnBand lt 256 i10OnBandt Set the location of the current band SetRect amp rectFill O Upper left X int iOnBand f Step Upper left Y receClient lt cightrl Lower right X int i1OnBand 1 f Step Lower right Y Create a brush with the appropriate color
128. second time there is no handler invoked the program exits abruptly without any further messages The reason for this behavior is that if a thread in your application causes an EXCEPTION STACK OVERFLOW then your thread has left its stack in a damaged state This is in contrast to other exceptions such as EXCEPTION ACCESS VIOLATION or EXCEPTION INT DIVIDE BY ZERO where the stack is not damaged This is because the stack is set to an arbitrarily small value when the program is first loaded just 4096 bytes 1 page The stack then grows on demand to meet the needs of the thread This is implemented by plac ing a page with PAGE GUARD access at the end of the current stack When your code causes the stack pointer to point to an address on this page an exception occurs The system then does the three following things 1 Remove the PAGE GUARD protection on the guard page so that the thread can read and write data to the memory 2 Allocate a new guard page that is located one page below the last one 3 Rerun the instruction that raised the exception If a thread in your program grows the stack beyond its limit 1MB with normal programs the step above will succeed but the step 2 will fail The system generates an exception and the first try block is executed This is OK but the stack has been left without a guard page Since the second time that we get a stack overflow there is no more stack left the program will pro voke an access violat
129. seen dia log boxes can be quite complicated full of edit windows to enter data buttons trees what have you It would be incredible tedious to write all the dozens of calls to the CreateWin dow API passing it all the coords of the windows to create the styles etc 96 When the IDE asks you if you want to open it as a resource say NO We want to look at the text of that file this time Introduction 219 To spare you this Herculean task the designers of the windows system decided that a small language should be developed together with a compiler that takes statements in that language and produce a binary file called resource file This resource files are bound to the executable and loaded by the system from there automat ically when using the DialogBox primitive Among other things then that procedure needs to know which dialog template should load to interpret it and it is this parameter that we pass with the MAKE TNTRESOURCE macro Ok that handles at least I hope the second parameter of the DialogBox API Let s go on because there are still two parameters to go The third one is NULL Actually it should be the parent window of this dialog box Normally dialog boxes are written within an application and they have here the window handle of their parent window But we are building a stand alone dialog box so we left this parameter empty 1 e we pass NULL The last parameter is the DialogFunc function that is defined se
130. several files that are stored in the lcc 1ib directory to bind the executable to the system DLLs used by all programs kernel32 dll crtdll dll and many others The workings of the lcc compiler are described in more detail in the technical documentation Here we just tell you the main steps e The source file is first pre processed The include directives are resolved and the text of the included files is inserted into the source file 7 e The front end of the compiler proper processes the resulting text Its task is to generate a series of intermediate code statements 7 The code generator that emits assembler instructions from it processes these e Eventually the compiler produces an object file with the obj extension This file is passed then possibly with other object files to the linker Icclnk that builds the executable Organizing all those steps and typing all those command lines can be boring To easy this the IDE will do all of this with the F9 function key 1 2 5 Technical notes The output shown in the wedit window above means the following 1 Size of code This is the number of bytes that the instructions of your program will use This includes the startup and the code for the statically linked c runtime functions like printf if necessary Lcc win32 uses the standard windows library CRTDLL DLL a C run time library provided by windows itself Most of the functions in that library are not usable if you want to s
131. t check if a drive is a CD drive drive H is listed and it has obviously 0 bytes available since it is read only 3 20 25 Mounting and unmounting volumes in NTFS 5 0 The windows file system allows you to mount disk drive in another directory and see the contents of the drive as if they were subdirectories of the directory where the drive is mounted Suppose for instance that you make a directory C mnt and in this directory you make a sub directory called cdrom Using the utility below you can mount the CDROM drive under the c mnt cdrom directory and you will see the contents of the cdrom drive in c mnt cdrom 3 20 25 1 Mount include lt windows h gt include lt stdio h gt define BUFSIZE MAA PATH int main int argc char argv BOOL bFlag Some Coding Tips 333 char Buf BUFSIZE temporary buffer for volume name Char but BUPSLZE temporary buffer for volume name DWORD nl flags char fsname 512 if argc 3 printf Usage mount lt directory gt lt drive gt n printr Mor exanp lennont cr Wine cdrom qe in gt Cebu L J53 We should do some error checking on the inputs Make sure there are colons and backslashes in the right places etc bFlag GetVolumeNameForVolumeMountPoint argv 2 input volume mount point or directory Buf output volume name buffer BUFSIZE size of volume name buffer E if bElag TRUE printi Retrieving volume name tor 2
132. t use it Then there is findnext that looks like this int fandnext Long handle struct tinddata fileinte It uses the unique value returned by findfirst and fills the fileinfo structure 1f it finds another file that matches the original specification If it doesn t find a file it will return 1 as findfirst If it does find another file t will return zero We see now that a FILE that was uniquely bound to a name is now a possible ambiguous file specification that can contain a_finddata_t whatever that is that can be used to read several FILEs We could formalize this within our program like this typedef struct tagStream char Name Struct _finddata t Findbata long handle PLE SELE STREAM Our function checkargs returns a FILE pointer now It could return a pointer to this STREAM structure we have just defined or NULL if there was an error Our program then would loop asking for the next file adding to our Frequencies array the new character frequen cies found The first function to be modified is checkargs We keep the interface with the calling function return NULL on error but we change the inner workings of it so that instead of calling fopen it calls findfirst STREAM checkargs ant argc cher argv STREAM Sst ile NULG Long findfirstResult Struct Tanddala t fid if argo x 2 4 printf Usage countchars lt file name gt n else findfirstResult
133. test the rightmost bit with the binary and operation The number one has only one bit set the rightmost one By the way one is a power of two 45 The expression p 0 could have been written in the form while p using the implicit test for a non zero result in any logical expression Any expression will be considered true if its value is anything but zero It is better however to make comparisons explicit 46 Different than is written in C instead of The symbol wasn t included in the primitive typewriters in use when the C language was designed and we have kept that approximation It is consistent with the usage of as logical not 1 e would mean not equal Simple programs 71 Note that the return expression could have also been written like this return bitcount 1 The intention of the program is clearer with the if expression How can this program fail The while loop has only one condition that n is different than zero 1 e that n has some bits set Since we are shifting out the bits and shifting in always zero bits since bitcount is unsigned in a 32 bit machine like a PC this program will stop after at most 32 iterations Running mentally some cases a good exercise we see that for an input of zero we will never enter the loop bitcount will be zero and we will return 0 the correct answer For an input of 1 we will make only one iteration of the loop Since 1 amp lis 1 bitcount will be in
134. that we can use the stream to read characters from it Another alternative to using the built in memory allocator would have been to declare a global variable call t CurrentStream that would contain all our data We could have declared some where in the global scope something like SLREAM Currentoctream and use always that variable This has several drawbacks however the bigger of it being that global variables make follow ing the program quite difficult They aren t documented in function calls they are always passed implicitly they can t be used in a multi threaded context etc Better 1s to allocate a new STREAM each time we need one This implies some memory man agement something we will discuss in depth later on Now we should modify our ProcessFile function since we are passing to ita STREAM and not a FILE This is easily done like this int ProcessFile STREAM infile CHARS Frequencies LTC COUNT 07 int c fgetc infile gt file while c EOF CONC ES PE Se Se T Freguencies c Frequencytt c fgetc infile gt file return count Instead of reading directly from the infile argument we use the file member of it That s all Note that infile is a pointer so we use the notation with the arrow instead of a point to access the file member of the structure But there is something wrong with the name of the function It wrongly implies that we are processing
135. the program becomes much difficult to follow This feature of the preprocessor can be abused to the point that is very difficult to see which code is being actually compiled and which is not The IDE of Icc win32 provides an option for preprocessing a file and showing all inactive lines in grey color Go to Utils the choose Show ifdefs in the main menu Note You can easily comment out a series of lines of program text when you enclose them in pairs of if 0 lines to be commented out endif 1 32 1 3 The pragma directive This directive is compiler specific and means that what follows the pragma is dependent on which compiler is running The pragmas that Icc wi32 uses are defined in the documentation In general pragmas are concerned with implementation specific details and are an advanced topic A closer look at the pre processor 147 1 32 1 4 The operator This operator allows you to concatenate two tokens define join a b a b a join anne bob When preprocessed this will produce a annebob This is useful for constructing variable names automatically and other more or less obscure hacks 1 32 1 5 The operator This operator converts the given token into a character string It can be used only within the body of a macro definition After defining a macro like this define toString Token Token an expression like toString MyToken will be translated after preprocessing into MyToken
136. the exception of the 16 C programming with Icc win32 Complex type they should appear in most C implementations and they do appear in all win dows compilers Type Size Description bytes Logical type can be either zero or one Da short Integer or unicode character stored in 16 bits Signed or unsigned w fa Character or small integer type Comes in two fla vours signed or unsigned 4 Integer stored in 32 bits Signed or unsigned l 2 ee eee a e R 4 Floating point single precision Approx 7 digits o ie O Floating point extended precision Approx 19 digits float _Complex 32 Complex numbers Each Complex is composed of double Complex 32 two parts real and imaginary part Each of those parts 1s a floating point number Include lt complex h gt when using them long double Complex 1 The actual type of the Boolean type should be bool but in the standard it was specified that this type wouldn t be made the standard name for now for compatibility reasons with already running code If you want to use bool you should include the header stdbool h These are the basic types of ANSI C Lcc win32 offers you other types of numbers To use them you should include the corresponding header file they are not built in into the com piler They are built using a property of this compiler that allows you to define your own kind bignum Extended precision number of numbers and their operation
137. the handle of the window where you want to put the control on For instance if you want to create somewhere in your window an edit field you would write hEditWnd CreateWindow EDIT window class is edit NULL WS CHILD WS VISIBLE ES MULTILINE WS _VSCROLL WS HSCROLL BS AUTOHSCROLL BES AUTOVSCROLL oF oF Rect right Rect left Assume a rectangle structure Rect bottom Rect top that contains the coordinates hParentWwnd HMENU 14376 Window identifier hinst Application instance NULL The controls edit listbox and others are already predefined when windows starts You can use them at any time Some others however are NOT like that and you need to call the API InitCommonControlsEx before you can use them A more complex example a clone of spy exe 259 3 10 A more complex example a clone of spy exe What can we do with the empty window that Wedit generates Let s do a more difficult problem We want to find out all the windows that are opened at a given time in the system We will display those windows in a tree control since the child win dows give naturally a tree structure When the user clicks in a window label the program should display some information about the window in the status bar We generate a skeleton with Wedit as described above We create a new project and generate a simple single window application 3 10 1 Creating the child windows OK
138. the loop variable for indexing an array this will work of course since the number of iterations is the same but any access to arrays using the loop index a common case will make the program access invalid memory at the end of the loop 28 The detailed description of what happens when we start a program what happens when we compile how the compiler works etc are in the technical documentation of Icc win32 With newer versions you can use the compilation driver Ic exe that will call the linker automatically 14 C programming with Icc win32 1 4 1 Iteration constructs We introduced informally the for construct above but a more general introduction to loops is necessary to understand the code that will follow There are three iteration constructs in C for do and while 1 4 1 1 for The for construct has 1 An initialization part 1 e code that will be always executed before the loop begins 2 A test part 1 e code that will be executed at the start of each iteration to determine if the loop has reached the end or not and 3 An increment part i e code that will be executed at the end of each iteration Normally the loop counters are incremented or decremented here The general form is then for init test increment y statement block Within a for statement you can declare variables local to the for loop The scope of these variables is finished when the for state
139. the notation 1 0f meaning 1 in float precision i ee O 08639 EZ Oi OS C0499 81 The round functions round their argument to the nearest integer value in floating point format rounding halfway cases away from zero regardless of the current rounding direction Ansi C standard page 232 82 I have this example from the very good book Numerical Mathematics and Scientific Computation by Germund Dahlquist and Ake Bj rck Available on line at http www mai liu se akbjo NMbook html Numerical programming 177 Lo 2 O04 308 29 4 te 0345805 LD 0 02 70974 6 DivOSLETIS IS a SOULS OATS Eo i Ox l90209 The first few numbers look correct but I6 is bigger than I5 what after the recurrence relation should never happen Moreover I7 is negative and later numbers are complete nonsense Why Well because the roundoff error e in I0 is multiplied by 5 in the first iteration then multiplied again by 5 in the next iteration so that after a few iterations the error becomes bigger than the result Writing this is double precision and replacing the precalculated constant with a computation of log 6 0 log 5 0 we get better results Finclude lt sta to ch gt tine lude lt math h gt ine mair yord gdouble x LO o0 Loo oeU for int z 1 z lt 29 z i 1 0 double z 5 0 i Prainte 1 s sds 290g n Zp F return 0 We get 70983922 05003 69 JOE 31307 gVS430635 0284684 JIAO TS 2012
140. the program that is running argv 1 The first argument 1 e foo argv 2 The second argument 1 e bar We use a memory location for an integer variable that will hold the current argument to be printed This is a local variable 1 e a variable that can only be used within the enclosing scope in this case the scope of the function main 3 We use the for construct 1 e an iteration The for statement has the following structure e Initialization Things to be done before the loop starts In this example we set the counter to zero We do this using the assign statement of C the sign The general form of this statement 1s 66__99 e variable value e Test Things to be tested at each iteration to determine when the loop will end In this case we test if the count is still smaller than the number of arguments passed to the program the integer argc e Increment Things to be updated at each iteration In this case we add 1 to the counter with the post increment instruction counter This is just a shorthand for writing counter counter 1 e Note that we start at zero and we stop when the counter is equal to the upper value of the loop Remember that in C array indexes for an array of size n elements always start at zero and run until n 1 27 4 We use again printf to print something in the screen This time we pass to printf the following arguments 25 This means that yo
141. the size the owner etc Since the user writes that function there is no need to give several options to filter that information One of the big advantages of C 1s its ability of using function pointers as first class objects that can be passed around and used as input for other procedures Without this feature this appli cation would have been difficult to write and would be a lot less flexible Note too that any error in the function pointer argument will provoke a crash since we do not test for the validity of the received function pointer But let s be clear the biggest drawback is that the user has to write a function in C Imagine telling your friends that before they use your program they just write a function in C compile it link it with your stuff etc Let s examine how we put function pointers to good use assume the following Problem Write a program to print all numbers from 1 to n where n integer gt 0 without using any control flow statements switch if goto while for etc Numbers can be written in any order Solution The basic idea is to use a table of function pointers as a decision table This can be done like this Finclude lt stdio n gt Finclude lt stdlib h gt typedef void callback int VO1d Zero int void greaterZero int We define a table of two functions that represent a boolean decision 152 C programming with Icc win32 indexed by either zero or one Callback callbac
142. they could call signal too and they are not reentrant Besides when we return from the signal handling function we will end up crashing anyway since the signal mechanism will continue at the point where the program failed Since signal disables the specific signal that was raised the second time we trap the program will crash A way out of this dilemma is to use signal together with the setjmp longjmp facility to recover somewhere else in the program Here is an example include lt signal h gt include lt stdio h gt Finclude lt stalib h gt 7 7 For exit include lt setjmp h gt jmp buf jumpbuffer This function will call longjmp to reestablish a previous context assumed in the jumpbuffer global variable void traphandler int s psignal s Error longjmp jumpbuffer 1 int main void Char p NULL void oldhandler int oldhandler signal SIGSEGV traphandler if Oldhandler SIG ERR printf Impossible to establish a signal handler n exit 1 if setjmp jumpbuffer 7 else signal SIGSEGV oldhandler printf Normal exit n return Uj This will print Advanced C programming with Icc win32 165 Error Segmentation fault Normal exit What happens The first time we arrive at the statement if setjmp jumpbuffer the setjmp function will return zero and we will enter the else clause There we produce a trap SIGSEGV what will raise the
143. this point 5 We finish the scope of the for statement with a closing brace This means the iteration definition ends here Now we are ready to run this program Suppose that we have entered the text of the program in the file args c We do the following he LGe proj eces args gt cc args MeV iGevoroyects args eclnk ros 6o7 We first compile the text file to an object file using the lcc compiler Then we link the result ing object file to obtain an executable using the linker IccInk Now we can invoke the program just by typing its name Hey leet oroyecrs args args Argument 0 args We have given no arguments so only argv 0 is displayed the name of the program in this case args Note that if we write h lcc projects args gt args exe Argument 0 args exe We can even write h lcec projects args gt h lcc projects args exe Argument 0 h lcc projects args exe But that wasn t the objective of the program More interesting 1s to write he lee projects args gt args foo bar zzz Argument O args Argument 1 foo Argument 2 bar Argument 3 Zzz The program receives 3 arguments so argc will have a value of 4 Since our variable count will run from 0 to argc 1 we will display 4 arguments the zeroth the first the second etc 27 An error that happens very often to beginners is to start the loop at 1 and run it until its value is smaller or equal to the upper value If you do NOT use
144. twice or when an identifier is missing a definition e The most difficult errors to catch are run time errors in the form of traps or incorrect results 1 7 Reading from a file For a beginner it 1s very important that the basic libraries for reading and writing to a stream and the mathematical functions are well known Here is an example of a function that will read a text file counting the number of characters that appear in the file A program is defined by its specifications In this case we have a general goal that can be expressed quickly in one sentence Count the number of characters in a file Many times the specifications aren t in a written form and can be even completely ambiguous What is impor tant is that before you embark in a software construction project at least for you the specifica tions are clear include lt stdai n gt 1 ine main int roc char argv 2 int count 0 chars read 3 EILE at bes 4 Vat ee 5 Reading froma file 23 infile fopen Cargv 1 2 7 6 c fgetc infile 7 while c BOF 8 Counc 9 c fgetc infile 10 DEAETE GA Count 11 return 0 1 We include the standard header stdio h again Here is the definition of a FILE structure 2 The same convention as for the args program is used here 3 We set at the start the count of the characters read to zero Note that we do this in the declaration of the variable
145. ulResult MessageBox hwndParent ptszMessage ptszTitle flags Finished with the timer a KillTimer NULL idTimer x voee if here is aA WM OULT message in the queue Tf so then you timed out Hat the message so you don t quit the entire application y if PeekMessage amp msg NULL WM QUIT WM QUIT PM REMOVE If you timed out then return zero oy Result QO return uiResult The key to creating a timed message box is exiting the dialog box message loop internal to the message box Since the message loop for a message box 1s part of USER you cannot modify it without using hooks and other such methods However all message loops exit when they receive a WM QUIT message Furthermore a nested message loop if it receives a WM QUIT message must break the loop and then re post the quit message so that the next outer layer can process it Therefore you can get the nested message loop to exit by calling PostQuitMessage The nested message loop will clean up and post a new quit message When the MessageBox returns you peek to see if there is a quit message If so then it means that the message loop was abnormally terminated You also consume the WM QUIT message instead of re posting 360 C Tutorial it so that the application continues running Essentially you have tricked the nested mes sage loop into thinking that the application is terminating When it returns you eat the quit
146. unions as structures during development and see where you access an invalid member When the program is fully debugged you can switch back to the union usage Using structures 95 1 19 Using structures Now that we know how we can define structures we can at last solve the problem we had with our character frequencies program We define a structure containing the name of the character like this typedef struct tagChars int CharacterValue int Frequency CHARS Note that here we define two things in a single statement we define a structure called tag Chars with two fields and we define a typedef CHARS that will be the name of this type Within the program we have to change the following things We have to initialize the name field of the array that now will be an array of structures and not an array of integers When each character is read we have to update the frequency field of the corresponding struc ture When displaying the result we use the name field instead of our count variable Here is the updated program include lt stdio h gt Fine Luce lt stdliibshz typedef struct tagChars int CharacterValue int Frequency CHARS CHARS Frequencies 256 Array of frequencies int compare const void argl const void arg2 CHARS Argl CHARS argl1 CHARS Arg2 CHARS arg2 Compare both integers return Arg2 gt Frequency Argl gt Frequency ine main int aroc
147. use in your code to make it safer and more robust 1 36 1 Always include a default in every switch statement It is very common that you write a switch statement just taking into account the normal cases 1 e the ones you expect This is not very clever if the data doesn t fit into the expected cases since the program will go on after the switch statement even with a completely unex pected result This will lead to strange errors further down what makes the error discovering more difficult Always include a default case even if you just write Switch input case xx default assert 0 The assert macro defined in lt assert h gt will stop the program with a clear error message indi cating the source line and file of the faulty code This means that you will be informed when an unexpected data item arrives and you can correct this during the debug phase 1 36 2 Pay attention to strlen and strcpy As we have seen before See page 69 the strlen and strcpy functions expect a well formed C string The strlen function will not stop until a zero byte 1s found This is not very dangerous since strlen just reads memory without modifying it Our strcpy function how ever expects a large enough destination buffer and a well formed source string If one of those requirements is not met a catastrophe happens strcpy will start destroying memory without any restriction Always check for those two conditions before
148. using it This is easier said than done though Consider this code void Eune char p 4 Char bur LOLs memset buf 0 sizeof buf Hr MAM Serine tO sO chars Sprint but ols 7 pIJ Dr rab Hello ssn bu Where is the error here We see that the destination buffer is cleaned with memset setting it to all zeroes We see that the size of the destination buffer is 10 1 1 e the programmer takes into account the terminat ing zero of the destination string We see too that the sprintf format string indicates a field of 10 positions Since the eleventh position is already set to zero with memset the destination buffer should be always a correct string of at most 10 characters finished with zero Well let s test our assumptions We make a test program like this include lt stdio h gt include lt string h gt Tht Mmadan o2c Char DUE Wy 180 C programming with Icc win32 Ine 1 memset buit 0 S1zeof bur gt for 1 0 1 lt 14 i 4 buf i a PEINE p Aad T ia tunc Durf return Q0 Sbock meds test tbuf oO Hello A i Hella aa tbuf_exe has encountered a problem and needs to close a J Hello aaa We are sorry for the inconvenience 3 Hello aaaa 4 Hello aaaaa Ss Hello Adaaaa 6 Hello aaaaaaa Fy Hello aaaaaaaa Hello aa aa aaaaaaa 9 Hello aa aaaaaaaaa 10 Hello aaaaaaaaaaa Yes we are sorry for the inconve
149. using the amp operator This operator yields the machine address of its argument 663499 5 You can access the data the pointer 1s pointing to by using the to access the integer pinteger is pointing to we write pinteger 7 operator When we want This assigns to the integer variable indirectly the value 7 In Icc win32 pointers can be of two types We have normal pointers as we have described above and references i e compiler maintained pointers that are very similar to the objects themselves References are declared in a similar way as pointers are declared Te fat Se declares an integer a int pa amp a declares a pointer to the integer a int amp ra a declares a reference to the integer a Here we have an integer that within this scope will be called a Its machine address will be stored in a pointer to this integer called pa This pointer will be able to access the data of 56 This has nothing to do with object oriented programming of course The word object is used here with its generic meaning 57 References aren t part of the C language standard and are in this sense an extension of Icc win32 They are wildly used in another related language C and the implementation of Icc win32 is compatible with the implementation of references of that language Pointers and references 87 66 99 a 1 e the value stored at that machine address by
150. using the access that data we write 66399 operator When we want to oa 8944 This means store at the address contained in this pointer pa the value 8944 We can also write Int mes GOS F ay This means add to 698 the contents of the integer whose machine address is contained in the pointer pa and store the result of the addition in the integer m We have a reference to a that in this scope will be called ra Any access to this compiler maintained pointer is done as we would access the object itself no special syntax is needed For instance we can write ra rar lS 7 ZR 663099 Note that with references the this for you operator is not needed The compiler will do automatically It is obvious that a question arises now why do we need references Why can t we just use the objects themselves Why is all this pointer stuff necessary Well this is a very good question Many languages seem to do quite well without ever using pointers the way C does The main reason for these constructs is efficiency Imagine you have a huge database table and you want to pass it to a routine that will extract some information from it The best way to pass that data is just to pass the address where it starts without having to move or make a copy of the data itself Passing an address is just passing a 32 bit number a very small amount of data If we would pass the table itself we would be forced to c
151. void process Person process amp Person Mary Smith 38 This is one of the new features of C99 The literal should be enclosed in braces and it should match the expected structure This is just syntactic sugar for the following Person 996 d15944ss E Mary smith 3 7 process amp 998815544ss The advantage is that now you are spared that task of figuring out a name for the structure since the compiler does that for you Internally however that code represents exactly what happens inside Icc win32 Casts as any other of the constructs above can be misused In general they make almost impossible to follow the type hierarchy automatically C is weakly typed and most of the weakness comes from casts expressions 1 11 31 Indirection The operator is the contrary of the address of operator above It expects a pointer and returns the object the pointer is pointing to For instance if you have a pointer pint that points to an integer the operation pint will yield the integer value the pointer pint is pointing to The result of this operator is invalid if the pointer it is de referencing is not valid In some cases de referencing an invalid pointer will provoke the dreaded window This program has performed an invalid operation and will terminate that windows shows up when a machine fault 1s detected In other cases you will be unlucky and the de referencing will yield a non sense resu
152. we destroy it when we receive the WM NCDESTROY message This technique can be used not only with list boxes but with many other controls We have WM CTLCOLORSCROLLBAR Scroll bar WM CTLCOLORSTATIC Static controls text etc WM_CTLCOLORLISTBOX A combo box sends both messages WM_CTLCOLOREDIT to the parent window All this messages have the same parameters as in the list box example and the procedure is exactly the same The WM CTLCOLORSTATIC is interesting because it allows you to add text in any font and color combination to a window or dialog by just calling SelectObject with a special font or font size using the passed HDC of this message 288 C Tutorial 3 14 2 Using the WM_DRAWITEM message Suppose we want to draw a list box that draws an image at the left side of the text in each line In this case just setting some properties of the HDC we receive with WM _CTLCOLORLISTBOX will not cut it We need to do the entire drawing of each line of the list box We can do this by setting the style of the list box to owner draw the resource editor will do this for you and we need to process the WM DRAWITEM message Windows sends us a pointer to a DRAWITEMSTRUCT that contains all the necessary information to do the draw ing in the LPARAM parameter This structure is defined as follows unsigned int CtlType This member can be one of the following values ODT BUTTON button ODT COMBOBOX combo box ODT_LISTBOX list box ODT _LISTVIEW Li
153. win32 will give up at 255 chars Identifiers are the vocabulary of your software When you create them give a mnemonic that speaks about the data stored at that location Anonymous identifiers or counters are usually the one letters 1 or c for char etc I think the habit of using 1 J k is quite ancient maybe inherited from fortran and physics 1 11 2 Constants 1 11 2 1 Evaluation of constants The expressions that can appear in the definition of a constant will be evaluated in the same way as the expressions during the execution of the program For instance this will put 1 into the integer constant d State Ine do as This will also put one in the variable d Static ant d 60 L 1703 1 11 2 2 Integer constants An integer constant begins with a digit but has no period or exponent part It may have a pre fix that specifies its base and a suffix that specifies its type A decimal constant begins with a nonzero digit and consists of a sequence of decimal digits An octal constant consists of the prefix 0 optionally followed by a sequence of the digits 0 through 7 only A hexadecimal con stant consists of the prefix Ox or 0X followed by a sequence of the decimal digits and the let ters a or A through f or F with values 10 through 15 respectively Here are various examples of integer constants 12345 integer constant decimal 0777 octal for Sil decimal OxF98A hexa for 63882 decimal 1234
154. window It will give us just the size of the drawing surface We have a status bar at the bottom and the area of the status bar must be subtracted from the total area We query this time using the GetWindowRect function since we are interested in the whole surface of the status bar window not only in the size of its drawing surface We sub tract the height of the window from the height that should have the tree control and then we move it to the correct position 1 e filling the whole drawing surface of the window And we are done with drawing 3 10 3 Starting the scanning Now we pass to the actual task of our program We want to fill the tree control with a descrip tion of all the windows in the system A convenient way to do this is to change the New menu item into Scan and start scanning for windows when the user chooses this item To do this we add an entry into the MainWndProc OnCommand function void MainWndProc OnCommand HWND hwnd int id HWND hwndCtl UINT codeNotify SWC 4 case IDM NEW BuildTree hwnd break Case LDM Earl PostMessage hwnd WM CLOSE 0 0 break A more complex example a clone of spy exe 261 Simple isn t 1t We just call BuildTree and we are done 3 10 4 Building the window tree We start with the desktop window we add it to the tree and then we call a procedure that will enumerate all child windows of a given window We have two directions to follow the child windows of a
155. writes a function called words we are doomed In this case and for this example the glo bal variable solution is easier but not as a general solution 134 C programming with Icc win32 1 29 4 Code review Now that we have a bare skeleton of our program up and running let s come back to it with a critical eye For instance look at our isWordStart function We have int 1swordStart int C IE NG S a FECUrTE 17 if c gt a amp amp c lt z LECUE d if c gt A amp amp c lt Z LOCU 3 return O A look in the ctype h system header file tells us that for classifying characters we have a lot of efficient functions We can reduce all this code to ine swordsterLiintk c return gt ih Sapnai The isalpha function will return 1 if the character is one of the uppercase or lowercase alphabetic characters Always use library functions instead of writing your own The isalpha function does not make any jumps like we do but indexes a table of property bits Much faster And what about error checking Remember we just open the file given in the command line without any test of validly We have to fix this Another useful feature would be to be able to report a line number associated with our file instead of just an error message that leaves to the user the huge task of finding where is the offending part of the input file that makes our program crash This is not ver
156. x amp auto locals stack events search Stopped MainradProc 254 2 Now wait a minute our window procedure that receives the message from the system is called indirectly from Windows we can t just follow the program blindly If we did that we would end up in the main loop wasting our time 123 Why didn t we use the DLL to ask for the string to search Mostly because I wanted to give you an overview of the whole process A good exercise would be to change the program to use the DLL Which changes would be necessary How would you link Filling the blanks 279 No we have to set a breakpoint there We set a breakpoint when we call the dialog using the F2 accelerator key We see that Wedit sets a sign at the left to indicate us that there is a break point there Then we press F5 again to start running the program H wedit winexample winexample c OP x File Edit Search Project Resources Debug Utile Modules Window Help x return FALSE int DoSearchTest char tzt HessagePos NULL tst Test to search is MB OE return 1 t r r E E EE EE EEEE EEEE EEEE E EEEE EEE EEEE EEEE SS EEEE The following code comes from ENIGE lib yizard aorol void MainWndProc OnCommand HWHD hwnd int id HUND hwndtltl switcht id 4 TODO Add new menu commands here case IDM SEARCH char text 1024 f 1 CallDialog IDD SEARCH SearchDlgProc LP DoSearchTest text h break case IDM
157. 0 WINAT S Systema CW INN T Veusten VAIN T CW IAAT apstema ACAINN T calc binh smedev binic Sritreskit k she MnP mikbes bin nedev bine Sperform include e Semalleittel bin k borandbec55 binzd Slech binc cormmor UK The system tells us that it can t find the dll Well if you reflect about this this is quite normal A DLL must be linked when the execution of the program starts The system will search in the start directory of the program and in all directories contained in the PATH environment variable If it doesn t find a dialog dll any where it will tell the user that it can t execute the program because a missing DLL that s all The solution is to copy the DLL into the current directory or copy the DLL in one of the direc tories in your PATH variable Another solution of course is to go to the directory where the DLL 1s and start execution of the program there UsingaDLL 241 This dependency on the DLL is quite disturbing All programs that use the DLL in this fashion would need to have the DLL in their startup directory to be able to work at all A way to get rid of this is to avoid linking with the DLL import library Yes you will say but how will we use the DLL DLLs can be loaded into the program s address space with the API LoadLibrary This API will do what the program loader does when loading a program that contains a reference to a DLL If the load succeeds the API will return us a handle to th
158. 1 000000e 019 We see that the gap between the numbers is huge 1e19 What are the results for double precision We modify our program and we get Needs 1 000000e 019 What Why are the results of double precision identical to the floating point precision We should find that the smallest format would yield gaps much wider than the other more precise format Looking at the assembler code generated by our floating point program we notice while fctf ftfctf flas lo 768bpp 7 Loads Tett in the floating pein Unit fadds 4 ebp adds to the number stored in the FPU fcomps 16 ebp compares the sum with fctf Looking at the manuals for the pentium processor we see that the addition 1s done using the full FPU precision 80 bits and not in floating point precision Each number is loaded into the FPU and automatically converted to a 80 bits precision number We modify our program to avoid this int main void ELOe tt Toter sums FoC LaCt 34 0 is f Ors Sum f fctf while fctf sum tS 2 Oe sum fctf f prince Necdss Sein ts return U gt Note that this modified program is mathematically equivalent to the previous one When we run it we obtain Needs 1 014120e 031 OK now we see that the gap between numbers using the float format is much bigger than the one with double precision Note that both versions of the program are mathematically equivalent but numerically co
159. 27 The exact values are RGB 63 181 255 RGB 23 64 103 and RGB 0 0 0 Building custom controls 293 42 43 44 EndPaint hwnd amp ps 45 SelectObject dcMemory oldBitmap 46 DeleteDC dcMemory 47 DeleteObject bmp 48 DeleteObject hbBkBrush The first thing our procedure does is to obtain a device context from Windows 2 This device context is already clipped to the area we should draw We suppose that the text of the lcd is stored in the variable Text and we get its length 3 To make the translation from the colors in the bitmap to the colors of our lcd window we use the primitive CreateMappedBitmap that translates a bitmap with a set of source colors into a bitmap with the colors translated according to a translation table This table is prepared in lines 12 to 17 then passed as argument to the API Now we have to create our memory device context We make a compatible context in line 19 and then select into it the bitmap we have just obtained after color translation We will use this memory bitmap to copy bits into our display Before that however we make a solid brush and fill the whole window with the background color lines 21 23 For each character in our text we do 1 Calculate a rectangle with the position in our memory bitmap of the bits of the given character Since we assume that all characters have the same width it is a simple multiplication of a known constant by the width o
160. 3 Sorn result SvsS tso T ox 201o 70 6 20 sa n wday name timeptr gt tm wday mon name timeptr gt tm_ mon timeptr stm mday Crmeprr gt tm hour timeptr tm Min CameptE 2tm sec L200 F CAmMeotr Sc year return result This function is supposed to output a character string of 26 positions at most including the ter minating zero If we count the length indicated by the format directives we arrive at 25 o 3 for the day of the week o l space o 3 for the month o 3 for the day in the month o l space o 8 for the hour in hh mm ss format Buffer overflows 117 o 1 space o 4 for the year o 1 newline It makes 25 characters and taking into account the terminating zero the calculation seems OK But it is not The problem is that the format d of the printf specification doesn t allow for a maximum size When you write 3d it means that at least 3 characters will be output but it could be much more if for instance the input 1s bigger than 999 In that case the buffer allocated for asctime is too small to contain the printf result and a buffer overflow will happen The consequences of that overflow will change from system to system depending on what data is stored beyond that buffer the alignment used for character strings etc If for instance a function pointer is stored just beyond the buffer the conse quences could be catastrophic in the sense that it would be very difficult to tr
161. 38 Control flow 39 Windows specific syntax 39 Extensions of Icc win32 40 A closer view 41 Identifiers 41 Constants 41 Arrays 43 Function call syntax 43 Functions with variable number of arguments 43 Assignment 44 Postfix 44 Conditional operator 44 struct 45 union 45 typedef 45 register 45 sizeof 45 enum 46 Prototypes 46 variable length array 46 const 46 unsigned 47 bit fields 47 stdcall 47 break and continue statements 48 Null statements 48 Comments 49 Switch statement 49 inline 50 Logical operators 50 Bitwise operators 51 Address of operator 51 Sequential expressions 52 Casts 52 Indirection 53 Precedence of the different operators 55 The printf family 56 Conversions 56 The conversion flags 57 The size specification 58 The conversions 59 Scanning values 60 Pointers 62 Operations with pointers 63 Null pointers 65 setjmp and longjmp 65 General usage 65 Register variables and longjmp 67 Simple programs 69 strchr 69 strlen 69 ispowerOfTwo 70 Write ispowerOfTwo without any loops 71 Striwr 72 paste 73 Using arrays and sorting 77 How to sort arrays 80 Summary of Arrays and sorting 85 Pointers and references 85 Structures and unions 88 Structures 88 Structure size 91 Defining new types 92 Unions 93 Using structures 95 Fine points of structure use 97 An important structure 97 Identifier scope and linkage 98 Top down analysis 100 Extending a program 102 Improving the design 108 Traditiona
162. 5L long integer constant 2634455LL long long integer constant 5488UL unsigned long constant 548ULL unsigned long long constant 1 11 2 3 Floating constants For floating constants the convention is either to use a decimal point 1230 0 or scientific notation in the form of 1 23e3 They can have the suffix F or f to mean that they are float constants and not double constants as it is implicitly assumed when they have no suffix GO 99 A suffix of I or L means long double constant A suffix of q or Q means a qfloat 7 42 Qfloats are an extension of lec win32 42 C programming with Icc win32 1 11 2 4 Character string constants For character string constants they are enclosed in double quotes If immediately before the double quote there is an L it means that they are double byte strings Example L abc This means that the compiler will convert this character string into a wide character string and store the values as double byte character string instead of just ASCII characters To include a double quote within a string it must be preceded with a backslash Example The string the Stringi as enclosed 1n quotes Note that strings and numbers are completely different data types Even if a string contains only digits it will never be recognized as a number by the compiler 162 is a string and to convert it to a number you must explicitly write code to do the transf
163. 9 farled n lt argv 2 return C 2 3 Check that the file system supports mounting bFlag GetVolumelInformation argv 2 bufl1 BUFSIZE NULL amp nl amp flags fsname 256 if 0 flags amp FILE SUPPORTS REPAROE POINTS 4 printf File system doesn t support mount Pointsin return 3 printt Volume name of 2919 nS argvi2 But Jy if AStrilen arov i gt lt 2 4 printf lncorrect path name ss n argv 1 gt return 4 strncpy fsname argv 1 sizeof fsname 1 fsname sizeof fsname 1 0 Add a trailing backslash if not this call will not work if ftsname Strrlen tsname y 1 ba TANT 4 strcat Fsnameg TANTS bFlag SetVolumeMountPoint fsname mount point Buf volume to be mounted E if bE Lag 4 printf Attempt to mount s at s failed Error code d n argv 2 argv 1 GetLastError else printf s mounted in s n argv 2 argv 1 return bFlag 3 20 25 2 Umount Once we have mounted a drive we can unmount it with the following utility 334 C Tutorial include lt windows h gt include lt stdio h gt int main int aroc Char argv BOOL bE lag char mpath 512 Is if argc 2 printf s unmounts a volume from the volume mount point n argv 0 print Ror example numount ef mnt cdrom nn Certurn strnepy mpath arogyv 1 gt 5sizeo mpath 3 7 mpath sizeof
164. 9767 01203968 SOLL 99 OLOS LIZ Ue OHS OO oZ Oa LAA i S6 U D005 2 94417 14 60 05 sUZEA 5249 s02 L220 s0 LOOO s0 L09269 TORSE O76 00920309 s00 920474 700903421 00746051 OTOI TS Fosaa z207 LIO eres PES O 2 CO OO O O O O O O O O O O O O O We see that now we can go up to the 19th iteration with apparently good results We see too that the increased precision has only masked a fundamental flaw of the algorithm itself The manner the calculation is done produces a five fold increase in the error term at each iteration This is an example of a numerically unstable algorithm 1 35 4 Complex numbers Complex numbers have a real and an imaginary part According to which concrete number representation is used to store those parts they can be 1 float Complex 2 double Complex 3 long double Complex 178 C programming with Icc win32 4 qfloat Complex In Icc win32 however all complex types will be condensed in the long double complex type This implementation can be changed later but in any case it is better that you are aware of this feature There are several reasons for this Using this representation allows memory stored numbers to be identical to numbers as used by the floating point unit Programs will give the same results even if they store intermediate results in memory It simplifies the compiler and the complexity of the code generation machinery All this types can be m
165. A more advanced window 244 Customizing the wizard generated sample code 251 Making a new menu or modifying the given menu 251 Adding a dialog box 251 Drawing the window 252 Initializing or cleaning up 252 Getting mouse input 252 Getting keyboard input 253 Handling moving resizing 253 Window controls 254 A more complex example a clone of spy exe 259 Creating the child windows 259 Moving and resizing the child windows 260 Starting the scanning 260 Building the window tree 261 Scanning the window tree 261 Review 262 Filling the status bar 264 Auxiliary procedures 265 Numerical calculations in C 268 Filling the blanks 273 Using the graphical code generator 282 Customizing controls 286 Processing the WM_CTLCOLORXXX message 286 Using the WM_DRAWITEM message 288 Building custom controls 291 The Registry 294 The structure of the registry 294 Enumerating registry subkeys 295 Rules for using the registry 297 Interesting keys 298 Etc 299 Clipboard 300 Serial communications 301 Files 301 File systems 302 Graphics 303 Handles and Objects 303 Inter Process Communications 303 Mail 304 Multimedia 304 Network 304 Hooks 304 Shell Programming 305 Services 305 Terminal Services 305 Windows 306 Advanced windows techniques 307 Memory mapped files 307 Letting the user browse for a folder using the shell 310 Retrieving a file from the internet 313 Opening a web site or an HTML file using the default browser 314 Creating a desktop shor
166. ANDLE int a PURPOSE Saves instance handle and creates main window In this function we save the instance handle in a global iy variable and create and display the main program window 2 BOOL InitInstance HINSTANCE hInstance int nCmdShow HWND hWnd RECT rect int splashwidth 3507 int splashheight 350 hInst hInstance Store instance handle in this global variable systemParametersInfo SPI_ GHTWORKAREA 0 LPVOID amp rect 0 hWnd CreateWindowEx WS EX TOOLWINDOW oplLashwWndClass NULL WS OVERLAPPED rectsriognt rect dert splashwidth 2 tect DOCCON rect top splashheight 72 splashwidth splashheight NUE hy NULL hinstance NULL if hWnd return FALSE ShowWindow hWnd nCmdShow UpdateWindow hWnd return TRUE LRESULT CALLBACK WndProc HWND hWnd UINT message WPARAM wParam LPARAM lParam Switch message case WM NCCALCSIZE CAPTURE THIS MESSAGE AND RETURN NULL return NULL case WM CREATE SetTimer hWnd De aT ME LAEE 1000 NULL SetTimer hWnd ID TIMER LOAD 20007 NULL SetTimer hWnd DD MB DONE 4000 NULL SetTimer hWnd TD TIMER GHOSE S0005 NULL break Case WM PATNI l l E PAINTSTRUC pa 0 47 RECT te G0 ey HDC hDC BeginPaint hWnd amp ps GetClientRect hWnd amp rc Pita ceReCE Gres 252s Rectang Le ADC 2e lerr Festo pr Pe ri ght Tre DOECO 346 C Tutorial InflateRect amp rc HFON
167. Cc capacity cbEncodedBlobzl src count cbEncodedBlob src content pbEncodedBlob return 1 3 22 Finding more examples and source code John Finlay has created a web site for source code for lcc win32 Here is what John writes about his work When I initially started using LCC Win32 searching the Internet revealed no good sources of material that one could download as examples so creating a web site dedicated to this end seemed a good idea If I needed help obviously others would too The web site http www btinternet com john findlay1 contains many examples that lcc win32 users can easily compile and learn from I have tried to place each example in an appro priate section to help in locating as the number of examples would be bewildering 1f there were no discrete departments These departments sections however are not absolute as exam ples do not always readily fit into any specific category The largest section is Windows Programming where you will find examples ranging from a simple Generic application to far more sophisticated software There are many other sections that may be of interest OpenGL DirectX Windows Common Controls Custom Controls MultiMedia Telephony Games etc There is also the Assembler section with texts and examples explaining and showing how to code in assembler using Icc win32 specifically as the asm syntax used is AT amp T not Intel as 1s with most other compilers 3 23 Overview of Icc w
168. D HANDLE VALUE CloseHandle hSrcFile if fResult SUCCESS printi eop se hos Tailed ni pszSrcFileName pszDstFileName DeleteFile pszDstFileName reLurmy TREs Summary To get a pointer to a memory mapped file do the following e Open the file with CreateFile e Create a mapping object with CreateFileMapping using the handle you receive from CreateFile e Map a portion or all of the file contents 1 e create a view of it with Map ViewOfFile 3 18 2 Letting the user browse for a folder using the shell A common task in many programming situations is to let the user find a folder directory in the file system hierarchy When you want to search for certain item for instance or when you need to allow the user to change the current directory of your application The windows shell offers a ready made set of functions for you and the resulting function is quite short Let s first see its specification 1 e what do we want as an interface to this function Required is a character string where the result will be written to and a title for the user inter face element The result should be 1 if the path contains a valid directory 0 if there was any error the user cancelled whatever To be clear about the specifications let s look at this example int main void char path MAX PATH if BrowseDir Choose a directory path printf You have choosen s n path else printf action cancelled
169. DWORD cbSecurityDescriptor size of security descriptor FILETIME ftLastWriteTime last write time DWORD i j DWORD rerCode retValue CHAR achValue MAX VALUE NAME DWORD cchValue MAX VALUE NAME CHAR achBuff 80 Get the class name and the value count RegQuerylInfokey hKey key handle achClass putter for class name amp cchClassName size of class string NULL reserved 296 C Tutorial amp cSubKeys number of subkeys amp cbMaxSubKey longest subkey size amp cchMaxClass longest class string amp cValues number of values for this key amp cchMaxValue longest value name amp cbMaxValueData longest value data amp cbSecurityDescriptor security descripror amp ftLastwWwriteTime J last write time setDlgItemText nDlg IDE CLASS achClass setDlgItemInt hDlg IDE CVALUES cValues FALSE SendMessage GetDlgItem hDlg IDL LISTBOX LB ADDSTRING 0 LONG Enumerate the child keys until RegEnumKeyEx fails Then get the name of each child key and copy it into the list box SetCursor LoadCursor NULL IDC WAIT fOr 1 0 retCode ERROR SUCCESS PeLCode ERROR SUCCESS iat retCode RegEnumKeyEx hKey ly achKey MAX PATH NULI NULL NULL amp ftLastWriteTime if retCode DWORD ERROR SUCCESS sendMessage GetDlgItem hDlg IDL LISTBOX LB ADDSTRING 0 LONG achKey SetCursor LoadCursor NULL IDC ARROW E
170. ER TYPE BINARY HANDLE hConnect hOpen char szUser szPass SzHoOst Sszrirtlel szEertle7 hOpen tnternetoOpen EIEPGEI bOCAL INTERNET ACCESS NU Diss Oy 0 if hOpen ErrorOut InternetOpen return 1 szHost www q software solutions com szUser anonymous szPass foo foo com hConnect InternetConnect hOpen szHost INTERNET INVALID PORT NUMBER szUser szPass INTERNET SERVICE FTP INTERNET FLAG PASSIVE 0 if hConnect szFilel pub 1lcc README 314 C Tutorial szFile2 README if FtpGetFile hConnect szFilel szFile2 FALSE INTERNET FLAG RELOAD dwType 0 ErrorOut FtpGetFrile else printf Remote file s gt local file s szFilel szFile2 if InternetCloseHandle hConnect ErrorOut InternetCloseHandle else Errorout Internet Connect InternetCloseHandle hOpen return 0 This program is about 400 bytes of code and 200 bytes of data for character strings When linked it is only 4K long The whole hard part of networking is hidden behind the windows interface provided by the wininet lib library and the wininet h header file Basically to get a file from a remote machine using the FTP File Transfer Protocol you need to open a connection to the remote server send it the path of the file to retrieve and that is it The rest is some logic for opening and initializing the wininet l
171. EXIT PostMessagethwnd WM CLOSE 0 0 break hilnstance yoid Uzl hPrevyilnstance void Uxld4d1es IlptUmdLine Uxldsaal ff 20 nomdShow 4210720 hinat void x amp auto locals stack events search Stopped DoSearchT ext 208 5 Our program starts running we go to the menu select the search item and Wedit springs into view We hit the breakpoint Well that means at least that we have correctly done things until here the message is being received We enter into the CallDialog procedure using the F8 accelerator We step and after going through the DialogBoxParam procedure we see no dialog and the return result is 1 The debugger display looks like this We see the current line highlighted in yellow and in the lower part we see the values of some variables Some are relevant some are not Luckily the debugger picks up r as the first one Its value is 1 280 C Tutorial Why 1 W wedit winexample winexample c IOJ x File Edit Search Project Resources Debug Utile Modules Window Help x HWHD CreatewinerampleWndClassWnd void return CreateWindowl winexampleWndllass winexanple WS MINIMIZEBOE WS VISIBLE WS CLIPSIBLINGS WS CLIPCHT CW USEDEFAULT 0O CW USEDEFAULT 1 HULL HULL hinst HULL int CallDialogfint 1d DLGPROC proc LPARAM parameter ries eo DialogBorPar mthinet WAREINTRESOURCESid F static BOOL CALLBACK SearchDlgProct HWHD hwnd UINT msg WPA
172. Functions concerning the precision of the fenv h calculations exception handling and related items See page 166 float h Characteristics of floating types float double long double qfloat See page 166 inttypes h Characteristics of integer types 1s0646 h Alternative spellings for some keywords If you prefer writing the opera tor amp amp as and use this header limits h Size of integer types locale h Definitions for the formatting of currency values using local conven tions math h Mathematical functions Non local jumps i e jumps that can go past function boundaries See setjmp h page 65 signal dang sdbool h sddeth stdint h Integer types stdio h Standard input and output stdlib h Standard library functions stddef h This file defines macros and types that are of general use in a program NULL oftsetof ptrdiff t size_t and several others string h String handling Here are defined all functions that deal with the standard representation of strings as used in C See Traditional string representa tion in C on page 109 stdarg h Functions with variable number of arguments are described here See page 43 time h Time related functions See page 134 wchar h Extended multibyte wide character utilities wctype h Wide character classification and mapping utilities 1 3 1 The stdheaders h include file Normally it is up to you to remember which header contai
173. GA Operator char estr struct Exception exc GetAnExceptionStructure StringA result PRECONDITION cstr NULL exc result count strlen cstr pesult capacity Calculate new Capacrty 0 lr resule count 7 result content allocate proper space result capacity oMAL if result content NULL PeLurIn invalrd stringAy SCLC PesulLt COnven ey Caer reran Tecur We build a new String structure from scratch We require a valid C string and calculate its length We determine the best capacity for the new string allocate the contents and copy We use this operator with a cast for instance void printName String amp s printName String Annie The inverse operator is the much simpler cast from a String to a char char EXPORT operator StringA amp str Lt isNullsteingA str 204 C programming with Icc win32 return NULL Str content str count 037 return str content We use this operator like this Sering Str Printt Casini 2 Char SSC Conversions from string pointers to char pointers is more difficult if we want to support point ers that span only a subset of the string For instance if we have a pointer of length 2 that points to the third character of the string This is it the pointer points to the first 1 and includes the 1 and the s but not more In that case we need to copy the contents before pass ing them to the
174. H switch imag case WH INITDIALOG return TRUE case WM CLOSE EndDialog hwnd 03 break h nat void x40 0 id 400 hwndMain void U 904a0 function proc SearchDlgProc 1e6f parameter 1243660 amp auto locals stack events search Stopped CallDialog 191 25 A quick look at the doc of DialogBoxParazm tells us If the function fails the return value is 1 Ahh how clear Yes of course it failed But why Mystery There are no error codes other than just general failure What could be wrong Normally this 1 means that the resource indicated by the integer code could not be found I have learned that the hard way and I am writing this tutorial for you so that you learn it the easy way The most common cause of this is that you forgot to correctly give a symbolic name to your dialog We close the debugger and return to the resource editor There we open the dialog box proper ties dialog box by double clicking in the dialog box title bar and we see that we forgot to change the name of the dialog to IDM SEARCH We correct that and we try again Filling the blanks 281 OK this looks better The dialog is showing ae winexample Text Search The rest is quite trivial most of the wok was done when building the DLL Actually the dialog box is exactly the same 74 124 Newer versions of Wedit check for this Older ones aren t so sophisticated so please take car
175. IT The drawing takes place in the edit control of an owner drawn combo box ODS _ DEFAULT The item is the default item ODS_DISABLED The item is to be drawn as disabled ODS_ FOCUS The item has the keyboard focus ODS GRAYED This bit is used only in a menu ODS_HOTLIGHT The item is being hot tracked that is the item will be highlighted when the mouse is on the item ODS_INACTIVE The item is inactive and the window associated with the menu is inactive ODS NOACCEL The control is drawn without the keyboard accelera tor cues ODS NOFOCUSRECT The control is drawn without focus indicator cues ODS _ SELECTED The menu item s status is selected With all this information we can do whatever we want inside the rcItem rectangle Here is the example for our problem of drawing a bitmap in each line of the combo box First in our dialog procedure we handle the message WM DRAWITEM of course BOOL WINAPI MyDlgProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam HDC HDC COLORREF oldcolor Switch msg case WM INITDIALOG LoadListboxBitmaps hwnd other initializations can follow case WM DRAWITEM DrawListboxLine hwnd LPDRAWITEMSTRUCT 1Param return 1 We processed this message case WM NCDESTROY DestroyListboxBitmaps hwnd other cleanup tasks can go here i Our procedure to draw each line of the dialog box can look like this long DrawListboxLine HWND hwndDlg LPDRAWITEMSTRUCT lpdis HBITMAP hbmpPicture
176. If the call to GetWindowsDirectory fails the program will access uninitialized memory This means that the drive value will be a random number between 0 and 255 Of course it is quite difficult to imagine that GetWindowsDirectory fails or is it In windows using Terminal Server it becomes much more complicated to figure out where is the windows directory of a particular user The GetWindowsDirectory API has to do a lot more stuff including allocating memory for buffers And that allocation can fail and the devel oper at Microsoft did the right thing and tested if that memory allocation call worked or not and if not it returns an error failure Besides that API will work now but who knows what the future versions of windows will do Why leave a possible bug in there But this is difficult to do Checking the return value of ALL API calls is feasible but is very complex and time consuming And as everyone knows it is not a matter of the developer only How big 1s the time budget allocated to you for developing this application How much effort should be spent in making this application 100 bullet proof Those questions should be answered but they are not only the responsibility of the developer 3 19 2 Always check allocations Even in this days of 512MB RAM being common configurations and with swap files extend ing into the gigabyte memory failures can happen Specially in the case of infinite loops where all bets are off and any memory
177. L result malloc sizeof STREAM memcpy result gt FindData amp fd SiLZeOr SEruce tanddata t 7 result gt handle stream gt handle result gt file fopen fd name rb return result In the same manner that we allocate RAM for our first STREAM we allocate now a new one and copy into it our finddata handle and we open the file We compile and we get a compiler warning De lec examples gt Loc g2 freqiscc Warning fregl c 44 missing prototype for memcpy Warning fregl c 94 missing prototype for memcpy O errors 2 warnings 106 C programming with Icc win32 Yes but where is memcpy defined We look at the documentation using F1 in Wedit and we find out that it needs the lt string h gt header file We recompile and we get BH lee examples gt lec tregl c Error fregl c 95 type error in argument 1 to memcpy found SErUCE _findda ta t expected pointer to void 1 errors 0 warnings Wow an error We look into the offending line and we see memcpy resulle bindData sid sizeoi Struct Tinddata t 7 Well we are passing it a structure and the poor function is expecting a pointer This is a serious error We correct it like this memcpy amp result gt FindData amp fd sizeof struct finddata t We take the address of the destination structure using the address of operator amp We see that we would have never known of this error until run time when our program w
178. L If the DLL isn t found the functionality it should fulfill can t be present but nothing more no catastrophes 108 In the documentation of windows you will find out that in the def file you can write other kinds of statements None of them are supported by Icc win32 and are silently ignored since they are redundant with the command line arguments passed to the linker Do not write anything else in the def file besides the names of the exports 109 The Macintosh works in the same manner albeit with a much more primitive system A more formal approach 243 3 6 Amore formal approach 3 6 1 New syntax Now that we know how to make a DLL we should be able to understand more of C so let s come back again to the syntax and take a closer look A problem area is function pointer casting what leads straight into gibberish looking code int APIENTRY pfn char char int Better is to typedef such constructs with typedef int APIENTRY pfn char char int Now we declare our function pointer just with pfn pfnGetString and we can cast the result of GetProcAddress easily with pfnGetString pfn GetProcAddress Hiding the gibberish in a typedef is quite useful in this situations and much more readable later 3 6 2 Event oriented programming In another level what those programs show us is how to do event oriented programs 1 e pro grams designed to react to a series of events furnished by the event stream
179. NTSTRUCI ps 2 HDC hDC BeginPaint hwnd amp ps 3 int len strlen Text 4 HBITMAP bmp oldBitmap 5 HDC dcMemory 6 COLORMAP ColorMap 4 7 int char ount 0 8 int linecount 1 9 RECT m rSCky tO 10 EAE 2y 12 ColorMap 0 from SEGM COLORS O 7 13 CoLormMap 0 cto PixelonColor 14 COloOrMap 1 from SHGM COLORS 1 4 LS ColorMapl i te PixelOrrcolor 16 ColorMap 2 from SEGM COLORS 2 17 ColorMap 2 to PixelBackColor 18 bmp CreateMappedBitmap hInst ResourcelId 0 ColorMap 3 19 dcMemory CreateCompatibleDC hDC 20 oldBitmap SelectObject dcMemory bmp Al HBRUSH hbBkBrush CreateSolidBrush PixelBackColor 22 GetClientRect hwnd amp m_ rect 23 PLUlRece nbGr 6m rect NOBKBIrUSIHEN 24 x ee 25 fOr Ane aS 0 ak lt dlen ase 4 26 GetCharBmpOffset amp rc char Text 1ix CharacterwWidth Zi CharacterXSpacing CharacterHeight CharacterYSpacing 28 BAcB Le hb sx vy Characterwiath Characterxspacing 29 CharacterHeight CharacterYSpacing dcMemory rc left 30 PCat OD ORCOCOPIJ y eal x f Characverwidth Characterxooacing SZ charcount 33 if charcount MaxXCharacters amp amp MaxYCharacters 1 34 break 35 else if charcount MaxXCharacters amp amp MaxYCharacters gt 1 36 37 if linecount MaxYCharacters 38 break 39 x Charcount U 40 y CharacterHeight CharacterYSpacing 41 LLAECOUNETFS 1
180. Now we come back to the task at hand The first thing to do is to create the tree control window A good place to do these kinds of window creations is to use the opportunity the sys tem gives to us when it sends the WM CREATE message to the main window We go to the procedure for the main window called MainWndProc and we add the WM CREATE case to the switch of messages LRESULT CALLBACK MainWndProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam static HWND hwndTree switch msg case WM CREATE hwndTree CreateTree hwnd IDTREEWINDOW break This is top down design We hide the details of the tree window creation in a function that returns the window handle of the tree control We save that handle in a static variable We declare it as static so that we can retrieve its value at any call of MainWndProc Our CreateTree function looks like this static HWND stdcall CreateTree HWND hWnd int ID return CreateWindowEx WS EX CLIENTEDGE WC TREEVIEW WS VISIBLE WS CHILD WS BORDER TVS HASLINES TVS HASBUTTONS TVS DISABLEDRAGDROP OO Og Oe hWnd HMENU ID hinst NULL This function receives a handle to the parent window and the numeric ID that the tree control should have We call the window creation procedure with a series of parameters that are well described in the documentation We use the value of the hInst global as the instance since the code generated by Wedit conveniently leaves that
181. OCESS DETACH unregistering the class we registered before With this our GetString procedure is simplified We do not need to test our flag to see if the class has been registered any more We can be certain that it was int APIENTRY _ declspec dllexport GetString char prompt char destbuffer int bufferlen int result result DialogBoxParam hinst MAKE INTRESOURCE IDD MAINDIALOG NULL DEGPROC Diralegrunc anit prompt in rasuli ay of strncpy destbuffer buffer bufferlen l destbuffer bufferlen 1 0 return result We compile and link our DLL by pressing F9 Note that when we are building a DLL Icc win32 will generate three files and not only one as with a normal executable 1 We obtain of course a dialog dll file that contains the DLL 2 We obtain an import library that allows other programs to be linked with this DLL The name will be dialog lib but this is not a normal library It is just a library with almost no code containing stubs that indicate the program loader that a specific DLL is used by the program 3 We obtain a text file called dialog exp that contains in text form the names that are exported from the DLL If for any reason we wanted to regenerate the import library for the DLL we could use this file together with the buildlib utility of lcc win32 to recreate the import library This can be important if you want to modify the names of the exported functions establish s
182. Old bmMemOld bmSaveOld HDC hdcMem hdcBack hdcObject hdcTemp hdcSave POINT DpUESize hdcTemp CreateCompatibleDC hdc SelectObject hdcTemp hBitmap Select the bitmap GetObject hBitmap sizeof BITMAP LPSTR amp bm ptSize x bm bmWidth Get width of bitmap ptSize y bm bmHeight Get height of bitmap DPtoLP hdcTemp amp ptSize 1 Convert from device to logical points Create some DCs to hold temporary data hdcBack CreateCompatibleDC hdc hdcObject CreateCompatibleDC hdc hdcMem CreateCompatibleDC hdc hdcSave CreateCompatibleDC hdc Create a bitmap for each DC DCs are required for a number of GDI functions Monochrome DC bmAndBack CreateBitmap ptSize x ptSize y 1 1 NULL Monochrome DC bmAndObject CreateBitmap ptSize x ptSize y 1 1 NULL bmAndMem CreateCompatibleBitmap hdc ptSize x ptSize y bmSave CreateCompatibleBitmap hdc ptsize x ptsize y Each DC must select a bitmap object to store pixel data bmBackOld SelectObject hdcBack bmAndBack bmObjectOld SelectObject hdcObject bmAndObject bmMemOld SelectObject hdcMem bmAndMem bmSaveOld SelectObject hdcSave bmSave Set proper mapping mode SetMapMode hdcTemp GetMapMode hdc Save the bitmap sent here because it will be overwritten BiacBiecihdcsave Ur 0 DESLZe x ptEsize y HNdcTemp U U SRCUCOPY Set the background co
183. Oxdeadbeef to Oxceadbeef Why The explanation is in the MSDN site I quote Advanced C programming with Icc win32 159 To make sure that you do not define a code that conflicts with an existing exception code set the third most significant bit to 1 The four most significant bits should be set as shown in the following table Bits Recommended Description setting 31 30 11 These two bits describe the basic status of the code 11 error 00 success 01 informational 10 warning Client bit Set to 1 for user defined codes 28 o Reserved bit Leave set to 0 You can set the first two bits to a setting other than 11 binary if you want although the error setting is appropriate for most exceptions The important thing to remember is to set bits 29 and 28 as shown in the previous table End quote Note that nowhere will be said that the actual code will be changed by the operating system Just recommendations But anyway Follow this schema and you may be happy with it 1 34 5 4 Giving more information A 32 bit integer can be too little data for describing what happened Additional data can be channeled through the exception arguments using the RaiseException API You can pass up to 15 arguments when you raise an exception For instance here we will pass the name of the function that provoked the error in the first parameter include lt stdio h gt fane Lude lt seh h gt int fn void unsigned argst
184. Programming with lec win32 by Jacob Navia and Q Software Solutions GmbH Acknowledgements Thanks to all people that have contributed to this work Thanks to the many people that sent me those bug reports that allowed me to improve the software To all that sent me messages of encouragement Thanks specially to Friedrich Dominicus John Findlay and Mike Caetano among many other people that collaborated to make Icc win32 what it is today 2000 2003 Jacob Navia and Q Software Solutions GmbH This document is part of the Icc win32 documentation Distribution in any form is explicitly not allowed Chapter 1 Introduction to C 1 Program organization 2 Hello 3 Program input 4 What are function parameters 5 Console mode programs and windows programs 6 An overview of the compilation process 6 Technical notes 7 The run time environment 8 An overview of the standard libraries 10 The stdheaders h include file 10 Windows specific headers 11 Passing arguments to a program 11 Iteration constructs 14 Basic types 15 Declarations and definitions 17 Variable declaration 17 Function declaration 19 Function definitions 20 Variable definition 20 Statement syntax 20 Errors and warnings 21 Reading from a file 22 Commentaries 27 Describing a function 28 Describing a file 30 An overview of the whole language 30 Statements 32 Declarations 35 Pre processor 37 Windows specific defined symbols 38 Structured exception handling
185. S ghwndMain ParamsDlgProc break You give to that API the instance handle of the application the numerical ID of the dialog enclosed in the MAKEINTRESOURCE macro the handle of the parent window and the name of the procedure that handles the messages for the dialog You will need the prototype of the function in some header file to be able to use the name of it so it is a good idea to write a dlg boxprotos h header file that is included in every source file of the application If you want to pass a parameter to the dialog box procedure you can use DialogBoxParam 3 8 3 Drawing the window You have to answer to the WM PAINT message See the documentation for a longer descrip tion This will provoke drawing when the window needs repainting only You can force a redraw if you use the InvalidateRect API You add code like this case WM PAINT PAINISTRUCT PpS HDC hDC BeginPaint hwnd amp ps L Code for painting using the HDC gqoes there EndPaint hwnd amp ps break You use the API BeginPaint to inform windows that you are going to update the window Win dows gives you information about the invalid rectangles of the window in the PAINTSTRUCT area You pass to windows the address of such an area and the handle to your window The result of BeginPaint 1s an HDC a Handle to a Device Context that 1s required by most drawing primitives like TextOut LineTo etc When you are finished you call EndPaint to inform
186. S82 ag then TI Other operations are supported like append insert erase replace etc They all use the C function table in each object Se Ae s2 append abc Now s2 is ABCabc The same operation in C is append sz abc 212 C programming with Icc win32 Implementation Common Lisp has a string data type that is defined as a specialized vector of charac Lisp ters Accessing an element is done with cha Abpea i Se fp Comparison is done with Sering String Suring2 There are other optional arguments to indicate a starting and ending point for the comparison The result is either true strings equal or false different For lexicographical comparisons there are the functions st ring lt etc To modify a character in a string you use setit char ApCca II yl gt lbpcd APL Apl is a language where vectors are the main data type in contrast to Lisp where lists are paramount APL strings are just vectors like all others The rich primitive operations of APL in vectors can be applied to strings The reverse operation is done with Ruby Ruby strings can contain characters or just binary data as our strings There is an elaborate escaping mechanism to specify numerical values within strings Embedded commands within strings allow specifications like Hol Oss Merry Christmas gt Ho Ho Ho Merry Christmas Search expressions are very sophisticated including regular exp
187. Subject asctime limits Summary The definition of the asctime function involves a sprintf call writing into a buffer of size 26 This call will have undefined behavior if the year being represented falls outside the range 999 9999 Since appli cations may have relied on the size of 26 this should not be corrected by allowing the implementation to generate a longer string This is a defect because the specification is not self consistent and does not restrict the domain of the argument Suggested Technical Corrigendum Append to 7 23 3 1 2 except that if the value of timeptr gt tm_ year is outside the range 2899 8099 and thus the represented year will not fit into four characters it is replaced by up to 4 implementation defined characters Committee Response From 7 1 4 paragraph 1 If an argument to a function has an invalid value such as a value outside the domain of the function or a pointer outside the address space of the program or a null pointer or a pointer to non modifiable stor age when the corresponding parameter is not const qualified or a type after promotion not expected by a function with variable number of arguments the behavior is undefined Thus asctime may exhibit undefined behavior if any of the members of timeptr produce undefined behavior in the sample algorithm for example if the timeptr gt tm_wday is outside the range 0 to 6 the function may index beyond the end of an array As always the ra
188. T hFont HFONT hOldFont DrawText hDC DT WORDBREAK amp rcC Loy os Ceeaterone 35 350 7 Oy 0 07 0 07 Og Op Og Oe Oey TEAT CTAC ei HFONT SelectObject hDC hFont SZ SPLASH Istrlen SZ SPLASH SelectObject hDC hOldFont EndPaint hWnd break amp PS case WM DESTROY PostQuitMessage 0 break case WM TIMER HDC HDC RECT re GetClientRect hWnd Kiril Tamer awnd wParam Switch case case SZ INIT case S72 OAD case SZ CLOSE Istrlen S4Z INIT lstrlen SZ LOAD GetDC hWnd E Oe obey rC wParam ID TIMER CLOSE DestroyWindow hWnd break ID TIMER INIT TEX COUT ADC ce Lght Z00 esborton Z O break ID TIMER LOAD PexeOuc ibe Tonton UU Pe POLECONA break ID TIMER DONE TEX COUT ADC Touro T NU weboLton Z 0 Ssurien Sf Choon 7 break ReleaseDC hWnd NDC break default return DefWindowProc hWnd message return OQ wParam lParam 3 21 13 How do I append text to an edit control Windows based applications often use edit controls to display text These applications some times need to append text to the end of an edit control instead of replacing the existing text There are two different ways to do this in Windows Use the EM SETSEL and EM REPLACESEL messages Use the EM_ SETSEL message with the clipboard functions to append text to the edit control s buffer T
189. TH wchar t WDesktopDir MAX PATH BSTR Decr We are going to create a pidl and it will need to be freed by the shell allocator Get the shell allocator object using API SHGetMalloc function Return zero if failure if FAILED SHGetMalloc amp ShellMalloc return U use the API to get a pidl for the desktop directory f function fails return zero if FAILED SHGetSpecialFolderLocation NULL CSIDL DESKTOPDIRECTORY amp DesktopPid1 return 0 Now convert the pidl to a character string return if function fails if SHGetPathFromIDList DesktopPidl DesktopDir ShellMalloc gt Free DesktopPid1 ShellMalloc gt Release return Uy At this point we are done with the pidl ShellMalloc gt Free DesktopPid1 We do not need the allocator object any more ShellMalloc gt Release You do not need to do this if Colnitialize was already done at program startup if SUCCEEDED CoInitialize NULL if SUCCEEDED CoCreateInstance amp CLSID ShellLink NULL CLSCTX INPROC SERVER amp IID IShellLink void amp pLink plLink gt SetPath file plLink gt SetArguments args pLink gt SetShowCmd SW SHOW if SUCCEEDED pLank QOueryinterface lt 1iLD IPersistPhile void amp pPersistFile if DesktopDir strlen DesktopDir 1 strcat DesktopDir strcat DesktopDir shortcutname mostowcs WDesktopDir DesktopDir 1 strlen DesktopDir
190. TR amp lpMsgBuf Querying the network parameters 377 0 NULL printf tError 39 lpMsgBuf LocalFree lIpMsgBuf Show the information for the ip address table MIB IPADDRTABLE pIPAddrTable DWORD dwSize struct in_addr IPAddr char strilPAddr pLPAddrTable MIB 1PADDRTABLE malloc sizect MIB ITPADDRTABLE dwSize 0 IPAddr S un S addr ntohl plPAddrTable gt table 1 dwAddr StELPadgr inet ntoa lL PAddr re GetIpAddrTable pIPAddrTable amp dwSize 0 if rc ERROR INSUFFICIENT BUFFER free plPAddrTable pilPAddrTable MIB ITPADDRTABLE malloc dwSize dwRetVal GetIpAddrTable pIPAddrTable amp dwSize O0 if dwRetVal NO ERROR printf Call to GetIpAddrTable failed nError d n GetLastError return 1 Now show the information printf Address x n pIPAddrTable gt table 0 dwAddr unsigned int mask plIPAddrTable gt table 0 dwMask printf Mask a 3d d d n Oxff mask Oxff amp mask gt gt 8 Oxff amp mask gt gt 16 0xff amp mask gt gt 24 Princr Indexi S ld n pIPAddrTable gt table 0 dwIndex Princr BCast S ld n pIlPAddrTable gt table 0 dwBCastAddr printf Reasm S ld n pIlPAddrTable gt table 0 dwReasmSize Get the statistics about IP usage MIB IPSTATS Dotaley Potats MIB IPSTATS malloc sizeot MIB IPSTATS if VdwRetVal Getipotartetics potars P NO ERROR
191. The Next char WOO a Always zero terminate E terWord iridburf jy pnter inko the table ESCU Ly D OR TO GO Orns We hold the index into our array in the identifier 1 for index It starts at one since we receive already the first character of a word Note that we test with this index if we are going to over flow our local table idbuf We said before that error checking should be abstracted when designing the program but as any rule that one has exceptions 66299 1 If we were going to leave a lot of obvious errors in many functions around we would need a lot of work later on to fix all those errors Fundamental error checking like a buffer overrun should always be in our minds from the beginning so we do it immediately Note that this test is a very simple one 1 29 1 The organization of the table Now we have no choice but to start thinking about that EnterWord function All the easy work is done we have to figure out now an efficient organization for our word table We have the following requirements 1 It should provide a fast access to a word to see if a given sequence of characters is there already 2 It should not use a lot of memory and be simple to use The best choice is the hash table We use a hash table to hold all the words and before entering something into our hash table we look if is in there already Conceptually we use the follow ing structure 130 C programming with Icc w
192. The loop variable 1 will decrease to zero but then the decrement operation will produce the unsigned number 4294967296 that is bigger than zero The loop goes on forever Note too that the common windows type DWORD 1s unsigned 1 37 11 Changing constant strings Constant strings are the literal strings that you write in your program For instance you write outScreen Please enter your name This constant string Please enter your name is stored under Icc win32 in the data section of your program and can be theoretically modified For instance suppose that the routine out Screen adds a r n to its input argument This will be in almost all cases a serious problem since 1 The compiler stores identical strings into the same place For instance 1f you write aa RS 1S sa Seg be SES aS es SEPP c there will be only one string in the program The compiler will store them under the same address and if you modify one the others will be automatically modified too since they are all the same string 2 If you add characters to the string with strcat for instance you will destroy the other strings or other data that lies beyond the end of the string you are modifying Some other compilers like gcc will store those strings in read memory marked as read only what will lead to an exception 1f you try to modify this Lcc win32 doesn t do this for different reasons but even if you do not get a trap it is a bad practice tha
193. The status convention Returning a status like HRESULT A HRESULT gt 0 such as S_OK is a success and a HRESULT lt 0 suchas E FAIL 1s a failure This would be OK but there is the problem that other API functions return an error code defined in windows h There is the BIG problem that ERROR SUCCESS l is defined there as zero In this schema the value zero is reserved to indicate that everything 1s OK and all other values 130 This part has been adapted from an excellent article by Jon Pincus published in MSDN June 2000 131 Simply looking at this name ERROR SUCCESS implies that there is a big problem with the peo ple that designed that stuff It is an error code or a success indication Error handling under windows 317 mean an error code Note that the value of zero that in the boolean convention above indicates failure means the contrary here 3 Returning a NULL pointer This failure indication is used in the standard C library malloc realloc and many others return NULL for failure As with the boolean convention some other means are necessary to distinguish the different kinds of failures 4 Returning an impossible value Sometimes this value is zero for instance in the API GetWindowsDirectory sometimes is 1 for instance the fgets function in the C library or many other values This convention becomes very difficult to follow and memorize when applied to a large API like the windows API 5 Throwing a C except
194. ULL 344 C Tutorial TCHAR SplashWndClass 28 int APIENTRY WinMain HINSTANCE hinstance HINSTANCE hPrevinstance LPSTR lpCmdLine int nCmdShow MSG msg lstrcpy SplashwWndClass TEXT SplashWindow a fi ie a a igs ATOM ai MyRegisterClass hInstance I Perform application initialization if InitInstance hInstance nCmdShow return FALSE Main message loop while GetMessage amp msg NULL 0 0 TranslateMessage amp msqg DispatchMessage amp msqg recur MsG wracam FUNCTION MyRegisterClass PURPOSE Registers the window class COMMENTS This function and its use is only necessary if you want this code to be compatible with Win32 systems prior to the RegisterClassEx function that was added to Windows 95 It is Important tO call this function so thet the application wild get well formed small icons associated with it MyRegisterClass HINSTANCE hInstance WNDCLASSEX wcex wcex cbSize sizeof WNDCLASSEX wcex style Co HREDRAW CS _ VREDRAW wcex lpfnWndProc WNDPROC WndProc wcex cbClsExtra Qe wcex cbWndExtra O wcex hinstance hinstance wcex hiIcon NULL wex NGUrSor LoadCursor NULL IDC ARROW wcex hbrBackground HBRUSH COLOR WINDOW 1 wcex lpszMenuName NULL wcex lpszClassName SpLlashnwndG lass wcex hiIconSm NULL return RegisterClassEx amp wcex FAQ 345 a FUNCTION InitInstance H
195. We change it like this FILE Fopen STREAM stream char name char mode BELGE regut char fullname 1024 p p strrchr stream gt Name if p NULL fullname 0 0 else tp 0 strcpy fullname stream gt Name strcat fullname The problems with C Strings 113 p strcat fullname name result fopen fullname mode if result NULL fprintf stderr Impossible to open ss n fullname gt exit 1 return result We declare a array of characters with enough characters inside to hold a maximum path and a few more Then and in the same declaration we declare a character pointer p This pointer will be set with strrchr If there isn t any backslash in the path we just set the start of our fullname to zero If there is a path we cut the path component as we did before and copy the path component into the fullname variable The library function strepy will copy the sec ond argument to the first one including the null character for terminating correctly the string We add then a backslash using the strcat function that appends to its first argument the second string It does this by copying starting at the terminator for the string and copying all of its second argument including the terminator We restore the string and append to our full path the given name In our example we copy into fullpath the character string src77 then we ad
196. We go int Main ant arg Char argy PingInterface p int r memset amp p 0 sizeof p We set the host name field p HostName argv 1 We modify the default time between packets p SleepTime 500 lf we time out more than 5 times we exit p MaxTimeouts 5 We set our callback p Callback PrintReport r ping amp p ol r 0 4 printf ss is down n p HostName return 1 peint n printf n d packets from s s p TotalPackets p HostName p ip printi Received 4d Sent td n o Total Received p TotalSent gt if p TotalPackets 0 p TotalPackets 1 printf Max time d ms Min time d ms Avg time g ms n p MaxTime p MinTime double p TotalTime double p TotalPackets return 0 380 C Tutorial 4 7 Client Server programming using sockets There are two distinct types of socket network applications Server and Client The server is normally the propietary of a ressource a data file an image or other information that it serves to its clients Clients request information from the server and display it to the user Servers and Clients have different behaviors therefore the process of creating them 1s differ ent Initialize WSA Initialize WSA Recomm 4 7 1 Common steps for server and client 4 7 1 1 Initializing All Winsock applications must be initialized to ensure that Windows sockets are supported on the system To initializ
197. a general solution to it It depends a lot of course upon the application and its general style But personally I prefer explicit error messages rather than implicit ones When you receive an error message you know exactly what is wrong and you can take easily steps to correct it When you see a menu item disabled it is surely NOT evident what the hell is happening and why the software is disabling those options I But there are other user interface considerations in our dialog box to take into account too One of them is more or less evident when you see how small the letters in the edit field are Dialog boxes use a default font that shows very thin and small characters It would be much better if we would change that font to a bigger one In the initialization procedure we set the font of the edit field to a predefined font Windows comes with several predefined items ready for you to use without much work One of them is the system font that comes in two flavors monospaced and proportional We use the mono spaced one Our initialization procedure then looks now like this static int InitializeApp HWND hDlg WPARAM wParam LPARAM lParam HFONT font font GetStockOb ect ANSI FIXED FONT sendDlgItemMessage hDlg IDENTRYFIELD WM SETFONT WPARAM font 0 EnableWindow GetDlgItem hD1lg IDOK 0 SetFocus GetDlgItem hDlg IDENTRYFIELD return 1 A HFONT is a font handle i e an integer that repres
198. a union that describes all of our possi ble data sources We fill the union by first assigning to it the type of the information that follows an integer that must be one of the defined constants above Then we copy to the union the corresponding structure Note that we save a lot of wasted space since all three structures will be stored beginning at the same location Since a data source must be one of the structure types we have defined we save wasting memory in fields that would never get used Another usage of unions is to give a different interpretation of the same data For instance an MMX register in an x86 compatible processor can be viewed as two integers of 32 bits 4 inte gers of 16 bits or 8 integers of 8 bits Lcc win32 describes this fact with a union LypeGer struck PWA char high Char low F packedword 16 bit integer pypeder Struct PDW 4 _packedWord high _packedWord low spackedDWord 32 it integer of two 16 bit integers typedef struct POWY _packedDWord high _packedDWord low packedQWord 64 bits of two 32 bit structures typedef union Union i _packedQWord packed int dwords 2 short words 4 char bytes 9 mmxdata This is the union of all those types Union usage is not checked by the compiler i e if you make a mistake and access the wrong member of the union this will provoke a trap or another failure at run time One way of debugging this kind of problem is to define all
199. able l argota pret unsigned func 7 RaiseException 0xe0000001 0 1 argstable return 0 Not reached int main vord unsigned code EA a fn _ except code GetExceptionCode EXCEPTION EXECUTE HANDLER 4 EXCEPTION POINTERS ex Gece xcepeloniniorlal lon 7 Princtk Brroer code 2Fx n code gt Prince ln function 7s n y 76 http msdn microsoft com library default asp url library en us vccore98 html _core raising software exceptions asp 160 C programming with Icc win32 char ex gt ExceptionRecord gt ExceptioniInformation 0 return OQ This will print Error codes Oxe0000001 le EUNC ELON en The keyword func will be substituted by the name of the current function by the compiler We put that name in the first parameter of the table We call then RaiseException with 1 argument and our table The exception handling code will get the exception information and print the first argument The function GetExceptionInformation returns a pointer to a copy of the exception informa tion received by the system by the Icc win32 runtime The structure EXCEPTION POINTERS contains two pointers the first points to an EXCEPTION RECORD and the second to a CONTEXT structure containing the machine registers at the time of the exception In the example we use the exception record to get to the parameters array and we print the first one Nowhere in the shown code there is a tes
200. able number of arguments To access the unnamed extra arguments you should include lt stdarg h gt To access the addi tional arguments you should execute the va_start then for each argument you execute a va arg Note that if you have executed the macro va start you should always execute the va_end macro before the function exits Here is an example that will add any number of integers passed to it The first integer passed 1s the number of integers that follow include lt stdarg h gt int Va add 2nt numbSrOfArgsy awa va list ap int n numberOfArgs 44 C programming with Icc win32 Lie SU OS va start ap numberOfArgs while n sum va argi ap int va_end ap return sum We would call this function with yanada roe STT or va aad 24I LI 1 11 6 Assignment An assignment has the left hand side of the equal s sign that must be a value that can be assigned to and the right hand side that can be any expression other than void int a 789 a is assigned 789 array 345 array 123 897 An element of an array is assigned Struct field sqrt b 9 0 A field of a structure is assigned p iteld SOrD 0 7 A field of a structure is assigned through a pointer Within an assignment there is the concept of L value 1 e any assignable object You can t for instance write O09 The constant 5 can t be assigned to It is not an L value the L
201. ace where the error is happening 1 26 1 1 Getting rid of buffer overflows How much buffer space we would need to protect asctime from buffer overflows in the worst case This is very easy to calculate We know that in all cases Sd can t output more characters than the maximum numbers of characters an integer can hold This is INT MAX and taking into account the possible negative sign we know that Number of digits N 1 ceil log10 double INT MAX For a 32 bit system this 1s 11 for a 64 bit system this is 21 In the asctime specification there are 5 d format specifications meaning that we have as the size for the buffer the expression 26 5 N bytes In a 32 bit system this is 26 55 81 This 1s a worst case oversized buffer since we have already counted some of those digits in the original calculation where we have allowed for 3 2 2 2 4 13 characters for the digits A tighter calculation can be done like this Number of characters besides specifications od or s in the string 6 Number of od specs 5 Total 6 5 11 61 terminating zero 62 The correct buffer size for a 32 bit system is 62 1 26 1 2 Buffer overflows are not inevitable As we have seen above a bit of reflection and some easy calculations allows us to determine how much we need exactly Most buffer overflows come from people not doing those calcula tions because C is full of buffer overflows anyway attitude What is absolutely incredib
202. ach function This storage is dynamic it grows and shrinks when procedures are called and they return At any moment we have a stack pointer stored in a machine register that contains the machine address of the topmost position of the stack 3 The heap Here is the space that we obtain with malloc or equivalent routines This also a dynamic data area it grows when we allocate memory using malloc and shrinks when we release the allocated memory with the free library function There is no action needed from your side to manage the initial data area or the stack The com piler takes care of all that The program however manages the heap 1 e 1t expects that you keep book exactly and with out any errors from each piece of memory you allocate using malloc This is a very exhausting undertaking that takes a lot of time and effort to get right Things can be easy if you always free the allocated memory before leaving the function where they were allocated but this is impossible in general since there are functions that precisely return newly allocated memory for other sections of the program to use There is no other solution than to keep book in your head of each piece of RAM Several errors all of them fatal can appear here e You allocate memory and forget to free it This is a memory leak e You allocate memory and you free it but because of a complicated control flow many ifs whiles and other constructs you free a piece of me
203. acro LCC If you want to code some thing only for this compiler you write ifdef LCC i statements endif Note that there 1s no way to decide if the expression SomeFn foo Is a function call to SomeFn or is a macro call to SomeFn The only way to know is to read the source code This 1s widely used For instance when you decide to add a parameter to Cre ateWindow function without breaking the millions of lines that call that API with an already fixed number of parameters you do define CreateWindow a b CreateWindowEx 0 a b This means that all calls to CreateWindow API are replaced with a call to another routine that receives a zero as the new argument s value It is quite instructive to see what the preprocessor produces You can obtain the output of the preprocessor by invoking lcc with the E option This will create a file with the extension i intermediate file in the compilation directory That file contains the output of the preproces sor For instance 1f you compile hello c you will obtain hello 1 1 32 1 Preprocessor commands The preprocessor receives its commands with lines beginning with the special character This lines can contain A closer look at the pre processor 145 1 Macros 2 Conditional compilation instructions 3 Pragma instructions 4 The operator 5 Line instructions 1 32 1 1 Preprocessor macros The define command has two forms depending on whe
204. ain Lint argc Char argy int fResult FAILURE ULARGE INTEGER liSrcFileSize Seet 1liBytesRemaining liMapSize liOffset HANDLE hSrcFile INVALID HANDLE VALUE hDstFile INVALID HANDLE VALUE hSrcMap 0 hDstMap 0 BYTE pore U ODS 07 char pszSrcFileName 0 pszDstFileName 0 if argc 3 test if two arguments are given in the command line printf usage copyfile lt srcfile gt lt dstfile gt n return FAILURE pszSrcFileName argv argc 2 Src is second to last argument 128 ULARGE_ INTEGER is defined in the windows headers like this typedef union _ULARGE INTEGER struct DWORD LowPart DWORD HighPart long long QuadPart ULARGE INTEGER PULARGE INTEGER The union has two members a anonymous one with two 32 bit integers and another with a long long integer 1 e 64 bits We can access the 64 bit integer s low and high part as 32 bit numbers This is useful for functions returning two results in a 64 bit number 308 C Tutorial pszDstFileName argv argc 1 Dst is the last argument We open the source file for reading only and make it available for other processes even if we are copying it We demand to the operating system to ensure that the file exists already hSrcFile CreateFile pszSrcFileName GENERIC READ Source file is opened for reading only FILE SHARE READ Shareable 0 OPEN EXISTING 0 0 if INVALID HANDLE VALUE hSrcFi
205. al There are many introductory books that augment their volume just with the easy way of including a lot of windows documentation in their text Here we will make an exception But what is important however is that you know how to look in the documentation Suppose you want to know what the hell is that CS_DBLCLKS constant and what does it exactly mean You press F1 in that identifier and nothing It is not in the index Well this constant appears in the context of RegisterClass API When we look at the docu mentation of RegisterClass we find a pointer to the doc of the WNDCLASS structure Going there we find in the description of the style field all the CS constants neatly explained Note that not all is in the index You have to have a feeling of where to look Lcc win32 comes with a help file of reasonable size to be downloaded with a standard modem It is 13 MB com pressed and it has the essentials A more detailed documentation complete with the latest stuff is in the Software Development Kit SDK furnished by Microsoft It 1s available at their Web site and it has a much more sophisticated help engine A more advanced window 247 The WinMain procedure is the right place for initializing other things like ColInitialize if you are going to use COM or WSAStartup if you are going to use the sockets layer etc The command line parameters are available in the lpCmdLine parameter The messages for the main window are handled in
206. all finds a value different than zero and skips the class regis tration code Libraries 233 We have to tell the IDE to produce a static library now instead of a normal executable file We do this by going into the linker configuration tab and checking the library radio button like this Configuration of Wedit Generate i Wie not meude tre a map Nie denug information gd Wig Hot INGIUude underscores Hal erpats You see the Static library radio button checked The name of the library is the name of the project with the lib extension Now we are ready to change our WinMain We change our WinMain function to be the Get String procedure like this static char buffer 1024 Static int classRegistered int APIENTRY GetString char prompt char destbuffer int bufferlen WNDCLASS wc int result HANDLE hinst hinst GetModuleHandle NULL if classRegistered 0 memset amp wc 0 sizeof wc we lprnWndProc DeftDigProc wec cboWndExtra DLGWINDOWEXTRA we hInstance hinst wc hCursor LoadCursor NULL IDC ARROW wc hbrBackground HBRUSH COLOR WINDOW Ly wc lpszClassName dialog RegisterClass amp wc classRegistered 1 234 C Tutorial result DialogBoxParam hinst MAKE INTRESOURCE IDD MAINDIALOG NULL DLGPROC DialogFunc Elica gy ove Wioies ee ie Rests IF 4 strncpy destbuffer buffer bufferlen 1 destbuffer bufferlen 1 0 return result We hav
207. allocation will fail And here the memory manager of lcc win32 will not help since it will return NULL also it can t do anything else Allocations can fail because of corrupted input data to the memory allocation function Sup pose this code ine allocsiz putter GC malloctallocs1z 4 If for any reason allocsiz goes negative GC _ malloc will receive a negative number that will interpret as a size_t ie as an unsigned integer This means that a negative request will be inter preted as an allocation request of more than 2GB Testing the result of an allocation allows a clean exit or an exception handling construct or other solutions that allow you to pinpoint with greater easy where the failure happened You should be aware of this problem when using flexible arrays When you write int fn int a int ae Canals Error handling under windows 319 Here you are allocating a integers in the stack when control reaches the function prologue There is no way for you to check 1f this worked or not the only failure notification will be a stack overflow if a has the wrong value 320 C Tutorial 3 20 Some Coding Tips Here are some useful receipts for solving specific windows problems 3 20 1 Determining which version of Windows is running BOOL InWinNT test for NT OSVERSIONINFO osv GetVers1ionEx amp OSv osv dwOSVersioninfoSize sizeof osv return osv dwPlatformId VER PLATFORM WIN32 NT 3 20 2 T
208. allows us to pass a small machine address around instead of a big FILE structure that has dozens of fields The big advantage of pointers 1s that they are efficient But as anything they are error prone There is no free lunch The contents of the pointer are undefined until you initialize it Before you initialize a pointer its contents can be anything it 1s not possible to know what is in there until you make an assignment A pointer before is initialized is a dangling pointer 1 e a pointer that points to nowhere A pointer can be initialized by 1 Assign it a special pointer value called NULL 1 e empty 2 Assignment from a function or expression that returns a pointer of the same type In the frequencies example we initialize our infile pointer with the function fopen that returns a pointer to a FILE 3 Assignment to a specific address This happens in programs that need to access certain machine addresses for instance to use them as input output for special devices In those cases you can initialize a pointer to a specific address Note that this is not possible under windows or Linux or many operating systems where addresses are virtual addresses More of this later 4 You can assign a pointer to point to some object by taking the address of that object For instance int integer int pinteger amp integer Here we make the pointer pinteger point to the int integer by taking the address of that integer
209. ame Char Address double balance tine Cast ipansaction unsigned hasACar 1 unsigned mailedAlready 1 bool UpdateBalance struct customer Customer double newBalance be The new field is a function pointer that contains the address of a function that returns a Bool ean result and takes a customer and a new balance and should eventually update the balance field that isn t directly accessed by the software other than trough this procedure pointer When the program starts you assign to each structure in the creation procedure for it the func tion DefaultGetBalance that takes the right arguments and does hopefully the right thing Structures and unions 91 This allows you the flexibility of assigning different functions to a customer for calculating his her balance according to data that is known only at runtime Customers with a long history of overdraws could be handled differently by the software after all But this is no longer C is the heart of the application True there are other languages that let you specify with greater richness of rules what and how can be sub classed and inherited C allows you to do anything there are no other rules here other the ones you wish to enforce You can subclass a structure like this You can store the current pointer to the procedure some where and put your own procedure instead When your procedure is called it can either Do some processing before calling the original
210. ameters into their respective parts and passes those to the MainWndProc OnCommand function When this window is destroyed we post the quit message The function for handling the commands looks like this void MainWndProc OnCommand HWND hwnd int id HWND hwndCtl UINT codeNotify Switch id TODO Add new menu commands here Case LDM EXILI PostMessage hwnd WM CLOSE 0 0 break We find a comment as to where we should add our new command We gave our menu item Search the symbolic ID of IDM SEARCH We modify this procedure like this void MainWndProc OnCommand HWND hwnd int id HWND hwndCtl UINT codeNotify swicteh id TODO Add new menu commands here case IDM SEARCH char text 1024 gt if CallDialog 1DD SEARCH SearchbDlgProc LPARAM text DoS Garch Text Text Filling the blanks 277 break Case LDM PAIL PostMessage hwnd WM CLOSE 0 0 break When we receive the menu message then we call our dialog Since probably we will make several dialogs in our text editor it is better to encapsulate the difficulties of calling it within an own procedure CallDialog This procedure receives the numeric identifier of the dialog resource the function that will handle the messages for the dialog and an extra parameter for the dialog where it should put the results We assume that the dialog will return TRUE if the user pressed OK FALSE if the user pressed th
211. and recycle it It is a very simple schema taken to almost perfection by several years of work from the part of the authors To use the memory manager you should add the gc lib library to your link statement or indi cate that library in the IDE in the linker configuration tab 1 27 1 Functions for memory allocation malloc Returns a pointer to a newly allocated memory block Releases a memory block Returns a pointer to a newly allocated zero filled memory block realloc Resizes a memory block preserving its contents all ca Allocate a memory block in the stack that is automatically destroyed when the function where the allocation is requested exits Returns the size of a block Increases the size of a block without moving it GC_malloc Allocates a memory block managed by the memory manager 1 27 2 Memory layout under windows A 32 bit address can be used to address up to 4GB of RAM From this potential address space windows reserves for the system 2GB leaving the other 2GB for each application These 68 This discussion is based upon the article of Randy Kath published in MSDN Memory management and memory layout 121 addresses of course are virtual since not all PCs have 2GB of real RAM installed To the windows memory manager those numbers are just placeholders that are used to find the real memory address Each 32 bit address is divided in three groups two containing 10 bits and the third 12 bits 22 21 12 11 o al
212. ans the argument is ptrdiff_ t under Iec win32 int X X a ERT pe d png Oy Means the argument is size_t in Icc win32 unsigned xp ak LRE Well now we can pass to the final part see ee S Pe e The printf family 59 1 12 4 The conversions Signed integer conversion is used and the argument is by default of type int If the h modifier is present the argument should be a short if the 11 modifier is present the argument isa long long Unsigned decimal conversion Argument should be of type unsigned int default unsigned short h modifier or unsigned long long 11 modifier Unsigned octal conversion is done Same argument as the u format Unsigned hexadecimal conversion If x is used the letters will be in lower case if X is used they will be in uppercase If the modifier is present the number will be prefixed with Ox The argument is printed as a character or a wide character if the modifier is present The argument is printed as a string and should be a pointer to byte sized charac ters default or wide characters if the modifier is present If no precision 1s given all characters are used until the zero byte is found Otherwise the maxi mum number of characters used is the given precision The argument is a pointer and is printed in pointer format Under Icc win32 this is the same as the unsigned format u The argument is a pointer to int default pointer to short h modifier or pointer t
213. any instructions that adjust the stack after the function call are not needed and replaced by a single instruction at the end of the called function Functions with this type of calling convention will be internally decorated by the compiler by adding the stack size to their name after an sign For instance a function called fn with 48 C programming with Icc win32 an integer argument will get called fn 4 The purpose of this decorations is to force the pre vious declaration of a stdcall function so that always we are sure that the correct declarations was seen if not the program doesn t link 1 11 21 break and continue statements The break and continue statements are used to break out of a loop or switch or to continue a loop at the test site They can be explained in terms of the goto statement while condition 0 doSomething if condition QO break doSomethingElse is equivalent to while condition 0 doSomething if condition QO goto labl doSomethingElse labli The continue statement can be represented in a similar way while condition 0 doSomething iE Conditioen 25 Continue doSomethingE1se is equivalent to restart while condition 0 doSomething Ltr oondition 25 goto restart doSomethingE1lse The advantage of avoiding the goto statement is the absence of a label Note that in the case of the for
214. application is fragile and very difficult to trust A small error in ten thousands of lines 1s almost inevitable as you may know Of course there 1s already an exception handling mechanism When a machine trap occurs windows displays the well known This application message and shuts down the program Couldn t the system make something better Well it can do something better and it does Structured exception handling within Icc win32 is built using the general exception handling mechanism of windows It has been around since the beginning of the win32 API i e 1995 1 34 5 2 How dol use SEH Structured exception handling allows you to build a solution for the above problems You enclose the possibly buggy code within special markers like this Finelude lt stdio h gt finclude lt seh h gt int main yord char p NULL __try Advanced C programming with Icc win32 157 __ except EXCEPTION EXECUTE HANDLER printf Ooops there was a problem with this program n printf Please call the maintenance team at 0 800 XXX n return 0 This will print De Lec mess testorest Ooops there was a problem with this program Please call the maintenance team at 0 800 XXX If we change it to fine lLude lt stdio h gt Fine bude lt sehn h gt int main void char p 10 EE a xp 10 printf No exceptions n except EXCEPTION EXECUTE HANDLER printf Ooops there was a problem with th
215. are going to pass to this function actually pointers to characters 1 e machine addresses to the start of character strings so we have to transform the arguments into a type we can work with For doing this we use a cast A cast is a transformation of one type to another type at compile time Its syntax is like this newtype expression In this example we cast a void to a char a pointer to a pointer of characters The whole expression needs quite a lot of reflection to be analyzed fully Return here after reading the section about pointers Note that our array argv can be used as a pointer and incremented to skip over the first ele ment This is one of the great weaknesses of the array concept of the C language Actually 54 Most compilers do not have the C99 standard implemented In those compilers you can t do this and you will have to declare the loop counter as a normal local variable Another reason to stick to Icc win32 Using arrays and sorting 83 arrays and pointers to the first member are equivalent This means that in many situations arrays decay into pointers to the first element and loose their array ness That is why you can do in C things with arrays that would never be allowed in another languages At the end of this tutorial we will se how we can overcome this problem and have arrays that are always normal arrays that can be passed to functions without losing their soul At last we are ready to call o
216. ars We assign to each character an integer from 0 to 256 that s all When we print our results we use that field to get to the name of the character since our array that before qsort was neatly ordered by characters is now ordered by frequency As before we write the character as a letter with the c directive and as a number with the od directive When we call this program with frequencies frequencies c we obtain at last 1311 chars in file D Il O OD w WO 102 Fh ma Il lt ajl al foafoa WO OV oO ve Ol OV J CO O lt 70 67 100 93 Hm Hm CO xe xwe xwe we w wa a l a a ee S a ee ee ee OO ws Q WO lt a o Il Ol N Lm am e AEA E Using structures 97 We see immediately that the most frequent character is the space with a count of 154 followed by the letter e with a count of 77 then n with 60 etc Strange where does z appear Ah yes in sizeof And that I Ah in FILE ok seems to be working 1 19 1 Fine points of structure use 1 When you have a pointer to a structure and you want to access a member of it you should use the syntax pointer gt field 2 When you have a structure OBJECT not a pointer you should use the syntax object field Beginners easily confuse this 3 When you have an array of structures you index it using the normal array notation syntax then use the object or the p
217. art of the name of the place where this customer lives e a double precision number containing the current balance e atime t time type date of last transaction e and other bit fields for storing some flags struct mailMessage Message Lb Li Gime date char Sender char Subject char Text char Attachements by This one starts with another type containing the message ID again a time t to store the date then the addresses of some character strings The set of functions that use a certain type are the methods that you use for that type maybe in combination with other types There is no implicit this in C Each argument to a function 1s explicit and there is no predominance of anyone A customer can send amailMessage to the company and certain functions are possible that handle mailMessages from customers Other mailMessages aren t from custom ers and are handled differently depending on the concrete application Because that s the point here an application is a coherent set of types that performs a certain task with the computer for instance sending automated mailings or invoices or sensing the temperature of the system and acting accordingly in a multi processing robot or whatever It is up to you actually Note that in C there is no provision or compiler support for associating methods in the struc ture definitions You can of course make structures like this struct customer 4 TAE LD char N
218. art then with a simple program to read files from the internet 4 2 Protocols Protocols are standardized exchanges between two automata a client that asks some infor mation or resource from the server automaton that manages that information and sends it through the network The information exchanged can be anything an image sound an e mail hyper text you name it It can be even a pdf file where you read this lines 4 3 The HTTP Protocol The Hyper Text Transfer Protocol relies on transactions i e a standardized exchange between two computers Within a HTTP transaction you exchange information with another computer elsewhere on a network The information exchanged can be a file that contains data in the form of text sound video or whatever or it can be the results of a database query A piece of information exchanged over a network is called a resource Normally the computer that sends a resource is the server and the computer that receives that resource is a client The process of obtaining a resource using the HTTP protocol requires that a series of mes sages be exchanged between the client and the server The client begins the transaction by sending a message that requests a resource This message is called an HTTP request or some times just a request An HTTP request consists of the following components 1 Method Uniform Resource Identifier URI protocol version number 2 Headers 3 Entity body Th
219. aseDC NULL HDC return hPal l II Create a 24 bit per pixel surface II HBITMAP Create24BPPDIBSection HDC hDC int iWidth int iHeight BITMAPINFO pmi HBITMAP hom LPBYTE PBLts Initialize to 0s ZeroMemory amp bmi sizeof bmi Initialize the header bmi bmiHeader biSize sizeof BITMAPINFOHEADER bmi bmiHeader biWidth iWidth bmi bomiHeader biHeight iHeight bmi bomiHeader biPlanes 1 bmi bmiHeader biBitCount 24 bmi bmineader biConpression BI RGB Create the surface hom CreateDIBSection hDC amp bmi DIB RGB COLORS amp pBits NULL return hbm OC 324 C Tutorial II Print the entire contents including the non client area of the specified window to the default printer BOOL PrintWindowToDC HWND hWnd HBITMAP hbm HDC hdcPrinter HDC hdcMemory HDC hdcWindow int iWidth ine i1Height DOCINEO di RECT ig DIBSECTION ds HPALETTE hPal Do we have a valid window if IsWindow hWnd return FALSE Get a HDC for the default printer hdcPrinter GetPrinterDC if hdcPrinter return FALSE Get the HDC for the entire window hdcWindow GetWindowDC hWnd Get the rectangle bounding the window GetWindowRect hWnd amp rc Adjust coordinates to client area O rrTselkect rc re leit re top gt Get the resolution of the printer device iWidth GetDeviceCaps hdcPrinter HORZRES iHeight GetDeviceCaps hdcPrin
220. at connects it to the network as well as a name that uniquely identifies it The network adapter determines the type of network generally either Ethernet WI FI or older types of networks like Token Ring The adapter also controls the media used for the net work coax twisted pair radio waves etc The important thing to recognize is that all of the machines in a simple network like this can communicate with all of the others equally A simple network 368 C Tutorial The machines send electrical signals through the medium used by the network be it coax twisted pair or radio waves This signals are encoded in precise bit patterns called protocols that give meaning to the bit stream To comunicate with one another machines follow specific rules for speech unlike people The slightest interference the slightest error in the sequence and the machines lose completely the conversation and get stuck Protocols are the base of all the network Many protocols have been used in the PC from the early LANMAN days to now where TCP IP has displaced all others With the rise of the internet the internet protocol has been accepted as a quasi universal stan dard This protocol runs over other more basic protocols like the ethernet protocol in the case of coax or token ring or whataver is actually sending and receiving the data But let s get practical Let s start a small program that we can do withouit a lot of effort We will st
221. at starts is the startup stub a small program that does some initialization and calls the main procedure It pushes the arguments to main in the same way as for any other procedure The main function starts by calling another function in the C library called printf This func tion writes characters using a console emulation where the window is just text This envi ronment is simpler conceptually and it is better suited to many things for people that do not like to click around a lot The printf function deposits characters in the input buffer of the terminal emulation program that makes the necessary bits change color using the current font and at the exact position needed to display each glyph Windows calls the graphic drivers in your graphic card that control the video output of the machine with those bits to change The bits change before your hand has had the time to move a millimetre Graphic drivers are fast today and in no time they return to windows that returns control to the printf function The printf function exits then control returns to main that exits to the startup that calls Exit Process and the program is finished by the operating system Your hand 1s still near the return key We have the following phases in this process Hello 9 1 Design time We wrote the program first 2 Compile time We compiled our design 3 Run time The compiled instructions are started and the machine ex
222. at the bias is 127 but in other formats this number will be different The range of this format is from 7f 7fffff to 00800000 in decimal 3 40282347e 38 to 1 17549435e 38 This numbers are defined in the standard header file lt float h gt as FLT MAX and FLT MIN The number of significant digits is 6 defined in float h as FLT DIG 1 35 1 2 Double 64 bit format This format uses one bit for the sign 11 bits for the exponent and 52 bits for the fraction struct doubleFormat 4 unsigned FractionLow unsigned FractionHigh 22 unsigned sign 1 168 C programming with Icc win32 Bits 0 51 contain the 52 bit fraction f with bit 0 the least significant and bit 51 the most sig nificant bits 52 62 contain the 11 bit biased exponent e and bit 63 contains the sign bit s The normalized numbers are represented with iera The bias for the exponent in this case is 1023 The range of this format is from 7fefffff ffffffff to 00100000 00000000 in decimal from 1 7976931348623157e 308 to 2 2250738585072014e 308 This numbers are defined in float h as DBL MAX and DBL MIN respectively The number of significant digits is 15 defined as DBL DIG 1 35 1 3 Long double 80 bit format This format uses one bit for the sign 15 bits for the biased exponent and 64 bits for the frac tion Bits 0 63 contain the fraction the bits 64 78 store the exponent and bit 79 contains the sign struct longdoubleFormat unsigned FractionLow unsigned Frac
223. ated the status bar since we would have to do that again after it is created We will speak about status bar later since that is not crucial now What really is important is the message loop that begins right after we call Show Window while GetMessage amp msg NULL 0O 0 if TranslateAccelerator msg hwnd hAccelTable amp msg TranslateMessage amp msg DispatchMessage amp msg l This loop calls the API GetMessage If that returns TRUE we call the API to translate the accelerators This API will convert a sequence of keystrokes into a WM COMMAND mes sage as it was sent by a menu if it finds a correspondence between the keystrokes and the accelerator table that we loaded just a few lines above If TranslateAccelerator doesn t find any correspondence we go on by calling TranslateMessage that looks for sequences of key pressing and key up messages and does the dirty work of debouncing the keyboard handling repeat sequences etc At last we dispatch our message to the procedure indicated in the win dow class And that is it We loop and loop and loop until we eventually get a WM QUIT that provokes that GetMessage returns FALSE and the while loop is finished 4 Wow Finished We have hardly started What is interesting now is that we have a skeleton to play with We will show in the next sections how we add things like a dialog box etc Summary Windows programming looks intimidating at first But it is just t
224. atements like if or while must be enclosed in parentheses In many languages that is not necessary and people write Ti va by eum GO 7 NOC Lm Cora in C the if statement requires a parentheses if Vasp Eune 36 There is a strong commitment from the part of the compiler writers to maintain the code that was written in the language and to avoid destroying programs that are working When the standards committee proposed the prototypes all C code wasn t using them yet so a transition period was set up Compilers would accept the old declarations without prototypes and just emit a warning Some people say that this period should be over by now it is more than 10 years that we have prototypes already but still new compilers like lcc win32 are supporting old style declarations Errors and warnings 21 The assignment in C is an expression 1 e it can appear within a more complicated expression Le xe Hz o gt 1S 2 OF This means that the compiler generates code for assigning the value of z to x then it compares this value with 13 and if the relationship holds the program will set z to zero 1 6 Errors and warnings It is very rare that we type in a program and that it works at the first try What happens for instance 1f we forget to close the main function with the corresponding curly brace We erase the curly brace above and we try h lec examples gt lcc args c Error aroseC Lo Syntax error Pound end OL Anp
225. ation 0x402004 4 202 500 in decimal contains the start of this data that goes up to 0x402094 4 202 644 When we write a function that should work with the data stored in that structure we give it just the number 4 202 500 That means The Gate starts at 4 202 500 No copying needed very efficient A pointer then is an integer that contains the machine address 1 e the number of the memory location where the data starts The integer that contains a memory location is not necessarily the same as a normal int that can be smaller or bigger than an address In 64 bit systems for instance addresses can be 64 bits wide but int can remain at 32 bits In other systems Win 32 for instance a pointer fits in an integer Pointers must be initialized before use by making them point to an object Before initialization they contain a NULL value if they are defined at global scope or an undefined value if they are local variables It is always a very bad idea to use an uninitialized pointer Pointers 63 Memory locations are dependent on the operating system the amount of memory installed and how the operating system presents memory to the programmer Never make many assumptions about memory locations For instance the addresses we see now under windows 32 bit could radically change in other context where they become 64 bit addresses Anyway under Win32 we use virtual memory so those numbers are virtual addresses and not real
226. ation of the current band SetRect Grectrill 0 Upper left X int 1OnBand fStep Upper left Y reccClient rightri Lower right X int iOnBandt1 fStep Lower right Y Create a brush with the appropriate color for this band hBrush CreateSolidBrush RGB 0O 0 255 i1OnBand Fill the rectangle FillRect nDC arectrill neBrush Get rid of the brush you created DeleteObject hBrush Give back the DC ReleaseDC hWnd NDC 3 21 6 How do I calculate print margins An application can determine printer margins as follows Calculate the left and top margins e Determine the upper left corner of the printable area calling GetDeviceCaps with the PHYSICALOFFSETX and PHYSICALOFFSETY indices For example Init our pt struct in case escape not supported PLx 0F pE y 0 Locate the upper left corner of the printable area pt x GetDeviceCaps PrnDC PHYSICALOFFSETX pt y GetDeviceCaps PrnDC PHYSICALOFFSETY Determine the number of pixels required to yield the desired margin x and y offsets by calling GetDeviceCaps using the LOGPIXELSX and LOGPIXELSY flags Figure out how much you need to offset output to produce the left and top margins for the output in the printer Note the use of the max macro It is possible that you are asking for margins that are not possible on this printer For example the HP LaserJet has a 0 25 unprintable area so we cannot get margins
227. b folder The file commmsg c contains the default procedure and all the machinery necessary for the run time of the framework Using the graphical code generator 283 Now when you save your work all the dialog procedures will be written for you But before we have to tell the framework several things The first will be the prefix to use for all the procedures that will be used in this dialog box We define this in the main properties dialog box obtained when you double click in the dialog title D1g400 is an automatic generated name not very convincing We can put in there a more meaningful name like DlgSearch for instance We will see shortly where this name is used What we want to do now is to specify to the editor where are the events that interest us For each of those events we will specify a callback procedure that the code generated by the editor will call when the event arrives Basically all frameworks no matter how sophisticated boil down to that a quick way of specifying where are the events that you want to attach some code to The events we can choose from are in the properties dialog boxes associated with each ele ment of the dialog box You have the general settings in the properties window associated with the dialog box that appears when you double click in the title and you have the buttons prop erties that appear when you right click in a button Those dialog boxes have generally a standard or Proper
228. bState amp amp keyState VK NUMLOCK amp 1 Simulate a key press keybd_ event VK _NUMLOCK 0 KEYEVENTE EXTENDEDKEY O Simulate a key release keyed event VK NUMLOCK 0 KEYEVENTE EXTENDEDKEY KEYEVENTF KEYUP 0 int Mair vou SetNumLock TRUE To send key strokes to a window you give the focus to the window or control using the SetFo cus API then you simulate the keyboard events you want 3 21 32 How can encrypt and decrypt a character string The easiest way is to use the String library of lcc win32 containers lib Using that it is just a matter of include lt strings h gt FAQ 363 include lt stdio h gt int main void String s Security 1S our business Strencrypt s otrdecrypt s princis n Ss Concent i If you want to stay within the C framework only here is the code for encrypting and decrypt ing a string You should change the interface of course For the purposes of this function a String is a structure with a count and a pointer to the contents include lt windows h gt include lt wincrypt h gt int Strdecrypt String Ssrc HCRYPTMSG hMsg unsigned int cbDecoded char pbDecoded this variables should be changed to some parameters if you want to change the interface of this function coEncodedBlob should contain the length of the blob and pbEncodedBlob should point to the start of it unsigned cbEncodedBlob Strle
229. based in different floating point formats In this formats a number is represented by its sign an exponent and a fraction Because the size and number of registers that any computer can have is limited only a subset of the real number continuum can be used in the calculations The floating point formats are an approximation of the continuum leaving wide gaps between each representable number The range and precision of this subset is determined by the IEEE Standard 754 for the types float double and long double The qfloat and the bignum data types have their own formats 1 35 1 1 Float 32 bit format This format uses one bit for the sign 8 bits for the exponent and 23 bits for the fraction struct LTloatrormat unsigned Fraction 37 unsigned Exponent 8 unsigned sign ly by Bits 0 22 contain the 23 bit fraction f with bit O being the least significant bit of the fraction and bit 22 being the most significant bits 23 30 contain the 8 bit biased exponent e with bit 23 being the least significant bit of the biased exponent and bit 30 being the most significant and the highest order bit 31 contains the sign bit s The normalized numbers are represented using this formula saI eit Here we have an exponent that uses 127 as bias This means that a constant is added to the actual exponent so that the number is always a positive number The value of the constant depends on the number of bits available for the exponent In this form
230. be added as _asm statements sudcals int sbdca ll TVO defined as long long for compatibility reasons with __int 4 big Microsoft s compiler 40 C programming with Icc win32 1 10 Extensions of Ilcc win32 operator opname args type amp id expr int fn int a int b 0 int overloaded fn int int overloaded fn double Redefine one of the operators like or others so that instead of doing the normal operation this function is called instead Identifier will be a reference to a single object of the given type References must be initialized immediately after their declaration Default function arguments If the argument is not given in a call the compiler will fill it with the specified compile time constant Generic functions These functions have several forms of invocation but the same name T Operavor PAT 2a ED A statements int amp ra a pa will be a reference to an integer A closer view 41 1 11 A closer view Let s explain a bit the terms above The table gives a compressed view of C Now let s see some of the details 1 11 1 Identifiers An identifier is a sequence of non digit characters including the underscore _ the lowercase and uppercase Latin letters and other characters and digits Lowercase and uppercase letters are distinct An identifier never starts with a digit There is no specific limit on the maximum length of an identifier but Icc
231. be already used without any extra effort Printf is one of those but are several thousands of pre built functions of all types and for all tastes We present an overview of them in the next section 1 2 2 What are function parameters When you have a function like int En int a a suse 3 the argument named a is copied into a storage area reserved by the compiler for the functions arguments Note that the function fn will use only a copy not the original value For instance Ine orl Cen ve a ati return a tnt En2 702 4 InG D Me fn 5 return b The fn2 function will always return 7 because function fnl works with a copy of b not with b itself This is known as passing arguments by value This rule will not be used for arrays in standard C When you see a statement like 17 If this doesn t work or you receive warnings you have an installation problem unless you made a typing mistake Or maybe I have a bug When writing mail to me do not send messages like It doesn t work Those messages are a nuisance since I can t possibly know what is wrong if you do not tell me exactly what is happening Wedit doesn t start Wedit crashes The computer freezes The sky has a black color Keep in mind that in order to help you I have to reproduce the problem in my setup This is impossible without a detailed report that allows me to see what goes wrong Wedit will make a default project for yo
232. ble in a header file 182 Confusing and 182 Forgetting to close a comment 182 Easily changed block scope 182 Using the or more than once in an expression 183 Unexpected Operator Precedence 183 Extra Semi colon in Macros 184 Watch those semicolons 184 Assuming pointer size is equal to integer size 184 Careful with unsigned numbers 185 Changing constant strings 185 Indefinite order of evaluation 186 A local variable shadows a global one 186 Careful with integer wraparound 186 Problems with integer casting 187 Octal numbers 187 Bibliography 187 Chapter 2 Strings 191 Design criteria 192 Memory management 192 The handling of exceptions 192 Efficiency considerations 193 C and C 193 Description 194 Creating strings 194 Copying 194 Accessing the characters in a String 194 String pointer operations 197 Implementation 198 String functions 198 Joining strings 199 Accessing 200 Mapping and filtering 202 Conversions 203 File operations 204 Reversing a String 205 Searching text 206 Making a string from a pipe 206 Joining strings 209 Strmap 210 Filters 211 Strings in other languages 211 Chapter 3 Windows Programming 213 Introduction 213 WinMain 216 Resources 219 The dialog box procedure 223 A more advanced dialog box procedure 226 User interface considerations 228 Libraries 231 Dynamically linked libraries DLLs 237 Using a DLL 240 A more formal approach 243 New syntax 243 Event oriented programming 243
233. bstr SysAllocString WDesktopDir pPersistPile gt SSave bstr TRUE pPersistFile gt Release SysFreeString bstr 316 C Tutorial pLink gt Release CoUninitialize return 1 int main void Creates horuCut er program filesy bec Worn donee MCOMpLIeryinik Leoc wineZ Compiler As shown this shortcut will produce the output in the desktop so you will get a new short cut to an obj file n ot very clever This can be solved by adding a line like this plimk gt SerworkingDirectory c my documents ree myoroyece References IShellLink Interface documentation 3 19 Error handling under windows The windows API is an ancient software construct Pieces of the original design started with windows 2 x under MSDOS with the 64K limitations of real mode are still buried within it Pieces of the Windows 3 1 16 bit protected mode software are still very much in evidence and the Win32 API is already 8 years old and counting Because those historical reasons there exists a bewildering set of failure results We have actually all possibilities a 1 The boolean convention Returning TRUE for success FALSE for failure This is a simple minded approach that is used in many APIs You code then if DoSomething failure handling The drawback of this convention is that with only two different values there is no room for explaining the failure reasons 2
234. but after the first declaration only declarations should follow For instance if you have SUrUCr i aire sey bie SEruict amp Serucesr for SETUCEF sa Gint 2202 25102244 is allowed but NOT for int i0 Struct a 6 5 2 lt 10e 145 77 Syntax error 1 4 1 2 while The while construct is much more simple It consists of a single test that determines if the loop body should be executed or not There is no initialization part nor increment part The general form 1s while test statement block Any for loop can be transformed into a while loop by just doing CALE while test statement block Increment 1 4 1 3 do The do construct is a kind of inverted while The body of the loop will always be executed at least once At the end of each iteration the test 1s performed The general form 1s do statement block while test Using the break keyword can stop any loop This keyword provokes an exit of the block of the loop and execution continues right afterwards The continue keyword can be used within any loop construct to provoke a jump to the end of the statement block The loop continues normally only the statements between the continue keyword and the end of the loop are ignored 1 4 2 Basic types The implementation of the C language by the Icc win32 compiler has the following types built in All this types are part of the standard ANSI C language With
235. c int InitializeApp HWND hDlg WPARAM wParam LPARAM lParam SetFocus GetDlgItem hDlg IDENTRYFIELD return 1 We add this call in the procedure InitializeApp We test and it doesn t work We still have to click in the edit field to start using 1t Why Because when we read the documentation of the WM_ INITDIALOG message it says WM INITDIALOG hwndFocus HWND wParam handle of control to receive focus lInitParam lParam initialization parameter Parameters hwndFocus Value of wParam Identifies the control to receive the default keyboard focus Windows assigns the default keyboard focus only if the dialog box procedure returns TRUE Well that is it We have to return FALSE and our SetFocus API will set the focus to the con trol we want We change that and it works Another bug is gone 0 Note that the SetFocus API wants a window handle To get to the window handle of a control in the dialog box we use its ID that we took care of defining in the dialog editor Basically we give to the SetFocus function the result of calling the API GetDlgItem This is nice since we actually need only one window handle the window handle of the dialog box that windows gives to us to get all other window handles of interest Now comes a more difficult problem When the user presses the OK button we want to get the text that he she entered How do we do that We have two problems in one the first is to decid
236. ccess syntax is the same as for structures we use always the point Using the definition above we can write inte main Yord uniron TatELOat LEL Haron Int loat olntrd arl DINGELL 25 Panciled 2 87 First we assign to the integer part of the union an integer then we assign to the double preci sion part a double Unions are useful for storing structures that can have several different memory layouts In general we have an integer that tells us which kind of data follows then a union of several types of data Suppose the following data structures struct fileSource char FileName int LastUse ie struct networkSource Ine SOC Kets char ServerName int LastUse Le struct windowSource WINDOW window 60 An identifier can also represent a macro or a macro argument but here we will assume that the pre processor already has done its work 94 C programming with Icc win32 int LastUse by All of this data structures should represent a source of information We add the following defines defaine ISFILE 1 define ISNETWORK 2 define ISWINDOW 3 and now we can define a single information source structure struct Source int type union struct fileSource file struct networkSource network struct windowSource window info pa We have an integer at the start of our generic Source structure that tells us which of the fol lowing possible types is the correct one Then we have
237. ce for editing them 1 8 1 Describing a function You place the mouse anywhere within the body of a function and you click the right mouse button A context menu appears that offers you to edit the description of the current function The interface that appears by choosing this option looks like this 40 The IDE of Icc win32 helps you by automatic the construction of those comments Just press edit description in the right mouse button menu Commentaries 29 There are several fields that you should fill Procedure description x Mame multiple Compiles a multiple regular expression Purpose Reads input from standard input Generates a regep structure Seyeral errors are displayed using the complain Emai function handling ba word multiple oid dSlecexamples regexpstry c lines 115 Cancel 1 Purpose This should explain what this function does and how it does it 2 Inputs Here you should explain how the interface of this function is designed the arguments of the function and global variables used if any 3 Outputs Here you should explain the return value of the function and any globals that are left modified 4 Error handling Here you should explain the error return and the behavior of the function in case of an error occurring within its body For the description provided in the screen shot above the editor produces the following out put E EEE E EE E E EEE E E E E E E E E
238. ceive a NULL pointer This would indicate to the calling function that the character wasn t found what is always true if our pointer doesn t point anywhere A more serious problem happens when our string 1s missing the zero byte In that case the program will blindly loop through memory until it either finds the byte is looking for or a zero byte somewhere This is a much more serious problem since if the search ends by finding a random character somewhere it will return an invalid pointer to the calling program This is really bad news since the calling program may not use the result immediately It could be that the result is stored in a variable for instance and then used in another completely unrelated section of the program The program would crash without any hints of what is wrong and where was the failure Note that this implementation of strchr will correctly accept a zero as the character to be searched In this case it will return a pointer to the zero byte 1 15 2 strlen Return the length of a given string not including the terminating zero This is solved by the strlen function We just count the chars in the string stopping when we find a zero byte int strlen char str 70 C programming with Icc win32 char Ip Str while p 0 Dery PeCULE D Sire We copy our pointer into a new one that will loop through the string We test for a zero byte in the while condition Note the expression
239. ch ORK This would do nicely We have now just to fill the gaps Let s start with the easy ones A word we said is a sequence of A Z a z followedby A Z a z 0 9 We write a function that returns 1 if a character is the start of an identifier word int 1swordStart int C IE CC a FECUTE 17 LE C gt gt Tat 66 G lt s uT LECUE d if c gt A amp amp c lt Z LOCUL 3 recurrm 0y This function will do its job but is not really optimal We leave it like that for the time being Remember optimizations are done later not when designing the program Counting words 129 Now we go to the more difficult task of scanning a word into the computer The algorithm 1s simple we just keep reading characters until we find a non word char that stops our loop We use a local array in the stack that will hold until MAXIDLENGTH chars define MAXIDLENGTH 512 Lit SCanword ant Tirstehar FLEE Af int a ly 47 tnd x tor the word butter e 0 Character read char idbuf MAXIDLENGTH 1 Buffer for the word idbuf 0 firstchar We have at least one char c fgetc f Read the next one while isWordStart c c gt 0 amp amp c lt 9 Labour ret cp 7 Sore 2 an the array if i gt MAXIDLENGTH Check for overflow LPrLner stderr NOEL fii COO Long rn Ty recurn 07 Returning zero will break the loop jf An the calling funclion j c fgetc f i Sean
240. complete when DefWindowProc returns WM EXITSIZEMOVE Sent one time to a window after it has exited the mov ing or sizing modal loop 3 9 Window controls A control is a technical name for a child window that has a characteristic appearence and fills a functionality for user input A list box for instance is a child window that has a rectangu lar appearence with lines and scrollbars that displays a list of items When the system creates a dialog box it creates all its child windows according to the specifi cations it finds in the executable file The dialog box procedure is the parent window of all the controls that appear in it When an event happens that possible needs that the control notifies the application about it the control sends a notification message For instance when the user types a character into an edit field the edit control sends a notification to the parent window specifying the character received Notifications can be sent in the form of a WM COMMAND message or in the form of a WM _ NOTIFY message Window controls 255 The following controls send a WM COMMAND message to notify the parent window of an event aor 22 4 Notines the parent window when has boca selected seethe doce the parent window when it has been selected See the doc umentation for the BN XXX messages Combobox These controls are a combination of a list box and an edit field so the notifications it sends are a combination of b
241. cremented and the test will make the routine return 1 the correct answer If n is three we make two passes and bitcount will be two This will be different than 1 and we return zero the correct answer Anh Vu Tran anhvu tran ifrance com made me discover an important bug If you change the declaration of n from unsigned int to int without qualification the above function will enter an infinite loop if n is negative Why When shifting signed numbers sign is preserved so the sign bit will be carried through pro voking that n will become eventually a string of 1 bits never equal to zero hence an infinite loop 1 15 4 Write ispowerOfTwo without any loops After working hard to debug the above program it is disappointing to find out that it isn t the best way of doing the required calculation Here is an idea I got from reading the discussions in comp lang c isPow2 x amp amp x 1 amp x How does this work Algorithm If x 1s a power of two it doesn t have any bits in common with x 1 since it consists of a single bit on Any positive power of two is a single bit using binary integer representation For instance 32 is a power of two It is represented in binary as 100000 32 1 31 is represented as 011111 32 amp 31 is 100000 amp O11111 gt U This means that we test if x 1 and x doesn t share bits with the and operator If they share some bits the AND of their bits will yield some non zer
242. ct n Vs 4 7 4 Sending and receiving data We can receive data from the network using the recv function A typical call looks like this int bytesReceived recv Socket buffer sizeof buffer 0O If we want to receive text we ensure the zero terminated string with buffer sizeof buffer 1 0 bytesReceived recv Socket buffer sizeof buffer 1 0 To send data we use the send function bytesSent send Socket buffer strlen buffer O This sends a character string through the network without the trailing zero 4 7 5 Simplifying sockets programming with Icc win32 Lec win32 provides functions that relieve you from programming all the above A client looks like this Fine lude lt sraro h gt include lt stdlib h gt FineLude nerurtd Leah ine manine arga Char arov 13 Session session ehar bur 25 69 memset amp session 0 sizeof session SeSS10Mn pork 2538 6 sessions Hoot 27 0 0 1 gt if ClientConnect amp session Prantl Unable to connect in goto end Client Server programming using sockets 383 if Send amp session 5 data print Unable to send n goto end if Receive amp session 5 buf printf Unable to receive n goto end buf session BytesReceived 0 printi Received 40 byves 4 5Sin session BytesReceived buf end CloseSession amp Session Simple isn t it A server looks like this fiancilude lt stdio h
243. ction that does that Stremp1 2 3 12 Filters The Strfilter function builds a new string with the characters that fulfill a predicate function passed to it as an argument or 1s a member of a given set For instance if you want to extract all numeric data from a string that contains numbers and other data you use bool isnumeric int c retuim 25s OY Ge GC lt Tr String sl Subject age is 45 years String S2 Strreileer si isnumeric 7 7 Now 62 te 745 Strfilter will also accept a String or char wide character string This means that only characters will be output in the result string that match some character in the given set For instance String sl Subject age is 45 years String 62 Striilter si7 0123456 89 gt 77 Now 62 26 45 Obviously this function accepts also two Strings as arguments 2 4 Strings in other languages Strings are a very common I would say almost universal data type Here is a comparison with the interface provided by other languages Implementation Crt The C strings package is very similar to the one proposed here I used a similar interface on purpose Avoid gratuitous incompatibilities with C Of course essential differences remain in C there are no constructors destructors templates etc C accepts many initializers forms you can write string mystring initial content SELLING MysScring Initial content SEEING S22 sl mystring 0 1 iy
244. cumentation But what happens if there is an event that is not foreseen by the framework With most frame works this is quite a problem happily not here You have just to check the button All in the dialog properties and the framework will generate a call to a default procedure named lt pre fix gt Default at each message There you can handle all events that the operating system sends I have tried to keep the framework open so that unforeseen events can be still treated correctly Another way to customize the framework is to modify the default procedure provided in the library weditres lib The source of that procedure is distributed in the source distributions of 7126 Icc win3 and is relatively easy to modify 126 To find that easily just press F12 and click in its name in the function list 286 C Tutorial 3 14 Customizing controls Under windows you have a set of building blocks at your disposal that is even it 1s quite rich fixed A plain listbox will look like a listbox and there is no obvious way to modify the appearence of it not even for doing such simple things like writing the text in red or painting the background in brown The reason for this is simple there are infinitely many ways of customizing a control and if Windows would provide an API for each one the windows API would not fit in a computer no matter what The solution provided by the system is a general interface that gives you enough elements t
245. d with the 0 flag 1 12 2 2 The precision In floating point numbers formats g G f e E this indicates the number of digits to be printed after the decimal point Used with the s format strings it indicates the maximum number of characters that should be used from the input string If the precision is zero the floating point number will not be followed by a period and rounded to the nearest integer 58 C programming with Icc win32 1 12 3 The size specification This table shows the different size specifications together with the formats they can be used The letter 1 with this formats means long or unsigned LONG The letter 1 with the n format means long 1 G Used with the c character format it means the character string is in wide character format all others No effect is ignored The letters 11 mean long longorunsigned long LONG With this format 11 means long long Cp gio Se With this formats h indicates short orunsigned short Means char or unsigned char Means char orunsigned char i A a E Means that the argument isa Long double Notice that the 1 By Gy Gr Gy modifier has no effect with those formats It is uppercase L Means the argument is of type intmax_ t 1 e the biggest inte ger type that an implementation offers In the case of Icc win32 thisis long long ye Means the argument is of type qf loat 350 bits precision This is an extension of lcc w1n32 Oy Ac Oy My Me
246. d somehow in the size of the system font and there are APIs to get from those units into pixels and from pixels into those units 97 You will be prompted for a header file where are stored the definitions for things like IDD_MAINDIALOG Choose the one generated by the wizard Its name is lt project name gt res h 1 e for a project named test we would have testres h 220 C Tutorial 2 The STYLE statement tells the interpreter which things should be done when creating the window We will see later when we create a real window and not a dialog box window that there can be quite a lot of them In this case the style indicates the appearance DS MODALFRAMBE that this window is visible has a caption and a system menu 3 The CAPTION statement indicates just what character string will be shown in the caption 4 In a similar way the FONT statement tells the system to use Helv 5 The following statements enumerate the controls of the dialog box and their descriptions are enclosed in a BEGIN END block We have two of them a push button that is the default push button and a normal pushbutton 6 the Cancel button Both of them have a certain text associated with them a set of coords as all controls and an ID that in the case of the OK button is the predefined symbol IDOK with the numerical value of 1 and in the case of the Cancel button IDCANCEL numerical value 2 To convert this set of instruction in this languag
247. d the backslash and then we add the rest of the name to build a name like src77 alloc c This done we look again into our program Yes there are things that could be improved For instance we use the 256 to write the number of elements of the array Frequencies We could improve the readability of we devised a macro NELEMNTS that would make the right calcula tions for us That macro could be written as follows define NELEMENTS array sizeof array sizeof array 0 This means just that the number of elements in any array is the size of that array divided by the size of each element Since all elements have the same size we can take any element to make the division Taking array 0 is the best one since that element is always present Now we can substitute the 256 by NELEMENTS Frequencies and even if we change our program to use Unicode with 65535 different characters and each character over two bytes our size will remain correct This construct like many others points to one direction making the program more flexible and more robust to change We still have our 256 in the definition of the array though We can define the size of the array using the preprocessor like this define FrequencyArraySize 256 This allows us later by changing this single line to modify all places where the size of the array 1s needed Lec win32 allows you an alternative way of defining this starre Const ant FPrequencyArray
248. d the keyboard accelerators we create the window the status bar we show our window and then we enter the message loop until we receive a WM QUIT that breaks it We return the value of the wParam parameter of the last message received WM QUIT of course Simple isn t it Now let s look at it in more detail The InitApplication procedure initializes the WNDCLASS structure with a little more care now since we are not using our DefDialogProc any more there are a lot of things we have to do ourselves Mostly that procedure uses the standard settings Static BOOL InitApplication void WNDCLASS wc memset amp wc 0 sizeof WNDCLASS The window style we style CS HREDRAW CS VREDRAW CS DBLCLKS wc lpfnWndProc WNDPROC MainWndProc 246 C Tutorial wc hiInstance hIinst The color of the background wc hbrBackground HBRUSH COLOR WINDOW 1 wc lpszClassName winexampleWndClass The menu for this class wc lpszMenuName MAKEINTRESOURCE IDMAINMENU default cursor shape an arrow wc hCursor LoadCursor NULL IDC ARROW default icon wc hIcon LoadIcon NULL IDI APPLICATION if RegisterClass amp wc return U II TODO Call module specific initialization routines here return 1 The style of the window used is a combination of integer constants like CS HREDRAW and others combined using the OR operator the vertical bar What does this mean This
249. d to integer types do not use the sign bit see unsigned on page 47 Declare that the given object changes in ways unknown to the implementation The compiler will not store this variable in a register even if optimizations are turned on SULUet COO rc 4 Inez ING yy be unsigned n 4 n is an unsigned int of 4 bits unworn dd 4 double d TAC sel hs Pe enum color red green blue t const int a unsigned char a ies volatile int hardware clock 36 C programming with Icc win32 Declare the prototype for the given function dnis soe type id args The arguments are a comma separated list see 3 Prototypes on page 46 i Declare a function pointer called id with the i X RYE ears given return type and arguments list eerie ce ees ene Definition of a function with return type lt type gt int addl int x and arguments lt args gt t Peru rn cr le type fn args statements This is a qualifier that applies to functions If double inline present it can be understood by the compiler as overPi double a a specification to generate the fastest function call possible generally by means of replicating return a 3 14159 the function body at each call site 41 Lec win32 doesn t yet implement the keyword restrict An overview of the whole language 37 1 9 3 Pre processor Double slashes introduce comments up commentary to the end of the line see
250. dA to LL otrvaLlidA r romi 4 t count r mMscCouUnt to capacity from capacity LOscConrene GC Mal loct ron Capacity memcpy LO Content Irom CONLeAL irom Count return true return false PRECONDITION StrvalidA from exc Sare E needed space gt elements To Car Tos ounte tO S SLE newh nccded spacer TO 7 SLENCaAL COs Content PLrOmecOontent elements CO Gaty LO eCount needed space 17 to content to count Os return true 2 3 10 2 Strcat bool EXPORT overloaded StrcatA StringA amp to Stringz S7 if from NULL return true s count strlen from SacapecCtey S Counce s content from return SeenCat lO Sy S cOume 2 3 11 Strmap Char from This function applies a function in sequence to all characters in a string It is useful for imple menting filters or other transformations to a given string For instance if we want to change all characters of a string into upper case we can do the following include lt strings h gt include lt ctype h gt int change int c if islower c c toupper c return C inte main int Argo cnar argy il Strings in other languages 211 SELIG Spal for int i 0 i lt argc i t s argv i sl Strmap s change Printia n Char sl y return OQ This program will output its arguments transformed in uppercase This is an example of course There is already a fun
251. define fn 7987 the definition above will be transformed in int 7987 int a 146 C programming with Icc win32 not exactly what you would expect This can be avoided by undefining the macros that you fear could clash with other identifiers in the program 1 32 1 2 Conditional compilation Very often we need to write some kind of code in a special situation and some other kind in another situation For instance we would like to call the function initUnix when we are in a UNIX environment and do NOT call that function when in other environments Besides we would like to erase all UNIX related instructions when compiling for a windows platform and all windows related stuff when compiling for Unix This 1s achieved with the preprocessor ifdef UNIX lines for the Unix system else lines for other non unix systems endif This means If the preprocessor symbol UNIX is defined include the first set of lines else include the second set of lines There are more sophisticated usages with the elif directive ifdef UNIX Unix stuff elif MACINTOSH Mac stuff elif WIN32 Windows stuff else error Unknown system endif Note the error directive This directive just prints an error message and compilation fails The lines that are in the inactive parts of the code will be completely ignored except of course preprocessor directives that tell the system when to stop Note too that the flow of
252. dle WinHttpQueryDatadyailable WinHttpQueryHeaders WinHttpReadD ata l Clasic We open a session connect and send requests In this case we are concerned only with retrieving the data 1 e a GET request We do then an open we connect and start a request for a resource We read from the headers some info before we read the data it would be nice to check that the resource actually exists and accordingly we read the content of the file or not 4 3 2 Implementation We open a session using the WinHttpOpen API hSession WinHttpOpen L lcc WinHTTP 1 0 WINHTTP ACCESS TYPE DEFAULT PROXY WINHTTP NO PROXY NAME WINHTTP NO PROXY BYPASS 0 370 C Tutorial Check to see if the session handle was successfully created if hSession NULL fRet GetLastError if fRet 0 fRet 1 return fRet The first argument to WinHttpOpen is the name of the application that issues the request for data or user agent The user agent is the client application that requests a document from an HTTP server so that the server can determine the capabilities of the client software In this case we send just a default name WinHttp uses a proxy if needed We rely that a configuration utility has already set up the proxy settings for us and request that WinHttp uses the default configuration If we can t open the session we just return the error code If all goes well we initialize our local variables W
253. dow An application can use the following two methods to translate dialog box units to screen units The MapDialogRect function provides the easier method This function converts dialog box units to screen units automatically For more details on this method please see the documentation for the MapDialogRect func tion in the Microsoft Windows Software Development Kit SDK 132 1 got the idea of this from http www kbcafe com articles HowTo Shell pdf by by Randy Charles Morin 352 C Tutorial Use the GetDialogBaseUnits function to retrieve the size of the dialog base units in pixels A dialog unit in the x direction is one fourth of the width that GetDialogBaseUnits returns A dialog unit in the y direction is one eighth of the height that the function returns For more details on this method see the documentation for the GetDialogBaseUnits function in the Windows documentation of Icc win32 3 21 20 initialize in WM CREATE but the values of my variable change Why Consider this code snippet Switch 1Msg case WM CREATE Pe Le 0s TEOT Ss hs rewurn 30s case WM PAINT hdc BeginPaint hwnd amp ps GetClientRect hwnd amp rect InG ey y for x 0 x lt 20 x t for y 0 y lt 20 ytt DrawBitmapNum hdc hBitmap rect letttx Lo rect topy Lor Pole lx ly 4 EndPaint hwnd amp ps recur Us case WM DESTROY PostQuitMessage 0 return 0 The programmer initializes the array Po
254. e 282 C Tutorial 3 13 Using the graphical code generator As we saw before writing all that code for a simple dialog is quite a lot of work It is impor tant that you know what is going on however But now we can see how we can make Wedit generate the code for us The code generator is not enabled by default You have to do it by choosing the Output item in the resources menu This leads to an impressing looking box like this Files to be generated h winexample winexample c T A Wwinesample winexampleres A FRE xl B Wineamiple Wwinesample res xl h WIheEH aM ple Wine ample 1c LI rrearen rrearen o reene h Wwinexarniple winexample cbk c i Alec Mincluide This dialog shows you the files that will be generated or used by Wedit Those that will be generated have a box at the right to enable or disable their generation The others are used if available but only for reading The last item is an additional path to look for bitmaps icons and other stuff that goes into resources You notice that the first item is disabled You enable it and type the full path of a file where you want Wedit to write the dialog procedures Notice that by default the name of this file is lt name of the project gt c This could provoke that your winexample c that we worked so hard to write could be overwritten gt Choose another name like dialogs c for instance 125 Look in the weditresli
255. e SystemTimeToTzSpecificLocalTime ones a Coordinated Universal Time UTC to a specified time zone s corresponding local time ing function include lt winbase h gt Pine ade lt winnte h gt include lt time h gt vod Unixlimelorilelime time it LPFLLETIME pir Ong kOe Le IL Int 3232 Tosa t LOQO00000 116444 736000000000 pft gt dwLowDateTime DWORD 11 138 C programming with Icc win32 pft gt dwHighDateTime ll gt gt 32 Once the UNIX time is converted to a FILETIME structure other Win32 time formats can be easily obtained by using Win32 functions such as FileTimeToSystemTime and FileTime ToDosDateTime void UnixTimeTosystemlime time t ty LPSYSTEMTIME pst FILETIME ft UnixTimeToFileTime t amp ft FileTimeToSystemTime amp ft pst 1 31 Using structures continued C allows implementation of any type of structure Here is a description of some simple ones so you get an idea of how they can be built and used 1 31 1 Lists Lists are members of a more general type of objects called sequences 1 e objects that have a natural order You can go from a given list member to the next element or to the previous one We have several types of lists the simplest being the single linked list where each member contains a pointer to the next element or NULL if there isn t any We can implement this structure in C like this bypeder struct List struct list Next
256. e startInfo hStdError hWritePipe result invalid SCringA processStarted CreateProcess cmdline arguments lpsa lpsa 1 CREATE NEW PROCESS GROUP NORMAL PRIORITY CLASS NULL NULL amp StartInfo amp pi1 if processStarted WaitForSingleObject pi hProcess INFINITE GetExitCodeProcess pi hProcess unsigned long amp Status CloseHandle pi hProcess CloseHandle pi hThread m 1 208 C programming with Icc win32 else m QO if tparams file fcl se tparams file if m 4 result Strfromfile tmpfile 1 remove tmpfile return resulti 2 3 9 1 Searching strings There are several find functions Here 1s an overview This functions perform primitive string searches For more sophisticated searches use the reg SErCEING 21st OF Finds the first character in a string that matches a given set For instance using the set of the tab character and space it finds the first whitespace character in a string Sirrind Jest or Finds the last character that matches the given set Using the example above it would find the last white space character Strfind first not of Find the first char not in the given set String ast NOt OT Find the last char not in the given set Shrcspn Finds the index of the first char that matches any of the given set The difference with Strfind_first_of is in the return value Strcspn returns the length of the string in case of error Strfind first of returns 1 F
257. e compiler emit all the warnings it would normally suppress You call the compiler with Lcc A lt filenames or set the corresponding button in the IDE in the compiler configuration tab Errors can appear in later stages of course The linker can discover that you have used a proce dure without giving any definition for it in the program and will stop with an error Or it can discover that you have given two different definitions maybe contradictory to the same identi fier This will provoke a link time error too But the most dreaded form of errors are the errors that happen at execution time 1 e when the program is running Most of these errors are difficult to detect they pass through the compila tion and link phases without any warnings and provoke the total failure of the software The C language is not very forgiving what programmer errors concerns Most of them will provoke the immediate stop of the program with an exception or return completely nonsense results In this case you need a special tool a debugger to find them Lcc win32 offers you such a tool and you can debug your program by just pressing F5 in the IDE Summary e Syntax errors missing semi colons or similar are the easiest of all errors to correct e The compiler emits two kinds of diagnostic messages warnings and errors e You can rise the compiler error reporting with the A option e The linker can report errors when an identifier is defined
258. e to 1 2 1 Program input If you know how an integrated development environment IDE works you can skip this sec tion When you click in the icon of Icc win32 you start a program designed to make it easy for you to type your program and to find information about it When you start it for the first time it will display a blank window expecting that you tell it what it should do The first thing to do is to go to the File menu and select the New gt File item This will indi cate to the IDE that you want to start a new program module You get prompted with a small window that asks for the file name Just enter hello c You will see than that a blank sheet of paper opens where you can enter the text of the program You should type the program as shown and pay attention to avoid any typing mistake Remember the machine doesn t under Versions Window Help a x wedit hello i temp hello c l File Edit Search Project Design Compiler include lt stdioc h lint maini voidi Utils printf hello n return I hello exe Built successfully 0 3 sec E build search stand anything If you forget a quote or any special sign it will not work and the compiler will spit error messages that can be confusing Check that you type exactly what you see above Once this is done you can compile and link edit your program by just clicking in the compile menu or pressing F9 7
259. e 51 a amp g expri amp expr2 Bitwise XOR expr1 with expr2 See Bitwise Lon 2 Lg TARA operators on page 51 Bitwise OR expr1 with expr2 See Bitwise 1 2 ae 3 eee operators on page 51 Evaluate expr1 If its result is zero stop evaluating the whole expression and set the result of the whole expression to zero If not continue evaluating expr2 The result of the expression is the logical AND of the results of evaluating each expression See Logical operators on page 50 a lt 5 amp amp a gt 0 This will be 1 if a is between to 4 Ifa gt 5 the second test is not performed expri amp amp expr2 Evaluate expr If the result is one stop evaluating the whole expression and set the result of the a a expression to 1 If not continue evaluating expr2 This will be 1 if either aisSor3 The result of the expression is the logical OR of the results of each expression See Logical operators on page 50 If expr evaluates to non zero true return vall a b 2 3 expr vall val2 otherwise return val2 a will be 2 if b is true 3 see Conditional operator on page 44 otherwise expr exprl Multiply expr by expr1 and store the result in expr expr exprl Divide expr by expr1 and store the result in expr f Calculate the remainder of expr expr1 and store expr 3 exprl i a 6 the result in expr expr exprl Add expr1 with expr and store the result in
260. e Cancel button If the user pressed OK we search the text within the text that the editor has loaded in the func tion DoSearch How will our function CallDialog look like Here it is int CallDialog int id DLGPROC proc LPARAM parameter int DialogBboxParam hAlnst MAKE INTRESOURCE 2d hwndMain proc parameter return r We could have returned the value of the DialogBoxParam API immediately but I like storing function return values in local variables You never know what can happen and those values are easily read in the debugger We have to write a dialog function much like the one we wrote for our string DLL above We write a rough skeleton and leave the details for later BOOL CALLBACK SearchDlgProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam Switch msg case WM INITDIALOG return TRUE case WM CLOSE EndDialog hwnd 0 break return FALSE This does nothing it doesn t even put the text in the received parameter but what we are inter ested in here is to first ensure the dialog box shows itself Later we will refine it I develop software like this as you may have noticed I try to get a working model first a first approxi mation Then I add more things to the basic design Here we aren t so concerned about design anyway since all this procedures are very similar to each other The other procedure that we need DoSearchText is handled similarly int DoSearchTe
261. e Winsock you should call the WSAStartup function giving it the ver sion number you want to use and the address of a WSADATA structure where windows writes information about the type of network software that is running A typicall call would be WSADATA wsadata if WSAStartup MAKEWORD 2 1 amp wsaData 0 return GetLastError The cryptic MAKEWORD 2 1 means we want at least version 2 1 of the network software Note that the library included with Icc win32 doesn t need this step since it will perform it automatically if it detects that the network wasn t initialized 4 7 1 2 Creating a socket Once initilized we can create a socket trough which we are going to send and receive the data We call for this the socket function SOCKET socket socket AF INET SOCK STREAM LPPROTO TCP Iy The error report of the socket call is a return value of INVALID SOCKET A typical sequence would be if Socket INVALID SOCKET printf Error Sld n WSAGetLastError Note that under the UNIX operating system socket descriptors are equivalent to file handles This is not the case under windows Furthermore under UNIX all sockets descriptors are small positive numbers This is not the case under windows You will see under UNIX code that looks like this Client Server programming using sockets 381 Ss socket if s 1 1E or see EO E PERN This will not work under windows or produce a seri
262. e actually calling a specific intrinsic routine of the compiler to perform the addition of two integers Conceptually it is like 1f you were doing int a 6 b 8 Int c operatorthi a b This operator function is inlined by the compiler The compiler knows about this operation and several others and generates the necessary assembly instructions to perform it at run time Lec win32 allows you to define functions written by you to take the place of the built in oper ators For instance you can define a structure complex to store complex numbers Lec win32 allows you to write COMPLEX operator COMPLEX A COMPLEX B Code for complex number addition goes here This means that whenever the compiler sees a b and a is a COMPLEX and b is a COM PLEX it will generate a call to the previously defined overloaded operator instead of com plaining about a syntax error This is called in tech speak operator overloading There are several rules for writing those functions and using this feature All of them explained in depth in the user s manual This short notice is just a pointer to show you what is possible The implementation of this feature 1s compatible with the C language that offers a similar facility Many other languages provide this functionality including for instance the venerable FORTRAN language gt 1 34 1 1 How to use this facility Operator overloading is a powerful
263. e context menu using the information returned by the control in the item handle hti hnewMenu CreateContextMenu hti f the creation of the menu did not work stop if hnewMenu HMENU O break menultem TrackPopupMenu hnewMenu TPM RIGHTBUTTON TPM TOPALIGN TPM RETURNCMD DEL peL lt y O hwnd NULLI DestroyMenu hnewMenu Here we would do some action indicated by the menultem code break This code begins with a cast of the Param message parameter into a pointer to a NMHDR structure Then it examines the passed notification code If it is a right click it fills a TV_ HITTESTINFO structure with the coordinates of the mouse and translates those into the coordinates of the tree control that this code supposes in a global variable hwndTree The control should return either NULL meaning there is no item at that position or the handle of an item that was right clicked with the mouse If there was an item a context menu is created shown and the result is an integer indicating which menu item was chosen if any This is one of the many ways you can interact with the window system Each control will have its own interface since they are all different and perform quite different actions You can see the above code in action when you click with the right button in an item of the project workspace window in Wedit You use the CreateWindow API with a predefined window class You pass it as the parent window parameter
264. e first argument of this call it s the address within the infile structure of the FindData Extending a program 107 member We take the address with the amp operator Since we are using a pointer we have to dereference a pointer i e with gt and not with the Note that the amp operator is used with the fd local variable to obtain a pointer from a structure member memcpy amp infile gt FindData amp fd SiZzeCr Struce finddata TI infile gt file fopen fd name rb intile gt handle findfirstResult return infile void Initialize void this is the same as the function before int ProcessStream STREAM instream CHARS Frequencies int count 0 int c fgetc instream gt file while c EOF count t Le G T T Freguencies c Frequencytt c fgetc instream gt file return Count void DisplayOutput CHARS Frequencies this is the same function as before STREAM GetNext STREAM stream STREAM result Struct Dinddata Fd long tindnextResule faindgnexe stream handile ird if findnextResult lt 0 return NULL result malloc sizeof STREAM memcpy amp result gt FindData amp fd SIze Struct fanddata Ut result gt handle stream gt handle result gt file fopen fd name rb result gt Name stream gt Name return result int main int eargc char argqy int coun
265. e instructions The first one is the define directive that instructs the software to replace a macro by its equivalent We have two types of macros Parameterless For example define PI 3 1415 Following this instruction the preprocessor will replace all instances of the identifier PI with the text 3 11415 Macros with arguments For instance define s2 a b a a b b 2 0 When the preprocessor finds a sequence like s2 x y It will replace it with x F yyh Za The problem with that macro is that when the preprocessor finds a statement like S2 x 6 10 y 4 lt 8 3 It will produce x 6 0 x 6 0 yt6 0 y 6 0 2 0 What will calculate completely another value FOP TO 1220 7 220 To avoid this kind of bad surprises it is better to enclose each argument within parentheses each time it is used define s2 a b a a b b 2 0 This corrects the above problem but we see immediately that the legibility of the macros suf fers quite complicated to grasp with all those redundant parentheses around Another problem arises when you want that the macro resembles exactly a function call and you have to include a block of statements within the body of the macro for instance to declare a temporary variable define s2 x y int temp x xty y x tempty tempt6 If you call it like this LE X lt i SZ a iy else x 0 This will be expanded to IE We A OW eane temp XA y RS cempry
266. e into a binary resource file that windows can interpret we use a compiler called a resource compiler Microsoft s one is called rc Borland s one is called brc and Icc win32 s one is called lrc All of them take this resource language with some minor extensions depending on the compiler and produce a binary resource file for the run time interpreter of windows The resource compiler of Icc win32 is explained in detail in the technical documentation and we will not repeat that stuff again here For our purposes it 1s enough to know that it 1s compat ible with the other ones The binary resource files generated by the resource compiler are passed to the linker that con verts them into resource specifications to be included in the executable Note that actually you do not need to know this language because the IDE has a resource edi tor that can be used to build graphically using drag and drop the dialog box But the emphasis here is to introduce you to the system so that you know not only what button should you push but why you should push that button too But we wanted originally to make a dialog box containing an edit field We are far away from our objective yet Introduction 221 We come back to Wedit after closing our text file dialog rc and we go to the Design menu bar and press Open new 8The resource editor opens up and we see the following display wt Wedit listbox resource listbox O
267. e later case this is a variable length array Define a new type name for the old type see typedef on page 45 Try to store the identifier in a machine register The type of identifier will be equivalent to signed integer if not explicitly specified see int als Mitt Spa pa will be a pointer to integers Mie epee Arra 756 7 Array of 56 ant pointers typedef unsigned we unt register Int f register on page 45 The definition of the identifier is in another extern Lat extern type id i module No space is reserved frequency Make the definition of identifier not accessible static type id Stacie ine i from other modules struct id declarations union id declarations yi enum identifier enum list const type identifier unsigned int type volatile type identifier Define a compound type composed by the enumeration of fields enclosed within curly braces Within a structure field declaration declare id as a sequence of n bits of type type See bit fields on page 47 Reserve storage for the biggest of the declared types and store all of them in the same place see union on page 45 Define an enumeration of comma separated identifiers assigning them some integer value see enum on page 46 Declare that the given identifier can t be changed assigned to within this scope see const on page 46 When applie
268. e library if not it will return us an INVALID HANDLE as defined in windows h After loading the DLL we can get the address of any exported function within that DLL just by calling another windows API GetProcAddress This API receives a valid DLL handle and a character string containing the name of the function to find and will return an address that we can store in a function pointer Let s do this include lt windows h gt 1 tinelude lt staro h gt 2 ine APLENTRY pinGerstring char char Sant 3 int mainint argo char argv Char buffer 1024 HANDLE dllHandle LoadLibrary 4 meleci examo Les dialog lee W dtalog di i if dllHandle INVALID HANDLE VALUE 3 prin i stderr Impossible to Load the GLINI exit 0 PIinGetotring int APIBNTRY Char char int Gethrockddress dlitandle Getstrang dl2 gt 6 if pfnGetString NULL tprintf stderr VIMOOSSiI ble EO find the procedure GerGrri ng n y exit 1 pfnGetString Enter a string buffer sizeof buffer printi Otrin 1S Com butter gt else pinti User cancel led n recurn 0 We go step by step We need to include windows h for getting the prototypes of LoadLibrary and GetProcAd dress besides some constants like INVALID HANDLE VALUE stdio h 1s necessary too since we use fprintf This is a function pointer called pfnGetString that points to a function that return
269. e press the OK button We force the user to enter some text before closing the dialog Since we haven t changed anything in the logic for the Cancel but ton the dialog box will still close when the user presses those buttons Only the behavior of the OK button will change The EndDialog API takes two parameters the dialog box window handle that it should destroy and a second integer parameter The dialog box will return these values as the result of the DialogBox call from WinMain remember Since WinMain returns itself this value as its result the value returned by the DialogBox will be the return value of the program 3 1 4 Amore advanced dialog box procedure Doing nothing and not closing the dialog box when the user presses OK is not a good inter face You expect a dialog box to go away when you press OK don t you A user interface like this makes for an unexpected behavior Besides 1f we put ourselves in the user s shoes how can he she find out what is wrong The software doesn t explain anything doesn t tell the user what to do to correct the situation it just silently ignores the input This is the worst behavior we could imagine Well there are two solutions for this We can disable the OK button so that this problem doesn t appear at all or we could put up a message using our MessageBox API informing the user that a text must be entered Let s see how we would implement the first solution To be really cl
270. e request is sent as plain text over the network It uses the TCP IP port 80 When a server receives a request 1t responds by sending a message back to the client The message sent by the server is called an HTTP response It consists of the following compo nents 1 Protocol version number status code status text 2 Headers 3 Entity body The HTTP Protocol 369 The response either indicates that the request cannot be processed or provides requested infor mation Depending on the type of request this can be information about a resource such as its size and type or can be some or all of the resource itself The part of a response that includes some or all of the requested resource is called the response data or the entity body and the response is not complete until all the response data is received 4 3 1 GetHttpUrl The interface for our function should be as simple as possible It will receive two character strings representing the name of the URL to retrieve and the name of the output file where the file should be stored If you are interested in using the resulting code you can skip this sec tion We start by opening an http session The general schema for an http session 1s like this WinHttpOpen WinHttpConnect WinHttpOpenRegquest WinHttpdddRequestHeaders j Ts WinHttoSetCredentials WinHttpSendRequest WinHttpwWriteD ata WinHttpReceveResponse WinHttp Query 4authsche mes WinHttpcloseHan
271. e screen a print preview 336 How do I change the color of an edit field 337 How do I draw a transparent bitmap 337 How do I draw a gradient background 339 How do I calculate print margins 340 How do I calculate the bounding rectangle of a string of text 341 How do I close an open menu 342 How do I center a dialog box in the screen 342 How do I create non rectangular windows 342 How do I implement a non blinking caret 343 How do I create a title window splash screen 343 How do I append text to an edit control 346 How do I determine the color settings 347 How do I spawn a process with redirected stdin and stdout 348 How to modify the width of the list of a combo box 349 How do I modify environment variables permanently 350 How do I add a menu item to the explorer right click menu 351 How do I translate between dialog units and pixels 351 I initialize in WM_CREATE but the values of my variable change Why 352 How do I translate between client coordinates to screen coordinates 352 When should I use critical sections and when is a mutex better 353 Why is my call to CreateFile failing when I use conin or conout 353 How can I conttrol the task bar under program control 353 How to erase a file into the recycle bin 354 Making a timed message box 358 How do I build a Property sheet control 360 How to tell Windows to run a program during startup 361 How do I disable the screen saver 361 How do I play a sound 362 How do
272. e several things to explain here 1 We move the declaration of our static buffer that was before further down to the beginning of the file so that we can use this buffer in the GetString procedure to copy its contents into the destination buffer 2 We declare our flag for testing if the class has been registered as a static int 1 e an integer visible only in this module We do not need to initialize it to zero since the C language guarantees that all non explicitly initialized static variables will be set to zero when the program starts 3 We modify the declarations of local variables in the GetString procedure adding a result integer variable and a HANDLE that will hold the instance of the current module Before we received this as a parameter in the arguments of WinMain but now we have to get it by some other means The solution is to call the GetModuleHandle API to get this We indicate it that we want the handle of the currently running executable by passing it a NULL parameter 4 We test then our global flag classRegistered If it 1s zero we haven t registered the class and we do it now Afterwards we set the variable to one so that this piece of code will not be executed again 5 We call our DialogBox procedure just like we did before but now we assign its result to an integer variable and we test 1f the result is one 1 e the user pressed OK If that is the case we copy the string from the temporary buffer to the de
273. e vertical bars align Explain why that option needs a complete rewrite of our program What is the hidden assumption above that makes such a change impossible Another feature that paste exe could have is that column headers are automatically under lined Explain why adding such an option 1s falling into the featurism that pervades all modern software Learn when to stop 1 16 Using arrays and sorting Suppose we want to display the frequencies of each letter in a given file We want to know the number of a s of b and so on One way to do this is to make an array of 256 integers one integer for each of the 256 possible character values and increment the array using each character as an index into it When we see a b we get the value of the letter and use that value to increment the corresponding posi tion in the array We can use the same skeleton of the program that we have just built for counting characters modifying it slightly 2 include lt stdio h gt tincrude lt stalriboih gt int Frequencies 256 Array of frequencies imne Main Int ro eC nee aor Local variables declarations int count 0 ELE ira kes 1a Ce er if arge lt 2 4 50 Yes code reuse is not only possible in object oriented programming 78 C programming with Icc win32 printf Usager countchars lt file name gt n exit 1 infile fopen argv 1 rb if infile NULL printt File s doesn t exist n
274. e when we want to get the text and the other is how to get that text 100 This example shows you how to get rid of those problems and the kind of problems you will encounter when programming under Windows The only solution in most cases is a detailed reading of the documentation Fortunately Windows comes with a clear documentation that solves most problems 101 All the notifications messages from edit fields begin with the EN prefix meaning Edit field Notification Introduction 225 For the first one the answer is clear We want to read the text only when the user presses the OK button If the Cancel button is pressed or the window is closed we surely aren t interested in the text if any We will read the text then when we handle the message that the OK button window sends to us when is pressed We change our dialog procedure like this case WM COMMAND Switch LOWORD wParam case IDOK ReadText hwndD1lg EnaDialog hwndDlg 1 return 1 case IDCANCEL EnaDialog hwndDlog 0 7 return 1 break We add a call to a function that will get the text into a buffer That function looks like this static char butter LOZA int ReadText HWND hwnd memset buffer 0 sizeof buffer if GetDlgItemText hwnd IDENTRYFIELD Purto sizeof buffer return Ly return 0 We define a buffer that will not be visible from other modules hence static We set a fixed buffer with a reasonable amount of s
275. e zero the rcContext structure where we store the relevant information for our session and we translate the name of the URL into UNI CODE The winhttp primitives are all in UNICODE and there is no ANSI equivalent 7 Initialize local stwtt ZeroMemory amp urlComp sizeof urlComp urlComp dwStructSize sizeof urlComp memset amp rcContext 0 sizeof rcContext mostowcs szWURL url i strien url 7 Use allocated buffer to store the Host Name urlComp lpszHostName szHost urlComp dwHostNameLength 617608 SZHOSE Sizeor szHost 0 Set non zero lengths to obtain pointer to the URL Path note if we threat this pointer as a NULL terminated string this pointer will contain Extra Into as well urlComp dwUrlPathLength 1 Crack HTTP scheme urlComp dwSchemeLength 1 Parsing an URL 1s a tricky business that we better leave for an API than trying to do this our selves if WinHttpCrackUrl szWURL O O amp urlComp goto cleanup Note that all errors are processed using a goto cleanup what simplifies the error handling The famous goto statement is not that bad after all This is it We attempt to open a connection now Open an HTTP session reContext hConnect WinHttpConnect hSession szHost ur lLComp nPorc 0 if NULL rcContext hConnect goto cleanup Note that no actual connection will be done until we start a request This is a GET
276. eListSize should contain the correct buffer size needed szCounterListBuffer LPTSTR malloc dwCounterListSize szinstanceListBuffer LPTSTR malloc dwinstanceListS1ize if szCounterListBuffer NULL szIinstanceListBuffer NULL printf nUnable to allocate buffers return 1 pdhStatus PdhEnumObjectItems NULL reserved NULL local machine Process object to enumerate szCou terListBuffer pass in NULL buffers amp dwCounterListSize an 0 length to get szInstanceListBuffer vrequired size amp dwiInstanceListSize of the buffers in chars PERF DETAIL WLAARD counter detail level 0 if pdhstatus ERROR SUCCESS 1 printf nRunning Processes walk the return instance list for szThisInstance sziInstanceListBuffer szThisinstance l 0 szThisInstance strlen szThisInstance 1 printi n ss szThisinstance Some Coding Tips 331 if szCounterListBuffer NULL free szCounterListBuffer if szInstanceListBuffer NULL free szInstanceListBuffer return 0 3 20 22 Changing a File Time to the Current Time The following example sets the last write time for a file to the current system time using the SetFileTime function BOOL SetFileToCurrentTime HANDLE hFile FPILETIME ft SYSTEMTIME st BOOL gt GetSystemTime amp st gets current time SystemTimeToFileTime amp st amp ft converts to file time format f
277. eak for instance if we had forgotten the call to the Re lease method at the end or it could use resources that are never released the list of identifiers that we obtain from the system etc 3 18 3 Retrieving a file from the internet The basic way of receiving sending data in the internet is TCP IP a protocol originally devel oped for Unix systems and adapted later to windows by Microsoft under the name of win sock for window sockets The first versions of TCP IP for windows were very difficult to use and required a good deal of network programming knowledge the code for establishing an FTP connection under win dows 3 1 was several thousand lines and required watching each transaction and following each possible error This has changed a lot since the internet wave required that each coffee machine in the world should have an internet connection Higher level interfaces were developed and added to the standard windows API Here is an example of a working program that will download the README file from the Icc win32 home q software solutions and write it to the disk of your machine in the current directory finciude lt stavo h gt include lt string h gt include lt windows h gt finclude lt direct HS include lt wininet h gt static void ErrorOut char where int err GetLastError pPranLr heror 2d Oxex when calling SAn errer where gt int main void DWORD dwType ETP TRANSF
278. ear the OK button should start disabled but become active immediately after the user has typed some text If during editing the user erases all text that has been entered the OK button should revert to its inactive state We can do this by processing the messages that our edit field sends to us Edit fields are very sophisticated controls actually a full blown mini editor in a small window Each time the user types anything in it the edit field procedure sends us a WM COMMAND message informing us of each event We change our dialog procedure as follows case WM COMMAND Switch LOWORD wParam case IDOK suppressed stays the same case IDCANCEL EndDialog hwndDlg 0 return 1 case IDENTRYFIELD switch HIWORD wParam Case EN CHANGE it GetDlgItemText hwndDlg IDENTRYFIELD burtier sa1zeo0t burter 4 FnableWindow GetDlgItem hwndDlg IDOK 1 else EnableWindow GetDlgItem hwndDlg IDOK 0 break break Introduction 227 break We add a new case for this message But we see immediately that this nested switch state ments are getting out of hand We have to split this into a function that will handle this mes sage We change again our dialog box procedure as follows case JDCANGCEL EndDialog hwndDlg 0 return 1 case IDENTRYFIELD return EntryFieldMessages hwndDlg wParam This is much clearer We put the code for handling the entry field messages in its own proce dure En
279. ecutes what we told it to do 1 2 6 1 We wrote the program first The central point in communicating with a printed circuit is the programming language you use to define the sequence of operations to be performed The sequence is prepared using that language first in your own circuit your brain then written down with another the keyboard controller then stored and processed by yet another a personal computer PC 1 2 6 2 We compiled our design Compiled languages rely on piece of software to read a textual representation first translating it directly into a sequence of numbers that the printed circuit understands This is optionally done by assembling several pieces of the program together as a unit 1 2 6 3 Runtime The operating system loads the prepared sequence of instructions from the disk into main memory and passes control to the entry point This 1s done in several steps First the main executable file is loaded then all the libraries the program needs When everything has been mapped in memory and all the references in each part have been resolved the OS calls the initialization procedures of each loaded library If everything goes well the OS gives control to the program entry point 10 C programming with Icc win32 1 3 An overview of the standard libraries This headers and the associated library functions are found in all ANSI compliant compilers 7 Header complex cypesh ero Floating point environment
280. ed since the application started or whatever Important is that you remember that in that function all initializations for this dialog box should be done including memory allocation populating list boxes checking check buttons or other chores The second callback will be called when the user presses the OK button What do you want to do when this event happens In our example we would of course start the search or setup a set of results so that the procedure that called us will know the text to search for and possibly other data Different controls will react to different events You may want to handle some of them For instance you may want to handle the event when the user presses a key in an edit field to check input You can use the framework to generate the code that will trap that event for you and concentrate in a procedure that handles that event How would you do this Using the graphical code generator 285 You open the properties dialog of the edit control and check the Update message This will prompt the editor to generate a call to a function of yours that will handle the event The details are described in the documentation of the resource editor and will not be repeated here What is important to retain are the general principles at work here The rest is a matter of read ing the docs to find out which events you can handle for each object in the dialog and writing the called functions with the help of the windows do
281. ed to draw transparent bitmaps e Create a DC to hold the image bitmap e Select the image bitmap into the DC e Create a memory DC to hold the final image This is the destination DC e Copy the portion of the screen that will be covered by the image into the destination DC e Create an AND mask that contains the mask of the colors to draw the nontransparent portions of the image To do this perform the following three steps e Set the background color of the image DC to the color that will be transparent in the image e Create a monochrome DC e BitBlt the image into the monochrome DC This will create an AND mask of the bitmap by setting pixels that match the background color to white 1 and setting all other pixels to black 0 e Use BitBlt with the SRCAND raster operation code to copy the AND mask onto the destination DC Use BitBlt with the SRCAND raster operation code to copy the inverse of the AND mask onto the image DC Use BitBlt with the SRCPAINT raster operation code to copy the image DC onto the destination DC Use BitBIt to copy the contents of the destination DC to the appropriate portion of the screen The following code is a function that demonstrates the preceding steps void DrawTransparentBitmap HDC hdc HBITMAP hBitmap short xStart short youatu COLORREF elransparentColor 338 C Tutorial BITMAP bm COLORREF CCOlor HBITMAP bmAndBack bmAndObject bmAndMem bmSave HBITMAP bmBackOld bmObject
282. ee that the DialogBox API was called in our WinMain function see above We should modify this call then but a new prob lem appears where does WinMain know which string to pass to the DialogBoxParam API Well we could decide that this string would be the parameters passed to WinMain in the IpC mdLine argument This is the most flexible way We modify then the call to DialogBox like follows return DialogBoxParam hinst MAKEINTRESOURCE IDD MAINDIALOG NULL DLGPROC DialogFunc int lpCmdLine Since our dialog box is now constructed with DialogBoxParam we receive in the Param mes sage parameter the same pointer that we gave to the DialogBoxParam API Now we have just to set that text in the caption of our dialog box and it s done We do that again in our initial ization procedure by adding SetWindowText hDlg char 1Param The SetWindowText API sets the caption text of a window if that window has a caption bar of course To test this we have to tell Wedit to pass a command line argument to the program when it calls the debugger or executes the program with Ctrl F5 We do this by selecting the debugger tab in the configuration of wedit File Edt Search Project Sesources aor lnerlleaaeWdeam dial Linker Lang Froect Help E Detugger 230 C Tutorial The debugger tab is in the upper left corner When we select it we arrive at the following tab Configuration of Wedit these
283. efer to use the registry then you need to create a new entry for your program in the HKEY LOCAL MACHINE Software Microsoft Windows CurrentVersion Run registry folder Windows will launch every program that is in this folder when the OS boots Your reg istry entry should be a string value The value of the string should be the full path to the exe cutable you want to run 3 21 29 How do I disable the screen saver In the main loop of your window procedure answer TRUE to the WM SYSCOMMAND mses sage like this 362 C Tutorial case WM SYSCOMMAND if wParam SC_SCREENSAVE return TRUE This disables the screen saver 3 21 30 How do play a sound You have several APIs to choose from PlaySound It will play a sound file name or a resource from the executable You have a flags argument to specify repeating or other characteristics MessageBeep Just a beep not very sophisticated waveOutxxx This are a series of functions to play sounds with much more control and fine tuning possibilities than the two functions above DirectX The Direct X software contains a direct sound API 3 21 31 How do simulate a key stroke to send it to another window You use the keybd_ event API Here is a simple code that turns on the NumLock key finelude lt windows h gt void SetNumLock BOOL bState BYTE Kkeyotvace 756 9 GetKeyboardState LPBYTE amp keyState if bState amp amp keyState VK NUMLOCK amp 1
284. egEdt32 exe when editing these values manually However note that modifications to the environment variables do not result in immediate change For example if you start another Command Prompt after making the changes the environment variables will reflect the previous not the current values The changes do not take effect until you log off and then log back on To effect these changes without having to log off broadcast a WM SETTINGCHANGE mes sage to all windows in the system so that any interested applications such as Program Man ager Task Manager Control Panel and so forth can perform an update FAQ 351 For example on Windows NT the following code fragment should propagate the changes to the environment variables used in the Command Prompt SendMessageTimeout HWND BROADCAST WM SETTINGCHANGE 0 LPARAM Environment SMTO ABORTIFHUNG 5000 amp dwReturnValue None of the applications that ship with Windows 95 including Program Manager and the shell respond to this message Thus while this article can technically be implemented on Windows 95 there is no effect except to notify third party applications The only method of changing global environment variables on Windows 95 is to modify the autoexec bat file and reboot 3 21 18 How do I add a menu item to the explorer right click menu When you press the right mouse button within the explorer window there is a pop up menu that shows you a series of options like
285. ell FindWindow Progman NULL PostMessage hwndShell WM QUIT 0 OL WinEkxec Explorer exe SW SHOW 3 20 13 Translating client coordinates to screen coordinates To determine the screen coordinates for the client area of a window call the ClientToScreen function to translate the client coordinates returned by GetClientRect into screen coordinates The following code demonstrates how to use the two functions together RECT rMyRecr GetClientRect hwnd LPRECT amp rMyRect ClientToScreen hwnd LPPOINT amp rMyRect left ClientToScreen hwnd LPPOINT amp rMyRect right 3 20 14 Passing an argument to a dialog box procedure You can pass a void to a dialog box procedure by calling result DialogBoxParam hInst Instance of the application MAKEINTRESOURCE id The resource ID or dialog box name GetActiveWindow The parent window DiGin The dialog box procedure DWORD Hello The arguments In your dialog box procedure here DlgFn you will find those arguments in the Param parameter of the WM _ INITDIALOG message 3 20 15 Calling printf from a windows application Windows applications do not have a console 1 e the DOS window To access the console from a Windows application create one initialize stdout and use it as you would normally use it from a native console application include lt windows h gt include lt stdio h gt include lt font int main void
286. en created but before the dialog is visible in the screen Here is done the initialization of the dialog box data structures or other things The wizard inserts here a call to a procedure for handling this message 99 You put the cursor under the WM_INITDIALOG identifier and press F1 224 C Tutorial 2 WM COMMAND This message is sent when one of the controls or child windows if you want to be exact has something to notify to the dialog a button has been pressed a check box has been pressed data has been entered in an entry field etc Since we can have several controls we use again a switch statement to differentiate between them Switch statements can be nested of course 3 WM CLOSE This message arrives when the user has pressed the close button in the system menu or has typed the Alt F4 keyboard shortcut to close the dialog Now the whole purpose of this exercise 1s to input a character string The text is entered by the user in our entry field It is important from a user s perspective that when the dialog box is displayed the cursor is at the beginning of the entry field It could be annoying to click each time in the entry field to start editing the text We take care of this by forcing the focus to the entry field Under windows there is always a single window that has the focus 1 e receives all the input from the keyboard and the mouse We can force a window to have the focus using the SetFo cus API Stati
287. ents a font for windows We get that integer using the GetStockObyect API This function receives an integer code indicating which object we are interested in and returns it There are several types of object we can get from it fonts brushes pens etc 1 Yet another point missing in our dialog box is a correct title or prompt The title of our dialog is now just dialog This tells the user nothing at all A friendlier interface would tell the user 103 Now is a good time to read the documentation for that API It will not be repeated here 104 We introduced that to see if we were really getting a string Since now we are returning that data to the calling program that message should disappear User interface considerations 229 what data the software is expecting from him her We could change the title of the dialog to a more meaningful string The program calling our dialog procedure could give this string as a parameter to the dialog box Dialog boxes can receive parameters as any other procedure They receive them in the parameters passed to the WM_INITDIALOG message A closer look to the documentation of the WM_INITDIALOG message tell us that the Param message parameter contains for the WM INITDIALOG 32 bits of data passed in the last parameter of an API called DialogBoxParam We have to modify our calling sequence to the dialog and instead of using DialogBox we use the DialogBoxParam API Looking into our program we s
288. epaint the rectangle that windows passes to us in that parameter Then we call the code to draw our galaxy and inform windows that we are done with painting Well this finishes the coding We need to add the include lt math h gt include lt time h gt at the beginning of the file since we use functions of the math library and the time function to seed the srand function We compile and we obtain el winexample Oy x File Edit Help T ea a sat yf E a a Peo r foul PPa al C ee eat sak Tana i ph al dete i MT EEE It would look better if we make a better background and draw more realistic arms but for a start this is enough 272 C Tutorial There are many functions for drawing under windows of course Here is a table that provides short descriptions of the most useful ones Function Purpose AngleArc Draws a line segment and an arc Draws an elliptical arc using the currently selected pen You specify the bounding rectangle for the arc ArcTo is similar to the Arc function except that the current position 1s updated Returns the current arc direction for the specified device context Arc and rectangle functions use the arc direction Draws a line from the current position up to but not LineTo l l l including the specified point MoveToEx Updates the current position to the specified point and optionally returns the previous position GetArcDirection Pol
289. er This is done using the fopen library function If the file exists and we are able to read from it the library function will return a pointer to a FILE structure defined in stdio h If the file can t be opened it returns NULL We test for this condition right after the fopen call We can read characters from a file using the fgetc function That function updates the current position 1 e the position where the next character will be read 51 Global variables provoke an undocumented coupling between several apparently unrelated procedures or modules Overuse of them is dangerous and provokes errors that can be difficult to understand and get rid of I learned this by experience in long debugging sessions and now I use global variables more sparingly Using arrays and sorting 79 But let s come back to our task We update the array at each character within the while loop We just use the value of the character that must be an integer from zero to 256 anyway to index the array incrementing the corresponding position Note that the expression Frequencies count means Frequencies count Frequencies count 1 1 e the integer at that array position is incremented and not the count variable Then at the end of the while loop we display the results We only display frequencies when they are different than zero 1 e at least one character was read at that position We test this with the statement if Frequencies count
290. er described in the windows documentation We will speak about opaque data structures later A COLORREF 1s a triple of red green and blue values between zero black and 255 white that describe the colors of the point We use a simple schema for debugging purposes we paint the first arm black 0 0 0 and the second red 255 0 0 In event oriented programming the question is which event will provoke the execution of this code Windows sends the message WM PAINT to a window when it needs repainting either because its has been created and it is blank or it has been resized or when another window moved and uncovered a portion of the window We go to out MainWndProc function and add code to handle the message We add case WM PAINT dopaint hwnd break We handle the paint message in its own function This avoids an excessive growth of the MainWndProc function Here it is void dopaint HWND hwnd PAINDSTRUCT pS HDC EDC hDC BeginPaint hwnd amp ps DrawGalaxy hDC 3 0 20000 2500 074000 0 13 1 7 EndPaint hwnd amp ps We call the windows API BeginPaint passing it the address of a PAINTSTRUCT a struc ture filled by that function that contains more information about the region that is to be painted etc We do not use it the information in it because for simplicity we will repaint the Numerical calculations in C 271 whole window each time we receive the message even if we could do better and just r
291. erability of the Decade Crispin Cowan Perry Wagle Calton Pu Steve Beattie and Jonathan Walpole Department of Computer Science and Engineering Oregon Graduate Institute of Science amp Technology URL http downloads securityfocus com library discex00 pdf Bibliography 189 190 C programming with Icc win32 191 strings Strings are a fundamental data type for a wide type of applications We have seen in the pre ceeding chapters the problems that C strings have Here is a proposal for a string library that allows you to avoid those problems It was started by Friedrich Dominicus and after his initial push we have both worked together in this The whole source code is available to you for easy customization At any time you can build a specialized version of it to fit a special need or to change one of the design parameters The string library is based in the abstract notion of a container 1 e a common set of interface functions that allow you some latitude when building your program Using the abstract index ing notation you can change your data representation from a vector to an array or even from a list to a vector without being forced to change a lot in your own programs Strings are a sequence of characters We can use one or two bytes for storing characters Occi dental languages can use fewer characters than Oriental languages that need two bytes to store extended alphabets But occidentals too need more than one byte in
292. eral way of using arrays and other data structures 1s possible 2 2 Description 2 2 1 Creating strings The simplest way to create strings is to assign them a C string For instance Selig w hws ee Sur Lag To allocate a string that will contain at least n characters you write Selig 6 Mew Str hag Cn The primitive new_ string is a versatile function It can accept also a character string SCING S S Mew String This IS 2a SL ring or a double byte character string Derg eS New string Ua has ae ce aS CENG Ty 2 2 2 Copying When you assign a String to another you make a shallow copy Only the fields of the String structure will be copied not the contents of the string To copy the contents of the string you use the copy function or its synonym Strdup String 62 copy sl 7 7 Equivalent to Strdup s1 Destructively copying a string is done with the Strcpy function String ol any pA Mabed Stropy sl752 7 Now sl contains Taped To destructively copy a certain number of characters into another string you use the Strncpy function Sering sa Veber Gar Zsa aoe SErncpy s1 S2 5 j7 Now sL contains I2 4p 2 2 3 Accessing the characters in a String The notation is used to access the characters as in normal C character strings Given the string Sering SL Tabo you access each character with an integer expression Description 195 me os Sie ff Now e Contains pb Yo
293. ere are a few examples of very simple programs The idea is to find a self contained solution for a problem that is simple to state and understand 1 15 1 strchr Find the first occurrence of a given character in a character string Return a pointer to the char acter if found NULL otherwise This problem is solved in the standard library by the strchr function Let s write it The algorithm is very simple We examine each character If it is zero this 1s the end of the string we are done and we return NULL to indicate that the character is not there If we find it we stop searching and return the pointer to the character position GHJE PimdCnearinoer ing ener Str aime en while str 0 amp amp str ch Stet if str ch return str return NULL We loop through the characters in the string We use a while condition requiring that the char acter pointed to by our pointer str is different than zero and it is different than the character given In that case we continue with the next character by incrementing our pointer 1 e mak ing it point to the next char When the while loop ends we have either found a character or we have arrived at the end of the string We discriminate between these two cases after the loop How can this program fail We do not test for NULL Any NULL pointer passed to this program will provoke a trap A way of making this more robust would be to return NULL if we re
294. es of compiler warnings about signed unsigned comparisons The preferred style is as shown above comparing explictely with the INVALID SOCKET constant 4 7 2 Server side 4 7 2 1 Binding a socket For a server to accept client connections it must be bound to a network address within the sys tem This code demonstrates how to bind a socket to an IP address and port Client applica tions use the IP address and port to connect to the host network First we create a sockkaddr object that contains the type of network we use AF INET the server IP number we use the local loop address 127 0 0 1 and the port in that IP number we want to connect to We can use any port number between 1024 and 65535 sockaddr in service Servicesin lani l y AF INET SOLViCe sin dddres addr S 1net lt addrt TLZ rusga jy Services sim port Atons 49025 Jy Second we bind the socket to this network address int re pindi mosoOcket SOCKADDR GSSrvice SLZ6OR Service J if rc SOCKET ERROR Prin et bine Tare kAnin 4 7 2 2 Listening on a socket After the socket is bound to an IP address and port on the system the server must then listen on that IP address and port for incoming connection requests To listen on a socket call the listen function passing the created socket and the maximum number of allowed connections to accept as parameters if listen Socket 1 SOCKET ERROR princi Error Listening Om Sockeu
295. es of type DataPoint as defined above Note that we could have written GC malloc 804 since we have struct DataPoint struct coordinate coords Lit Data De We can add the sizes Two integers of 4 bytes for the coordinate member makes 8 bytes plus 4 bytes for the Data member makes 12 that multiplies 67 to make 804 bytes But this is very risky because of two reasons Compiler alignment could change the size of the structure If you add a new member to the structure the sizeof specification will continue to work since the compiler will correctly recalculate it each time If you write the 804 however when you add a new member to the structure this number has to be recalculated again making one more thing that can go wrong in your program In general it is always better to use compiler calculated constants like sizeof instead of hard wired numbers 1 18 3 Defining new types Structures are then a way of augmenting the type system by defining new types using already defined ones The C language allows you to go one step further in this direction by allowing you to specify a new type definition or typedef for short This syntax for doing this 1s like this typedef lt already defined type gt lt new name gt For instance you can specify a new type of integer called my integer with typedef int my integer Then you can use this new type in any position where the int keyword would be expected
296. es the current local date and time GetSystemTime Retrieves the current system date and time Determines whether the system is applying periodic time GetSystemTimeAdjustment adjustments to its time of day clock at each clock interrupt along with the value and period of any such adjustments GetSvstemTimeAsFileTime Obtains the current system date and time The information is in y Coordinated Universal Time UTC format Retrieves the number of milliseconds that have elapsed since the GetTickCount a system was started It is limited to the resolution of the system timer Retrieves the current time zone parameters These parameters GetTimeZoneInformation control the translations between Coordinated Universal Time UTC and local time een PAET Converts a local file time to a file time based on the Coordinated LocalFileTimeToFileTime Universal Time UTC eee Sets the date and time that a file was created last accessed or last SetFileTime modified SetLocalTime Sets the current local time and date Sets the current system time and date The system time is expressed See LL in Coordinated Universal Time UTC SetSystemTimeAdjustment Tells the system to enable or disable periodic time adjustments to its time of day clock SetTimeZonelInformation Sets the current time zone parameters These parameters control translations from Coordinated Universal Time UTC to local time SystemTimeToFileTime Converts a system time to a file tim
297. eton of a windows application Let s see it in more detail We start as always in the same place We go to the WinMain function and we try to figure out what is it doing Here it is int WINAPI WinMain HINSTANCE hinstance HINSTANCE hPrevinstance LPSTR lpCmdLine INT nCmdShow MSG msg HANDLE hAccelTable Saves in this global variable the instance handle that must be passed as an argument to many window functions hinst hiInstance f the initialization of the application fails WinMain exits if linitApolicarion return U Loads the keyboard accelerators for common menu options hAccelTable LoadAccelerators hinst MAKEINTRESOURCE IDACCEL Creates the main window and exits if it can t be created if hwndMain CreateApplWndClassWnd HWND 0 return 0 7 Creates the status bar at the bottom of the main window CreateSBar hwndMain Ready 1 Shows the main window ShowWindow hwndMain SW_ SHOW Starts the message loop When the main window post the quit message GetMessage will return NULL while GetMessage amp msg NULL 0O 0 if TranslateAccelerator msg hwnd hAccelTable amp msg TranslateMessage amp msqg DispatchMessage amp msqg Returns the wParam of the WM_ QUIT message return msg wParam We have the same schema that we saw before but this time with some variations We start the application registering the window class etc we loa
298. etrieve an appropriate screen font e Get the character width from the TEXTMETRIC structure returned by the EnumFonts function in step 2 above Use this information to calculate the page position of each character to be printed in the printer font e Allocate a block of memory and specify the spacing between characters Make sure that this information is in screen resolution units e Specify the address of the memory block as the lpDx parameter to ExtTextOut GDI will space the characters as listed in the array 3 21 3 How dol change the color of an edit field See page 286 3 21 4 How do I draw a transparent bitmap A portion of a graphic image that does not change the contents of the screen is termed trans parent The DrawIcon function can create an image that contains transparent portions It is also possible to obtain this functionality using the BitBlt function however there are some additional steps involved The first step is to obtain the contents of the area where the bitmap will be drawn and to store this background image in a memory display context DC Mask out the area of the back ground that corresponds to the nontransparent portion of the image bitmap and mask out all transparent pixels from the image bitmap Use the XOR raster operation to merge the image bitmap into the background bitmap Finally use the BitBlt function to move the merged image to the destination DC The following nine steps describe a process us
299. ets trans mitted connections etc you can measure exactly how is the performance of your network application 4 6 Writing ping Ping 1s a small program that attempts to send an echo request to another machine If the response arrives the other machine is up and running if not well there is a problem with the physical connection somewhere or the other machine is down Simple Lec win32 provides a ping function that can be used to ping a host under program con trol To use that it is just necessary to include the ping h header file The simplest program using ping can be written like this include lt ping h gt include lt stdio h gt int main int argo char fargyv hI PingInterface p memset amp p 0 Ssizeof p p HostName argv l if ping amp p ps ia DELOC Host Ts LS UPN yaron LLIN else Print Host 2s 25 down n aroyv i 4 4 6 1 How does it work The algorithm followed by the implementation of ping is to open a connection a socket using the raw state 1 e without using any higher level protocol not even the TCP protocol Using this socket we write an ICMP packet Internet Control Management Protocol into the buffer we are going to send and we wait for the answer When the answer arrives we record how much time it took for the packet to make the round trip It sounds simple but it isn t It took me quite a while to make an implementation that i
300. eturn PSNRET NOERROR case WM COMMAND switch HIWORD wParam Handle the messages from the controls here exactly as you would in a dialog box break return OQ When designing the dialog boxes of your property sheet keep in mind that all dialog boxes should have the same size Windows will adjust the size of the dialog boxes but they will not look very good if they were designed with different sizes When you have designed all dialog boxes and written all dialog box procedures you have all data necessary to call the PropertySheet API This API takes a complicated set of parameters in a custom structure One way to fill this structures is the following define NUMBEROFPAGES 16 Static void DoPropertySheet HWND hwndOwner PROPSHEETPAGE psp NUMBEROFPAGES PROPSHEETHEADER psh int i memset psp 0 sizeof psp FAQ 361 First we fill the PROPSHEETPAGE array with some items that will be common to all pages This is not necessary and maybe you will find it useful to fill individually this settings for i 0 i lt NUMBEROFPAGES it psp i dwSize sizeof PROPSHEETPAGE psp i dwFlags PSP USETITLE PSP DEFAULT psp i hInstance hInst l Now we starting filling each page with the unique information it needs We fill the resource ID the callback procedure and the title 2 U psp i pszTemplate MAKEINTRESOURCE IDD GENERALSETTINGS pspla pEnDIGgProce EditInto psp i p
301. etwork functions see Retrieving a file from the internet page 313 3 17 11 Hooks A hook is a mechanism by which a function can intercept events messages mouse actions keystrokes before they reach an application The function can act on events and in some cases modify or discard them This filter functions receive events for example a filter func tion might want to receive all keyboard or mouse events For Windows to call a filter function Etc 305 the filter function must be installed that is attached to an entry point into the operating system a hook for example to a keyboard hook If a hook has more than one filter function attached Windows maintains a chain of those so several applications can maintain several hooks simultaneously each passing or not its result to the others in the chain 3 17 12 Shell Programming Windows provides users with access to a wide variety of objects necessary for running appli cations and managing the operating system The most numerous and familiar of these objects are the folders and files but there are also a number of virtual objects that allow the user to do tasks such as sending files to remote printers or accessing the Recycle Bin The shell organizes these objects into a hierarchical name space and provides users and applications with a con sistent and efficient way to access and manage objects 3 17 13 Services A service application conforms to the interface rules of t
302. exi printf Exception handler 1X n GetExceptionCode Sleep 2000 return Q0 1 34 5 6 The _ retry construct You can correct the error condition that provoked the exception and then restart again using the retry construct A simple example of this is the following include lt stdio h gt include lt seh h gt int main void char p NULL ty d op SIAT printi 3s n p except EXCEPTION EXECUTE HANDLER 4 p abc __ Kerry return Q0 Advanced C programming with Icc win32 163 The first execution of the try yields an exception since the pointer p is NULL Within the except block we correct this condition by assigning to that pointer a valid value then we restart with the retry The output of this program is Abc 1 34 6 The signal function Besides the structured exception handling mechanism outlined above Icc win32 offers the standard signal utility of the standard C language 1 34 6 1 Software signals Software signals are the same thing as the exceptions we described in the proceeding para graphs They can be raised by the CPU traps or simply raised by the function raise To give you an idea of how this mechanism works let s repeat the example of above structured exception handling using the signal mechanism include lt signal h gt Finclude lt stdio h gt include lt stdlib h gt For exit This function will be called by the signal mechanism
303. f any of them is provided in this tutorial But before we start just a quick answer to the question why learn C C has been widely criticized and many people are quick to show its problems and drawbacks But as languages come and go C stands untouched The code of Icc win32 has software that was written many years ago by many people among others by Dennis Ritchie the creator of the language itself The answer to this question is very simple if you write software that is going to stay for some time do not learn the language of the day learn C C doesn t impose you any point of view It is not object oriented but you can do object ori ented programming in C if you wish It is not a functional language but you can do functional programming with it if you feel like Most LISP interpreters and Scheme interpreters compil ers are written in C You can do list processing in C surely not so easily like in lisp but you can do it It has all essential features of a general purpose programming language like recur sion procedures as first class data types and many others that this tutorial will show you Many people feel that C lacks the simplicity of Java or the sophistication of C with its tem plates and other goodies True C is a simple language without any frills But it 1s precisely this lack of features that makes C adapted as a first time introduction into a complex high level language that allows you fine contro
304. f arguments in the call It is not possible to declare a function overloaded after a call to this function is already gener ated The following code will NOT work decals 2377 int overloaded docals double pd Here the compiler will signal an error 156 C programming with Icc win32 1 34 4 Default arguments Default arguments allow you to simplify the interface of a function by providing arguments that if not present will assume a default value For instance Int LY aint D 7s This declares a function called fn that takes one argument and optionally a second When the second is not given the compiler will arrange for it being 78 For instance PAZ is equivalent to Phe Oo y 1 34 5 Structured exception handling 1 34 5 1 Why exception handling As you know very well the following program will provoke a trap include lt stdio h gt int main void char p NULL ky 0e B 07 printf This will never be reached n return OF There is no way you can catch this trap and try to recover or at least exit the program with an error message This means that there isn t any way for you to prevent your program from failing catastrophi cally at the smallest error It suffices to have a bad pointer somewhere and you are doomed If you use a third party library you have to trust it 100 meaning that the slightest problem in the library will provoke the end of your application The whole
305. f f OO Scarr free buf LOCUL CrUS else return false Everything looks normal and perfect in the best of all worlds here We test if the size if smaller than a specified limit and we then allocate the new string But what happens if cbSize is zero Our call to malloc will ask for 0 1 bytes and using 32 bit arithmetic we will get an integer wrap around to OxfffffL f f or 1 We are asking then for a string of 4GB The program has died in the spot 87 I got this example from the excellent column of Michael Horward in the msdn security column Bibliography 187 1 37 15 Problems with integer casting In general the compiler tries to preserve the value but casting from signed to unsigned types can produce unexpected results Look for instance at this sequence Char 0x802 7 128 now we cast it to short short s shore ec now s Oxff80 still 128 unsigned short us unsigned short s us Oxff80 which is 65408 In general you should not try to mix signed unsigned types in casts Casts can occur automatically as a result of the operations performed The operators addi tion bitwise negation minus will cast any type shorter than an int into a signed int If the type is larger than an integer it will be left unchanged 1 37 16 Octal numbers Remember that numbers beginning with zero are treated as number written in base 8 The number 012 is decimal 10 not 12 This error is di
306. f the characters We leave that calculation to the GetCharBmpOftset function lines 26 27 2 Using that rectangle we copy the bits from our memory bitmap to the display using the BitBlt API lines 28 30 3 The rest of the lines in the loop updates the position of the destination and take care of advancing to the next line 4 Lines 44 48 concern the cleanup We tell windows that we are finished with drawing using the EndPaint API line 44 We deselect our bitmap from the memory device context line 45 then we delete the memory DC Note that we must do things in that order since a bitmap can t be deleted if it is selected in a DC Then we delete the background brush we created 294 C Tutorial 3 16 The Registry The registry stores data in a hierarchically structured tree Each node in the tree is called a key Each key can contain both sub keys and values Sometimes the presence of a key 1s all the data that an application requires other times an application opens a key and uses the values associated with the key A key can have any number of values and the values can be in any form Registry values can be any of the following types e Binary data e 32 bit numbers e Null terminated strings e Arrays of null terminated strings The array ends with two null bytes e Expandable null terminated strings These strings contain variables like sPATH or Swindirs that are expanded when accessed 3 16 1 The structure of the regist
307. f the combo box Windows sends it a WM CTLCOLOR message with the HIWORD set to CTLCOLOR LISTBOX when the list box control needs to be painted The LOWORD of the Param contains the handle of the list box control Once you obtain the handle to the list box control window you can resize the control by using the MoveWindow API The following code sample demonstrates how to do this This sample assumes that you have placed the combo box control in a dialog box LRESULT CALLBACK NewComboProc HWND hWnd UINT message WPARAM wParam LPARAM 1Param prototype for the combo box subclass proc HANDLE hiInst 7 Current app instance BOO bFirst A flag ji Dialog procedure for the dialog containing Che combo box BOOL CALLBACK DialogProc HWND hDlg UINT message WPARAM wParam LPARAM lParam FARPROC lpfnNewComboProc Switch message case WM INI TDIALQG bFirst TRUE Set flag here see below for usage Subclass the combo box lpfnOldComboProc FARPROC SetWindowLong GetDigitem hnDig IDC COMBOL jy GWL WNDPROC LONG NewComboProc break case WM DESTROY FARPROC SetWindowLong GetDlgItem hDlg TDG COMBOT Jy GWL WNDPROC LONG tpin0 LdaCombOoProc 7 break default break return FALSE E77 End dialog proc 350 C Tutorial Combobox subclass proc LRESULT CALLBACK NewComboProc HWND hWnd UINT message WPARAM wParam LPARAM lParam static HWND hwndhList Static RECT rectui
308. fficult to find because everything will com pile without any error after all this is a legal construct 1 38 Bibliography Here are some books about C I recommend you to read them before you believe what I say about them C Unleashed Richard Heathfield Lawrence Kirby et al Heavy duty book full of interesting stuff like structures matrix arithmetic genetic algorithms and many more The basics are covered too with lists queues double linked lists stacks etc Algorithms in C Robert Sedgewick I have only the part 5 graph algorithms For that part that covers DAGs and many others I can say that this 1s a no nonsense book full of useful algorithms The code is clear and well presented C a reference manual Fifth edition Samuel P Harbison Guy L Steele Jr If you are a professional that wants to get all the C language described in great detail this book is for you It covers the whole grammar and the standard library with each part of it described in detail The C programming language Brian W Kernighan Dennis Ritchie second edition This was the first book about C that I got and it is still a good read With many exercises it 1s this tutorial in a better rendering A retargetable C compiler design and implementation Chris Fraser and Dave Hanson This book got me started in this adventure It is a book about compiler construction and not really about the C language but if you are interested
309. fies if a given font is a device font Get a DC for the screen Convert the IfHeight and IfWidth members of the LOGFONT structure from printer resolution units to screen resolution units If a mapping mode other than MM TEXT is used round off error may occur Call CreateFontIndirect with the LOGFONT structure Call SelectObject GDI will select the appropriate screen font to match the printer font Release the printer device context or information context and the screen device context If a screen font that corresponds to the selected printer font 1s not available the process 1s more difficult It is possible to modify the character placement on the screen to match the printer font to show justification line breaks and page layout However visual similarity between the printer fonts and screen fonts depends on a number of factors including the num ber and variety of screen fonts available the selected printer font and how the printer driver describes the font For example if the printer has a serifed Roman style font one of the GDI serifed Roman style fonts will appear to be very similar to the printer font However if the printer has a decorative Old English style font no corresponding screen font will typically be available The closest available match would not be very similar To have a screen font that matches the character placement of a printer font do the following FAQ 337 e Perform the preceding seven steps to r
310. findfirst argv 1 amp fd if findfirstResult lt 0 printf File s doesn t exist n argv 1 return NULL infile malloc sizeof STREAM infile gt Name argv 1 memcpy amp infile gt FindData amp fd sizeof struct finddata t infile gt File fopen fd name rb infile gt handle findfirstResult return Inia les We store in the local variable findfirstResult the long returned by findfirst We test then if smaller than zero 1 e if something went wrong If findfirst failed this is equivalent to our former program when it opened a file and tested for NULL 104 C programming with Icc win32 But now comes an interesting part If all went well we ask the system using the built in mem ory allocator malloc for a piece of fresh RAM at least of size STREAM If this call fails there is no more memory left For the time being see later we ignore this possibility We want to store in there all the parameters we need to use the findfirst findnext function pair with easy and we want to copy the finddata_t into our own structure and even put the name of the stream and a FILE pointer into it To do that we need memory and we ask it to the mal loc allocator Once that done we fill the new STREAM with the data e we Set its name using the same pointer as argv 1 e we copy the fd variable into our newly allocated structure and e we Set the file pointer of our new structure with fopen so
311. for this band hBrush CreateSolidBrush RGB O 0 255 iOnBand Fill the rectangle FillRect hDC amp rectFill hBrush Get rid of the brush you created DeleteObject hBrush be 14 Give back the DC ReleaseDC hWnd NDC 3 20 7 Capturing and printing the contents of an entire window II Return a HDC for the default printer II HDC GetPrinterDC void PRINTDLG pdlg Some Coding Tips 323 memset amp pdlg 0 sizeof PRINTDLG pdlg 1lStructSize sizeof PRINTDLG pdlg Flags PD RETURNDEFAULT PD RETURNDC PrintDig odlaG return pdlg hDC II Create a copy of the current system palette II HPALETTE GetSystemPalette HDC HDC HPALETTE hPal HANDLE hLogPal LPLOGPALETTE IpLogPal Get a DC for the desktop hDC GetDC NULL Check to see if you are a running in a palette based video mode if GetDeviceCaps hDC RASTERCAPS amp RC PALETTE ReleaseDC NULL HhDC return NULL Allocate memory for the palette lpLogPal GlobalAlloc GPTR sizeof LOGPALETIE 256 sizeof PALETTEENTRY if hLogPal return NULL Initialize lpLogPal gt palVersion 0x300 lpLogPal gt palNumEntries 256 Copy the current system palette into the logical palette GetSystemPaletteEntries hDC 0 256 LPPALETTEENTRY lpLogPal gt palPalEntry Create the palette hPal CreatePalette lpLogPal Clean up GlobalFree lpLogPal Rele
312. g arrays and sorting 77 One of the first things to notice is that the program tests with strcmp to see if two files are the same This means that when the user passes the command line paste Filel filEl our program will believe that they are different when in fact they are not Windows is not case sensitive for file names The right thing to do there is to compare the file names with stricmp that ignores the differences between uppercase and lowercase But an even greater problem is that we do not test for NULL when opening the files If any of the files given in the command line doesn t exist the program will crash Add the necessary tests before you use it Another problem is that we test if we have the right number of arguments i e at least two file names but if we have more arguments we simply ignore them What is the right behavior Obviously we could process and paste several files at once Write the necessary changes in the code above Note that if you want to do the program really general you should take into account the fact that a file could be repeated several times in the input 1 e paste filel file2 filel file3 Besides the separator char in our program is now hardwired to the tab character in the code of the program Making this an option would allow to replace the tab with a vertical bar for instance But the problem with such an option is that it supposes that the output will be padded with blanks for making th
313. g single byte strings and StrepyW for copying wide char strings 192 C programming with Icc win32 You can use the generic names with only one type of strings either wide or ascii but not both These names are implemented like this ifdef UNICODE define Strcpy StrcpyWw else define Strcpy StrcpyA endif Of course both functions are available if called explicitely The advantage of this schema is that there is only one set of names and a simple rule for using all the string functions To copy a string you use Strcpy period The functions are patterned after the traditional C functions but several functions are added to find sets of characters in a string or to read a file into a string In general the library tries as hard as possible to mimic the known functions and notation of the existing C strings The string library introduces the concept of iterators or fat pointers This data structure con sists of a pointer to some character within the container in this case the string a count and a pointer to the whole strings String pointers are called Stringp and they come in two flavors too wide and single byte strings There are two properties of the string you will want to have access to its length and its capac ity The length is the number of characters that the string contains and the capacity is the num ber of characters the string can store before a resize operation is needed You can access those properties w
314. ge wParam lParam HWND hDlg unsigned message WORD wParam FAQ 335 DWORD lParam switch message Use other messages to update the progress or activity indicator se case WM COMMAND Switch wParam case ID CANCEL ID CANCEL 2 Cancel TRUE default return FALSE default return FALSE The following describes the ProgressYield procedure which should be called after each unit of the CPU intensive subtask is completed The ProgressYield procedure uses the IsDialog Message function described in the Microsoft Windows Software Development Kit Refer ence Volume 1 IsDialogMessage will convert keyboard messages into selection commands for the corresponding dialog box void ProgressYield HWND hwnd MSG msg Remove all available messages for any window that belong to the current application a7 while PeekMessage amp msg NULL 0 U PM REMOVE Translate and Dispatch the given message if the window handle is null or the given message is not for the 7 modeless dialog box hwnd if hwnd IsDialogMessage hwnd amp msg TranslateMessage amp msqg DispatchMessage amp msqg The following describes how to incorporate the progress dialog as part of an application s sub task that is CPU intensive The PROGRESS DLG resource should contain a button with an ID of 2 because this is the wParam of the WM COMMAND that will be se
315. given window and the sibling windows of a given window This is true for the desktop window too Let s look at the code of Bui ldTree int BuildTree HWND parent HWND Start GetDesktopWindow HWND hTree GetDlgItem parent IDTREEWINDOW IV INSERTSTRUCT TreeCtrilitem HTREEITEM hNewNode memset amp TreeCtrlitem 0 sizeof TreeCtrlitem HresCtrilitem nrarent IVI ROOT PECCCERLIELCH AINSSI CALCO INI BASTI TreeCtrlitem item mask CVE eT EVLE PARAM TreeCtrlItem item pszText Desktop hNewNode TreeView InsertItem hTree amp TreeCtrliItem Start Getwindow Start GW CHILD Scan hTree hNewNode Start return 1 We start at the start and we ask windows to give us the window handle of the desktop window We will need the tree window handle too so we use Get D1lgItem with the parent window of the tree control and it s ID This works even 1f the parent window is a normal window and not a dialog window We go on by filling our TV INSERTSTRUCT with the right values This is a common inter face for many window functions Instead of passing n parameters we just fill a structure and pass a pointer to it to the system Of course it 1s always a good idea to clean the memory space with zeroes before using it so we zero it with the memset function Then we fill the fields we need We say that this item is the root item that the insertion should happen after the last item that the item will conta
316. grams are easier to automate and make them part of bigger applications as independent components that receive command line arguments and pro duce their output without any human intervention 1 2 4 An overview of the compilation process When you press F9 in the editor a complex sequence of events all of them invisible to you produce an executable file Here is a short description of this so that at least you know what s happening behind the scene Wedit calls the C compiler proper This program is called Icc exe and is in the installation directory of lcc in the bin directory For instance 1f you installed lce in c l cc the compiler will be inc lcc bin This program will read your source file and produce another file called object file that has the same name as the source file but a obj extension C supports the separate compilation model 1 e you can compile several source modules producing several object files and rely in the link editor Icclnk exe to build the executable 19 This has nothing to do with object oriented programming of course Hello 7 Leclnk exe is the link editor or linker for short This program reads different object files library files and maybe other files and produces either an executable file or a dynamically loaded library a DLL When compiling your hello c file then the compiler produced a hello oby file and from that the linker produced a hello exe executable file The linker uses
317. gs in C Forgetting to initialize a pointer is something that you can never afford to do Another error 1s initializing a pointer within a conditional expression char BuggqyFunction int a char result if a gt 34 4 result malloc a 34 return result If the argument of this function is less than 35 the pointer returned will be a dangling pointer since it was never initialized A closer view 55 1 11 32 Precedence of the different operators In their book C a reference manual Harbison and Steele propose the following table Fe i ee e e ma e 9 ei mo estore nary ooo i pee ooo i pe oe itor e amp te 56 C programming with Icc win32 1 12 The printf family The functions fprintf printf sprintf and snprintf are a group of functions to output formatted text into a file fprintf printf or a character string sprintf The snprintf is like sprintf func tion but accepts a count of how many characters should be put as a maximum in the output string Function Prototype TOLI wate Lic Por ener Ce Lie Streams CONS Char Xim asar printf EnC PELMEE CONS Char Ene na SPELET Char OUPpUESEIING CONSE Char Sintrol snprintri 1 Anpe Ne EO har Toute rent Maxchare Const Chiat ATM wsady The printf function is the same as fprintf with an implicit argument stdout 1 e the standard output of the program that in most cases is the console window FOri
318. h We see the following FILE Fopen STREAM stream char name char mode FILE result char fullname 1024 p p strrchr stream gt Name if p NULL fullname 0 0 else xp Q fullname sizeof fullname 1 0 strncpy fullname stream gt Name sizeof fullname 1 strncat fullname sizeof fullname 1 Ao a NE strncat fullname name sizeof fullname 1 result fopen fullname mode if result NULL fprintf stderr Impossible to open Ss n fullname exit ys return result j If p is NULL we will initialize the first char of fullname to zero Then execution continues at the strncat call after the else statement and we will copy at most sizeof fullname 1 chars into it overwriting the zero and maybe leaving the fullname character array without the termi nating zero if the length of the passed buffer is bigger than the size of fullname That could lead to a crash in fopen that surely expects a well formed string The solution is to finish the fullname buffer in ALL cases FILE Fopen STREAM stream char name char mode FILE Pesce char fullname 1024 p p strrchr stream gt Name fullname sizeof fullname 1 0 ii p NULLI 4 fullname 0 O else to S07 strncpy fullname stream gt Name sizeof fullname 1 strncat fullname sizeof fullname 1 116 C programming with Icc win32 Rp ES strncat
319. h array These arrays are based on the evaluation of an expression that is computed when the program is running and not when the program is being compiled Here is an example of this construct ink Function int n int tablelf n The array of integers called table has n elements This n 1s passed to the function as an argument so its value can t be known in advance The compiler generates code to allocate space for this array in the stack when this function is entered The storage used by the array will be freed automatically when the function exits 1 11 17 const Constant values can t be modified The following pair of declarations demonstrates the differ ence between a variable pointer to a constant value and a constant pointer to a variable value CONSE ING IPEE LO Cono tant int const CONS tant ptr A closer view 47 The contents of any object pointed to by ptr to constant shall not be modified through that pointer but ptr to constant itself may be changed to point to another object Simi larly the contents of the int pointed to by constant ptr may be modified but constant ptr itself shall always point to the same location 1 11 18 unsigned Integer types long long long int short and char have the most significant bit reserved for the sign bit This declaration tells the compiler to ignore the sign bit and use the values from zero the 2 for the values of that type For in
320. hTree GetDlgItem hwnd IDTREEWINDOW HT REE LEM HEL HWND hwndStart nmhdr NMHDR lParam Switch nmhdr gt code case NM CLICK memset G testinio 0 si z6e0r lV AITIESTINEO gt GetCursorPos amp testinfo pt MapWindowPoints HWND_ DESKTOP hTree amp testInfo pt 1 hia Sj Preeview Hitlest hires OCES CINTO if hti HTREEITEM 0O break hwndStart GetTreeItemiInfo hTree ht1 SetTextInStatusBar hwnd hwndStart break return DefWindowProc hwnd WM NOTIFY wParam 1Param We just handle the NM CLICK special case of all the possible notifications that this very com plex control can send We use the NMHDR part of the message information that is passed to us with this message in the Param message parameter Our purpose here is to first know if the user has clicked in an item or somewhere in the back ground of the tree control We should only answer when there 1s actually an item under the coordinates where the user has clicked The algorithm then is like this Get the mouse position Since windows has just sent a click message the speed of current machines is largely enough to be sure that the mouse hasn t moved at all between the time that windows sent the message and the time we process it Besides when the user is clicking it is surely not moving the mouse at super sonic speeds Map the coordinates we received into the coordinates of the tree window Ask the tree control if there is a
321. he more complicated GUI Graphical User Interface programs Windows knows how to differentiate between console windows programs by looking at cer tain fields in the executable file itself If the program has been marked by the compiler as a console mode program windows opens a window with a black background by default and initializes the standard input and standard output of the program before it starts If the program is marked as a windows program nothing is done and you can t use the text output or input library functions For historical reasons this window is called sometimes a DOS window even if there is no MSDOS since more than a decade The programs that run in this console window are 32 bit programs and they can open a window if they wish They can use all of the graphical features of windows The only problem is that an ugly black window will be always visible even if you open a new window You can change the type of program Icc win32 will generate by checking the corresponding boxes in the Linker tab of the configuration wizard accessible from the main menu with Project then Configuration Under other operating systems the situation is pretty much the same Linux offers a console and even the Macintosh has one too In many situations typing a simple command sequence 1s much faster than clicking dozens of menus options till you get where you want to go Besides an additional advantage is that console pro
322. he EM SETSEL message can be used to place a selected range of text in a Windows edit control If the starting and ending positions of the range are set to the same position no selec FAQ 347 tion 1s made and a caret can be placed at that position To place a caret at the end of the text in a Windows edit control and set the focus to the edit control do the following HWND hEdit GetDlgItem hDlg ID EDIT int ndx GetWindowTextLength hEdit SetFocus hEdit SendMessage hEdit EM SETSEL WPARAM ndx LPARAM ndx Once the caret is placed at end in the edit control you can use the EM REPLACESEL to append text to the edit control An application sends an EM REPLACESEL message to replace the current selection in an edit control with the text specified by the IpszReplace lParam parameter Because there is no current selection the replacement text is inserted at the current caret location This example sets the selection to the end of the edit control and inserts the text in the buffer SendMessage hEdit EM SETSEL WPARAM ndx LPARAM ndx SendMessage hEdit BM REPLACESEL 0 LPARAM LPSTR szBuffer Another way to insert text into an edit control is to use the Windows clipboard If the applica tion has the clipboard open or finds it convenient to open the clipboard and copies the text into the clipboard then it can send the WM PASTE message to the edit control to append text Of course any data that was in the cli
323. he Service Control Manager SCM A user through the Services control panel applet can start it automatically at system boot or by an application that uses the service functions Services can execute even when no user 1s logged on to the system 3 17 14 Terminal Services When a user logs on to a Terminal Services enabled computer a session is started for the user Each session is identified by a unique session ID Because each logon to a Terminal Services client receives a separate session ID the user experience is similar to being logged on to mul tiple computers at the same time for example an office computer and a home computer The console session on the Terminal Server is assigned the session ID 0 The Remote Desktop Protocol RDP provides remote display and input capabilities over net work connections for Windows based applications running on a server RDP is designed to support different types of network topologies and multiple LAN protocols On the server RDP uses its own video driver to render display output by constructing the ren dering information into network packets using RDP protocol and sending them over the net work to the client On the client RDP receives rendering data and interprets the packets into corresponding graphics device interface API calls For the input path client mouse and key board events are redirected from the client to the server On the server RDP uses its own vir tual keyboard and mouse driver to
324. he looks Before we go on however as promised let s look in more details to how flags are set unset in C Flags are integers where each bit is assigned a predefined meaning Usually with a pre processor define statement powers of two are assigned a symbolic meaning like in the case of CS DBLCLKS above In a 32 bit integer we can stuff 32 of those We test those flags with 114 Never forget this local variables do NOT retain their value from one call of the function to the next one 250 C Tutorial if flag amp CONSTANT we set them with flag CONSTANT we unset them with flag amp CONSTANT This last statement needs further explanations We use the AND operator with the complement of the constant Since those constants have only one bit set the complement of the constant is an integer with all the bits turned into ones except the bit that we want to unset We AND that with our flag integer since all bits but the one we want to set to zero are one we effectively turn off that bit only leaving all others untouched Customizing the wizard generated sample code 251 3 8 Customizing the wizard generated sample code The generator can be configured for different types of applications Use first the simple win dow application This setup produces a standard WinMain procedure like this You can add code for the initialization of your application in the InitApplication function The standard version just registe
325. her functions that relate to strings Besides some relicts of the 16 bit past like Istrcat and others we find really useful functions especially for UNICODE handling CharLower CharLowerBuff CharNextExA CharPrev CharPrevExA CharToOem CharToOemBuff CharUpper CharUpperBuff CompareString FoldString GetStringTypeA GetStringTypeEx GetStringTypeW IsCharAlpha Ipo far upaa IsCharLower IsCharUpper LoadString Numeric The problems with C Strings 111 OemToCharBuff WideCharToMultiByte 1 25 The problems with C Strings After we examined how strings are presented in C let us apply our new knowledge The program looks ok and running it with a few files in the current directory works Let s try then H lcc examples gt freql src77 c more CRASH What s happening Following the program in the debugger we see that we do not test for NULL when opening a file We correct this both in checkargs and GetNext We write a function Fopen using the same model as xmalloc if it can t open a file it will show an error message in stderr and exit the program FILE Fopen char name char mode FILE result fopen name mode if result NULL fprintf stderr Impossible to open s n name exit l return result Ok we change all fopen into Fopen recompile and we test again H lcc examples gt fregql src77 c more Impossible to open Alloc c Well this looks better but why
326. hes any of case int expr the integer expressions defined in each of the case constructs If the statements comparison succeeds execute the statements in sequence beginning with that break case statement default If the evaluation of expression produces a value that doesn t match any of the statements cases and a default case was specified execute the default case statements in sequence See Switch statement on page 49 goto label Transfer control unconditionally to the given label Within the scope of a for do while loop statement continue with the next iteration of the loop skipping all statements until the end of the loop See break and continue statements on page 48 break Stop the execution of the current do for while loop statement End the current function and return control to the calling one The return value of return expression the function if any can be specified in the expression following the return keyword 1 9 7 Windows specific syntax Use the stdcall calling convention for this function or function pointer the called function cleans up the stack See stdcall on page 47 __declspec Export this identifier in a DLL to int _declspec dllexport dllexport make it visible from outside A ain Gules Chee ie Do not add the standard prologue or __declspec epilogue to the function The return int declspec naked naked instruction and any other code should fn int
327. his is used a lot The reason is an historical one In windows 16 bits there were several types of pointers near 16 bit pointers far long pointers of 32 bits and generally the near pointers were prefixed with NP the 32 bit ones with LP This was retained for compatibility reasons until today even if there are only 32 bit pointers now This structure contains then the following fields e hwnd The handle of the specific window to which the message is directed e message A 16 bit value identifying the message e wparam A 32 bit value identifying the first message parameter Its meaning depends on the message being sent e Param A 32 bit value identifying the second message parameter e time A 32 bit value identifying the time when the event that provoked this message happened e pt This is a POINT structure containing the coordinates of the mouse in the instant the event happened that provoked this message 248 C Tutorial return 0 Having all this menues in place is nice but if you are used to use the keyboard something is lacking A nice way to use your keyboard After initializing the window class the WinMain function loads the accelerators for the appli cation This table is just a series of keyboard shortcuts that make easy to access the different menu items without using the mouse and leaving the keyboard In the resource editor you can edit them add delete change etc To do this you start the resource editor
328. iated template traits default template arguments casted for non constness default copy constructors being called when trying to copy a memory block Here a memory block copy is that a memory block copy and no copy constructors are called anywhere Actually there are no constructors at all unless you call them explicitely You can do copy constructors of course and the library provides copy list copy_bitstring etc But you call them explicitely the compiler will not try to figure out when they should be called All this makes programs clearer we know what is being called and the calls do not depend any more on the specific compiler version Yes the compiler does some automatic calls for you You can redefine operators and you have generic functions This introduces many problems you are aware of if you know C Here however the complexity is enourmously reduced since there are no systematic implicit calls and objects are not automatically clustered in classes You can make classes of objects of course but you do it explicitely No implicit conversions are grained in the language itself Here we have a library for using simple data structures Nothing is hidden from view behind an opaque complex construct You have the source and a customizing tool C has a formidable power of expression because it gives an accurate view of the machine a view that has been quite successful C is a derived language from C It introduced the not
329. ibrary and taking care of possi ble errors Please be aware that all this supposes that you have a working TCP IP network connection and that the lower layers of the network are working Besides note that the paths given here may change etc etc Network programming is covered in more detail in chapter 3 3 18 4 Opening a web site or an HTML file using the default browser The ShellExecute API will call the registered default browser when invoked like this 1 Opening an HTML file in the local hard drive ShellExecute Handle open d website index htm NULL NULL SW_ SHOWDEFAULT 2 Opening a web site ShellExecute Handle open http www cs virginia edu lcc win32 NULL NULL SW_ SHOWDEFAULT 3 18 5 Creating a desktop shortcut Here is a small utility and test program to create a shortcut in the desktop It receives three parameters 1 The name of the file that will be executed by the shell In the example is the lcc compiler 2 The name of the shortcut 1 e the name that will appear under the shortcut in the desktop 3 An optional commentary string include lt windows h gt include lt objidl h gt include lt shlobj h gt Advanced windows techniques 315 include lt shobjidl h gt include lt wchar h gt int Cr eateshortCut const char rile char shortcutname char args TIShellLink pLink IPersistFile pPersistFile LPMALLOC ShellMalloc LPITEMIDLIST DesktopPidl char DesktopDir MAX PA
330. ice Using function pointers 149 1 33 Using function pointers A very common programming problem is to recursively explore a certain part of the file sys tem to find files that have a certain name for instance you want to know all the files with the c extension in a directory and in all subdirectories To build such a utility you can do 1 Build a list or table containing each file found and return those results to the user 2 For each file that is found you call a user provided function that will receive the name of the file found The user decides what does he she want to do with the file Note that solution 2 includes solution 1 since the user can write a function that builds the list or table in the format he wants instead of in a predefined format Besides there are many options as to what information should be provided to the user Is he interested in the size of the file Or in the date Who knows You can t know it in advance and the most flexible solution is the best We can implement this by using a function pointer that will be called by the scanning function each time a file is found We define typedef int callback char This means a function pointer called callback that points to a function that returns an int and receives a char as its argument This function pointer will be passed to our scanning func tion and will return non zero scanning should be continued or zero scanning should stop
331. if Gethasthrror ERROR INSUFPICTIENT BUEFER 4 goto cleanup dwSizet count the trailing zero swzheaders malloc dweize ssrze0t wehar t szHeaders malloc dwSize if swzHeaders NULL szHeaders NULL goto cleanup dwS1ize WinHttpQueryHeaders rcContext hRequest WINHTTP QUERY RAW HEADERS CRLF WINHTTP HEADER NAME BY INDEX swzHeaders amp dwSize WINHTTP NO HEADER INDEX We got the headers Now we parse them to find the return code in them The standard HTTP specifies a response like HETE 1 200 OR Date Fri O7 May 2004 09 08 14 GMT Server Microsort LisS 6 0 PSPs lt CP ALG LND DOP COR ADM CONG CUR CUSO IVAO IVDO PSA PSD TAL TELO OUR SAMo CNT COM INT NAV ONL PHY PRE PUR UNI X Powered By ASP NET Content Length 39601 Content Type text html Expires Fri O7 May 2004 09 08 14 GMT Cache control private 372 C Tutorial We are interested in the first line that contains the return code for the operation We just skip the HTTP 1 1 and get it memset szHeaders 0 dwSize wcstombs szHeaders swzHeaders dwS1ize char p szHeaders while p Diy while p 5s T DE sscant D TdT Ere if rc 404 rcContext Status 404 goto cleanup The next thing to do is to open the output file If we can t open it there is no point in going further We close the session and return an error code reContext OutputFile fopen outfile wb
332. ify the BuildTree procedure as follows int BuildTree HWND parent HWND Start GetDesktopWindow HWND hTree GetDlgItem parent IDTREEWINDOW TV SENSERE STRUCT IreeCrri item HTREEITEM hNewNode sendMessage hTree WM SETREDRAW 0 0 A more complex example a clone of spy exe 263 TreeView DeleteAllitems hTree memset amp TreeCtrlitem 0 sizeof TreeCtrlitem TrecCeriitem nrarecnt TVI ROOT TrecCerlinen hinscruArtter Tvl LAST TreeCtrlitem item mask IVI IEAI TVIF PARAM TreeCtrlitem item pszText Desktop hNewNode TreeView InsertItem hTree amp TreeCtrliItem Start GetWindow Start GW CHILD Scan hTree hNewNode Start TreeView Expand hTree hNewNode TVE EXPAND sendMessage hTree WM SETREDRAW 1 0 return 1 We enclose all our drawing to the control within two calls to the SendMessage function that tell essentially the tree control not to redraw anything The third parameter 1 e the wParam of the message is a Boolean flag that indicates whether redrawing should be on or off This solves the second problem After setting the redraw flag to off we send a command to the control to erase all items it may have This solves our first problem Here 1s the output of the program after we press the Scan menu item E windowtree x File Help Desktop H BaseBar tooltips class32 BaseBar tooltips class32 BaseBar BaseBar tooltips class32 H Avance Sound Effect C
333. iles to be included tn the link dialog lib teconio lib Now when creating the project we ask the wizard to create a console application We leave everything by default but when we arrive at the linker settings dialog we add our dialog lib to the libraries entry field like this Another issue to remember is the following We need a resource file Since in our library there are no resources we have to add those resources to our test program This is easy to do in this case we just add the dialog rc resource file to the project The interface for the users of the library however is terrible All programs that use our library will be forced to include somehow the resource for the dialog box Includ ing a resource in another resource file 1s difficult to say the least Wow this looks like a showstopper actually OK This presents an unexpected and serious trouble for our library project but we will not leave things at midway We finish our test program by changing our main function like this extern int APIENTRY GetString char prompt char buf int len int main void char burrer 1024 if GetString Enter a string buffer sizeof buffer PrantLE String is s n butter else printf User cancelled n return Uy 106 It could be argued that this could be done with DLLs too the linker should export all externally visible symbols In practice is better only to export symbols that should be visible
334. ill be assumed to be external functions that return an int the default this will make the compiler generate code to read an integer instead of reading a double what will result in completely nonsensical results 270 C Tutorial A break statement breaks the loop This statement means r r cos theta 5 and NOT r r cos theta CENTER In line 8 we use the rand function This function will return a random number between zero and RAND MAX The value of RAND MAX is defined in stdlib h If we want to obtain a random number between zero and 1 we just divide the result of rand by RAND MAX Note that the random number generator must be initialized by the program before calling rand for the first time We do this in WinMain by calling srand unsigned time NULL This seeds the random number generator with the current time We are missing several pieces First of all note that CENTER is define CENTER 400 because with my screen proportions in my machine this is convenient Note that this shouldn t be a define but actually a calculated variable Windows allows us to query the horizontal and vertical screen dimensions but for a simple drawing of a spiral a define will do The function PlotPixelAt looks like this void PlotDotAt HDC hdc double x double y COLORREF rgb Secrixe lL hdc ane shine yobs The first argument is an HDC an opaque pointer that points to a device context not fur th
335. ill see more of this when we fill this structure below The shell uses a lot of stuff and we have to take care to avoid filling our brain with unending details What is an ITEMLIST Actually I haven t even bothered to read the docs about it since the only use I found is to pass it around to other shell functions The result of the function is initialized to zero 1 e we will set this result to 1 only and only if there is a valid path in the buffer OK Here we start The first thing to do then is to get the pointer to the shell allocator If any thing goes wrong there there is absolutely nothing we can do and the best thing is to return immediately with a FALSE result We have to clean up the structure note that this is a local variable so its contents are as yet undefined We use the primitive memset and set all members of the structure to zero This 1s a common idiom in C clear all memory before using and assign to it a known value Since the default value of many structure members is zero this easies the initialization of the structure since we do not have to explicitly set them to NULL or zero We start the filling of the relevant members We need to put the owner window handle in the hwndOwner member We get the handle of the current active window using a call to a win dows API The shell needs place to store the display name of the chosen path Note that this is not what we want the full path but just the last item in the pa
336. ime Allows editing text with different typefaces bold italic with different fonts in different colors The basic building block to build a text processor Used to display status information at the bottom of a window Tab controls The building block to make property sheets Toolbar controls A series of buttons to accelerate application tasks Show explanations about an item currently under the mouse in a Tooltips pop up window Trackbars Analogical volume controls for instance Advanced windows techniques 307 Displays hierarchical trees 3 18 Advanced windows techniques Windows is not only drawing of course It has come a long way since windows 3 0 and is now a sophisticated operating system You can do things like memory mapped files for instance that formerly were possible only under UNIX Yes mmap exists now under windows and it is very useful 3 18 1 Memory mapped files Memory mapped files allow you to see a disk file as a section of RAM The difference between the disk and the RAM disappears You can just seek to a desired position by incre menting a pointer as you would do if you had read the whole file into RAM but more effi ciently It is the operating system that takes care of accessing the disk when needed When you close the connection the operating system handles the clean up Here is a small utility that copies a source disk file to a destination using memory mapped files int m
337. in knowing how Icc win32 works this is surely the place to start 188 C programming with Icc win32 C interfaces and implementations David R Hanson This is an excellent book about many subjects like multiple precision arithmetic lists sets exception handling and many others The implementation is in straight C and will compile without any problems in Icc win32 Safer C Les Hatton As we have seen in the section Pitfalls of the C language C 1s quite ridden with problems This book address how to avoid this problems and design and develop you work to avoid get ting bitten by them C Programming FAQs Steve Summit C Programming FAQs contains more than 400 frequently asked questions about C accompa nied by definitive answers Some of them are distributed with Icc win32 but the book is more complete and up to date The Standard C Library P J Plauger This book shows you an implementation with the source code of the standard C library done by somebody that is in the standards committee and knows what he is speaking about One of the best ways of learning C 1s to read C This will give you a lot of examples of well written C and show you how a big project can be structured The C Standard John Wiley and Sons This is the reference book for the language It contains the complete C standard and the ratio nale explaining some fine points of the standard Buffer Overflows Attacks and Defenses for the Vuln
338. in the text Desktop and that we want to reserve place for a pointer in the item itself TVIF PARAM Having done that we use the macro for inserting an item into the tree The root item created we should then scan the siblings and child windows of the desktop Since the desktop is the root of all windows it has no siblings so we start at its first child The GetWindow function gives us a handle to it 3 10 5 Scanning the window tree We call our Scan function with the handle of the tree control the handle to the just inserted item and the window handle of the first child that we just obtained The Scan function looks like this void Scan HWND hTree HTREEITEM hTreeParent HWND Start HWND hwnd Start hwndl TV INSERTSTRUCT Ereectr LL Leem HTREEITEM htiNewNode char buftTxt 256 butClassName Z256 0utput 1024 262 C Tutorial while hwnd NULL SendMessage hwnd WM GETTEXT 250 LPARAM bufTxt GetClassName hwnd bufClassName 250 wsprintf Output Ss Ss bufTxt bufClassName memset amp TreeCtrlitem 0 sizeof TreeCtrlitem TreeCtrlitem hParent hTreeParent LeeeCiULl tem MinsertArter IVE BASI TreeCtrlitem item mask TYLE EBAL ITVEF PARAM TreeCtrlitem item pszText LPSTR Output TreeCtrlitem item 1Param LPARAM hwnd htiNewNode TreeView lnsertitem hires TrescCtrlicvem if hwnd1l GetWindow hwnd GW CHILD NULL Scan hTree htiNewNode hwndl1 hwnd GetWind
339. in32 Slot word table lista of VYOROLIST Structures Our word table is a sequence of lists of words Each list is longer or shorter depending on the hash function that we use and how good our hash function randomizes the input If we use a table of 65535 positions slots and a good hash algorithm we divide the access time by 65535 not bad To enter something into our table we hash the word into an integer and we index the slot in the table We then compare the word with each one of the words in the list of words at that slot If we found it we do nothing else than increment the count of the word If we do not find it we add the word at the start of that slot Note that this requires that we define a structure to hold each word and its associated count Since all the words are in a linked list we could use the following structure borrowing from the linked list representation discussed above typedef struct Wordhist i iit Count Struct Wordhist gt Next Char Word t WORDLIS T We have an integer that holds the number of times this word appears in the text a pointer to the next word in the list and an unspecified number of characters just following that pointer This is a variable sized structure since each word can hold more or less characters Note that variable sized structures must have only one flexible member and it must be at the end of the definition Our EnterWord function can look like this
340. in32 s documentation The documentation of lcc win32 comes in four files 9 Manual chm This is the user s manual where you will find information about how the system is used command line options menu descriptions how to use the debugger etc It explains how to build a project how to setup the compiler each compiler option all that with all the details 10 c library chm This file contains the documentation for all functions in the C runtime library It will be automatically invoked by the IDE when you press the F1 function key This two files c library chm and manual chm are distributed in manual exe 11 Lee win32 doc This is a technical description for interested users that may want to know how the system is built how the programs that build it were designed the options I had when writing them etc The documentation of the windows API is distributed in a relatively large file called win32hlp exe This is absolutely essential unless you know it by heart When installed this file will become Win32 hlp That file is not complete however More documentation for the new features of Win32 can be found in the win32apidoc exe file also in the lce distribution site When installed that file will install e Shelldoc doc This documents the windows shell its interfaces function definitions etc e Wininet doc This documents the TCP IP subsystem for network programming e CommoncControls doc This explains the new co
341. inds the first occurrence of a given character in a string Finds the last ocurence of a given character in a string Finds the first occurrence of a pattern in a string Strspn Finds the index of first char that doesn t match a charac ter in a given set The difference with Strfind first not of 1s in the return value Strspn returns the string length when no match is found instead of 1 ular expression package or the perl regular expression package pcre Finding the first whitespace character in a string SELL Ind ELTSE Or sOurce NE I Finding the end of the first word in a string char alphabet ABCDEFGHIJKLMNOPORSTUVWXY Zabcdefghijkimnopgrstuvwxyz SEELiIng Taret nov Or oource alphabet Finding a word in a string Implementation 209 String s A long short Sentence Stringp ps Strstr s tence Now ps points to tence Note that Strstr returns a pointer structure not a new string You can conevrt the pointer into a string with the Strdup function 2 3 9 2 Strfind_first_of int Overloaded SUrringd first OFA SeringA 6S string ser PRECONDITION StrvalidA s amp amp StrvalidA set exc char STrConeents Ss COnuent p inte Ly i COUNT S COUNtT SeLCOUNS Set count Tne ey if set count s count 0 return 1 for 1 0 i lt count itt p SSlULCOonrency c strcontents i for j 0 j lt setcount j if c p j return 1 ret
342. ine parameters This would work but the problem of getting the string from the user would be quite compli cated to solve Programs can only return an error code and in some situations this error code can only be from zero to 255 We can t pass pointers just like that from one program to another we can t just pass a pointer to a character string as the result of the program Why Because windows as other systems like linux Solaris and UNIX in general uses a protected virtual address schema The machine addresses that the program uses are virtual as if the pro gram was the only one running in the machine It is the operating system and the CPU that does the translation of those virtual addresses into real RAM locations in the machine you are using This means the addresses of each program aren t meaningful for another program We can pass special pointers shared memory within windows but that s too advanced stuff for an introductory text sorry But there are many other ways of solving this problem without costly interface development What do we want Let s get that clear first worrying about implementation details later int GetString char prompt char buffer int bufferlen This routine would return either true or false depending if the user has pressed OK or can celled the operation If the user pressed OK we would find the string that was entered in the buffer that we pass to GetString To avoid any overflow proble
343. ing printf tLease Obtained ld n pAdapter gt LeaseObtained l else printf tDHCP Enabled No n if pAdapter gt HaveWins printf t tPrimary Wins Server t s n pAdapter gt PrimaryWinsServer IpAddress String printf t tSecondary Wins Server t s n pAdapter gt SecondaryWinsServer IpAddress String else princi thHave Wins Nona pAdapter pAdapter gt Next We query now the interface information IP INTERFACE INFO pinto pinto IP INTERFACE INFO malloc sizo IP INTERFACE INFO J7 re GetInterfacelInfo piInfo amp ulOutBufLen if rc ERROR INSUFFICIENT BUFFER free pInfo pinto IP INTERFACE INFO malloc uLOutButhlen printf ulLen ld n ulOutBufLen else printf GetInterfaceInfo failed with error d n GetLastkError return i1 dwRetVal GetInterfaceInfo pInfo amp ulOutBufLen if dwRetVal NO ERROR printf Adapter Name S n piInfo gt Adapter 0 Name printf Adapter Index ld n pInfo gt Adapter 0 Index printf Num Adapters ld n piInfo gt NumAdapters Instead of printing a more or less meaningless error message we can use FormatMessage to give a more comprehensible description of the problem if dwRetVal LPVOID lpMsgBur if FormatMessage FORMAT MESSAGE ALLOCATE BUFFER FORMAT MESSAGE FROM SYSTEM FORMAT MESSAGE IGNORE INSERTS NULL dwRetVal MAKELANGID LANG NEUTRAL SUBLANG DEFAULT LPTS
344. ings and using some character string as the name of the user agent mOpen Invlernevopen TETP ice y INTERNET OPEN TYPE PRECONFIG NULL O 0 if hOpen return 1 We establish now the connection using the default FTP port and passive mode We pass NULL as user name and password This means that we always use the anonymous login hConnect InternetConnect hOpen host INTERNET INVALID PORT NUMBER NULL NULL INTERNET SERVICE FTP INTERNET FLAG PASSIVE 0 if hConnect OK We arrive at the interesting part We retrieve the file using INTERNET FLAG RELOAD what means a download is forced of the requested file object or directory listing from the origin server not from the cache Besides this we always use binary mode for all transfers 134 134 The FTP protocol has two modes of transmission binary where no modifications are done to the transmitted data and text where the sequence r n will be translated as a single n The text mode will destroy an executable file or zip file that can contain embedded r n sequences 374 C Tutorial fret FtpGetFile hConnect infile outfile FALSE 7 DO fot Tarl 1f local Tile exists INTERNET FLAG RELOAD FIP TRANSFER TYPE BINARY OF 3 Le Chive 10 fret GetLastError else Fret j 304 4i Cleanup InternetCloseHandle hConnect else Pret GetLastError InternetCloseHandle hOpen recur iret int main void
345. input format string we force the system to skip a new line 6 Calls to scanf can t be intermixed with calls to getchar to the contrary of calls to printf and putchar 7 When scanf fails it stops reading at the position where it finds the first input character that doesn t correspond to the expected sequence If you are expecting a number and the user makes a mistake and types 465x67 scanf will leave the input pointing to the x that must be removed by other means Because of this problem it 1s always better to read one line of input and then using sscanf in the line buffer rather than using scanf directly with user Input The printf family 61 Here are some common errors to avoid int integer short shortint Char burfer s0 char str buffer providing the variable instead of a pointer to it sscanf Sd integer wrong 7 sscanf Sd amp integer right 7 providing a pointer to the wrong type or a wrong format to the right pointer sscani ed gt shorting wrong sscant shda cshortint J rignt providing a pointer to a string pointer instead of the string pointer itself some people think once amp always amp sscanf ss amp str J wrong 7 sscant lt s Str right Consider the following code include lt stdio h gt int main void ine i Char 0 scant od 7 61 7 scant sc amp c printi d 26 n 1 0 4 Assume you
346. int argc Char argyll int count 0 chars read FILE infile IAGO IF argo lt 2r 4 printf Usage countchars lt file name gt n exit 1 infile fopen argv 1l r if infile NULL printf File s doesn t exist n argv 1 exit l1 C Egete ints le while c BOF count t c fgetc infile PELDE s n county return 0 We try again He lec examples gt Lec countchars c H Whee examples gt Lecink countchars ob7 26 C programming with Icc win32 H lcc examples gt countchars sfsfsfsfs File sfsfsfsfs doesn t exist H lcc examples gt Well this error checking works But let s look again at the logic of this program Suppose we have an empty file Will our program work If we have an empty file the first fgetc will return EOF This means the whole while loop will never be executed and control will pass to our printf statement Since we took care of initializ ing our counter to zero at the start of the program the program will report correctly the num ber of characters in an empty file zero Still it would be interesting to verify that we are getting the right count for a given file Well that s easy We count the characters with our program and then we use the DIR directive of windows to verify that we get the right count H lcec examples gt countchars countchars c 466 H lcc examples gt dir countchars c O77 01 00 Tess 1p 492 countcehars c 1 File s 492 bytes
347. ion This is very nice in C but it will never work with C or with COM It is illegal to throw a C exception in COM Besides the runtimes of different compilers handle C exceptions in a different way so they are incompatible with each other Anyway if you work with Icc win32 you will be spared this 6 Using the RaiseException API This is the normal way of using structured exception handling in Icc win32 It has its drawbacks too since it doesn t fit very well with COM for instance and it is maybe not compatible with some other compilers It is compatible with Microsoft compilers and maybe Borland since all of them use the same binary approach to this problem imposed by the windows API 7 Using some other mechanism of structured exception handling Many other libraries exists for structured exception handling sometimes using setjmp longjmp sometimes using the signal mechanism or some other conventions If you find yourself working with some code that does this either you use it without any modifications or you just drop it Trying to fix modify this kind of code is best left to very experienced programmers 8 Using GetLastError to get information about the error This would seem evident but in their infinite wisdom the windows API designers decided to provide different error codes for the same failures in the different versions of the operating system Under windows 95 98 the error codes would be different than the error code
348. ion of well classified objects an idea that was put forward by many people among others Betrand Meyer and Xerox with their Smalltalk system Unfortunately what was a good paradigm in some situations becomes a nightmare in others When we try to make a single paradigm a fits all solution the mythical silver bullet nothing comprehensible comes out To be object oriented meant many things at once and after a while nothing at all 194 C programming with Icc win32 For C the object oriented framework meant that functions were to be called automatically by the compiler for creating and destroying objects The compiler was supposed to figure out all necessary calls This is one solution for the memory management problem Another solution and the one Icc win32 proposes is to use a garbage collector C did not introduce a GC for reasons I have never understood This solution is much simpler than mak ing a complex compiler that figures out everything automatically The destructor is the GC that takes care of the left overs of computation Then it becomes possible to make temporary objects without worrying about who disposes of temps The GC does Operators can return dynamically allocated temporary objects without any problem The equivalent of C automatic object destruction 1s attained with the GC and the complexity of the software is reduced At the same time bounds checked arrays and strings become possible A gen
349. ion when it attempts to use the stack within the code of the exception handling procedure except _handler3 that receives the exception from windows This will provoke the dreaded double fault exception that terminates immediately the program no ques tions asked Note that not even the this program has attempted an illegal operation dialog box appears The correct way of handling stack overflow 1s then to do the following Get the page size from the system 2 Set the page to guard page again An example is given below tinclude xintrinsics nh gt Bor GeustackPointer ine main int aroc char argy Loe C 162 C programming with Icc win32 __try StackOverflow 0 excepi EXCEPTION EXECUTE HANDLER LPBYTE lpPage static SYSTEM INFO Salle static MEMORY BASIC INFORMATION mi static DWORD dwOldProtect Get page size of system GetSystemInfo amp si Find SP address IpPage GertotackPormter 7 Get allocation base of stack VirtualQuery lpPage amp mi sizeof mi Go to page beyond current page lpPage LPBYTE mi BaseAddress si dwPageSize Free portion of stack just abandoned if VirtualFree mi AllocationBase LPBYTE lpPage LPBYTE mi AllocationBase MEM DECOMMIT lf we get here exit there is nothing that can be done exit Lis Reintroduce the guard page if VirtualProtect lpPage si dwPageSize PAGE GUARD PAGE READWRITE amp dwOldProtect S
350. ions maintain separate IO buffers When redi rected these buffers might not be flushed immediately after each IO call As a result the out put to the redirection pipe of a printf call or the input from a getch call is not flushed immediately and delays sometimes infinite delays occur This problem is avoided if the child process flushes the IO buffers after each call to a C run time IO function Only the child pro cess can flush its C run time IO buffers A process can flush its C run time IO buffers by call ing the fflushQ function FAQ 349 NOTE Windows 95 and Windows 98 require an extra step when you redirect the standard handles of certain child processes 3 21 16 How to modify the width of the list of a combo box The combo box in Windows is actually a combination of two or more controls that s why it s called a combo box To make the combo box list wider or narrower you need the handle of the list box control within the combo box This task 1s difficult because the list box is actually a child of the desk top window for CBS DROPDOWN and CBS DROPDOWNLIST styles If it were a child of the ComboBox control dropping down the list box would clip it to the parent and it wouldn t display A combo box receives WM CTLCOLOR messages for its component controls when they need to be painted This allows the combo box to specify a color for these controls The HIWORD of the Param in this message is the type of the control In case o
351. ipboard GetClipboardData allows you to read it SetClipboardData to write it etc You implement this way the famous Cut Copy and Paste commands that are ubiquitous in most windows applications Predefined data formats exist for images CF BITMAP CF METAFILEPICT CF TIFF sound CF WAVE CF RIFF text CF TEXT pen data CF PENDATA a list of files CF _HDROP and sev eral others When you pass a block of data to the clipboard that memory should be allocated since win dows expects that it can free it when it is no longer used Since it is the clipboard that should free the allocated memory you can t use the standard allocation functions you should use the GlobalAlloc API to get memory to be used by the clipboard To transfer a character string to the clipboard then we could use the following function int CopyToClipboard char str HWND hwnd int len strlen str 1 HANDLE h h GlobalAlloc GHND GMEM DDESHARE len if h HANDLE 0 Etc 301 return 0 txt GlobalLock h StCLCp yy CXE SCI if OpenClipboard hwnd EmptyClipboard setCliapboardData CP TEXT CloseClipboard return TRUE return FALSE We allocate space for our character string then obtain a pointer from the given handle We can then copy the data into this memory block We obtain access to the clipboard by opening it giving it the handle of a window that will own the clipboard If the operation succeeds we clear the pre
352. ips 329 at a sufficient privilege level can define redefine or delete Win32 device mappings by calling the DefineDosDevice API 3 20 19 Retrieving the Last Write Time The following example uses the GetFileTime function to retrieve the last write time for a file It converts the time to local time based on the current time zone settings and creates a date and time string that can be shown to the user BOOL GetLastWriteTime HANDLE hFile LPSTR String FILETIME ftCreate ftAccess ftWrite SYSTEMTIME stUTC etlocal Retrieve the file times for the file if GetFileTime hFile amp ftCreate amp ftAccess amp ftWrite return FALSE Convert the last write time to local time FileTimeToSystemTime amp ftWrite amp stUTC SystemTimeToTzSpecificLocalTime NULL amp StUTC amp stLocal Build a string showing the date and time Sprintr String s02d s020 s4d s0Z2d 302d stLocal wDay stLocal wMonth stLocal wYear stLocal wHour stLocal wMinute return TRUE 3 20 20 Setting the System Time The following example sets the system time using the SetSystemTime function BOOL SetNewTime WORD hour WORD minutes SYSTEMTIME st char pc GetSystemTime amp st 7 gets current time st wHour hour adjusts hours st wMinute minutes and minutes if SetSystemTime amp st sets system time return FALSE return TRUE 3 20 21 Getting the list of running processes You ca
353. ir Tai er xini if fileexists files gt Name if bQuiet amp amp bPrompt 2 kell user Tm eecyclang thas tite Forinte Stderr ss Ssin bZap Deleting Recycling files gt Name if bDisplayOnly if bPrompt confirm files gt Name ee Eimealiy Recycle he tile Use CRecyclerile int err Recycle files gt Name bZap if err 0 nDel else Can t recycle display error message Forint stcerr Error Sdi 2S err GetErrorMsg err else iprint stderr File mot round 2s in tales sNamey gt rf DOuiet 4 forinti stderr sd Tiles recycled n aDelj FAQ 357 return Q0 void usage void printf Usage RECYCLE QNPZ file n void help void printf Purpose Send one or more files to the recycle bin n perinti Format RECYCLE 7 0 7N 7P 72 ile sas i 3 prince Q uiet no messages n prance N othing don t delete just show files n Prince P rompt confirm each file n prince Z ap really deletesame as del n Make a file name absolute with respect to current directory char MakeAbsolute char relname Get current directory char cwd GetCurrentDir char absname if relname 0 amp amp relname 1 amp amp relname 1 relname is already absolute absname relname alsa af c lnamelOj 4 relname begins with add drive letter a
354. is a standard way of using bit flags in C If you go to the definition of CS HREDRAW right click in that name and choose the Goto definition option you will see that the value is 2 Other constants like CS_DBLCLKS have a value of 8 All those numbers are a power of two Well a power of two by definition will always have a single bit set All other bits will be zero If you OR those numbers with each other you will obtain a number that has the bits set that correspond to the different values used In our case this statement is equivalent to we style 2 1 8 8 ored with is 1 0 0 1 ored with 2 is 1 0 1 1 what is equal to 11 in decimal notation This is a very common way of using flags in C Now if you want to know if this window is a window that answers to double clicks you just have to query the corresponding bit in the style integer to get your answer You do this with the following construct if wce style amp CS DBLCLKS We test in this if expression if the value of the style integer ANDed with 8 is different than zero Since CS DBLCLKS is a power of two this AND operation will return the value of that single bit 3 Note too that 1 is a power of two since 2 to the power of zero is one We will return to this at the end of this section Coming back to our initialization procedure there are some new things besides this style set ting But this is just a matter of reading the windows documentation No big de
355. is program n printf Please call the maintenance team at 0 800 XXX n return 0 This will now print No exceptions We have three parts here The first one is the protected code block enclosed by try This block can contain code that provokes exceptions To leave it prematurely you use the leave expression The second part is an integer expression that appears between parentheses after the except keyword This expression should eventually evaluate to one of the three constants defined in the lt seh h gt header file EXCEPTION EXECUTE HANDLER 1 means that the code in the following expression should be executed EXCEPTION CONTINUE SEARCH 0 means that the system should go on looking for another handler EXCEPTION CONTINUE EXECUTION 1 means that the system should attempt to go on at the same point in the program where the exception happened In this case we decided that any exception would provoke the execution of the block following the except 1 34 5 3 Auxiliary functions Of course you are surely keenly interested in the actual exception code The pseudo function GetExceptionCode will return the current exception code If we change our program to include lt stdio h gt include lt seh h gt int main void char p NULL unsigned code 158 C programming with Icc win32 D a soo Or prance No exceptions n __except code GetExceptionCode EXCEPTION EXECUTE HANDLER printf Ooop
356. is worth some explanation Now we have a registered class and we call the DialogBox API with the following parameters DialogBox Hinst MAKEINTRESOURCE IDD MAINDIALOG NULL DLGPROC DialogFunc The hinst parameter that many APIs still want is the one we received from the system as a parameter to WinMain Then we use the MAKEINTRESOURCE macro to trick the compiler into making a special pointer from a small integer IDD MAINDIALOG that in the header file generated by the wizard is defined as 100 That header file is called dialogres h and is quite small We will come to it later What is this MAKE INTRESOURCE macro Again history history In the prototype of the DialogBox API the second parameter is actu ally a char pointer In the days of Windows 2 0 however in the cramped space of MSDOS with its 640K memory limit passing a real character string was out of the question and it was decided to save space that instead of passing the name of the dialog box resource as a real name it should be passed as a small integer in a pointer The pointer should be a 32 bit pointer with its upper 16 bits set to zero and its lower 16 bits indicating a small constant that would be searched in the resource data area as the name of the dialog box template to load Because we need to load a template 1 e a series of instructions to a built in interpreter that will create all the necessary small windows that make our dialog box As you have
357. isplay results only don t erase BOOL bZap FALSE delete don t recycle test if file exists int fileexists LPCTSTR pFilename SELUCE Stal Su return stat pFilename amp sSt 0 Adds to the list of file a new name Allocates memory with the garbage collector FILELIST AddToList FILELIST start char name FILELIST newlist newlist GC malloc sizeot FILELISI 7 newlist gt Name GC malloc strilen name 1 strcpy newlist gt Name name if start newlist gt Next start return newlist int main int argc TCHAR argv TCHAR envp Parse command line building list of file names Switches can come in any order FILELIST files NULL for ant a ly a lt argqc7 Pre f Ac argv i Oli 7 I argv i LO 4 Switch tolower argv i 1 Case g i bQuiet TRUE break case n 356 C Tutorial bDisplayOnly TRUE break case p bPrompt TRUE break case Trt bZap TRUE break case help rerucn O7 default usage return OF else iy Gort aE Le names Make at absolute and adc to direst files AddToList files MakeAbsolute argv i if files NULL No files specified tell bozo user how to use this command usage return 0 A Delete recycle alL the files an he bast int nDel 0 loop over list of files and recycle each one for files files files gt Next if OOM Bee ye
358. ist if WM CTLCOLORLISTBOX message 32 bits has new message s this message for the list box control in the combo AE DO Only the very first time get the lise box handle and the list box rectangle Note the use of GetWindowRect as the parent of the list box is the desktop window IE OC Baise ie 4 hwndList HWND lParam ii AWND 1S 32 BILES GetWindowRect hwndList amp rectList bFirst FALSE Resize listbox window cx by 50 use your size here MoveWindow hwndList rectList left rectList top C BSECCLUSt rrohnt Trect hist beret 50 i reECtList DOLT Trectlist lt top TRUER J Call original combo box procedure to handle other combo messages return CallWindowProc lpfnOldComboProc hWnd message wParam lParam 3 21 17 How dol modify environment variables permanently You can modify user environment variables by editing the following Registry key HKEY CURRENT USER Environment You can modify system environment variables by editing the following Registry key HKEY LOCAL MACHINE Sro LEM CurrentControlSset CONCTOL Session Manager Environment Note that any environment variable that needs to be expanded for example when you use SYSTEM must be stored in the registry asa REG EXPAND SZ registry value Any val ues of type REG SZ will not be expanded when read from the registry Note that RegEdit exe does not have a way to add REG EXPAND SZ Use R
359. ith ro ea ell 9 femmes lle inn bei Ger Sze Cel 2 1 Design criteria What are the design decisions that make the base of the library 2 1 1 Memory management The first versions of the library contained for each container a pair of pointers for the memory allocation and memory release functions This increases the size of the library and consider ably increases the number of things that can go wrong Each container had its own memory management for releasing elements and maintaining free lists This was cumbersome and has been discarded Memory management is better done by the memory manager 1 e the garbage collector Since lcc win32 features a garbage collector GC in the standard distribution this simplifies the library Other environments like Java or the recent Net architecture of Microsoft feature as a standard library feature the garbage collector too 2 1 2 The handling of exceptions All containers check any indexed access for errors Badly formed input is detected at run time and the program by default is stopped with an error message Any of the functions in the interface can throw an exception if given incorrect inputs This can be disabled by redefining the macro PRECONDITIONS to be an empty operation This is surely not recommended but the possibility exists Design criteria 193 Each routine inthe library specifies in the PRECONDITIONS section the terms of the contract it has with its callers Internal r
360. ith the API EnableWindow If there is NO text we disable the DOK button with the same API Since we are getting those notifications each time the user types a character the reaction of our IDOK button will be immediate But we have still one more thing to do before we get this working We have to modify our Ini tializeApp procedure to start the dialog box with IDOK disabled since at the start there is no text in the entry field Static int InitializeApp HWND hDlg WPARAM wParam LPARAM lParam 102 I remember calling the software support when installing some hardware many of the options of the installation software were disabled but there was no way of knowing why 228 C Tutorial SetFocus GetDlgItem hDlg IDENTRYFIELD Disable the IDOK button at the start EnableWindow GetDlgItem hDlg IDOK 0 return 1 We recompile and it works The OK button starts disabled grayed and when we type the first character it becomes active just as we wanted When we select all the text in the entry field and then erase it we observe that the button reverts to the inactive state 3 2 User interface considerations There was another way of informing the user that text must be entered a MessageBox call telling him her precisely what is wrong This alternative making something explicit with a message or implicit like the solution we implemented above appears very often in windows programming and it is very difficult to give
361. iticized for being quite obscure This is true there is no point in negating an evident weakness In his book Deep C secrets gt Peter van der Lin den writes a simple algorithm to read them He proposes chapter 3 the following The Precedence Rule for Understanding C Declarations Rule 1 Declarations are read by starting with the name and then reading in precedence order Rule 2 The precedence from high to low is 2 A Parentheses grouping together parts of a declaration 2 B The postfix operators 2 B 1 Parentheses indicating a function prototype and 2 B 2 Square brackets indicating an array 2 B 3 The prefix operator the asterisk denoting pointer to Rule 3 If a const and or volatile keyword is next to a type specifier e g int long etc it applies to the type specifier Otherwise the const and or volatile keyword applies to the pointer asterisk on its immediate left Using those rules we can even understand a thing like Char gt CONSE C nexr Ine ay aie p gt We start with the variable name in this case next This is the name of the thing being declared We see it 1s in a parenthesised expression with an asterisk so we conclude that next is a pointer to well something We go outside the parentheses and we see an asterisk at the 33 Machine addresses are just integers of course For instance if you have a machine with 128MB of memory you have 134 217 728 memory locations They
362. ived by the user In normal applications this can take a bit less than a second in large memory pools The collector tries to improve this by doing small partial collections each time a call to its allocator function is done 4 If you have only one reference to a block the block will be retained If you have stored somewhere a pointer to a block no longer needed it can be very difficult indeed to find it 5 The garbage collector of lcc win32 is a conservative one 1 e if something in the stack looks like a pointer it will be assumed that this is a pointer fail safe and the memory block referenced will be retained This means that if by chance you are working with numeric data that contains numbers that can be interpreted as valid memory addresses more memory will be retained than strictly necessary The collector provides special APIs for allocating tables that contain no pointers and whose contents will be ignored by the collector Use them to avoid this problems 1 28 7 Mixed strategies Obviously you can use any combination of this methods in your programs But some methods do not mix well For instance combining malloc free with automatic garbage collection exposes you to more errors than using only one strategy If you pass to free a pointer allocated with GC malloc chaos will reign in your memory areas To the contrary the stack allocation strategy can be combined very well with all other strategies since it is specially adapted to the al
363. ixed in an expression and most operators like or are defined for them with the exception of less less equal greater and greater than You should always include the complex h standard header file when you use this type of numbers In that header file the basic keyword Complex is replaced by just complex and it will be used here as an equivalent keyword 1 35 4 1 Complex constants They can be written in two ways include lt complex h gt doulb le complex S 123 0t12 317 Or include lt complex h gt double complex a 123 0712 6 1 Note that the first notation is not standard but used in the gcc compiler system and it applies only to explicit constants Please do not assume that if you have a variable x just writing xi will transform it into a complex number When in your code you build a complex number using variables you use the standard nota tion double complex w w 65 0 angl e 2 445 6 angler In this example the real part of the number is 65 0 angle 2 and the imaginary part is 45 8 angle The constant I represents 0 1 or csqrt 1 and is defined in complex h Programming with security in mind 179 1 36 Programming with security in mind The C language doesn t give you many security nets Actually there is no security net You are supposed to make no mistakes This is very difficult to achieve of course Here I will try to give you some simple advice that you can
364. ized to NULL automatically by the compiler and will keep its value from one call to the next We test before using it if the chunk has enough room for the given memory size we want to allocate or if it is NULL 1 e this is the very first word we are entering If either of those 1f true we allocate a new chunk and initialize its fields Otherwise we have some room in our current chunk We increase our counters and return a pointer to the position within the memory field where this chunk starts We clean the mem ory with zeroes before returning it to the calling function Note that we do not keep any trace of the memory we have allocated so it will be impossible to free it after we use it This is not so bad because the operating system will free the memory after this program exists The downside of this implementation is that we can t use this pro gram within another one that would call our word counting routine We have a memory leak built in into our software A way out of this is very easy though We could just convert our mem structures into a linked list and free the memory at the end of the program 1 29 3 Displaying the results After all this work we have a program that will compile when run but is missing the essential part showing the results to the user Let s fix this We need to sort the words by frequency and display the results We build a table of pointers to word list structures and sort it But
365. k time In this way just switching that linker flag on again will allow you to debug the program The debug information generated by Ilcc win32 uses the NBO9 standard as published by Microsoft and Intel This means that the programs compiled with Icc win32 can be debugged using another debugger that understands how to use this standard Filling the blanks 275 In the Resources submenu we find a New item with several options in it We choose the dialog option The dialog editor builds an empty dialog and we are shown the following parameters dialog Dialog 600 Ei Properties Events DLG 0800 Symbol value au Position 6 18 180 180 Caption text Dialog Title Menu none gt Class Font MS Sans Serif Font size g Frame Border style Styles Even if this quite overwhelming we are only interested in two things the title of the dialog and the symbolic identifier We leave all other things in their default state We name the dialog IDD_SEARCH and we give it the title Text search After editing it looks like this Advanced styles Dialog IDD SEARCH x Properties o TS IDD SEARCH So e Symbol value oT Position bH Ha Caption text Text search j Meru mt Class Font HS Sans Serif Font size g FrameBorder style Styles es We press the OK button and we do what we did with the dialog in the DLL our first example The finished dialog should
366. kTable 2 zero greater4Zero te void zero int a exit 0 This terminates recursion void greaterZero int a printi dn a callbackTable a gt 0 a recurse with a 1 int main int argc char argy assume correct arguments n gt 0 greaterZero atoi argv 1 return 0 Error checking can be added to the above program in a similar way This is left as an exercise for the interested reader Of course the utility of function tables is not exhausted by this rather artificial example Deci sion tables can be used as a replacement of dense switch statements for instance When you are very interested in execution speed this is the fastest way of making multi way branches Instead of writing Switch a case 1 some code break case 2 break you could index a table of functions each function containing the code of each case You would construct a function table similar to the one above and you would go to the correct case function using Tablel a The best is of course to use the switch syntax and avoid the overhead of a function call Lec win32 allows you to do this with pragma density 0 This will modify the threshold parameter in the switch construction in the compiler so that a dense table of pointers is automatically generated for each case and all of the cases that aren t represented This is dangerous if your code contains things like
367. ke things more specific let s say we want a hash table of 128 elements which will store list of strings that have the same key Suppose then we have the string abc We add the ASCII value of a b c and we obtain 97 98 99 294 Since we have only 128 positions in our table we divide by 128 giv ing 2 and a rest of 38 We use the rest and use the 3gth position in our table This position should contain a list of character strings that all map to the 3gth position For instance the character string aE 97 69 166 mod 128 gives 38 Since we keep at each position a single linked list of strings we have to search that list to find if the string that is being added or looked for exists A sketch of an implementation of hash tables looks like this define HASHELEMENTS 128 typedef struct hashTable Tait A pasitn Char Sering 3 LILISL PabLle HASHE ELEMENTS HASH TABLE We use a pointer to the hash function so that we can change the hash function easily We build a hash table with a function HASH TABLE newHashTable int hashfn char HASH TABLE fLesubt CC malbloe suzeot HAol TABLE 9 result gt hashfn hashfn return result To add an element we write Lisl Hasnalabileinsere aash TABLE Leable char Astr 142 C programming with Icc win32 int h table gt hashfn str LIST slotp table gt Table h HASHELEMENTS while slotp ae OMSt
368. ks bSuccess FillConsoleOutputCharacter hConsole TCHAR dwConSize coordScreen amp cCharsWritten PERR bSuccess FiliConsoleOutputCharacter get the current text attribute bSuccess GetConsoleScreenBufferInfo hConsole amp csbi PERR bsuccess ConsolescrescnBurteriniro now set the buffer s attributes accordingly bSuccess FillConsoleOutputAttribute hConsole csbi wAttributes dwConSize coordScreen amp cCharsWritten PERR bSuccess FiliConsolecOutputAttribute put the cursor at 0 0 bSuccess SetConsoleCursorPosition hConsole coordScreen PERR bSuccess SetConsoleCursorPosition return This function can be called like this cls GetStdHandle STD OUTPUT HANDLE The library TCCONIO LIB contains many other functions for text manipulation using the console interface The corresponding header file is TCCONIO H which is automatically included when you include conio h This library was contributed by Daniel Guerrero daguer geocities com 3 20 4 Getting a pointer to the stack To get a pointer to the stack use the following code far MyFunction int x INC tar y LK NOTE This pointer will not be valid when the function is exited since the stack contents will change 3 20 5 Disabling the screen saver from a program Under Windows NT you can disable the screen saver from your application code To detect if the screen
369. l open a file given in the command line that is supposed to contain several regular expressions to test If any errors are discovered the results are printed to stdout As with the other standard comment the editor will re read this comment into the interface This features are just an aid to easy the writing of comments and making them uniform and structured As any other feature you could use another format in another environment You could make a simple text file that would be inserted where necessary and the fields would be tailored to the application you are developing Such a solution would work in most systems too since most editors allow you to insert a file at the insertion point 1 9 An overview of the whole language Let s formalize a bit what we are discussing Here are some tables that you can use as refer ence tables We have first the words of the language the statements Then we have a dictio An overview of the whole language 31 nary of some sentences you can write with those statements the different declarations and control flow constructs And in the end is the summary of the pre processor instructions I have tried to put everything hoping that I didn t forget something You will find in the left column a more or less formal description of the construct a short explanation in the second column and an example in the third In the first column this words have a special meaning id meaning an identifier
370. l over what your program is doing without any hidden 1 For an overview of the lec win32 documentation see How to find more information 2 Dennis Ritchie wrote the pre processor of the lcc win32 system 3 Objective C generates C as does Eiffel and several other object oriented languages C precisely because of this lack of a programming model is adapted to express all of them Even C started as a pre processor for the C compiler 4 See the Illinois FP language implementations in C and many other functional programming languages that are coded in C 2 C programming with Icc win32 features The compiler will not do anything else than what you told it to do The language remains transparent even if some features from Java like the garbage collection are incorpo rated into the implementation of C you are going to use As languages come and go C remains It was at the heart of the UNIX operating system devel opment in the seventies it was at the heart of the microcomputer revolution in the eighties and as C Delphi Java and many others came and faded C remained true to its own nature 1 1 Program organization A program in C is written in one or several text files called source modules Each of those modules is composed of functions 1 e smaller pieces of code that accomplish some task and data i e variables or tables that are initialized before the program starts There is a special function called
371. l string representation in C 109 The problems with C Strings 111 Buffer overflows 114 A buffer overflow in the C standard document 116 Memory management and memory layout 119 Functions for memory allocation 120 Memory layout under windows 120 Memory management strategies 122 Static buffers 122 Stack based allocation 122 Arena based allocation 123 The malloc free strategy 123 The malloc with no free strategy 124 Automatic freeing garbage collection 124 Mixed strategies 125 A debugging implementation of malloc 125 Counting words 128 The organization of the table 129 Memory organization 131 Displaying the results 132 Code review 134 Time and Date functions 134 Using structures continued 138 Lists 138 Hash tables 141 A closer look at the pre processor 143 Preprocessor commands 144 Things to watch when using the preprocessor 147 Using function pointers 149 Advanced C programming with Icc win32 154 Operator overloading 154 References 155 Generic functions 155 Default arguments 156 Structured exception handling 156 The signal function 163 Numerical programming 166 Floating point formats 167 What can we do with those numbers then 169 Numerical stability 176 Complex numbers 177 Programming with security in mind 179 Always include a default in every switch statement 179 Pay attention to strlen and strcpy 179 Do not assume correct input 181 Watch out for trojans 181 Pitfalls of the C language 182 Defining a varia
372. l study this program in an in depth manner But note how short this program actually is Many people say that windows programs are impossible huge programs full of fat This is just not true But first we press F9 to compile it Almost immediately we will obtain dialog exe built successfully 0 0 sec 216 C Tutorial Dialog exe built successfully Well this is good news Let s try it You execute the program you just built using Ctrlt F5 When we do this we see our generated program in action Cancel Just a dialog box with the famous OK Cancel buttons and nothing more But this 1s a start We close the dialog either by pressing the x button at the top right corner or just by using OK or Cancel they both do the same thing now since the dialog box 1s empty We come back to the IDE and we start reading the generated program in more detail It has three functions e WinMain e InitializeApp e DialogFunc If we ignore the empty function InitializeApp that is just a hook to allow you to setup things before the dialog box is shown only two functions need to be understood Not a very difficult undertaking I hope 3 1 1 WinMain Command line programs those that run in the ill named msdos window use the main function as the entry point Windows programs use the WinMain entry point The arguments WinMain receives are a sample of what is waiting for you They are a mess of his
373. lank It would look better if we would draw something in it isn t it By the way this is an introduction to C not to windows What can we draw Let s draw a galaxy In his wonderful book Computers Pattern Chaos and Beauty Clifford A Pickover writes We will approximate a galaxy viewed from above with logarithmic spirals They are eas ily programmable in a computer representing their stars with just dots One arm is 180 degrees out of phase with the other To obtain a picture of a galactic distribution of dots simply plot dots at r 0 according to ry ol tan o p ol O tan where rl and r2 correspond to the intertwined spiral arms The curvature of the galactic arms is controlled by which should be about 0 2 radians for realistic results In addi tion 0 lt 0 lt 1000 radians For greater realism a small amount of random jitter may be added to the final points He is kind enough to provide us with a formal description of the program in some computer language similar to BASIC Here it 1s Algorithm How to produce a galaxy Notes The program produces a double logarithmic spiral The purpose of the random number generator 1s to add jitter to the distribution of stars Variables in curvature of galactic arm try in 2 maxit maximum iteration number scale radial multiplicative scale factor cut radial cutoff f final cutoff Code loops Do Or CO max ce theta te lOat 4 7 505
374. lation options valid at the moment of the structure definition or in the concrete settings of the structure packing as specified with the pragma pack construct gt Normally you should never make any assumptions about the specific size of a structure Com pilers and Icc win32 is no exception try to optimize structure access by aligning members of the structure at predefined addresses For instance if you use the memory manager pointers must be aligned at addresses multiples of four if not the memory manager doesn t detect them and that can have disastrous consequences 59 Note that putting structure names in typedefs all uppercase is an old habit that somehow belongs to the way I learned C but is in no way required by the language Personally I find those all uppercase names clearer as a way of indicating to the reader that a user defined type and not a variable is used since I have never used an all uppercase name for a variable name Separating these names by upper lower case improves the readability of the program but this is a matter of personal taste 92 C programming with Icc win32 The best thing to do is to always use the sizeof operator when the structure size needs to be used somewhere in the code For instance 1f you want to allocate a new piece of memory managed by the memory manager you call it with the size of the structure GC Mal loc Si7eOr Struct DalaroIney 67 hy This will allocate space for 67 structur
375. le printf couldn t open s n pszSrcFileName goto DONE We open the destination file for reading and writing with no other access allowed We demand the operating system to create the file if it doesn t exist i hDstFile CreateFile pszDstFileName GENERIC READ GENERIC WRITE 0 0 CREATE ALWAYS 0 0 if INVALID HANDLE VALUE hDstFile printf couldn t create s n pszSrcFileName goto DONE ha We need to query the OS for the size of this file We will need this information later when we create the file mapping object Note that we receive a 64 bit number splitted in two We receive a 32 bit integer containing the result s lower 32 bits and we pass to the function the address where it should put the remaining bits Well if you find this interface strange why not return a 64 bit integer please do not complain to me Note too the strange form of the error checking afterwards we check for a return value of all bits set to one and check the result of the GetLastError API j SetLastError 0 liSrcFileSize LowPart GetFileSize hSrcFile amp liSrcFileSize HighPart if OxXFFFFFFFF 1liSrcFileSize LowPart amp amp GetLastError NO ERROR perinti couldn t g t Size f source filen goto DONE J Special case If the source file is zero bytes we don t map it because there s no need to and anyway CreateFileMapping cannot map a zero length file But since we ve created the destination
376. le first when it handles the creation message And the programmer expects that the value will stay from one invocation of this function to the next This will NOT be the case unless the variable is declared with the static keyword Only then values will be preserved from one call to the next and this becomes correct code This is a very common error 3 21 21 How do I translate between client coordinates to screen coordinates To determine the screen coordinates for the client area of a window call the ClientToScreen function to translate the client coordinates returned by GetClientRect into screen coordinates The following code demonstrates how to use the two functions together REG wMVyRect GetClientRect hwnd LPRECT amp rMyRect ClientToScreen hwnd LPPOINT amp rMyRect left ClientToScreen hwnd LPPOINT amp rMyRect right FAQ 353 3 21 22 When should I use critical sections and when is a mutex better Critical sections and mutexes provide synchronization that is very similar except that critical sections can be used only by the threads of a single process There are two areas to consider when choosing which method to use within a single process Speed The Synchronization overview says the following about critical sections e Critical section objects provide a slightly faster more efficient mechanism for mutual exclusion synchronization e Critical sections use a processor specific test and set i
377. le however 1s to find a buffer overflow in the text of the last official C standard An international standard should present code that is 100 right There are so few lines of code in the standard that making those lines buffer overflow free is not a daunting task by any means 118 C programming with Icc win32 1 26 1 3 The attitude of the committee I am not the first one to point out this problem In a Defect Report filed in 2001 Clive Feather proposed to fix it The answer of the committee was that if any of the members of the input argument was out of range this was undefined behavior and anything was permitted including corrupting memory Corrupting memory provokes bugs almost impossible to trace The symptoms vary and the bug can appear and disappear almost at random depending on the linker and what data was exactly beyond the overflowed buffer This means that the asctime function can t be relied upon Any small mistake like passing it an uninitialized variable will provoke no immediate crash but a crash later in some completely unrelated program point When I reported this bug in the newsgroup comp std c one of the committee members Mr Plauger got completely out of his mind and started insulting the trivial reaction when some body reports a bug 67 Defect Report 217 Submitter Clive Feather UK Submission Date 2000 04 04 Reference Document N A Version 1 3 Date 2001 09 18 15 51 36
378. le is a classic and appears already in the tutorial of the C language published by B W Kernighan in 1974 four years before the book The C programming language was published Their example would still compile today albeit with some warnings Main T peint Hello world n 4 13 The name of the include file is enclosed within a lt gt pair This indicates the compiler that it should look for this include file in the standard include directory and not in the current directory If you want to include a header file in another directory or in the compilation directory use the double quotes to enclose the name of the file like include myfile h 14 This is one of the two possible definitions of the main function Later we will see the other one 15 Character strings can contain sequences of characters that denote graphical characters like new line n tab t backspace b or others In this example the character string is finished by the new line character n 4 C programming with Icc win32 Programs in C are defined in text files that normally have the c file extension You can create those text files with any editor that you want but Icc win32 proposes a specialized editor for this task called Wedit This program allows you to enter the program text easily since it is adapted to the task of displaying C source text To make this program then we start Wedit and enter the text of that program abov
379. lications to use with each application creating its own subkey under the lce key 3 HKEY LOCAL MACHINE Registry entries under this key define the physical state of the computer including data about the bus type system memory and installed hardware and software It contains subkeys that hold current configuration data including Plug and Play information the Enum branch which includes a complete list of all hardware that has ever been on the system network logon preferences network security information The Registry 295 software related information such as server names and the location of the server and other system information Note that you must be the administrator user to be able to modify this tree 4 HKEY USERS Registry entries subordinate to this key define the default user configuration for new users on the local computer and the user configuration for the current user 5 HKEY CURRENT CONFIG Contains information about the current hardware profile of the local computer system The information under HKEY CURRENT CONFIG describes only the differences between the current hardware configuration and the standard configuration Information about the standard hardware configuration is stored under the Software and System keys of HKEY LOCAL MACHINE Actually this key is an alias for HKEY LOCAL MACHINE System CurrentControlSet Hardware Profiles Current This keys provide you with an entry point into the registry To open a key you
380. ll see this in more details in the exceptions section further down 1 35 2 What can we do with those numbers then Let s do some experiments with this formats 1 35 2 1 Range OK We have seen how floating point numbers are stored in memory To give us an idea of the range and precision of the different formats let s try this simple program It calculates the fac torial of its argument and it is not very efficient since it will repeat all calculations at each time fine lLude Aside include lt math h gt fLOaC Tact E Lloat E float resulcaHl 0 while f gt 0 result A gt ay Ee Clase Printer rf break oy return result we Marn VOLE rloat L r 0f fener 2 0 170 C programming with Icc win32 while 1 fE facti foti Te CrLSIINICEL LE break DEINE 210 08 A02 n AICCE Ey sig Oe AS een ee Prince Max Pactorial ie og na ren 1 recur O7 We start with the smallest format the float format We test for overflow with the standard function is_finitef that returns 1 if its float argument is a valid floating point number zero oth erwise We know that our fact function will overflow and produce a NAN Not A Num ber after some iterations and we rely on this to stop the infinite loop We obtain the following output 1 i 2 2 a4 6 4 24 5 A 6 FAO 7 5040 8 40320 91 3623 60 10 3628800 LLL SIILOS0 G 12 4779001600 32
381. lling longymp it is incremented Its value should be two At exit localVariable 1s incremented again at should be three We would expect the output 68 C programming with Icc win32 l 1 22 3 3 And this is indeed the output we get if we compile without any optimizations When we turn optimizations on however we get the output l 22 a2 Why Because localVariable will be stored in a register When longjmp returns it will restore all registers to the values they had when the setjmp was called and if local Variable lives in a reg ister it will return to the value 1 even if we incremented it before calling longymp The only way to avoid this problem is to force the compiler to allocate local Variable in mem ory using the volatile keyword The declaration should look like this int volatile localVariable This instructs the compiler to avoid any optimizations with this variable 1 e it forces allocat ing in the stack and not in a register This is required by the ANSI C standard You can t assume that local variables behave normally when using longjmp setjmp The setyjmp longjmp functions have been used to implement larger exception handling frame works For an example of such a usage see for example Exceptions and assertions in C Interfaces and implementations of David Hanson Chapter 4 Simple programs 69 1 15 Simple programs To give you a more concrete example of how C works h
382. location of small buffers that make for many of the calls to the allocator functions 1 28 8 A debugging implementation of malloc Instead of using directly malloc free here are two implementations of equivalent functions with some added safety features 1 Freeing NULL is allowed 126 C programming with Icc win32 2 Double freeing is made impossible 3 Any overwrite immediately at the end of the block is checked for 4 Memory is initialized to zero 5 A count of allocated memory is kept in a global variable define MAGIC OxFFFF define SIGNATURE 12345678L size t AllocatedMemory void allocate size_t size register char r register int ip NULL size 3 sizeof int r malloc size if rc NULL return fr AllocatedMemory size ip ant At the start of the block we write the signature xip SIGNATURE Then we write the size of the block in bytes ipt int size We zero the data space memset ip size 3 sizeof int We write the magic number at the end of the block just behind the data section ip ant e risize sizeof int ip MAGIC Return a pointer to the start of the data area return t 2 sizeof int void release void pp register int ip NULL int S register char p pp if p NULL Freeing NULL is allowed return The start of the block is two integers before the data p 2 sizeof int ip Int 7 pi if ip
383. lor of the source DC to the color contained in the parts of the bitmap that should be transparent cColor SetBkColor hdcTemp cTransparentColor Create the object mask for the bitmap by performing a BitBIt from the source bitmap to a monochrome bitmap BiacBle hdcOb ject Uy Us Dtsize x Droize y AdcTemp VU U ySRCCOPY Set the background color of the source DC back to the original color setBkColor hdcTemp cColor Create the inverse of the object mask FAQ 339 BitBle hdcBack U Oy DtSize x ptSizesy HdcOb ect 0 0 NOTSRCCOPY 3 I Copy the background of the main DC to the destination BirtBlte hdcMem O05 Oy DPESIZesx ptSaze y hdc xStart VYoteley oRCCOrY s Mask out the places where the bitmap will be placed BitBit hdcMem 0 Uy DPESILZesx PESizesy BadcObyect 0 OU SRCAND Mask out the transparent colored pixels on the bitmap BatBle hdcTemp O 0 ptSize x pPtsize y ndcBack 0 0 SRCAND 7 XOR the bitmap with the background on the destination DC BitBitc hdcMem U Oy DPtESize x ptSize y hdcTemp 0 0 SRCPAINT Copy the destination to the screen BitBle hdc XStart yotart Pptsizezx ptsize y NdcMem 0 Oy SRCCOPY 7 Place the original bitmap back into the bitmap sent here Bate le hadctemp U Oy ptSize x PESize y hdcSave Up Ur SRCUCOPY 4 Delete the memory bitmaps DeleteObject SelectObject hdcBack bmBackOld DeleteObject SelectObject
384. lt For instance this program will crash int main void Char Fo return 1 We have never assigned to p an object where it should point to We are using a dangling pointer When we follow this program we obtain 54 C programming with Icc win32 lid wedit crash c A int maini void char p return 1 p Usttftasasa The debugger tells us that a machine exception has occurred with the code 0xc0000005 This means that the CPU has detected an invalid memory reference and has called the exception mechanism of windows that notified the debugger of the problem Note the value of the pointer in the output window Oxfffa5a5a Lec win32 follows the philosophy that the sooner you see an error the better When it allo cates the stack frame of the function it will write this value to all memory that has not been explicitly initialized by the program When you see this value in the debugger you can be highly confident that this is an unitialized pointer or variable This will not be done if you turn on optimizations In that case the pointer will contain whatever was in there when the compiler allocated the stack frame Note that many other compilers do not do this and some programs run without crashing out of sheer luck Since Icc win32 catches this error it looks to the users as if the compiler was buggy I have received a lot of complaints because of this This kind of problem is one of the most common bu
385. lues If the input value doesn t match any of the enumerated cases and there is no default statement no code will be executed and execution continues after the switch Conceptually the switch statement above is equivalent to if pet CAT Pier Ns S aS seh ea 50 C programming with Icc win32 j else if pet DOG prine This is a dog j else if pet MOUSE PrLinCE INIS rS a Mouse else printf Unknown animal Both forms are exactly equivalent but there are subtle differences Switch expressions must be of integer type The if form doesn t have this limitation In the case of a sizeable number of cases the compiler will optimize the search in a switch statement to avoid comparisons This can be quite difficult to do manually with if s Cases of type other than int or ranges of values can t be specified with the switch statement contrary to other languages like Pascal that allows a range here Switch statements can be nested to any level 1 e you can write a whole switch within a case statement but this makes the code unreadable and is not recommended 1 11 25 inline This instructs the compiler to replicate the body of a function at each call site For instance int inline f int a return at1l Then int a f ot ey will be equivalent to writing Lite av Colyer gt Note that this expansion is realized in the Icc win32 compiler only when optimizations are ON In a normal
386. ly memory locations inside the circuit board See the description of virtual memory under win dows page 120 A pointer can store the start address of an object but nothing says that this object continues to exist If the object disappears the pointers to 1t contain now invalid addresses but it 1s up to the programmer to take care of this An object can disappear if for instance its address is passed to the free function to release the memory An object can disappear if its scope i e the function where it was defined ends It 1s a beginner s mistake to write rat fin a WE a return amp a The a variable has a duration defined until the function fn exits After that function exits the contents of all those memory locations containing local variables are undefined and the function is returning a pointer to memory that will be freed and recycled immediately Of course the memory location itself will not disappear but the contents of it will be reassigned to something else maybe another function maybe another local variable nobody knows A pointer that is not initialized or that points to an object that has disappeared is a dangling pointer and it is the nightmare of any C programmer The bugs produced by dangling pointers are very difficult to find since they depend on whether the pointers destroy or not some other object This programs tend to work with small inputs but will crash mysteriously with c
387. ly DVD ROM UDF is included in the DVD specification and is more flexible than CDFS 3 17 5 Graphics GDI is the lowest level the basic machinery for drawing It provides you e Bitmap support e Brush support for painting polygons e Clipping that allows you to draw within the context of your window without worrying that you could overwrite something in your neighbor s window Filled shapes polygons ellipses pie rectangle lines and curves e Color management palettes etc e Coordinate spaces and transforms e Text primitives for text layout fonts captions and others e Printing But higher levels in such a vast field like graphics are surely possible Lcc win32 offers the standard jpeg library of Intel Corp to read write and display jpeg files Under windows you can do OpenGl an imaging system by Silicon Graphics or use DirectX developed by Microsoft 3 17 6 Handles and Objects An object is implemented by the system with a standard header and object specific attributes Since all objects have the same structure there is a single object manager that maintains all objects Object attributes include the name so that objects can be referenced by name secu rity descriptors to rule access to the information stored in those objects and others for instance properties that allow the system to enforce quotas The system object manager allows mapping of handles from one process to another the DuplicateHandle function and is res
388. memory when loaded including all the above items For alignment reasons this 1s greater than a simple sum of the above parts This size must be a multiple of 4096 bytes a page What does this mean Program size has lately become a non issue Machines have grown so enormously that most people think that if the program makes 2MB or 20MB it doesn t matter This has some justifi cation of course but it is not the philosophy of Icc win32 or C in general Wedit has several tools to get the size of each function and it reports summaries for size information about your program Remember that smaller programs fit better in the cache of the CPU and execute faster since they require less resources 1 2 6 The run time environment The program starts in your machine A specific operating system is running a certain file and hard disk configuration is present you have so many RAM chips installed etc This is the run time environment The file built by the linker IcclInk is started through a user action you double click in its icon or by giving its name at a command shell prompt or by the action of another program that requests to the operating system to start it The operating system accesses the hard disk at the specified location and reads all the data in the file into RAM Then it determines where the program starts and sets the program counter of the printed circuit in your computer to that memory location The piece of code th
389. ment ends include lt stdio h gt int main void for 10t a OF a ZILE A rintef outer 1 26 70m ftor int a Osi lt 22 1b 4 BEINET i dAn return 0 j The output of this program as outer iis 0 i 0 i 1 outer iis 1 i 0 i 1 Note that the scope of the identifiers declared within a for scope ends just when the for state ment ends and that the for statement scope is a new scope Modify the above example as follows to demonstrate this Finelude lt stdio h gt TE Maii Yord for int b 07 I lt eee 4T Pprinc outer a 8 ONN 2 IE ay oe for Inte L Opa 27144 44 prance IS AAND 74 75 6 7 recur 0 8 Passing arguments to a program 15 At the innermost loop there are three identifiers called 1 eThe first i is the outer 1 Its scope goes from line to 7 the scope of the for statement eThe second 1 87 is a local identifier of the compound statement that begins in line 1 and ends in line 7 Compound statements can always declare local variables eThe third 1 is declared at the innermost for statement Its scope starts in line 4 and goes up to line 6 It belongs to the scope created by the second for statement Note that for each new scope the identifiers of the same name are shadowed by the new ones as you would normally expect in C When you declare variables in the first part of the for expression note that you can add state ments and declarations
390. mes sage hello Pine wide lt stdioch gt int main void Peiner ASLO wa ENI 1 2 3 4 crecurn Os 5 6 WSs we oar ia 1 Using a feature of the compiler called pre processor you can textually include a whole file of C source with the include directive In this example we include from the standard includes of the compiler the stdio h header file gt 2 We define a function called main that returns an integer as its result and receives no arguments void 15 3 The body of the function is a list of statements enclosed by curly braces 4 We call the standard function printf that formats its arguments in a character string that is displayed in the screen A function call in C is written like this function name argument list In this case the function name is printf and its argument list is the character string Wello n gt Character strings are enclosed in double quotes They are represented in C as an array of characters finished by a zero byte 5 The return statement indicates that control should be returned hence its name to the calling function Optionally it is possible to specify a return result in this case the integer Zero 6 The closing brace finishes the function scope 11 In C only one return value is possible A function however can return several return values if it modifies its environment 12 This examp
391. met pwszPath 4 The error here is the assumption that the path is a reasonable path that will not overrun the des tination buffer Machine names are normally at most 10 15 chars long If you are not expect ing unreasonable input you can just use the above code And that code was running for quite a long time before this time bomb exploded and a clever hacker found out that he she could gain control of the machine with this sloppy programming snippet 1 36 4 Watch out for trojans The windows API CreateProcess can be given the name of the program to execute in two ways as its first argument or as a whole command line in its second parameter leaving the first empty as NULL Suppose this CreateProcess NULL C Program Files myprogram exe Suppose now that somebody has left a c program exe executable in the right place What will happen CreateProcess will start executing c program instead of the indicated pro gram A simple way to avoid this is to enclose the name of the program in quotes CreateProcess NULL C Program Files myprogram exe K F Notice that the related API WinExec will scan its input for the first space making it worst than CreateProcess In the above example the code WinExec C program files myprogram exe will always try to execute c program if it exists 83 Microsoft Security Bulletin MS03 026 Buffer Overrun In RPC Interface Could Allow Code Execu tio
392. mory twice This corrupts the whole memory allocation system and in a few milliseconds all the memory of your program can be a horrible mess e You allocate memory you free it once but you forget that you had assigned the memory pointer to another pointer or left it in a structure etc This is the dangling pointer problem A pointer that points to an invalid memory location Memory leaks provoke that the RAM space used by the program is always growing eventu ally provoking a crash if the program runs for enough time for this to become significant In short lived programs this can have no consequences and even be declared as a way of mem ory management The lcc compiler for instance always allocates memory without ever both ering to free it relying upon the windows system to free the memory when the program exits Freeing a piece of RAM twice is much more serious than a simple memory leak It can com pletely confuse the malloc system and provoke that the next allocated piece of RAM will be 120 C programming with Icc win32 the same as another random piece of memory a catastrophe in most cases You write to a vari able and without you knowing it you are writing to another variable at the same time destroy ing all data stored there More easy to find since more or less it always provokes a trap the dangling pointer problem can at any moment become the dreaded show stopper bug that crashes the whole program and makes the user
393. mpletely different Note too that the results differ by 12 orders of magnitude just by modifying slightly the calcu lations We modify our program for double precision and now we obtain Needs 3 777893e 022 Numerical programming 173 The gap using double precision is much smaller 9 orders of magnitude than with single pre cision Using qfloats now we write include lt qfloat h gt include lt stdio h gt int main void gfloat f 34 fctf LOCLE faceg i 7 E Tetit iL ee Is Ti 4 Prine TOKO else PLLINCECNOC ok in return U7 This prints OK at the first try Using the extremely precise qfloat representation we obtain gaps smaller than 1 even when the magnitude of the numbers is 10 on This extension of Icc win32 allows you to use extremely precise representation only in the places where it is needed and revert to other formats when that precision is no longer needed 1 35 2 3 Going deeper Let s take a concrete example 178 125 Suppose this program include lt stdio h gt No compiler alignment pragma pack 1 In this structure we describe a simple precision floating point 77 number typedef union float tly struct y unsigned f 23 lt Traction part unsigned e 8 exponent part Unsigned aiey Saan pyre t mumbar if Thus Tuncel on pr NCS Ce parte Or a lodar ng perme number in binary and decimal notation void pfloat number t XPEI Mtr OIJ Qy exponent
394. ms we would pass the length of the character string buffer so that the GetString routine stops input when we reach that limit The C language supports code reuse You can compile code that is useful in many situations and build libraries of routines that can be reused over and over again The advantages are many e The code has to be written once and debugged once e The size of our program stays small since we call a routine instead of repeating the code all over the place Function calls are the mechanism of code reuse since a function can be used in many situa tions Libraries are just a collection of routines that are linked either directly or indirectly with the main program From the standpoint of the user of the library not the one who 1s building it the usage is quite simple 1 You have to include the header file of the library to make the definition available to the compiler 2 You use the functions or data 3 You add the library to the set of files that the linker uses to build your program This simplicity of usage makes libraries a good way to reuse and share the code between dif ferent applications Under windows we have two types of libraries 232 C Tutorial Static libraries These libraries are built in files that normally have the lib extension and are linked with the program directly 1 e they are passed to the linker as arguments The linker takes the code of the needed functions from the library and c
395. n 823980 Originally posted July 16 2003 Revised September 10 2003 Cited by Michael Hor ward in his excellent series about security in msdn The URL for one of its articles is http msdn microsoft com library default asp url library en us dncode html secure09 112003 asp 182 C programming with Icc win32 1 37 Pitfalls of the C language Look I am not a religious person C is not a religion for me and this means that I see some of the pitfalls of the language I write this so that you see them at the start and they do not bite you 1 37 1 Defining a variable in a header file If you write Static Int FOO 75 in a header file each C source file that includes that header will have a different copy of foo each initialized to 7 but each in a different place These variables will be totally unrelated even if the intention of the programmer is to have a single variable foo If you omit the static at least you will get an error at link time and you will see the bug Golden rule Never define something in a header file Header files are for declarations only 1 37 2 Confusing and If you write 66 99 you are assigning to a the number 6 instead of testing for equality The if branch will be always taken because the result of that assignment is different from zero The compiler will emit a warning whenever an assignment in a conditional expression is detected 1 37 3 Forgetting to close a c
396. n an unused parameter that will always contain zero maintained there for compatibil ity reasons with older software lpCmdLine This one is important It is actually a pointer to a character string that contains the command line arguments passed to the program Note that to the contrary of main there isn t an array of character pointers but just a single character string containing all the com mand line nCmdShow This one contains an integer that tells you if the program was called with the instruction that should remain hidden or should appear normally or other instructions that you should use when creating your main window We will ignore it for now OK OK now that we know what those strange parameters are used or not used for we can see what this function does int APIENTRY WinMain HINSTANCE hinst HINSTANCE hinstPrev LPSTR lpCmdLine int nCmdShow WNDCLASS wc A structure of type WNDCLASS memset amp wc 0 sizeof wc We set it to zero wc lpfnWndProc DefDlgProc Procedure to call for handling messages wce cbWndExtra DLGWINDOWEXTRA wc hInstance hinst wc hCursor LoadCursor NULL IDC ARROW wc hbrBackground HBRUSH COLOR WINDOW 1 wc lpszClassName dialog RegisterClass amp wc return DialogBox hinse MAKEINTRESOURCE IDD MAINDIALOG NULL DLGPROC DialogFunc We see that the main job of this function 1s filling the structure wc a WNDCLASS structure with data
397. n src char pbEncodedBlob src content StringA result Open a message for decoding hMsg CryptMsgOpenToDecode MY ENCODING TYPE Encoding type Oy Flags CMSG DATA Look for a data message NULL j Cryptographic provider NULL Recipient information NULL if hMsg return U Update the message with an encoded BLOB Both pbEncodedBlob the encoded data and cbEncodedBlob the length of the encoded data must be available 1f CryptMsgUpdate hMsg Handle to the message pbEncodedBlob Pointer to the encoded BLOB cbEncodedBlob Size of the encoded BLOB TRUE Last call return OF Get the size of the content if CryptMsgGetParam hMsg Handle to the message CMSG CONTENT PARAM Parameter type Oy Index NULL Address for returned information amp cbDecoded Size of the returned return 0 Allocate memory pbDecoded malloc cbDecodedt l Get a pointer to the content if CryptMsgGetParam hMsg Handle to the message CMSG CONTENT PARAM Parameter type 0 Index pbDecoded Address for returned 364 C Tutorial information amp cbDecoded return 0 jj Clean up if hMsg CryptMsgClose hMsg SrCcvG apacicy cbDecodedt 1 SrC Counc cbDecoded sro content pbDecoded return 1 Int SLrencrypt String src HCRYPTMSG hMsg BYTE pbContent DWORD cbContent DWORD cbEncodedBlob BYTE pbEncodedBlob
398. n dereferences the pointer and retrieves the entire object it is pointing to making it the exact opposite of the amp address of operator Only two kinds of arithmetic operations are possible with machine addresses Addition or sub traction of a displacement or subtraction of two machine addresses No other arithmetic oper ators can be applied to pointers 1 13 1 1 Addition or subtraction of a displacement Adding a displacement an integer to a pointer means Using the address stored in that pointer find the lt nth gt object after it If we have a pointer to int and we add to it 5 we find the 5th integer after the integer whose address was stored in the pointer Example mie LLOTI ine pint sai The number stored in pint is the memory location index where the integer d starts say 0x4202600 The size of each integer is 4 so the 3th integer after 402600 starts at 0x4202608 If we want to find the fifth integer after 0x4202608 we add 20 5 sizeof int 20 and we obtain 0x420261C To increase a pointer by one means adding to it the size of the object it 1s pointing to In the case of a pointer to integer we add 4 to 0x204600 to obtain the next integer This is very often written with the shorthand Dinca or FO Lit This is a short hand for Move the pointer to point to the next element Obviously this is exactly the same for subtraction Subtracting a displacement from a pointer means to point it
399. n fier i e the symbolic name that we will use in our program to l Month Calendar refer to it EES List view 4 Tab control Th iF iea Tree control File Edit Search Project Desi mn Progress control Name IDENTRYFIELD Spin button eh Slider FS DateTime We will refer then in our program to this entry field with the name IDENTRYFIELD maybe not a very cute name but at least better than some bare number The editor will write a define IDENTRYFIELD 101 in the generated header file The number 101 is an arbitrary constant chosen by the editor We resize the dialog box a bit I like dialogs that aren t bigger than what they should be and we press the test button We see a display like this dialog x ea Cancel We can enter text in the entry field and pushing Cancel or OK will finish the test mode and return us to the dialog box editor Introduction 223 OK seems to be working We save and close the dialog box editor We come back to our dia log procedure where we will use this new entry field to get some text from the user 3 1 3 The dialog box procedure static BOOL CALLBACK DialogFunc HWND hwndDlg UINT msg WPARAM wParam LPARAM lParam switch msg A case WM INITDIALOG InitializeApp hwndDlg wParam lParam return TRUE case WM COMMAND Switch LOWORD wParam case IDOK EndDialog hwndDlg 1 return 1 case IDCANCEL EndDialog hwndDlg 0 PecC
400. n getc The intention was to assign the value from getc to chr then to test the value against EOF The problem occurs in the first line which says to call the library function getc The return value from getc an integer value representing a character or EOF if end of file is detected is compared against EOF and if they are not equal it s not end of file then 1 is assigned to the object chr Otherwise they are equal and 0 is assigned to chr The value of chr is therefore always 0 or 1 The correct way to write this code fragment is it Chr getc TS EOE Jo 4 peere ihe value oF chews Sans ENE J3 The extra parentheses force the assignment to occur first and then the comparison for equality is done gt Another operator precedence error is the following Fine lide stdion 84 Doing assignment inside the controlling expression of loop or selection statements is not a good programming practice These expressions tend to be difficult to read and problems such as using instead of are more difficult to detect when in some cases is desired 85 How does it work He tests first if the lower 16 bits contain a bit The number 65535 consists of eight 1s in binary notation since 65535 2 1 If the test fails this means that the least significant bit can t be in the lower 16 bits He increases the counter by 16 and shifts right the number to skip the 8 bits already known to contain zero If
401. n item under this coordinates If there is none we stop Now we have a tree item We need to know which window 1s associated with this item so that we can query the window for more information Since we have left in each item the window handle it is displaying we retrieve this information We hide the details of how we do this in a subroutine Get TreeItemInfo that returns us the window handle A more complex example a clone of spy exe 265 Using that window handle we call another function that will display the info in the status bar We pass all messages to the default window procedure this is a non intrusive approach The tree control could use our notifications for something We just need to do an action when this event happens but we want to disturb as little as possible the whole environment 3 10 8 Auxiliary procedures To retrieve our window handle from a tree item we do the following static HWND GetTreeItemiInfo HWND hwndTree HTREEITEM hti IV LTEM tvi memset Gtvi 0 sizeor IV ITEM J7 tVvismask IVIE PARAM eyishi tem HTL TreeView GetItem hwndTree amp tv1 return HWND tvi lParam As you can see it is just a matter of filling a structure and querying the control for the item we are interested only in the PARAM part of the item More complicated is the procedure for querying the window for information Here is a simple approach void SetTextInStatusBar HWND hParent HWND hwnd RECT FOJ
402. n that ends the program immediately 2 We use the conditional statement 1f to test for a given condition The general form of it is if condition statements else statements 3 We use the exit function to stop the program immediately This function receives an integer argument that will be the result of the program In our case we return the error code 1 The result of our program will be then the integer 1 Now when we call countchars without passing it an argument we obtain a nice message h lcec examples gt countchars Usage countchars lt file name gt This is MUCH clearer than the incomprehensible message box from the system isn t it Now let s try the following h lcc examples gt countchars zzzssqaqqqq And we obtain the dreaded message box again Why Well it is very unlikely that a file called zzzssqqqqq exists in the current directory We have used the function fopen but we didn t bother to test if the result of fopen didn t tell us that the operation failed because for instance the file doesn t exist at all A quick look at the documentation of fopen that you can obtain by pressing F1 with the cur sor over the fopen word in Wedit will tell us that when fopen returns a NULL pointer a zero it means the open operation failed We modify again our program to take into account this possibility Fine LUude lt stdio h gt fine tude lt Srdlibsh gt Ino o main
403. n the ulOutBufLen the necessary buffer length Using this information we allocate the necessary memory and then call GetNetworkParams again This is a common interface with many network APIs that need buffers of varying length Ei Prixedinto FIXED INFO y malloc Sizeof FIXED INFO uULOUCBUrLen size0r FIXED INFO rc GetNetworkParams pFixedInfo amp ulOutBufLen if rc ERROR BUFFER OVERFLOW 4 free pFikedInfo prixedinio FIXED INFO malloc ulOutButlen else return GetLastError failed for another reason Exit Now this call is for real dwRetVal GetNetworkParams pFixediInfo amp ulOutBufLen if dwRetVal NO ERROR printf Call to GetNetworkParams failed nError code d n GetLastError return 1 l Show the retrieved information printf tHost Name s n pFixedInfo gt HostName printf tDomain Name s n pFixediInfo gt DomainName princi CDNS Servers n 3 printf t t3s n pFixedInfo gt DnsServerList IpAddress String The server list is stored as a linked list Go through that list until we hit a NULL pIPAddr pFixediInfo gt DnsServerList Next while pIPAddr printf t t Ss n pIPAddr gt IpAddress String pIPAddr pIPAddr gt Next i I Show the other parameters printf tEnable Routing s n pFixediInfo gt EnableRouting Yes No printi tEnable Proxy s n PFixedinfo gt ENeblecProxy
404. n use pdh lib to get a list of all the running processes here 1s a simple code that will print this list in the standard output i Using pdh lib to get a list of the running processes This sample is adapted from the similar sample code in the windows SDK Compile with Ic listproc c pdh lib I include lt windows h gt include lt winperf h gt include lt malloc h gt 330 C Tutorial include lt stdio h gt include lt pdh h gt include lt pdhmsg h gt int main void PDA ofAlus pdhStatus ERROR SUCCESS LPISTR szCounterListBuffer NULL DWORD dwCounterListsize 0 LPTSTR szinstanceListBuffer NULL DWORD dwiInstanceListsSize 0 LPTSTR szThisInstance NULL call the function to determine the required buffer size for the data pdhStatus PdhEnumObjectIitems NULL reserved NULL local machine Process object to enumerate szCounterListBuffer pass in NULL buffers amp dwCounterListSize an 0 length to get szInstanceListBuffer vequired size amp dwinstanceListSize of the buffers in chars PERF DETAIL WIZARD counter detail level 0 if pdhStatus ERROR SUCCESS amp amp pdhStatus PDH MORE DATA printf nUnable to determine the buffer size required return 1 allocate the buffers and try the call again PdhEnum functions will return ERROR _SUCCESS in WIN2K but PDH_MORE_DATA in XP and later In either case dwCounterListSize and dwinstanc
405. n windows file systems allow you to track file operations and access their journal data You can encrypt data and at last under windows 2000 Unix s mount operation is recognized You can establish symbolic links for files 1 e consider a file as a pointer to another one This pointer is dereferenced by the file system when accessing the link Windows supports several file systems 1 NTFS NTFS is the preferred file system on Windows It was designed to address the requirements of high performance file servers and server networks as well as desktop computers and in doing so address many of the limitations of the earlier FAT16 and FAT32 file systems Etc 303 2 FAT32 The File Allocation Table FAT file system organizes data on fixed disks and floppy disks The main advantage of FAT volumes is that they are accessible by MS DOS Windows and OS 2 systems FAT is the only file system currently supported for floppy disks and other removable media FAT32 is the most recently defined FAT based file system format and it s included with Windows 95 OSR2 Windows 98 and Windows Millennium Edition FAT32 uses 32 bit cluster identifiers but reserves the high 4 bits so in effect it has 28 bit cluster identifiers 3 UDF file system The implementation is compliant with ISO 13346 and supports UDF versions 1 02 and 1 5 OSTA Optical Storage Technology Association defined UDF in 1995 as a format to replace CDFS for magneto optical storage media main
406. n with single linked lists too Given a pointer to the start of the list and an element of it we can write a Previous function like this Using structures continued 141 LIST Previous LIST root LIST element if root NULL return NULL while root amp amp root gt Next element root root gt Next LeCurN LOOT Circular lists are useful too We keep a pointer to a special member of the list to avoid infinite loops In general we stop when we arrive at the head of the list Wedit uses this data structure to implement a circular double linked list of text lines In an editor reaching the previous line by starting at the first line and searching and searching would be too slow Wedit needs a dou ble linked list and a circular list makes an operation like wrapping around easier when search ing 1 31 2 Hash tables A hash table is a table of lists Each element in a hash table is the head of a list of element that happen to have the same hash code or key To add an element into a hash table we construct from the data stored in the element a number that is specific to the data For instance we can construct a number from character strings by just adding the characters in the string This number is truncated module the number of elements in the table and used to index the hash table We find at that slot the head of a list of strings or other data that maps to the same key modulus the size of the table To ma
407. n32 D Sercnr g 7 Cut the specification at the separator char if p p 0 h FindFirstFile q amp data if h INVALID HANDLE VALUE do 4 if data dwFileAttributes amp FILE ATTRIBUTE DIRECTORY We have found a matching file Call the user s function sprintf fullname s s dir data cFileName if fn fullname return U j while FindNextFile h amp data FindClose h Restore the input specification It would be surprising for the user of this application that we destroyed the character string that was passed to this function if p torr Tees Advance q to the next specification q Pr while q OK We have done all the files in this directory Now look if there are any subdirectories in it and if we found any recurse hdir FindFirstFile amp dirdata if hdir INVALID HANDLE VALUE do if dirdata dwFileAttributes amp FILE ATTRIBUTE DIRECTORY This is a directory entry Ignore the and entries if dirdata cFileName 0O amp amp dirdata cFileName 1 dirdata cFileName 1 We change the current dir to the subdir and recurse chdir dirdata cFileName ScanFiles spec fn Restore current directory to the former one Choir dar gt while FindNextFile hdir amp dirdata FindClose hdir return 1 This function above could be used in a program like this
408. nTa 4 7 2 3 Accepting connections Once the socket is listening for a connection we must handle connection requests on that socket To accept a connection on a socket we create a temporary socket object for accepting connections SOCKET AcceptSocket Create a continuous loop that checks for connections requests If a connection request occurs call the accept function to handle the request prine e WateinG Or a CLvene ao connects tn 2 3 while 1 RECepLSOCKeE SOCKET ERROR while ACCepESOCker SOCKET ERROR 4 AcceptSocket accept Socket NULL NULL When the client connection has been accepted assign the temporary socket to the original socket and stop checking for new connections 382 C Tutorial penti Client Connected yng Socket AcceptSocket break There we go we have a socket ready to send and receive data 4 7 3 Client side For a client to communicate on a network it must connect to a server To connect to a socket we create a sockaddr in object and set its values sockaddr im clientservice elientservice lt sin Lamily Ar INET ClUeneservice sin addres addr Inet addr TIZ sO OL y clieniservicessin port htoens 49025 J7 Call the connect function passing the created socket and the sockaddr _in structure as parame ters ine EO rc connect Socket SOCKADDR amp clientService sizeof clientService if re SOCKET ERROR Prince Paa led tOo conne
409. nd colon memmove relname 2 relname strlen relname 1 relname 0O cwd 0 relname 1 cwd 1 absname relname else file name begins with letter relname begins with a letter prepend cwd strcat cwd relname absname cwd return absname MATT Get current directory For some reason unknown to mankind getcwd returns C FOO no at end if dir is NOT root yet it returns C with if cwd is root Go figure To make the result consistent for appending a file name GetCurrentDir adds the missing if needed Result always has final MATT char GetCurrentDir void static Char dir MAX PATH getcwd dir sizeof dir Append if needed int lastchar strlen dir 1 358 C Tutorial i lastchar gt 0 6 amp 6 dirilastchar f at last char isn t strcat dir add one return dir IALTA IIT TEL IES Get user confirmation to recycle delete a file ELIT TAT IP ET eTeee BOOL confirm LPCTSTR pFileName while TRUE printf Recycle s Y N Al11 pFileName char c getch if e457 t Prince Cn exit 0 prance n switch tolower c case a bPrompt FALSE fall through case y return TRUE case n return FALSE VIITITT SII re Get Windows system error message SIALL ASAA TIT Tiers LPCTSTR GetErrorMsg int err Static Char but BUFSIZ buf 0 0 Only Windows
410. ndow instead of drawing a blank window we add a handler for the WM_ PAINT message like this LRESULT CALLBACK MainWndProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam Switch msg case WM PAINT DoPaint hwnd break case WM DESTROY return 0 In our DoPaint procedure we will do just that paint the lcd window We need first to draw a simple character set from which we will copy the characters into the display Here is a simple one In this bitmap we use three colors a light blue for drawing the body of the characters a darker blue for drawing the background of the characters and black to draw the space 292 C Tutorial between each character Our drawing procedure DoPaint will make a mapping between the bitmap colors and the color we want to give to our simulated display To draw the characters we will make a memory display context where we will store the bit map of characters When we want to draw one char we will copy from the memory bitmap to the display window the portion of the bitmap that contains our character translating the colors as we go We have to take care of scrolling if necessary and many other things The purpose here is not to show you how you implement the best ever lcd display in a PC but to show the interfaces of a custom control so we will keep the logic to the bare minimum Let s see our DoPaint procedure static void DoPaint HWND hwnd il PAI
411. ndowRen to set this as the clipping region for the window Subsequent painting and mouse messages are limited to this region and Windows automatically updates underlying windows FAQ 343 that show through the non rectangular window The application need only paint the window as desired For more information on using SetWindowRgn see the Win32 API documentation 3 21 11 How do I implement a non blinking caret Although Windows is designed to blink the caret at a specified interval a timer function and SetCaretBlinkTime can be used to prevent Windows from turning the caret off by following these three steps e Call SetCaretBlinkTime 10000 which instructs Windows to blink the caret every 10 000 milliseconds 10 seconds This results in a round trip time of 20 seconds to go from OFF to ON and back to OFF or vice versa e Create a timer using SetTimer specifying a timer procedure and a 5 000 millisecond interval between timer ticks e In the timer procedure call SetCaretBlinkTime 10000 This resets the timer in Windows that controls the caret blink When an application implements this procedure Windows never removes the caret from the screen and the caret does not blink 3 21 12 How dol create a title window splash screen A splash screen title screen can be used by an application to display important information about a program The splash screen can also be used as an activity indicator during application Star
412. ner and Windows 95 98 Organization HKEY LOCAL MACHINE SOFTWARE Microsoft Win dows CurrentVersion Windows NT 2000 XP HKEY LOCAL MACHINE SOFTWARE Microsoft Win dows NT CurrentVersion Change the version of the Icc win32 HKEY_CURRENT_USER software lcc compiler to a new location or to an older newer version Disabling tooltips Although ToolTips may be helpful you might find it annoy ing To disable it go to HKEY USERS DEFAULT Control Panel Desktop On the right pane double click UserPrefer encemask and change the value to 3E 00 00 00 To enable it again change the value back to BE 00 00 00 a Windows registry guide http www winguides com registry where I took some of the examples above They distribute for free a very interesting guide in windows help format full of tips like that Another similar site 1s http www activewin com tips reg index shtml Etc 299 3 17 Etc At last count there was around 17000 APIs in the file Icc lib apilist txt This file is used by the linker to figure out in which library a given API 1s found You can look at it to get an impression of the richness of the windows API There are functions for many kinds of stuff and here I will just try to give a very superficial overview of all that You are invited to down load the SDK documentation for free from the Microsoft MSDN site Lec win32 gives you access to all this Clipboard Just that A common repository for shared data
413. ner s aot her ON r e ssa pene e LO The value returned by all this functions is EOF End Of File usually 1 if an error occurred during the output operation Otherwise all went OK and they return the number of characters written For sprintf the returned count does not include the terminating zero appended to the output string The fmt argument is a character string or control string It contains two types of charac ters normal characters that are copied to the output without any change and conversion spec ifications that instruct the function how to format the next argument In the example above we have just the string hello n without any conversion specification so that character string is simply copied to the destination There should be always at least as many arguments to this functions as there are conversion specifications If you fail to do this with Ilcc win32 you will get a warning from the compiler Other compilers can be less user friendly so do not rely on that 1 12 1 Conversions A conversion specification begins with a percent sign and is made of the following ele ments 1 Zero or more flag characters 0 or space which modify the meaning of the operation 2 An optional minimum field with Note well this The printf function will not truncate a field The specified width is just that a minimum 3 An optional precision field made of a period followed by a number
414. nge of undefined behavior permitted includes Corrupting memory Aborting the program Range checking the argument and returning a failure indicator e g a null pointer Returning truncated results within the traditional 26 byte buffer There is no consensus to make the suggested change or any change along this line Memory management and memory layout 119 1 27 Memory management and memory layout We have until now ignored the problem of memory management We ask for more memory from the system but we never release it we are permanently leaking memory This isn t a big problem in these small example applications but we would surely run into trouble in bigger undertakings Memory is organized in a program in different areas 1 The initial data area of the program Here are stored compile time constants like the character strings we use the tables we input as immediate program data the space we allocate in fixed size arrays and other items This area is further divided into initialized data and uninitialized data that the program loader sets to zero before the program starts When you write a declaration like int data 78 the data variable will be stored in the initialized data area When you just write at the global level int data the variable will be stored in the uninitialized data area and its value will be zero at program start 2 The stack Here is stored the procedure frame 1 e the arguments and local variables of e
415. ngle character 1s accomplished by the Strinsert function or its alias insert that should work with all containers POOLE Cr TSS Ll String 6S 627e e pos int Mewval 89 Note that in C is not possible to distinguish between this two There is no operator Implementation 201 Ghar Content int New Capacity struct Exception exc GetAnExceptionStructure PRECONDITION Strvalid s exc PRECONDITION pos lt s count exc new Capacity Calculate new Capacity S Capacily S capacityrl if New capacity gt S2Capacity 4 content allocate proper space new capacity SMALL if content NULL return Crue Memepy COntent S COnUvent S COUNT S Capacity new Capacity s content content else content s content memmove content pos 1 content tpos s count pos SCONE content pos newval content s count 0 return true The preconditions are a valid string and a valid index We call the calculate new capacity function to get an estimate of the best new size 1f a string resize is needed This is a relatively expensive operation so we always allocate more space than strictly needed to avoid resizing the string at each character added After we have ensured that we have the space needed we make place for the new character by moving the tail of the string one position up The erase function or Strerase will remove a character from the string at the indicated po
416. nience And no it doesn t help to call Microsoft It is not their fault this time What happened Obvious The printf specification 10s will NOT limit the copy to 10 characters It just says that the string will be padded at the left with blanks if it is shorter than 10 chars If not sprintf will continue to copy the characters without any limit Our function can be made safe very easily by just using snprintf instead of its dangerous cousin sprintf The snprintf function will take an optional integer argument after the for mat string telling it how many characters it should write at most into its destination buffer void func char p char buf 10 1 memset buf 0 sizeof buf fy dimit string to 10 chars by sing snaprinct snprintf buf 10 10s p printf Hello s n buf l This time we see the expected output O J Hello a 1 Hello aa 2 Hello aaa o gt Helio aaaa 4 Hello aaaaa 5 Hello aaaaaa 6 Hello aaaaaaa 74 Helle aaaaaaaa 8 Hello aaaaaaaaa 9 Hello aaaaaaaaaa 10 Hello aaaaaaaaaa 11 Hello aaaaaaaaaa 12 Hello aaaaaaaaaa Programming with security in mind 181 1 36 3 Do not assume correct input Do you remember the Blaster worm Here is the code that allowed the Blaster worm to exist HRESULT GetMachineName WCHAR pwszPath WCHAR wszMachineName N 1 LPWSTR pwszServerName wszMachineName while pwszPath L pwszServerNa
417. ns the declaration of which func tion This can be a pain and it 1s easy to confuse some header with another To avoid this over loading of the brain memory cells Icc win32 proposes a stdheaders h file that consists of 23 Inthe user s manual there is an exhaustive list of the entire set of header files distributed with lcc win32 Please look there for an in depth view Passing arguments to a program 11 include lt assert h gt include lt complex h gt ete Instead of including the standard headers in several include statements you just include the stdheaders h file and you are done with it True there is a very slight performance lost in compilation time but it is not really significant 1 3 2 Windows specific headers There are several megabytes of windows header files and we will not explain them all here windows h All windows definitions Creating a window opening a window this is an extensive header file makes approx half a megabyte of definitions Note that under lcc win32 several headers like winbase h of other distri butions are concentrated in a single file Network tcpip shellapi h Windows Shell 1 4 Passing arguments to a program We can t modify the behavior of our hello program with arguments We have no way to pass it another character string for instance that it should use instead of the hard wired hello n We can t even tell it to stop putting a trailing new line charac
418. nstruction to determine mutual exclusion Deadlock The Synchronization overview says the following about mutexes e Ifa thread terminates without releasing its ownership of a mutex object the mutex is considered to be abandoned A waiting thread can acquire ownership of an abandoned mutex but the wait function s return value indicates that the mutex is abandoned e WaitForSingleObject will return WAIT ABANDONED for a mutex that has been abandoned However the resource that the mutex is protecting is left in an unknown State e There is no way to tell whether a critical section has been abandoned 3 21 23 Why is my call to CreateFile failing when use conin or conout If you attempt to open a console input or output handle by calling the CreateFile function with the special CONIN or CONOUTS filenames this call will return INVALID HANDLE VALUE if you do not use the proper sharing attributes for the fdw ShareMode parameter in your CreateFile call Be sure to use FILE SHARE READ when opening CONIN and FILE SHARE WRITE when opening CONOUT 3 21 24 How can I conttrol the task bar under program control You can control the state of the task bar or query the characteristics using the SHAppBarMes sage API This is a complex API that allows you to change where the tasklbar is localted whether it is automatically hidden etc For instance this small program will show you 1f the task bar auto hide feature is on or off
419. nt when the user presses the ESC key The button should also have the BS DEFPUSHBUTTON style so that the ENTER key will also result in the termination of the CPU intensive subtask FARPROC lpProgressProc HWND hwndProgress This needs to be global if accessed by other modules Initialize before starting CPU intensive work EF 336 C Tutorial lpProgressProc MakeProciInstance ProgressDlgProc hinsty 7 Current Instances hwndProgress CreateDialog hInst Current Instances PROGRESS DLG 7 Resource a hwndParent Parent handle X7 loProgressProc Instance address ShowWindow hwndProgress Start CPU intensive work here Before or after each unit of work the application 1s should do he tol owing a ProgressYield hwndProgress if Cancel TRUE break Terminate CPU intensive work immediately End CPU intensive work here DestroyWindow hwndProgress FreeProcinstance lpProgressProc 3 21 2 How do show in the screen a print preview If a screen font is available that exactly matches or at least very closely corresponds to the chosen printer font then the process 1s very straightforward and consists of seven steps Retrieve a Device Context DC or an Information Context IC for the printer Call EnumFontFamilies to obtain a LOGFONT structure for the selected printer font The nFontType parameter to the EnumFontFamilies callback function speci
420. ntaries of course but in their content There are several rules to keep in mind Always keep the commentaries current with the code that they are supposed to comment There is nothing more frustrating than to discover that the commentary was actually mislead ing you because it wasn t updated when the code below changed and actually instead of help ing you to understand the code it contributes further to make it more obscure Do not comment what are you doing but why For instance recordt increment record by one This comment doesn t tell anything the C code doesn t tell us anyway recordi Pass LO mMext record The boundary tests are done at the beginning of the loop above This comment brings useful information to the reader At the beginning of each procedure try to add a standard comment describing the purpose of the procedure inputs outputs error handling etc At the beginning of each module try to put a general comment describing what this module does the main functions etc Note that you yourself will be the first guy to debug the code you write Commentaries will help you understand again that hairy stuff you did several months ago when in a hurry The editor of lcc win32 provides a Standard comments feature There are two types of com ments supported comments that describe a function and comments that apply to a whole file This comments are maintained by the editor that displays a simple interfa
421. ntrols added to windows after 1995 366 C Tutorial Note that Wedit will detect if the documentation is installed and will allow you to see the doc umentation of any function just with pressing the F1 key This is a nice feature especially for beginners Install a full version if you aren t an expert A version without the documentation it is a pain since you have to go fishing for that information each time you want to call an API not a very exciting perspective But if you want to get serious about windows programming you should download the Microsoft Software Development Kit SDK from the msdn site and install it in your machine Wedit will automatically recognize the msdn library or the SDK if installed and will call them instead of using the win32 hlp file 3 24 Bibliography Here are some books about programming in Windows I recommend you to read them before you believe what I say about them Programming Windows Charles Petzold Microsoft Press This 1s a very easy to read introduction to the windows API that covers in depth all aspects of windows programming You can download an electronic version of this book at the site of the author www cpetzold com Windows Network Programming Ralph Davis Addison Wesley This 1s a very extensive introduction to this side of programming If you want an in depth cov erage of sockets net bios etc etc here you will find it Windows System programming Secrets Mat
422. numerate the key values SetCursor LoadCursor NULL IDC WAIT if cValues fOr J U retValue ERROR SUCCHOS J lt cValues Jtt cchValue MAX VALUE NAME achValue 0 407 retValue RegEnumValue hKey J achValue amp cchValue NULL NULL amp dawType NULL amp boData NULL amp bocData if retValue DWORD ERROR SUCCESS SCheure lO T0 Add each value to a list box The Registry 297 if lstrlen achValue lstrcpy achValue lt NO NAME gt WSPELNEL achBurrt sdr zs Ti Te sachValue sendMessage GetDlgItem hDlg IDL LISTBOX2 LB ADDSTRING 0 LONG achButt gt SetCursor LoadCursor NULL IDC ARROW 3 16 3 Rules for using the registry Although there are few technical limits to the type and size of data an application can store in the registry certain practical guidelines exist to promote system efficiency An application should store configuration and initialization data in the registry and store other kinds of data elsewhere Generally data consisting of more than one or two kilobytes K should be stored as a file and referred to by using a key in the registry rather than being stored as a value Instead of dupli cating large pieces of data in the registry an application should save the data as a file and refer to the file Executable binary code should never be stored in the registry For instance lcc win32 stores just the name of the
423. ny more this dreaded problem that took us so many debugging hours with the primitive debugger of that time In the C language the compiler will abort compilation if a function is used without prototypes I have thought many times to introduce that into Icc win32 because ignor ing the function prototype is always an error But for compatibility reasons I haven t done it yet g 1 5 3 Function definitions Function definitions look very similar to function declarations with the difference that instead of just a semi colon we have a block of statements enclosed in curly braces as we saw in the function main above Another difference is that here we have to specify the name of each argument given these identifiers aren t optional any more they are needed to be able to refer to them within the body of the function Here is a rather trivial example int addOne int input return inputtl 1 5 4 Variable definition A variable is defined when the compiler allocates space for it For instance at the global level space will be allocated by the compiler when it sees a line like this InG A7 or int a 67 In the first case the compiler allocates sizeof int bytes in the non initialized variables section of the program In the second case it allocates the same amount of space but writes 67 into it and adds it to the initialized variables section 1 5 5 Statement syntax In C the enclosing expressions of control st
424. o be able to do whatever you want to do You can 1 customize the appearance of a control by making some of its parts owner draw 1 e drawed by yourself 2 Process some special windows messages that allow you to change the font the background color and other characteristics by modifying the settings of a passed device context HDC In both cases the interface is quite simple Windows sends a message to the procedure of the parent window of the control to ask it to draw a specific part of the control Some or all of the control behavior is retained but the appearance can be changed as you like 3 14 1 Processing the WM_CTLCOLORXXX message We can start with a simple example that draws a listbox in a special way Let s use the second method first since it is easier Suppose we want to display the text in a listbox in red color In the dialog procedure which owns the list box or in the windows procedure if it is a list box created independently you receive the WM CTLCOLORLISTBOX message In the wparam parameter you receive an HDC that you can customize using SetTextColor to draw the text with the color you wish To inform windows that you have processed this message you should return a handle to a brush that will be used to paint the background of the listbox Notice that windows does not destroy this object You should destroy it when the dialog box finishes Creating and destroying the brush that you should return is cumber
425. o bits The only case where this will not happen is when x is a power of two Of course if x 1s zero not a power of two this doesn t hold so we add an explicit test for zero with the logical AND operator 47 For amore detailed discussion see the section News groups at the end of this tutorial 72 C programming with Icc win32 xx amp amp expression Negative powers of two 0 5 0 25 0 125 etc could share this same property in a suitable fraction representation 0 5 would be 0 1 0 250 would be 0 01 0 125 would be 0 001 etc This snippet and several others are neatly explained in http www caam rice edu dougm twiddle 1 15 5 strilwr Given a string containing upper case and lower case characters transform it in a string with only lower case characters Return a pointer to the start of the given string This is the library function st r1lwr In general is not a good idea to replace library functions even if they are not part of the standard library as defined in the C standard like this one We make the transformation in place 1 e we transform all the characters of the given string This supposes that the user of this program has copied the original string elsewhere 1f the orig inal is needed again include lt ctype h gt needed for using isupper and tolower include lt stdio h gt needed for the NULL definition Char strTolower char str iterates through str unsigned char p un
426. o long long 11 modifier Contrary to all other conversions this conversion O writes the number of characters written so far in the address pointed by its argu ment Signed decimal floating point conversion Argument is of type double default or long double withthe L modifier or qf loat with the q modifier The result will be displayed in scientific notation with a floating point part the letter e for the e format or the letter E for the E format then the exponent If the precision is zero no digits appear after the decimal point and no point is shown If the flag is given the point will be printed Signed decimal floating point conversion Argument is of type double default or long double with the L modifier If the argument is the special value infinite inf will be printed If the argument is the special value NAN the letters nan are written This is the same as the above but with a more compact representation Argu ments should be floating point Trailing zeroes after the decimal point are removed and if the number is an integer the point disappears If the flag is present this stripping of zeroes is not performed The scientific notation as in format e is used 1f the exponent falls below 4 or is greater than the precision that defaults to 6 How do you insert a sign in your output Well by using this conversion 3 60 C programming with Icc win32 1 12 4 1 Ata glance The printf family
427. o program and debug As always an the appearance of the user interface is not only dictated by the user comfort but also by the programming effort necessary to implement it You will see this shortly when you are faced with similar decisions 274 C Tutorial We have at the left side the tree representing our menu Each submenu is a branch and the items in the branch the leaves are the items of the submenu We select the File submenu and press the insert key We obtain a display like this Menu editor File Edit Help A new item is inserted after the currently selected one The name is Popup and the first item is New item We can edit those texts in the window at the right We can change the symbolic name and set unset several options When we are finished we press Apply to write our changes to the resource re OK we change the default names to the traditional Edit and Search to obtain this display Menu editor File Edt Help We will name the new item IDM SEARCH I am used to name all those constants starting with IDM_ from ID Menu to separate them in my mind from IDD ID Dialog We can now start drawing the Search dialog Just a simple one a text to search and some buttons to indicating case sensitivity etc We close the menu editor and we start a new dialog 122 A debugger is a program that starts another program the program to be debugged or debuggee
428. o vast that nobody wants to assume it and we get stuck with software for compatibility reasons Here is yet another example 49 If remembering which headers contain which definitions bothers you as it bothers me just use the lt stdheaders h gt header file included with lcc win32 That file is just an include of all standard header files Simple programs 73 loop When the loop finishes because we hit the zero byte that terminates the string we stop and return the saved position of the start of the string Note the cast that transforms str from a char into an unsigned char The reason 1s that it could exist a bad implementation of the toupper function that would index some table using a signed char Characters above 128 would be considered negative integers what would result in a table being indexed by a negative offset with bad consequences as you may imagine How can this program fail Since we test for NULL a NULL pointer can t provoke a trap Is this a good idea Well this depends This function will not trap with NULL pointers but then the error will be detected later when other operations are done with that pointer anyway Maybe making a trap when a NULL pointer is passed to us is not that bad since it will uncover the error sooner rather than later There is a big probability that if the user of our function 1s calling us to trans form the string to lower case is because he she wants to use it later in a display
429. of 0 1 xOffset max 0 GetDeviceCaps hPrnDC LOGPIXELSX ninchesWeWant pt x yOffset max 0 GetDeviceCaps hPrnDC LOGPIXELSY ninchesWeWant pt y When doing all the output you can either offset it by the above values or call SetViewportOrg to set the point 0 0 at the margin offset you calculated SetViewportOrg hPrnDC xOffset yOffset all other output here FAQ 341 e Calculate the bottom and right margins Obtain the total size of the physical page including printable and unprintable areas calling GetDeviceCaps with the PHYSICALWIDTH and PHYSICALHEIGHT indices in Windows NT Determine the number of pixels required to yield the desired right and bottom margins by calling GetDeviceCaps using the LOGPIXELSX and LOGPIXELSY flags Calculate the size of the printable area with GetDeviceCaps using the HORZRES and VERTRES flags The following code fragment illustrates steps a through c Get the size of the printable area pt x GetDeviceCaps hP pt y GetDeviceCaps hP xOffsetOfRightMargin yOffsetOfBottomMargin wilnchesWeWant rnos PAHYSICALWLIDIE 3 rnDC PHYSICALHEIGHT xOLTESet GetDeviceCaps hPrnDC HORZRES Dl GetDeviceCaps hPrnDC LOGPIXELSX wincheswWeWant yOffset GetDeviceCaps hPrnDC VERTRES pt y gt GetDeviceCaps hPrnDC LOGPIXELSY NOTE Now you can clip all output to the rectangle bounded by xOffset yOffset xOffsetOf Righ
430. of arg N gt double sqrt double Note that an identifier can be added to the declaration but its presence is optional We can write double sqrt double x if we want to but the x is not required and will be ignored by the compiler Functions can have a variable number of arguments The function printf is an example of a function that takes several arguments We declare those functions like this int Printi Char Fy res The ellipsis means some more arguments Why are function declarations important When I started programming in C prototypes for functions didn t exist So you could define a function like this int fn int a return atg and in another module write PACIA 35 The interface for using functions with a variable number of arguments is described in the standard header file stdarg h See Functions with variable number of arguments on page 43 20 C programming with Icc win32 without any problems Well without any problems at compile time of course The program crashed or returned non sense results When you had a big system of many modules written by several people the probability that an error like this existed in the program was almost 100 It is impossible to avoid mistakes like this You can avoid them most of the time but it is impossible to avoid them always Function prototypes introduced compile time checking of all function calls There wasn t a
431. of the list box s client area NRecthelght re bottom re top This counter will hold the number of visible items nVisibleItems 0 Loop until the bottom of the list box or the last item has been reached of the list 326 C Tutorial while nRectheight gt 0 amp amp ntop lt nCount Get current line s rectangle SendMessage hwndList LB GETITEMRECT ntop DWORD amp itemrect Subtract the current line height nRectheight nRectheight itemrect bottom itemrect top nVisibleItems Increase item count Ntoptt Move to the next line 3 20 10 Starting a non modal dialog box Non modal dialog boxes behave as independent top level windows They can be started using the CreateDialog function HWND CreateDialog HINSTANCE hiInstance handle to application instance LPCTSTR lpTemplate Identifies dialog box template name HWND hWndParent Handle to owner window DLGPROC lpDialogFunc Pointer to dialog box procedure 7 Non modal dialog boxes should be used with care since they are equivalent to starting another thread of execution In addition you should never forget that the user can restart the same sequence of events that led to that dialog box causing a second dialog box to appear 3 20 11 Propagating environment variables to the parent environment Under Windows there is no export directive as in Unix systems To propagate the value of an environment
432. ointer in the array If you have an array of pointers to structures you use array index gt field 4 If you have an array of structures you use array index field 5 If you are interested in the offset of the field 1 e the distance in bytes from the beginning of the structure to the field in question you use the of fSetof macro defined in stddef h offsetof structure or typedef name member name For instance to know the offset of the Frequency field in the structure CHARS above we would write offsetof CHARS Frequency This would return an integer with the offset in bytes 1 19 2 An important structure A special structure is used in C to deal with the files on your disk This structure is named FILE Files are a sequence of bytes They are central to most programs Here is a short over view of the functions that use files fprintf Formatted output to a file Puts a character in a file 98 C programming with Icc win32 Puts a character to stdout Puts a string in a file fread Reads from a file a specified amount of data into a buffer freopen Reassigns a file pointer fscanf Reads a formatted string from a file fsetpos Assigns the file pointer Assigns the file pointer the current position current position fae Moves ee current position relative to the start of the file to the end of the file or relative to the current position ftell returns the current returns the current position 1 20 Identifier
433. olumn The notifications use the prefix HDN XXX Not currently supported in the resource editor Hot key controls A hot key control is a window that enables the user to enter a combi nation of keystrokes to be used as a hot key A hot key 1s a key com bination that the user can press to perform an action quickly For example a user can create a hot key that activates a given window and brings it to the top of the z order The hot key control displays the user s choices and ensures that the user selects a valid key combi nation Not supported in the resource editor IP address control Allows to input an IP address Not currently supported in the resource editor Month calendar Allows the user to choose a month or a calendar date The notifica tions use the prefix MCN XXX Pager control A pager control is a window container that is used with a window that does not have enough display area to show all of its content The pager control allows the user to scroll to the area of the window that is not currently in view Not supported in the editor Progress bar A progress bar is a window that an application can use to indicate the progress of a lengthy operation It consists of a rectangle that is grad ually filled with the system highlight color as an operation progresses This control sends no notifications but receives messages that use the PBM _ XXX prefix Window controls 257 Tab controls A tab control is analogous to the di
434. om plex and big inputs The reason is that in a more complex environment object recycling is done more often what means that the memory locations referenced by the dangling pointers are more likely used by another object 1 13 1 Operations with pointers The most common usage of a pointer is of course the dereferencing operation 1 e the oper ator gt or the unary This operations consist of reading the contents of a pointer and using the memory address thus retrieved either fecth the data stored at that place or at some displacement from that place For instance when we use a pointer to the person structure above the operation struct person pJoe amp Joe pJoe gt weight means 1 Fetch the contents of the pJoe pointer 2 Using that address add to it sizeof Name MAXNAME sizeof int sizeof bool 3 Retrieve from the updated memory location a double value The operation 2 is equivalent to finding the offset of the desired field within a given structure This is often required and the language has defined the macro offsetof in the stddef h header file for using it within user s programs 64 C programming with Icc win32 Pointers can be used to retrieve not only a portion of the object operation gt but to retrieve the whole object using the notation In the example above the operation pJoe would yield as its result the whole structure This operatio
435. omment If you write a b this is a bug c d c d will never happen The comment in the first line is not terminated It goes one through the second line and is fin ished with the end of the second line Hence the assignment of the second line will never be executed Wedit helps you avoid this by coloring commentaries in another color as normal program text 1 37 4 Easily changed block scope Suppose you write the following code if someCondition ERLE else OLherEn This is OK but if you add some code to debug for instance you end up with if lt someCond1 tion fel else printi Calling Olhertin a OtherFn The else is not enclosed in curly braces so only one statement will be taken The end result is that the call to OtherFn is always executed no matter what Pitfalls of the C language 183 Golden rule ALWAYS watch out for scopes of if or else not between curly braces when adding code 1 37 5 Using the or more than once in an expression The ANSI C standard specifies that an expression can change the value of a variable only once within an expression This means that a statement like i i is invalid This one 1s invalid too oe ae in clear i i 1 37 6 Unexpected Operator Precedence The code fragment 1 chr getc EOF Dene OC hevaliwie Of che aS oN ene s will always print 1 as long as end of file 1s not detected i
436. ompanion control which is called a buddy window The documentation for all this controls is very detailed and it would be impossible to repro duce here Note that many of the controls not directly supported in the resource editor can be created by hand by just calling the CreateWindow procedure Most of them are not spe cially useful in the context of a dialog box To handle the messages with the WM NOTIFY interface you should add code to handle the message of interest in the window procedure Suppose for instance that you have a tree con trol and you want to be notified when the user has clicked on an an item with the right mouse button case WM NOTIFY LPNMHDR nmhdr LPNMHDR lParam Switch nmhdr gt code case NM RCLICK TV HITTESTINFO Lest iInro The structure testInfo will be filled with the coordinates of the item at this particular point memset testinio 0 sizeot TV_HITTESTINFO Get the cursor coordintes GetCursorPos amp testIinfo pt pti testInfo pt Translate the coordinates into coordinates of the tree window MapWindowPoints HWND DESKTOP hwndTree amp testInfo pt 1 118 See The windows user interface in the online documentation of Icc win32 258 C Tutorial Now ask the tree view control if there is an item at this position hti TreeView HitlTest hwndlree testinio lf nothing is found stop if hti HTREEITEM 0 break There is something Show th
437. on 1s done without any extra cost when the function where the variables are located exits Drawbacks 1 There is no way to know if the allocation fails If the stack has reached its maximum size the application will catastrophically fail with a stack overflow exception Memory management strategies 123 2 There is no way to pass this memory block to a calling function Only functions called by the current function can see the memory allocated with this method 3 Even if the C99 standard is already several years old some compilers do not implement this Microsoft compilers for instance do not allow this type of allocation A work around is to use the alloca function Instead of the code above you would write Chal workspace S sdlloca s1z 1 28 3 Arena based allocation This strategy is adapted when a lot of allocations are done in a particular sequence of the pro gram allocations that can be released in a single block after the phase of the program where they were done finishes The program allocates a large amount of memory called arena and sub allocates it to the consuming routines needing memory When a certain phase of the pro gram is reached the whole chunk of memory is either marked as free or released to the operat ing system The windows operating system provides support for this strategy with the APIs CreateHeap HeapAlloc and others Advantages 1 Fewer calls to memory allocation deallocation routines
438. ontrol Panel 4lcEaxCplClass tooltips classs2 tooltips class32 NetDDE Agent NODE Agnt H tooltips class 32 H windowtree windawtreeWindClass H smallTextPopup F Wwedit windowtree d downloads windowtreeWwindowtree c clMD Frame oo Timer ATLISTATIC H C tukorial doc Microsoft Word Opus4pp Font Office Tooltip H Edit MsoCommandBarPopup i Irfanview3z lt Clipboard gt 485 x 508 x 8BPP Irfanviewaz F Ho To Select a Window 32770 Hl How To Select a Rectangle 32770 Screen Capture WinCap Wo E E E A E E E a S A lot of code is necessary to make this work but thankfully it is not our code but window s The window resizes redraws etc without any code from us 264 C Tutorial 3 10 7 Filling the status bar Our task consisted in drawing the tree but also of displaying some useful information about a window in the status bar when the user clicks on a tree item First we have to figure out how we can get notified when the user clicks in an item The tree control as many other controls sends notifications through its WM NOTIFY mes sage We add a snippet of code to our MainWndProc procedure case WM CREATE hwndTree CreateTree hwnd IDTREEWINDOW break case WM NOTIFY return HandleWmNotify hwnd wParam lParam The function HandleWmNotify looks as follows LRESULT HandleWmNotify HWND hwnd WPARAM wParam LPARAM lParam NMHDR nmhdr IN HITTITE SLTINEO tCestinio HWND
439. oordinate Gre iC c x 67 Assigns the field x c y 78 Assigns the field y pce amp c We make pe point to c pc gt x 67 We change the field x to 67 pce gt y 33 We change the field y to 33 rc x 88 References use the point notation Structures can contain other structures or types After we have defined the structure coordinate above we can use that structure within the definition of a new one struct DataPoint struct coordinate coords int Data be This structure contains a coordinate structure To access the x field of our coordinate in a DataPoint structure we would write struct Dataroint dp dpe coOords x 13 Structures can be contained in arrays Here we declare an array of 25 coordinates struct coordinate CoordArray 25 7 4th To access the x coordinate from the 4 member of the array we would write COOrdArray lolx 997 Note again that in C array indexes start at zero The fourth element is numbered 3 Many other structures are possible their number is infinite SELUCT customer 4 Ine ID char Name Char Address double balance 90 C programming with Icc win32 time t Last Transaction unsigned hasACar 1 unsigned mailedAlready 1 by This is a consecutive amount of storage where e an integer contains the ID of the customer e amachine address pointing to the start of the character string with the customer name e another address pointing to the st
440. operation at the point where the representation of the numbers is the densest In IEEE754 representation this number has an exponent value of the bias and a fraction of 1 If you add a number smaller than this to 1 0 the result will be 1 0 For the different representations we have in float h define FLT EPSILON 1 19209290e O7F float define DBL EPSILON 2 2204460492503131le 16 double define LDBL EPSILON 1 084202172485504434007452e 19L long double qfloat epsilon truncated so that it fits in this page define QFLT EPSILON 1 09003771904865842969737513593110651 E 106 This defines are part of the C99 ANSI standard and should be defined in all compilers that implement that standard When in C you convert a floating point number into an integer the result 1s calculated using rounding towards zero To see this in action look at this simple program tineclude lt Stavoc n gt void fn double a printf int g Sd int g d n a int a a int a int main void 4 for double a L 2 de lt 220 do 0x3 fnd return 0 This leads to the following output note the lack of precision 0 3 can t be exactly represented in binary Pie as oO Sal an b ait LZ Sak int 1 2 1 int 0 9 0 int 0 9 0 Int 0s 6 0 int 0 6 0 int 0 3 0 int 0 3 0 int 1 110226 016 0 int 1 11022e 016 0 ant 0 3 0 int 0 3 0 int 0 6 0 i C063 O int 0 9 0 int
441. opies the code into the pro gram Dynamic libraries These aren t copied into the main program but are resolved at load time by the program loader When you double click a program s icon you activate a system pro gram of windows called program loader that goes to the disk finds the code for the execut able you have associated with the icon and loads it from disk into RAM When doing this the loader finds if the program needs any dynamic libraries that normally have the DLL extension and reads their code too linking it dynamically to the program being loaded Which one should we use in this application Static or not static That is the question Our program needs a class registration before it can call the DialogBoxParam API If we use the static library approach we would have to require that the user of the library calls some 1in1 tialization routine before to allow us to register our class with windows But this would complicate the interface We introduce with this requirement yet another thing that can go wrong with the program yet another thing to remember A way out of this dilemma would be to take care of doing the registration automatically We could setup an integer variable that would start as zero Before calling our DialogBoxParam procedure we would test the value of this variable If it is zero 1t means that our class wasn t registered We would register our class and set this variable to one so that the next c
442. opy a huge amount of data into the called function what would waste machine resources The best of all worlds are references They must always point to some object there is no such a thing as an uninitialized reference Once initialized they can t point to anything else but to the object they were initialized to 1 e they can t be made to point to another object as normal pointers can For instance in the above expressions the pointer pa is initialized to point to the integer a but later in the program you are allowed to make the pa pointer point to another completely unrelated integer This is not possible with the reference ra It will always point to the integer a When passing an argument to a function if that function expects a reference and you pass it a reference the compiler will arrange for you passing only the address of the data pointed to by the reference 88 C programming with Icc win32 1 18 Structures and unions 1 18 1 Structures Structures are a contiguous piece of storage that contains several simple types grouped as a single object 8 For instance if we want to handle the two integer positions defined for each pixel in the screen we could define the following structure struct coordinates InG X ning yea Ar by Structures are introduced with the keyword struct followed by their name Then we open a scope with the curly braces and enumerate the fields that form the str
443. or do other things e When the program that loads them starts or ends a new thread the system arranges for calling the same function This allows us to take special actions when this event occurs We do not need this feature for our application here but other software do e When the library is unloaded either because the program explicitly does it or because simply the program is finished we get notified Here we can reverse the actions we performed when the library was loaded we can for instance unregister our window class e DLLs can contain resources This solves the problem of forcing the user of the library to link a bunch of resources to his her program DLLs need to specify which functions are going to be exported 1 e made visible to the outside world With static libraries this 1s not really necessary since the librarian will write all the sym bols with the external type to the library symbol table automatically 0 We can declare that a symbol will be exported using two methods 1 We can put in the declaration of the symbol the __declspec dllexport mark 2 We can write the name of the symbol in a special file called definitions file with the def extension and pass this file to the linker Which method you use is a matter of taste Writing __ declspec dllexport in the source code is quite ugly and may be non portable to other systems where the conventions for dynamically linked code may be completely different A
444. ork as intended We overload the operator and the operator to mimic this behavior Int Operator J Const StLingp amp stringl IAE 1 Lf A2sNulIStringp string e amp 21 0 return QO return 1 We allow only comparisons with zero The operator 1s very similar Int Operator Const Stringp amp stringl In 1 if 1 0 amp amp isNullStringpA stringl1 return 1 return 0 2 3 Implementation 2 3 1 String functions The string library supports all the standard functions defined in string h The names chosen are the same with the first letter in upper case strcat is Strcat strcmp is Strcmp etc Most of those functions are very simple the specifications for the C run time library are quite primitive Here is for instance the Strcmp function Implementation 199 inc Overloaded Stremp String si String SZ struct Exception exc GetAnExceptionStructure PRECONDITION Strvalid sl amp amp Strvalid s2 exc conversion widening the smaller to the wider string type if 0 sl count amp amp s2 count Q Veturn OF Ve 40 Blh COUNT return 17 LE OSHS SZ COUNT recur q3 ine lem silscount lt S2 count 2 sl count sZ22count return memcmp sl content s2 content len Stremp accepts also a char so that users can write if Ser emp scr Annie a eax a This syntax is widespread and it is important to supp
445. ormation Within the string the following abbreviations are recognized r C i Insert at the current position the Any since any digit can be x lt hex digits gt character with the integer value of entered Example ABC xA is the hexadecimal digits equivalent to ABC n The same as the x case above but with values entered as 3 octal digits Any Example The string lt octal number gt i e numbers in base 8 Note that no ABC 012 is equivalent to special character is needed after the ABC n backslash The octal digits start immediately after it Character string constants that are too long to write in a single line can be entered in two ways char a This is a long string that at the end has a backslash that allows it to go on in the next line Another way introduced with C99 is Char a MIs 2s a long String written in two Lines Note too that character string constants should not be modified by the program Lcc win32 stores all character string constants once even if they appear several times in the program text For instance if you write char a abc char lb abe Both a and b will point to the SAME string and if either 1s modified the other will not retain the original value A closer view 43 1 11 3 Arrays Here are various examples for using arrays imc alas Array of 45 elements alo 232 A7 Sets first element to 235 afa 0 56 Sets the 24
446. ort it Here is a different version of Strcmp that accepts char pointers LiMo sOver Loaded Stremo Serindg amp string Const char str int len struct Exception exc GetAnExceptionStructure PRECONDITION Stivalid string Ge str I NULL F exc len strlen str if QO string count amp amp len 0 return 0 i AO eS SEPing count Tern lt 1 if 0 len return 1 len len lt string count len string count return memcmp string content str len There are other variations for supporting wide chars and changing the order of the arguments 2 3 2 Joining strings To join several C strings into a single string the library proposes Strcatv It receives a series of strings transforming them into a single String SEF ING reat yi Chae Sys int len strlen s Ve list ap Save char next p SeErIinge result va_start ap s Save ap Nexe ya arg apy char Ty while next ten Strlen next 3 nest va arg ap char 88 This is essentially the same function as Str_catv from Dave Hanson s C Interfaces and implementa tions 200 C programming with Icc win32 va a start ap s result NEw seri ngAt ten streat result Contents p result content strlen s Next va arg apychar 7 while next while next oO i eM cacy next Va_arg 4ap cChar A Oe result count p result content return result
447. ot is opened for a write operation applications can easily implement a simple message passing facility within a domain e Pipes Conceptually a pipe has two ends A one way pipe allows the process at one end to write to the pipe and allows the process at the other end to read from the pipe A two way or duplex pipe allows a process to read and write from its end of the pipe e Memory mapped files can be used as a global shared memory buffer 3 17 8 Mail The Messaging API MAPI allows you to program your messaging application or to include this functionality into your application in a vendor independent way so that you can change the underlying message system without changing your program 3 17 9 Multimedia Audio You can use Mixers MIDI and waveform audio using MCI DirectSound offers a more advanced sound interface Input devices You can use the joystick precise timers and multimedia file input output Video Use AVI files to store video sequences or to capture video information using a simple message based interface 3 17 10 Network Windows Sockets provides you will all necessary functions to establish connections over a TCP IP network The TCPIP subsystem even supports other protocols than TCPIP itself But whole books have been written about this so here I will only point you to the one I used when writing network programs Ralph Davis Windows NT Network programming from Addi son Wesley For an example of n
448. oth See the docu mentation for CBN XXX messages Edit These controls are used for text input They notify the parent when a character has been received or in general when the text has been modified See the EN XXX messages Listbox These controls display a variable length list They notify the parent window when an item has been selected or clicked Scrollbar These controls let the user choose the amount of scrolling that should be done for the information being displayed They notify the parent window when they are used Static These controls do not send any notifications hence they are called static They are text strings or lines rectangles Rich edit controls They are used to display text with more than a single font or color They have a long list of notifications you can even specify that you want to be notified when the user clicks in an URL in the text This control uses both the WM COMMAND interface and the WM NOTIFY interface The interface using the WM COMMAND message was described above See page 259 Another interface used by many controls is the WM NOTIFY interface This message has the following format l1Result SendMessage returns LRESULT HWND hWndControl handle to parent window UINT WM NOTIFY message ID WPARAM wParam 7 WPARAM int 2dcerl LPARAM lParam LPARAM LPNMHDR pnmh This code is executed by the control when it sends a message to the parent window The impo
449. ould have crashed with no apparent reason a difficult error to find Note always use the right header file to avoid this kind of errors Our program now looks like this include lt stdio h gt We need it for using the FILE structure include lt stdlib h gt We need it for using malloc include lt io h gt We need it for using findfirst findnext include lt string h gt We need it for memcpy typedef struct tagChars int CharacterValue The ASCII value of the character int Frequency How many seen so far F CHARS typedef struct tagStream char Name Input name with possible Struct ftinddata t FindData long handle FILE file An open file STREAM CHARS Fregquencies 256 Array of frequencies int compare Skipped it is the same as above STREAM checkargs int argc char argv WHT NOW or chars in it STREAM infile NULL long findfirstResult Struct tinddata t id if argc lt 2 Test if enough arguments were passed printf Usage countchars lt file name gt n else Call the _findfirst function with the name and info buffer Tindiirsi Result finciirs gt arov sfa 7 Test result of findfirst and return immediately NULL if wrong if findfirstResult lt 0 printf File s doesn t exist n argv 1 return NULL Ask more memory to the allocator infile malloc sizeof STREAM Set the name of the new stream infile gt Name argv 1 Note th
450. ountchars c 1 File s 493 bytes Yes 493 bytes instead of 492 before since we have added a b to the arguments of fopen Still we read the docs about file handling and we try to see if there are no hidden bugs in our program After a while an obvious fact appears we have opened a file but we never closed it 1 e we never break the connection between the program and the file it is reading We correct this and at the same time add some commentaries to make the purpose of the program clear Commentaries 27 Ga i a a gg pi a a E a ee Se Module H LCC EXAMPLES countchars c Author Jacob Project Tutorial examples State Finished Creation Date July 2000 Description This program opens the given file and prints the number of characters in it fine Lude lt Sstaio h gt tinelude lt stdlib h gt int maintint argc ochar argy int count 0 FILE ratie it a Ce Er RE Yarga 2 Aq printf Usage countchars lt file name gt n exit 1 infile fopen argv 1 rb if infile NULL printf File s doesn t exist n argv 1 exit 1 c fgetc infile while c EOF count t c fgetc infile felose infile pera r 0 n coun return O The skeleton of the commentary above is generated automatically by the IDE Just right click somewhere in your file and choose edit description Summary e A program is defined by its specifications In this example counting the
451. outines 1 e routines only called from within the library can assume their inputs valid and make less checks That interface is not available to the user code however 2 1 3 Efficiency considerations The C language has an almost obsesive centering in efficiency Actually as everybody knows efficiency depends on the algorithm much more than in the machine efficiency with which operations are coded Length delimited strings are by nature more efficient than normal C strings since the often used strlen operation takes just a memory read instead of starting an unbounded pointer memory scan seeking the trailing zero Efficiency must be weighted against security too and if we have to chose when implementing the container library security has been always more important than machine efficiency Some operations like array bound checking can add a small overhead to the run time but this will be of no concern to the vast majority of the applications done with this library Using a hash table will be always more efficient than a plain linear scan through a hastily constructed table Even if we code the table lookup in assembler In this version efficiency has been left out The weight of the effort has gone into making a library that works and has fewer bugs 2 1 4 C and C If you know the C language most of this things will sound familiar But beware This is not C There is no object oriented framework here No classes instant
452. ow hwnd GW_HWNDNEXT We loop through all sibling windows calling ourselves recursively with the child windows In our loop we do We get the text of the window to show it in our tree We do this by sending the WM _GETTEXT message to the window We get the class name of the window We format the text enclosed in quotes and the class name in a buffer We start filling the TV INSERTSTRUCT These steps are very similar to what we did for the desktop window After inserting our node in the tree we ask if this window has child windows If it has we call Scan recursively with the new node and the new child window Then we ask if this window has sibling windows If it has the main loop will go on since GetWindow will give us a non null window handle If it hasn t we are done and we exit 3 10 6 Review Let s look at our BuildTree function again and ask us How could this fail We notice immediately several things We always add items to the tree at the end but we never cleanup the tree control This means that after a few times the user has clicked in the menu we will have several times all the win dows of the system in our tree All nodes should be deleted when we start The tree control will redraw itself several times when we add items This is unnecessary and produces a disturbing blinking in the display We should hold the window without any redraw ing until all changes are done and then redraw once at the end We mod
453. p fun NUCL return SE Ldup Ecom PRECONDITION otrvalid fron amp amp map t m NULL exc result new String Irom Counts result scounk From counc for Int i 0 2 x Promcounce t result Contentia map TUN irom content return result Note that a NULL function pointer means that the identity function is assumed and the whole operation becomes just a copy of the source string We do not need to test for the valid ity of the source string in that case since Strdup does that for us We allocate a string that will contain at most so many characters as the source string including always a terminating zero If the predicate function filters most of the characters the string will be almost empty Since we keep track of this in the capacity field of the String structure this is less terrible than it looks like The other solution would be to call twice the predicate function but that would be very expensive in CPU usage A similar function is Strfilter that will output into the result string only those characters that satisfy a boolean predicate function Strfilter will accept either Strings or character strings Here is the version that uses character strings String overloaded Strfilter String amp from char set CrO Testli int setlength struct Exception exc GetAnExceptionStructure PRECONDITION Strvalid from amp amp set NULL exc setlength strlen set resultsContent
454. package As much as possible from the old syntax should be understood 2 2 3 4 Imitating pointer addition With traditional C strings it is valid to add an integer to a string pointer to obtain a pointer to the middle of the string We can mimic this behavior by overloading the addition operator StringpA EXPORT operator StringA amp sl int n StringpA result struct Exception exc GetAnExceptionStructure PRECONDITION StrvalidA sl amp amp n gt 0 amp amp ie lt lt Sl sCourt exe result count Ssi count nm FeSuULE lt COnLeNne Sil content n result parent amp sl return result We test for validity of the given string and check that the offset passed is correct We return a Stringp not a String that is initialized to point to the specified offset The result of this opera tion is to produce a fat pointer and not a String This will cause problems since even if the library tries to hide most differences a Stringp is another kind of beast than a normal String Note too that adding negative offsets is no longer possible 2 2 4 String pointer operations The library introduces the notion of string pointer structures 1 e fat pointers that contain besides the normal pointer to the contents a count and a pointer to the parent string Pointer operations on this structures are few and they try to mimic the normal pointer behavior This pointers can be used as iterator objects to go through a po
455. path to the lcc installation directory in the registry and all other data is stored in files in the Icc lib directory This saves registry space A value entry uses much less registry space than a key To save space an application should group similar data together as a structure and store the structure as a value rather than storing each of the structure members as a separate key Storing the data in binary form allows an application to store data in one value that would otherwise be made up of several incompatible types 298 C Tutorial 3 16 4 Interesting keys The registry is an endless source of useful tips There is for instance a nice site that provides Change the Location of System and HKEY_CURRENT_USER Software Microsoft Win Special Folders dows CurrentVersion Explorer User Shell Folders Configure CoolSwitch Application HKEY CURRENT USER Control Panel Desktop Swapping Value Name CoolSwitch CoolSwitchColumns CoolSwitch is a feature available CaniSaiichRous within Windows to quickly switch between tasks and programs by using the Alt TAB keys Value Data 0 disabled 1 enabled Modify the value named CoolSwitch and set it to 0 to disable task switching or 1 to enable it Data Type REG SZ String Value To change the size of the CoolSwitch popup modify the val ues named CoolSwitchColumns and CoolSwitchRows Logoff or restart Windows for the changes to take effect Change the Registered Ow
456. pboard will be lost Before sending the WM_ PASTE message the caret must be placed at the end of the edit con trol text using the EM SETSEL message Below is pseudo code that shows how to imple ment this method OpenClipBoard EmptyClipBoard SetClipBoardData SendMessage hEdit EM SETSEL WPARAM ndx LPARAM ndx SendMessage hEdit WM PASTE GO OEI This pseudo code appends text to the end of the edit control Note that the data in the clip board must be in CF_ TEXT format 3 21 14 How do I determine the color settings Here is a small code snippet that will show the current screen color settings include lt windows h gt finclucde lt stdio h gt fincilide lt stdbool h gt int main void HDC NDC hDC GetDC HWND DESKTOP int BitsPerPixel GetDeviceCaps hDC BITSPIXEL int Planes GetDeviceCaps hDC PLANES BitsPerPixel Planes bool UsesPalettes bool Get DeviaceCaps hDC RASTERCAPS amp RC PALETTE if UsesPalettes printf System uses palettes n Switch BitsPerPixel case S22 348 C Tutorial PEINT DILE Croc colon break case 24 printf 24 h17c true color break case 16 PEC LODIG hagh coloru 4 break case 8 PELNEL 256 Color mode break case 4 princi LO color mode break case li printf Monochrome mode break prance TY ReleaseDC HWND DESKTOP hDC 3 21 15 How do I spawn a proce
457. ponsible for cleanup when the object handle 1s closed 3 17 7 Inter Process Communications You can use the following primitives e Atoms An atom table is a system defined table that stores strings and corresponding identifiers An application places a string in an atom table and receives a 16 bit integer called an atom that can be used to access the string The system maintains a global atom 304 C Tutorial table that can be used to send information to from one process to another instead of sending a string the processes send the atom id e Clipboard This is the natural way to do inter process communications under windows Copy and Paste e Mailslots A mailslot is a pseudofile it resides in memory and you use standard Win32 file functions to access it Unlike disk files however mailslots are temporary When all handles to a mailslot are closed the mailslot and all the data it contains are deleted A mailslot server is a process that creates and owns a mailslot A mailslot client is a process that writes a message to a mailslot Any process that has the name of a mailslot can put a message there Mailslots can broadcast messages within a domain If several processes in a domain each create a mailslot using the same name the participating processes receive every message that is addressed to that mailslot and sent to the domain Because one process can control both a server mailslot handle and the client handle retrieved when the mailsl
458. pplications can t share data by sending just pointers around A pointer is meaningful only in the application where it was created Special mechanisms are needed and provided by Windows to allow sharing of data between applications 69 Note that this is a logical view of this address translation process The actual implementation is much more sophisticated since Windows uses the memory manager of the CPU to speed up things Please read the original article to get a more in depth view including the mechanism of page protection the working set and many other things 70 Since this is stored in a 32 bit integer the counter will overflow somewhere in year 2038 I hope I will be around to celebrate that event 122 C programming with Icc win32 1 28 Memory management strategies Each program needs some workspace to work in How this space is managed allocated recy cled verified makes a memory allocation strategy Here is a short description of some of the most popular ones 1 28 1 Static buffers This is the simplest strategy You reserve a fixed memory area buffer at compile time and you use that space and not a byte more during the run time of the program Advantages 1 Itis the fastest possible memory management method since it as no run time overhead There is no memory allocation nor recycling that incurs in run time costs 2 In memory starved systems embedded systems micro controller applications etc it 1s good to
459. r 45 has no address 52 C programming with Icc win32 The result of the operator amp is a pointer with the same type as the type of its argument If you take the address of a short variable the result is of type pointer to short If you take the address of a double the result is a pointer to double etc If you take the address of a local variable the pointer you obtain is valid only until the func tion where you did this exits Afterward the pointer points to an invalid address and will pro duce a machine fault when used if you are lucky If you are unlucky the pointer will point to some random data and you will get strange results what 1s much more difficult to find In general the pointer you obtain with this operator is valid only if the storage of the object is pointing to is not released If you obtain the address of an object that was allocated using the standard memory allocator malloc this pointer will be valid until there is a free call that releases that storage Obviously if you take the address of a static or global variable the pointer will be always valid since the storage for those objects 1s never released Note that if you are using the memory manager gc making a reference to an object will pro voke that the object 1s not garbage collected until at least the reference goes out of scope 1 11 29 Sequential expressions A comma expression consists of two expressions separated by a comma The left operand
460. r dialog boxes our case here we have the DefDlgProc procedure When creating a class of windows it is our job to tell windows which procedure should call when something for this window comes up so we use the class registration structure to inform it that we want that all messages be passed to the default dialog procedure and we do not want to bother to treat any of them We do this with we lopfnWndProc DefDlgProc As we saw with the qsort example functions are first class objects in C and can be passed around easily We pass the address of the function to call to windows just by setting this field of our structure This is the most important thing conceptually that we do here Of course there 1s some other stuff Some people like to store data in their windows We tell windows that it should reserve some space in this case the DLGWINDOWEXTRA constant that in win h is defined as 30 We put in this structure too for obscure historical reasons the hinst handle that we received in WinMain We tell the system that the cursor that this window uses is the system cursor 1 e an arrow We do this with the API LoadCursor that returns a handle for the cursor we want The brush that will be used to paint this window will be white and the class name is the character string dialog And finally we just call the RegisterClass API with a pointer to our structure Windows does its thing and returns The last statement of WinMain
461. r empty strings that can be compared for equality without provoking any errors Two empty strings are considered equal If either of the strings 1s empty and the other isn t then they can t be equal Those tests done both strings must be valid They are equal if their count and contents are equal Note that we use memcmp and not strcmp since we support strings with embedded zeroes in them The wide character version differs from this one only in the length of the memory comparison The function isNullString tests for the empty string 1 e a string with a count of zero and contents NULL An empty string is returned by some functions of the library to indicate failure It is semanti cally the same as the NULL pointer 196 C programming with Icc win32 The other relational operators are a bit more difficult Here is less for instance int Operator lt Const String s1 const String S342 Doo Sma isNurlo tring bool s2null 1sNulLlsSrring s2 5 if slnull amp amp s2null1 return OF if slnull amp amp s2null1 return 1 if silnull amp amp s2null return U gt struct Exception exc GetAnExceptionStructure PRECONDITION Strvalid sl amp amp Strvalid s2 exc if sl count 0 amp amp s2 count 0 return ly if sl count amp amp s2 count 0 return 0 int len sl count lt s2 count Si scour amp isZ22eCounet return memcmp sl content s2 content len lt 0
462. ram with that data and we obtain n lcec testpaste fileli filez File 2 L1 File 1 Line 1 Line 1 File 1 Line 2 File 2 Line 2 File 1 Line 3 File 2 Line 3 File 1 Line 4 File lane 4 File 1 Line 5 FA Line File 1 Line 6 File 1 Line F File 1 Line amp ee ese The line five of file one was read and since file two is already finished we repeat it Is this a bug or a feature We received vague specifications Nothing was said about what the program should do with files of different sizes This can be declared a feature but of course is better to be aware of it 76 C programming with Icc win32 We see that to test hypothesis about the behavior of a program there is nothing better than test data 1 e data that is designed to exercise one part of the program logic In many real cases the logic is surely not so easy to follow as in this example Building test data can be done automatically To build file one and two this small program will do include lt stdio h gt int main void FILE f fopen filel w fOr ainte 1 OF 2371 forint lr rile we Time Sd van relose t s fopen file2 w for ane E ie a x ee a Borah tb Gh FLE ee deme Sd in fa fclose f return Uz This a good example of throw away software software you write to be executed once No error checking small and simple so that there is less chance for mistakes And now the answer to the other bug above Usin
463. ramming with Icc win32 Many other functions are possible and surely necessary They are not very difficult to write the data structure is quite simple Double linked lists have two pointers hence their name a Next pointer and a Previous pointer that points to the preceding list element Our data structure would look like this typedet struct dlilast Struct Gibist Nex Scruct dibiee Previous void Gata F DLLLIST Our Append function above would look like new material in bold LIST AppendDI DLLIST pListRoot void data DLLIST rvp pLiscRooc is the list empty if rvp NULL Yes Allocate memory pLIstRoot mvp GC malloc sizeor DLLIST rvp gt Previous NULL else find the last element while rvp gt Next EVD EVp gt NeExXC Add an element at the end of the list tvp gt Next GC malloc sizeoft DLLIST rvp gt Next gt Previous rvp rvp ryp NeExc initialize the new element rvp gt N Next NULL rvp gt Data data FOCUN IVD The Insert function would need some changes too LIST Insert LIST list LIST element iol Em7 if list NULL return NULL if list element reLcurn 11S tmp List gt Next list gt Next element if element element gt Next tmp element gt Previous list if tmp tmp gt Previous element return 11st Note that we can implement a Previous functio
464. ranslating the value returned by GetLastError into a readable string This utility function uses the system FormatMessage to do the bulk of the work of caring about locale settings like language setup etc BOOL GetFormattedError LPTSTR dest int size DWORD dwLastError GetLastkError if dwLastError return 0 BYTE width 0 DWORD flags flags FORMAT MESSAGE MAX WIDTH MASK amp width flags FORMAT MESSAGE FROM SYSTEM flags FORMAT MESSAGE IGNORE INSERTS return 0 FormatMessage flags NULL dwLastError MAKELANGID LANG NEUTRAL SUBLANG DEFAULT dest Size NULL 3 20 3 Clearing the screen in text mode The following code will clear the screen in text mode include lt windows h gt Standard error macro for reporting API errors define PERR bSuccess api if bSuccess printf ssikrror zd from 3s on line d n _ FILE GetLastError api LINE 7 void cls HANDLE hConsole COORD coordScreen 0 0 Home the cursor here BOOL bSuccess DWORD cCharsWritten CONSOLE SCREEN BUFFER INFO csbi to get buffer info DWORD dwConSize number of character cells in the current buffer get the number of character cells in the current buffer bSuccess GetConsoleScreenBufferInfo hConsole amp csbi Some Coding Tips 321 PERR bsuccess GetConsolesScreenBurterin oe j dwConSize csbi dwSize X csbi dwSize Y fill the entire screen with blan
465. rd generates and will fit our purposes quite well But let s go step by step First we create a project The first thing you see is a dialog box not very different from the one we are going to build that asks for a name for the new project You enter a name like this Enter the new project name Froject name dialog Cancel You press OK and then we get a more complicated one that asks quite a lot of questions 91 note 82 214 C Tutorial You enter some directory in the second entry field make sure the windows executable at the Definition of a new project d Slocexamples dialog bottom is selected and press ok Then we get You press the yes button This way we get into the wizard Information Introduction 215 The first panel of the wizard is quite impressing with many buttons etc Ignore all but the type of application panel There select a dialog based application like this Application charactenstics a Aloo wizard dSlecexamples dialog feo fee Iv E a a E amen o You see the Dialog based check button at the upper left is checked Then press the OK but ton Then we get to different dialogs to configure the compiler You leave everything with the default values by pressing Next at each step At the end we obtain our desired program For windows standards this is a very small program 86 lines only including the commentaries We wil
466. re the output should go We use the predefined file of standard error instead of the normal output file stdout that printf implicitly takes Why Because it 1s possible that the user redirects the output to a file instead of letting the output go directly to the screen In that case we would write our error messages to that file and the user would not see the error message gt We change all occurrences of malloc by xmalloc and this error is gone We change too all other error reporting functions to take into account stderr But there are other issues Take for instance our finddata t structure that we carry around in each STREAM structure What s its use We do not use it anywhere just copy it into our STREAM But why we introduced that in the first place Well we didn t really know much about findfirst etc and we thought it could be useful So we are stuck with it No not really Actually it is very easy to get rid of it We just change the structure STREAM like this typedef struct tagStream char Name long handle Ribera les STREAM 65 Some people would say that this is not Standard C since the standard doesn t explicitly allow for this But I would like to point out that the standard explicitly states page 96 of my edition that An implementation may accept other forms of constant expressions The implementation Icc win32 then is free to accept the above declaration as a constant expre
467. reMp Str char Selot data 4 return slotp slotp slotp gt Next return Append amp table gt Table h HASHELEMENTS element All those casts are necessary because we use our generic list implementation with a void pointer If we would modify our list definition to use a char instead they wouldn t be neces sary We first call the hash function that returns an integer We use that integer to index the table in our hash table structure getting the head of a list of strings that have the same hash code We go through the list to ensure that there isn t already a string with the same contents If we find the string we return it If we do not find it we append to that list our string The great advantage of hash tables over lists is that if our hash function is a good one 1 e one that returns a smooth spread for the string values we will in average need only n 128 compar isons n being the number of elements in the table This is an improvement over two orders of magnitude over normal lists A closer look at the pre processor 143 1 32 A closer look at the pre processor The first phase of the compilation process is the pre processing phase This consists of scan ning in the program text all the preprocessor directives 1 e lines that begin with a charac ter and executing the instructions found in there before presenting the program text to the compiler We will interest us with just two of thos
468. reak The semi colon in the definition was not treated as an end of statement indicator as expected but was included in the definition of the macro MAXVAL The substitution then results in a semi colon being placed in the middle of the controlling expression which yields the syntax error Remember the pre processor does only a textual substitution of macros 1 37 8 Watch those semicolons Yes speaking about semicolons look at this ales aa Wie ae AS ZS The semicolon after the condition of the if statement 1s considered an empty statement It changes the whole meaning of the code to this ie Wig Dey A STe S 254 The x j 25 statement will be always executed 1 37 9 Assuming pointer size is equal to integer size Today under Icc win32 the sizeof void is equal to the sizeof int This is a situation that will change in the future when we start using the 64 bit machines where int can be 32 bits but Pitfalls of the C language 185 pointers would be 64 bits This assumption is deeply rooted in many places even under the windows API and it will cause problems in the future Never assume that a pointer is going to fit in an integer 1f possible 1 37 10 Careful with unsigned numbers Consider this loop tie Ay form Gi Be a SS 10 a SS Prine Cr cdn e iy This will terminate after 6 iterations This loop however will never terminate unsigned int i fom C 52 A SS a Sa A PELET SS Sa is iy
469. reasing the printing precision increases even more the range 3207 2e68OU3s30Z24 72136024 7253929032638 12212360937 193424601679833 3208 8 61080144281060123673190600609037446957728096447914618e 9856 3209 Ze COlSLeeZzog7 9255086 Zee oo s Oo4I 6 2607 3849461501 S560Llet 9560 Max factorial is 3209 The range increases by more than 3 000 orders of magnitude 1 35 2 2 Precision What is the precision of those numbers We modify the first program as follows Tit mailin vVvord float f 1 0f fctf 1 0 ECCE Tacti 34 0F s E ECET IOE 7 7 Add one to tert Be feti LSA ap a errotia equal Lo EOL orr printer OK m else PEIRCE NOt Ok ya return Q0 We obtain the factorial of 34 We add to it 1 Then we compare if it 1s equal or not to the same number Against all mathematical expectations our program prints Not ok In floating point maths 1 N N Why this The density of our format makes the gaps between one number and the next one bigger and bigger as the magnitude of the numbers increases At the extreme of the scale almost at over flow the density of our numbers is extremely thin We can get an idea of the size of the gaps by writing this int main vord float f 1 0f fctf 1 0 fett facti 34048 f 1 0 While err firctij 4 C A EO 172 C programming with Icc win32 peint Needs ce nnn f return Oz We get the output Needs
470. receive these keyboard and mouse events To optimize performance it is good practice for applications to detect whether they are run ning in a Terminal Services client session For example when an application is running on a remote session it should eliminate unnecessary graphic effects like 1 Splash screens Transmitting a splash screen to a Terminal Services client consumes extra network bandwidth and forces the user to wait before accessing the application 2 Animations which consume CPU and network bandwidth 3 Direct input or output to the video display You can detect if you are running in a remote session by using the following code BOOL IsRemoteSession void return GetSystemMetrics SM REMOTESESSION 306 C Tutorial 3 17 15 Windows Here is a short overview of the types of controls available to you Group boxes static text filled rectangles Used for labels grouping and separation Used to start an action Radio buttons Used for choosing one among several possible choices Used for scrolling a view a Used to make a scrollable region that contains other controls You scroll the controls into view with the pager Pager Used in lengthy operations to give a graphic idea of how much Progress bar ee eas l j time is still needed to finish the operation Property Sheets Used to pack several dialog boxes into the same place avoiding user confusion by displaying fewer items at the same t
471. record for the linker telling it that this object is defined elsewhere 32 Note that when you do not provide for a declaration and use this feature definition is a declaration you can only use the defined object after it is defined A declaration placed at the beginning of the program module or in a header file frees you from this constraint You can start using the identifier immediately even if its definition comes much later or even in another module 18 C programming with Icc win32 double En double T 4 double d sqrt f more statements Note that initializing a value with a value unknown at compile time is only possible within a function scope Outside a function you can still write ine se nS Or ipte a COIS AO nay LG but the values you assign must be compile time constants i e values that the compiler can fig ure out when doing its job Pointers are declared using an asterisk ime ta This means that a will contain the machine address of some unspecified integer You can save some typing by declaring several identifiers of the same type in the same decla ration like this Ine cao Cr Note that c is a pointer to an integer since it has an asterisk at its left side This notation is somehow confusing and forgetting an asterisk 1s quite common Use this multiple declara tions when all declared identifiers are of the same type and put pointers in separate lines The syntax of C declarations has been cr
472. rection of positive infinity 3 Round downwards Choose always the next lower grid point in the direction of negative infinity 4 Round to zero We choose always the next grid point in the direction of zero If the number is positive we round down if it is negative we round up This rounding modes are defined in the standard header file fenv h as Rounding direction macros define FE TONEAREST 0 define FE DOWNWARD l define FE UPWARD 2 define FE TOWARDZERO 3 You can change the default rounding precision by using the function fesetround int also declared in the same header file Numerical programming 175 The rationale for this rounding modes is the following To know if an algorithm is stable change your rounding mode using the same data and run your program in all rounding modes Are the results the same If yes your program is numerically stable If not you got a big prob lem and you will have to debug your algorithm For a total of N floating point operations you will have a rounding error of 1 For round to nearest is sqrt N machine epsilon 2 For round up is N machine epsilon 3 For round down is N machine epsilon 4 For round to zero is N machine epsilon 1f the number is positive N Machine Epsilon if the number is negative The number you actually obtain will depend of the sequence of the operations The machine epsilon is the smallest number that changes the result of an addition
473. ressions There are more than 75 methods for the string library Here is for instance the slice method ne he ehere slice 1 SS gt 10 so uce Cle S gt ell slice lh lt 3 gt Ue Ls a slice 4 2 gt her Note that slicing a string with only one index produces an integer in this case the ASCII value of h a a a a Introduction 213 Windows Programming 3 1 Introduction OK up to now we have built a small program that receives all its input from a file This is more or less easy but a normal program will need some input from the user input that can t be passed through command line arguments or files At this point many introductory texts start explaining scanf and other standard functions to get input from a command line interface This can be OK but I think a normal program under windows uses the features of windows We will start with the simplest application that uses windows a dialog box with a single edit field that will input a character string and show it in a message box at exit The easiest way to do this is to ask wedit to do it for you You choose new project in the project menu give a name and a sources directory and when the software asks you if it should generate the application skeleton for you you answer yes You choose a dialog box application when the main dialog box of the wizard appears since that is the simplest application that the wiza
474. ring into the string contents Another often needed operation is reading a line from a string LG oe reere o CELIA 4 Source 29 fy FILE Eron Inte 2 v7als if StrvalidA source om gt source capacity SGULCE CONLGNE allocate proper spece nrl SMALE 4 if source content NULL return O7 Source Capacity n l j for i 07 lt A J f val fgetc from if val EOF val n break Li Vad f get A source content i val source content i 0 SOULCE COUNT 13 returm 17 2 3 1 Reversing a String Reversing the order of elements in a string is accomplished by our Strreverse or our reverse string function Both names lead to the same function DOOL Teverse SEring oer ing SS if Strvalid s return false char p s content Char g gt ps Inc L Scounty p t 1 While 0 of AG di t ta OF return true 206 C programming with Icc win32 2 3 8 Searching text The Strstr searches a pattern in a given string and returns a fat pointer to a string Stringp or an invalid string if not found DtLbingp Overloaded strstr String string String find this ehar Strp end LG Lest char ry struct Exception exc GetAnExceptionStructure ERE CONDITION 1otrval co String Se Strvalid find ths 7 exe PLESt Char iid this Convent 7 Strip mMemchr String convent first char strings count Lt strip A end
475. rn Stricmpo char argl Char aroz int Main int argc Char argv Eliminate argv 0 from sort 4 argvutt argc Sort remaining args using qsort 5 qsore VO10 jarogv Size T argc Ssizeor Char compare Output sorted list FOr ainet i OF 1 lt argc Fri 6 printi ss argv i J3 printi in J 7 return 0 The structure of this example is as follows We build a program that will sort its arguments and output the sorted result To use qsort we define a comparison function that returns an integer which encodes the rela tive lexical ordering of the two arguments passed to it We use a library function for doing that the stricmp gt function that compares two character strings without caring about case differ ences But there is quite a lot of new material in this example and it is worth going through it in detail We include the standard header string h to get the definitions of string handling functions like stricmp We define our comparison function with int Compare Const void argl const void argZ 1 ss This means that our compare function will return an int and that takes two arguments named argl and arg2 that are pointers to any object void The objects pointed to by arg1 and arg2 will not be changed within this function 1 e they are const We need to get rid of the void within our compare function We know we
476. rn invalid results depending on whether the block was reallocated or not 5 It can be slow Malloc free was a big bottleneck for performance using the Microsoft C runtime provided by the windows system for windows 95 98 for instance 1 28 5 The malloc with no free strategy This strategy uses only malloc never freeing any memory It is adapted to transient programs i e programs that do a well defined task and then exit It relies on the operating system to reclaim the memory used by the program Advantages 1 Simplified programming since all the code needed to keep track of memory blocks disappears 2 It is fast since expensive calls to free are avoided Drawbacks 1 The program could use more memory than strictly needed 2 Itis very difficult to incorporate software using this strategy into another program 1 e to reuse it This strategy can be easily converted into an arena based strategy though since only a call to free the arena used by the program would be needed It is even easier to convert it to a garbage collector based memory management Just replace malloc by GC malloc and you are done 1 28 6 Automatic freeing garbage collection This strategy relies upon a collector 1 e a program that scans the stack and the global area of the application looking for pointers to its buffers All the memory blocks that have a pointer to them or to an inner portion of them are marked as used the others are considered free Thi
477. rrmsg Show the indicated error to the user terror undefined cpu pragma instructions special compiler directives Special compiler directives This is a Fa ae on _Pragma string C99 feature Pragma optimize Con 38 C programming with Icc win32 If a appears at the end of a line just before the newline character the line AN and the following line will be joined by this is a comment the preprocessor and the character will be eliminated LINE Replace this token by the current line printi error Laine zdan number __LINE_ FILE Replace this token by the current file Printer error file nsan gt a name ELILE Ja Fane Replace this token by the name of the Princo im 2S ue current function being compiled se e Defined as 1 This allows you to ECE conditionally include or not code for lcc if LCC _ win32 1 The parentheses ensure the correct evaluation of the macro 2 The different pragma directives of lcc win32 are explained in the user s manual 1 9 4 Windows specific defined symbols WINVER Evaluates to the version of windows you ee ar eee are running Evaluates to the version of the internet _WIN32_IE explorer software installed in your if WIN32 IE gt 0x500 system 1 9 5 Structured exception handling __try protected block Introduces a protected block of code _ except integer expression If the integer expression evaluates to 1 the associated code block
478. rs the class of the main window In the next paragraphs we will try to see how we modify this skeleton to add different items you may want to add to your application 3 8 1 Making a new menu or modifying the given menu Add your item with the resource editor and give it an identifier normally written in uppercase like IDMENU_ ASK PARAMETERS or similar This is surely not the text the user will see but a symbolic name for an integer constant that windows will send to the program when the user presses this option We can then continue our beloved programming traditions Once that is done and your menu displays correctly go to the wizard code in theMainWnd Proc function gt There you will see a big switch with different code to handle the events we are interested in The menu sends a command event called WM COMMAND In there you see that this event will be handled by the HANDLE COMMAND macro It is just a shorthand to break down the 64 bits that windows sends us in smaller pieces disassembling the message information into its constituent parts This macro ends calling the MainWndProc OnCommand function that is a bit higher in the text There you will find a switch with the comment TODO Insert new commands here Well do exactly that and add as a new case in the switch your new identifier IDMENU ASK PARAMETERS There you can do whatever you want to do when that menu item 1s clicked 3 8 2 Adding a dialog box Dra
479. rtant parameters of this message are idCtrl This is a numerical constant an integer that is used as the ID of this control 2 pnmh This is a pointer to a structure that contains further information about the message It points to a NMHDR structure that contains the following fields typedef struct tagNMHDR HWND hwndF rom DINE 2dr iom UINT code NMHDR 256 C Tutorial 3 This struture can be followed by more data in some of the notifications that a control can send In that case this fixed fields will be membbers of a larger structure and they will be always at the same position The controls that use this interface were introduced into windows later in 1995 than the first ones that were present in all the earlier versions of windows They are the following Animation control An animation control is a window that displays an Audio Video Interleaved AVI clip An AVI clip 1s a series of bitmap frames like a movie Animation controls can only display AVI clips that do not contain audio This control is currently not supported by the resource editor Date and time They allow the user to input a date or a time The notifications use picker controls the prefix DTN XXX Header controls A header control is a window that is usually positioned above col umns of text or numbers It contains a title for each column and it can be divided into parts The user can drag the dividers that separate the parts to set the width of each c
480. rtion or all the string contents You can obtain an iterator to the beginning of the string with SELing Str new Sstring 15 7 Stringp postr begin str The polymorphic function begin returns a pointer to the beginning of a sequential container The operations supported with string pointers are 198 C programming with Icc win32 2 2 4 1 Pointer subtraction int Operator SEringop esl iStringp 432 struct Exception exc GetAnExceptionStructure PRECONDITION Strvalidp sl amp amp Strvalidp s2Z amp amp sl parent s2 parent exc return sl content s2 content The operator verifies that both pointers are valid and that they point to the same string The Operation is more restricted than in traditional C since a subtraction operation is considered invalid if the pointers do not point to the same parent 2 2 4 2 Addition of pointer and integer This operation moves the given pointer forwards of backwards a specified number of charac ters Stringer Operarort Stringo sslyint i struct Exception exc GetAnExceptionStructure PRECONDITION CStrvalide sl e I lt SiL Counta Sl COumE ay sl content n return sl 2 2 4 3 Comparisons of a string pointer with zero Several string functions return an invalid string pointer to indicate failure It is practical that this pointer equals to NULL so that code snippets like LE CUSt neh strane a lt 4 w
481. ry To view and edit the registry you can use the system tool regedit When it starts 1t shows the basic structure of the root trees Registry Editor Fie Edit View Favorites Help a J My Computer fy HKEY CLASSES ROOT H E HKEY CURRENT LISER E HEEY LOCAL MACHINE HEEY_USERS HKEY_CURRENT CONFIG value not seb ss My ComputertHEEY CLASSES ROOT 4A HKEY CLASSES ROOT Registry entries under this key define types or classes of documents and the properties associated with those types Shell and COM applications use the information stored under this key File viewers and user interface extensions store their OLE class identifiers in HKEY CLASSES ROOT and in process servers are registered in this key To change the settings for the interactive user store the changes under HKEY CURRENT USER Software Classes rather than HKEY CLASSES ROOT 2 HKEY CURRENT USER Registry entries under this key define the preferences of the current user These preferences include the settings of environment variables data about program groups colors printers network connections and application preferences This key makes it easier to establish the current user s settings the key maps to the current user s branch in HKEY USERS In HKEY CURRENT USER software vendors store the current user specific preferences to be used within their applications Lcc win32 for example creates the HKEY CURRENT USER Software lcc key for its app
482. s This is called operator overloading and will be explained fur ther down 29 In most compilers the char short int long types are present but their sizes can change from machine to machine Some embedded systems compilers do not support floating point Many compilers do not implement the recent types Bool long long or long double Within the windows environment how ever the char short int long float double types are identical to this ones in all 32 bit windows compil ers I know of 30 Microsoft Visual C implements long double as double and calls the long long type int64 To remain compatible with this compiler lcc win32 accepts int64 as an equivalent of long long Declarations and definitions 17 1 5 Declarations and definitions It is very important to understand exactly the difference between a declaration and a definition in C A declaration introduces an identifier to the compiler It says in essence this identifier is a xxx and its definition will come later An example of a declaration 1s extern double sqrt double With this declaration we introduce to the compiler the identifier sqrt telling it that it is a func tion that takes a double precision argument and returns a double precision result Nothing more No storage 1s allocated for this declaration besides the storage allocated within the compiler internal tables gt A definition tells the compiler to allocate storage for the identifier For instance when we
483. s there was a problem with this program printi Error coder arxi Code return 0 This will print Ooops there was a problem with this program Error code Oxc00Q00005 We use a comma expression within the except to catch the value of the exception code into a local variable The comma expression returns EXCEPTION EXECUTE HANDLER as its result with the side effect of storing the exception code in a local variable In other compilers the GetExceptionCode function can be called only within an except expression Lec win32 let s you call it anywhere you want it will always return the exception code of the last exception that was executed or zero if there weren t any Another useful function 1s void RaiseException unsigned code unsigned flags unsigned nbArgs unsigned args We can use it to call the exception handling mechanism in the same way as a real exception would Example fine Lwde lt stdio h gt finclude lt seh h gt int main void char p 10 unsigned code ee A to S10 printi No exceptions n i RaiseException 0xdeadbeef 0 0 NULL Except COode Gethxcept1onCode EXCEPTION EXECUTE HANDLER 4 printf Ooops there was a problem with this program n printf Error codes tx n Code Vecurm Oy This will print No exceptions Ooops there was a problem with this program Error code Oxceadbeef Note that the system will change the exception code from 0
484. s an int and takes a char another char and an int as arguments If you do not like this syntax please bear with me Even Dennis Ritchie says this syntax isn t really the best one We store in our dllHandle the result of calling LoadLibrary with an absolute path so it will always work at least in this machine Note that the backslashes must be repeated within a character string 242 C Tutorial We test if the handle received is a correct one If not we put up some message and we exit the program We are now ready to assign our function pointer We must cast the return value of GetProcAd dress to a function like the one we want The first part of the statement is just a cast using the same construction that the declaration of the function pointer before with the exception that we do not include the identifier of course since this is a cast But the arguments to Get Pro cAddress are weird We do not pass really the name of the function Get String but a name GetString 12 Where does this name come from The rest of the program stays the same To understand where this weird name comes from we have to keep in mind the following facts Icc win32 like many other C compilers adds always an underscore to the names it generates for the linker Since our function is declared as _ stdcall windows conventions require that we add to the name of the function the character followed by the size of the function arguments Since
485. s assigning values at zero but you can change the values using the equals sign An enumeration like enum a b c will provoke that a will be zero b will be 1 and c will be 2 You can change this with enum a 10 b 25 c 76 1 11 15 Prototypes A prototype is a description of the return value and the types of the arguments of a function The general form specifies the return value then the name of the function Then enclosed by parentheses come a comma separated list of arguments with their respective types If the function doesn t have any arguments you should write void instead of the argument list If the function doesn t return any value you should specify void as the return type At each call the compiler will check that the type of the actual arguments to the function is a correct one The compiler cannot guarantee however that the prototypes are consistent across different compilation units For instance if in filel c you declare int fn vor then the call fn will be accepted If you then in file2 c you declare another prototype VOL TAIN and then you use Fr 6 the compiler cannot see this and the program will be in error crashing mysteriously at run time This kind of errors can be avoided if you always declare the prototypes in a header file that will be included by all files that use that function Do not declare prototypes in a source file if the function is an external one 1 11 16 variable lengt
486. s at the same time easy to use and robust For instance what happens if the other side never answers It would be really bad if ping would freeze waiting for an answer that will never come Many other problems can occur and within the PingInterface structure there are a lot of fields that inform you what is going on The basic design principle is that you establish a callback function that is called by the ping function each time a packet arrives or a timeout is detected Writing ping 379 A more sophisticated usage of ping is the remake of the program of the same name Here is a possible implementation of that First we write a callback function to show progress in the screen as we receive a packet include lt ping h gt int PrintReport PingInterface Data if Data gt Errorcode WSAETIMEDOUT Prine Timed our n gt return 1 printf sd bytes from s Data gt Bytes Data gt 1p Printer temp seq 2d Data gt Seq print time Sd ms Data gt Time brine Va return 1 This function is called by ping and just prints out the fields Note that we test the error code flag to see if we are being called because of a timeout or because of a packet arrived In this function we could send a message to a GUI window or we would update some pregress control etc The main function is now trivial We zero the interface structure we set some fields and there
487. s fail somewhere Any computation involving computer representable numbers that map onto the real line as its arguments can potentially produce a result that lies in between two representable numbers In that case that number is rounded off to one of the grid points And this incurs round off error Any practical numerical analyst one who uses a computer to carry out numerical com putations must have a method of bounding estimating and controlling both the round off error at each numerical step as well as the total round off error What do we want from the representation of numbers then 1 The grid points should be as dense as possible 2 The range the span between the smallest and the largest number should be as wide as possible 3 The number of bits used should be as small as possible Numerical programming 167 4 The rules of arithmetic should be mimicked as closely as possible 5 The rules should be such that they can be implemented in hard wired computer logic Note that all those requirements are completely contradictory If we want a dense representa tion we have to use more bits If we increase the range we have to thin the spacing between numbers etc 1 35 1 Floating point formats In Icc win32 we have a plethora of numeric types ranging from the smallest single precision format to the bignum indefinite precision numbers All the numeric types including the complex numbers type but excluding the bignums are
488. s for the same failure under windows NT 2000 When you mix all those error handling strategies in a single program as you have to do to pro gram with the API the resulting mix can be very entertaining Consider this extern BOOL DoSomething void Uses the boolean strategy BOOL ok DoSomething rT PATLERD CO WRONG return The macro FAILED tests if the HRESULT 1s less than zero Here is the definition define FAILED S HRESULT S lt 0 In the above case the code for failure 0 will not be less than zero and it will not be detected as a failure code Rule Do not use the FAILED or SUCCEEDED macros for anything other than HRESULTS Since you know that FALSE is defined as zero FAILED FALSE is zero not really an expected result The opposite problem leads to headaches too Always use the FAITLED SUCCEEDED mac ros with HRESULTS and never write things like this HRESULT RE hr ISomething gt DoSomething LE USNE WRONG return 318 C Tutorial Note too that in their infinite wisdom the designers of this API decided that S FALSE is a success code NOT a failure code and it is defined as 1 one This means that SUCCEEDED gt FALSE gt TRUE Nice isn t it 3 19 1 Check the return status of any API call Consider this code TCHAR cDriveLetter TCHAR szWindowsDir MAX PATH GetWindowsDirectory szWindowsDir MAX PATH cDriveLetter szWindowsDir 0 WRONG
489. s if we just write h lcc examples gt countchars We get the following box that many of you have already seen several times gt countchars exe Application Error x The instruction at Os 76415ce referenced memory at Osb eidb4 The memory could not be read Click on OF to terminate the application Click on CANCEL to debug the application Cancel Why Well let s look at the logic of our program We assumed without any test that argv 1 will contain the name of the file that we should count the characters of But if the user doesn t sup ply this parameter our program will pass a nonsense argument to fopen with the obvious result that the program will fail miserably making a trap or exception that the system reports We return to the editor and correct the faulty logic Added code is in bold include lt stdio h gt include lt stdlib h gt 1 int main int arg char argv int count 0 chars read FILE intitle iid 6 if argc lt 2 2 printf Usage countchars lt file name gt n exit 1 3 infile fopen argv 1 r c fgetc infile while c EOF count t C oetc intile Prince 20 n count return 0 39 This is the display under Windows NT In other systems like Linux for instance you will get a Bus error message Reading from a file 25 1 We need to include lt stdlib h gt to get the prototype declaration of the exit functio
490. s no distinction between functions and procedures in C A procedure is a function of return type void 8 Actually the startup code calls main When main returns the startup code regains control and ends the program This is explained in more detail in the technical documentation 9 Any program in any computer in any language has two main types of memory at the start The code of the program 1 e the sequence of machine instructions that the program will execute This section has an entry point the above mentioned main procedure in C or other procedure that is used as the entry point The static data of the program i e the string literals the numbers or tables that are known when the program starts This data area con be further divided into an initialized data section or just empty reserved space that is initialized by the operating system to zero when the program is loaded 10 There is no way to import selectively some identifiers from another included file Either you import all of it or none Hello 3 The body is a series of expressions separated by semicolons Each statement can be an arith metic operation an assignment a function call or a compound statement i e a statement that contains another set of statements 1 2 Hello To give you an idea of the flavor of C we use the famous example given already by the authors of the language We build here a program that when invoked will put in the screen the
491. s strategy combines easy of use and reclaiming of memory in a winning combination for most applications and it is the recommended strategy for people that do not feel like messing around in the debugger to track memory accounting bugs Advantages 1 Program logic is simplified and freed from the chores of keeping track of memory blocks Memory management strategies 125 2 The program uses no more memory than needed since blocks no longer in use are recycled Drawbacks 1 It requires strict alignment of pointers in addresses multiple of four Normally this is ensured by the compiler but under certain packing conditions compilation option Zp1 the following layout could be disastrous pragma pack 1 struct 4 S1orC a echar sot SF The pointer ptr will NOT be aligned in a memory address multiple of four and it will not be seen by the collector because the alignment directive instructs the compiler to pack structure members 2 You are supposed to store the pointers in memory accessible to the collector If you store pointers to memory allocated by the collector in files for instance or in the windows extra bytes structure maintained by the OS the collector will not see them and it will consider the memory they point to as free releasing them again to the application when new requests are done 3 Whenever a full gc is done a full scan of the stack and the heap a noticeable stop in program activity can be perce
492. s to push that address in the stack When we write software in today s powerful micro processors it 1s important to get rid of the frame of mind of twenty years ago when saving every cycle of machine time was of utmost importance Pushing an extra argument in this case the address of the Frequencies array takes 1 cycle At a speed of 1400 2500 MHz this cycle isn t a high price to pay Continuing our analysis of our main function we notice that the next task is displaying the output of the frequencies array This is quite a well defined task since it takes the array as input and should produce the desired display We define then a new function DisplayOut put that will do that Its single parameter is the same Frequencies array void DisplayOutput CHARS Frequencies 63 We find very often the expression while c fgetc infile EOF instead of the expression above Both expressions are strictly equivalent since we first execute the fgetc function assigning the result to c then we compare that result with EOF In the second slightly more complicated we need a set of parentheses to force execution to execute the fgetc and the assignment first There is the danger that c would get assigned the result of the comparison of the fgetc result with EOF instead of the character itself 64 The standard files defined by the standard are stdin or standard input to read from the current input device the stdout or
493. scope and linkage Until now we have used identifiers and scopes without really caring to define precisely the details This is unavoidable at the beginning some things must be left unexplained at first but it is better to fill the gaps now An identifier in C can denote e an object e a function e atag or a member of a structure union or enum e a typedef e a label For each different entity that an identifier designates the identifier can be used is visible only within a region of a program called its scope There are four kinds of scopes in C The file scope is built from all identifiers declared outside any block or parameter declaration it is the outermost scope where global variables and functions are declared A function scope is given only to label identifiers The block scope is built from all identifiers that are defined within the block A block scope can nest other blocks The function prototype scope is the list of parameters of a function Identifiers declared within this scope are visible only within it Let s see a concrete example of this 61 You see the infinite loop here Tell me why is this loop never ending Look at the code again Identifier scope and linkage 99 static int Counter 780 file scope extern void fn int Counter function prototype scope void function int newValue int Counter Block scope double d newValue label Lor ent L 0s 2 Oia if i lt newValue
494. scope of this integer will be only the scope of the enclosing for block It can t be used outside this scope Note that we have written the for construct without curly braces This is allowed and means that the for construct applies only to the next statement nothing more The print n 1s NOT part of the for construct Ok now let s compile this example and make a few tests to see 1f we got that right h lcec examples gt sortargs aaa bbb hhh sss ccc nnn ada DDD ccc Anh mnn sss OK it seems to work Now we have acquired some experience with qsort we can apply our knowledge to our frequencies example We use cut and paste in the editor to define a new compare function that will accept integers instead of char We build our new comparison function like this Int compare const void argl const void argZ FECU 4 of ae eos Se A ea GZ a We just return the difference between both numbers If arg is bigger than arg2 this will be a positive number if they are equal it will be zero and if argl is smaller than arg2 it will be a negative number just as qsort expects Right before we display the results then we add the famous call we have been working so hard to get to 55 The compiler emits a record for the linker telling it to put there the address of the global if the argument is a global variable or will emit the right instructions to access the address of a local using the
495. sed WM MOUSEMOVE This 1s posted to a window when the cursor moves If the mouse is not captured the message is posted to the window that con tains the cursor Otherwise the message is posted to the window that has captured the mouse WM MOUSEHOVER This is posted to a window when the cursor hovers over the cli ent area of the window for the period of time specified in a prior call to TrackMouseEvent WM_MOUSELEAVE This 1s posted to a window when the cursor leaves the client area of the window specified in a prior call to TrackMou seEvent 3 8 6 Getting keyboard input Handle the WM_KEYDOWN message or the WM CHAR message Windows allows for a fine grained control of the keyboard with specific messages when a key is pressed released repeat counts and all the keyboard has to offer Here 1s a small description of each Message Meaning Window is being either activated or desactivated WM_CHAR The user has typed a character Here you receive characters like m for instance WM_KEYDOWN A key has been pressed Here you can use keys like the arrows of the keyboard Del Insr etc A key has been released 3 8 7 Handling moving resizing You get WM MOVE when your window has been moved WM SIZE when your window has been resized In the parameters of those messages you find the new positions or new size of your window You may want to handle those events when you have child windows that you should move with your main window
496. sense because a Win32 process s address space is 4GB of which only 2GB 2431 bytes may be used by the process However for the sake of making 64 bit arithmetic work below for file offsets we need to make sure that all 64 bits of limpest are initialized correctly I liBytesRemaining QuadPart liSrcFileSize QuadPart This assignment sets all 64 bits to this value liMapSize QuadPart MAX VIEW SIZE do 4 Now we start our copying loop The min macro returns the smaller of two numbers liMapSize QuadPart min liBytesRemaining QuadPart liMapSize QuadPart 1i10ffset QuadPart 11SrcFileSize QuadPart 1liBytesRemaining QuadPart poro BYTE MapViewOtPile hsreMap FILE MAP READ 1i10ffset HighPart 1i0ffset LowPart liMapSize LowPart PDst BYTE MapViewOfFile hDstMap FILE MAP WRITE IIOTLSetsHighPart 1i0ffset LowPart liMapSize LowPart We use memcpy to do the actual copying memcpy pDst pSrc 1liMapSize LowPart UnmapViewOfFile pSrc UnmapViewOfFile pDst 1iBytesRemaining QuadPart 1iMapSize QuadPart while liBytesRemaining QuadPart gt 0 fResult SUCCESS DONE We are done Note the error treatment of this function We use gotos to reach the end of the function and here we cleanup everything 310 C Tutorial if hDstMap CloseHandle hDstMap if hDstFile INVALID HANDLE VALUE CloseHandle hDstFile if hSrcMap CloseHandle hSrcMap if hSrcFile INVALI
497. si tion bool erase SUEINgG String amp s S17e 0 POS imc Clement s1 767 char pcontents wchar t pwcontents if lStrva lid s return false if s count 0 return false struct Exception exc GetAnExceptionStructure PRECONDITION pos lt s count exc PEONCENCS SvCOncenr Lf pos s count 1 4 pcontents pos 0 So COUN return true memmove pcontents pos pcontentstpostl s count pos l SCout 7 pcontents s count 0 return true 202 C programming with Icc win32 We allow erasing characters from an empty string and just return false if that is the case This allows for loops that will use the result of Strerase to stop the iteration In this case we just return false Otherwise we require a valid String and a valid index A small optimization is peformed when the character to erase is the last character in the string We spare us a memmove call by just setting the character to zero and decreasing the count field of the string structure Otherwise we have to move the characters from the position we are going to use one position down 2 3 4 Mapping and filtering A mapping operation in a string means applying a function to each character in the source string and storing the result of that call in the new string that is the result of the operation SELING Strap String S from Int A map Tun Lnr string result struct Exception exc GetAnExceptionStructure IE ma
498. signal mechanism that will call the traphandler func tion In there we print the name of the signal using the standard library function psignal and then we make a longjmp that will return to the same if setimo jumpbuffer but this time with a value of 1 Instead of getting into the else arm of the 1f statement we enter the branch with the empty statement and we go out normally after the trap Note how this code starts to look very similar to the structured exception handling code The difference is that here we have to trap all possible signals then run our code then unset all the signals to their former values The only reason to prefer using signal to the structured exception handling 1s portability The signal mechanism will work in many other environments For instance the program above will run unmodified in a UNIX system producing the same output 77 The psignal function is not part of the standard but it exists in many implementation specially in UNIX systems 166 C programming with Icc win32 1 35 Numerical programming Computers are done for making calculations well at least originally that was their objective Playing games internet browsing word processing etc came later The problem of storing numbers in a computer however is that the continuum of numbers is infinite and computers are limited Yes we have now many times the RAM amount that we had just a few years ago but that amount is finite
499. signed char str if str NULL return NULL while p str tolower p Dir return str We include the standard header ctype h which contains the definition of several character classification functions or macros like isupper that determines if a given character is upper case and many others like isspace or isdigit We need to include the stdio h header file too since it contains the definition for NULL The first thing we do is to test if the given pointer is NULL If it is we return NULL Then we start our loop that will span the entire string The construction while p tests if the con tents of the character pointer p is different than zero If this is the case we transform it into a lower case one We increment our pointer to point to the next character and we restart the 48 This convention is used in the library function Actually it is a quite bad interface since the return value doesn t give any new information to the user besides the expected side effect of transforming the given string A better return value would be the number of changed characters for instance that would allow the caller to know if a transformation was done at all or the length of the string or several others But let s implement this function as it is specified in the standard library Many times you will see that even if it is obvious that software must be changed the consequences of a change are s
500. size 256 This will work just like the pre processor definition 66 Memory allocation problems plague also other languages like C that use a similar schema than C 114 C programming with Icc win32 1 26 Buffer overflows Let s come back to the code snippet above else strcpy fullname stream gt Name streatdftullname gt ROS E PACES strcat fullname name If the length of stream gt Name 1s bigger than the size of the buffer a security hole appears the program will write over the local variables of the function and later over the return address stored in the stack when our function is active We have a stack layout like this local variables of the calling function arguments to the current function return address saved frame pointer local variables p is at the lowest address then fullname then result saved registers stack pointer is here An overflow when copying the Name field would destroy the saved frame pointer and maybe destroy the return address The copy starts at the lowest address the start of the fullname buffer then goes on to higher addresses After the overflow occurs the function would continue normally until it executes the return statement Depending on the type of overflow the return address would contain characters from the Name field that in most cases would lead to a wrong return address and a program crash But that 1s not always the case It could be that a user
501. some If you are not inter ested in modifying the background you can use the API GetStockObject returning the han dle of the white brush like this return GetStockObject WHITE BRUSH Objects created with GetStockObejct do not need to be destroyed so you spare yourself the job of creating and destroying the brush The code would look like this BOOL WINAPI MyDlgProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam HDG DC COLORREE obledecolor Switch msg case WM CTLCOLORLISTBOX hDC HDC wParam Color RGB 192 0 0 47 red Corlor Set lexctCcolor haDG color gt return GetStockObject WHITE BRUSH Customizing controls 287 If you want to return another brush than white you should handle the WM_INITDIALOG message to create the brush and the WM NCDESTROY message to destroy the brush you created to avoid memory leaks In this case the above example should be augmented with BOOL WINAPI MyDlgProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam HDC ADC COLORREE oldcolors static HBRUSH hBrush Switch msg case WM INITDIALOG hBrush CreateSolidBrush BK COLOR other initializations go here case WM CTLCOLORLISTBOX hDC HDC wParam Color REB 192 0 Oe 77 red color Ser lexvteColor hDC color return hBrush case WM NCDESTROY DeleteOb ject hBrush break We create the brush at the initialization of the list box we use it when we receive the WM CTLCOLORLISTBOX message and
502. ss with redirected stdin and stdout The CreateProcess API through the STARTUPINFO structure enables you to redirect the standard handles of a child console based process If the dwFlags member is set to STARTF USESTDHANDLES then the following STARTUPINFO members specify the standard handles of the child console based process HANDLE hStdInput Standard input handle of the child process HANDLE hStdOutput Standard output handle of the child process HANDLE hStdError Standard error handle of the child process You can set these handles to either a pipe handle file handle or any handle that can do syn chronous reads and writes through the ReadFile and WriteFile Q API The handles must be inheritable and the CreateProcess API must specify that inheritable handles are to be inher ited by the child process by specifying TRUE in the bInheritHandles parameter If the parent process only wishes to redirect one or two standard handles specifying GetStdHandle for the specific handles causes the child to create the standard handle as it normally would without redirection For example if the parent process only needs to redirect the standard output and error of the child process then the hStdInput member of the STARTUPINFO structure 1s filled as follows hotdinput Getstebhandle sTD INPUT HANDLE NOTE Child processes that use such C run time functions as printf and fprintf can behave poorly when redirected The C run time funct
503. ssion Traditional string representation inC 109 and we take care to erase any references to that member We eliminate the memcpy calls and that s all Our program is smaller uses less memory and what is essential does the same thing quicker than the older version since we spare the copying It is very important to learn from the beginning that software gains not only with the lines of code that you write but also with the lines of code that you eliminate 1 24 Traditional string representation in C In C character strings are represented by a sequence of bytes finished by a trailing zero byte For example if you got char Name lcec win32 You will have in memory something like this EE l c c W 1 n ros 99 99 fas a a L 50 We will have at each of the position of the string array a byte containing a number the ASCII equivalent of a letter The array will be followed by a zero byte Zero is not an ASCII charac ter and can t appear in character strings so 1t means that the string finishes there This design is quite ancient and dates to the beginning of the C language It has several flaws as you can immediately see e There is no way to know the length of a string besides parsing the whole character array until a zero byte is found e Any error where you forget to assign the last terminated byte or this byte gets overwritten will have catastrophic consequences e There is no way to enforce inde
504. st view control ODT MENU Owner drawn menu item ODT_STATIC static control ODT_TAB Tab control unsigned int CtlID Specifies the identifier of the combo box list box button or static con trol This member is not used for a menu item unsigned int itemID Specifies the menu item identifier for a menu item or the index of the item in a list box or combo box For an empty list box or combo box this member can be 1 This allows the application to draw only the focus rectangle at the coordinates specified by the rcItem member even though there are no items in the control unsigned int itemAction Specifies the drawing action that windows expect us to perform This action is indicated with the following flags ODA_DRAWENTIRE The entire control needs to be drawn ODA_FOCUS The control has lost or gained the keyboard focus The itemState member should be checked to determine whether the control has the focus ODA_SELECT The selection status has changed The itemState mem ber should be checked to determine the new selection state HWND hwndItem Window handle of the control RECT rcItem Rectangle where we should do our drawing unsigned long itemData Specifies the application defined value associated with the menu item Customizing controls 289 unsigned int itemState State of the item after the current drawing action takes place This can be a combination of the following values ODS _ CHECKED This bit is used only in a menu ODS COMBOBOXED
505. stance a signed short goes from 32767 to 32767 an unsigned short goes from zero to 65535 Ory See the standard include file lt stdint h gt for the ranges of signed and unsigned integer types 1 11 19 bit fields A bit field is an unsigned or signed integer composed of some number of bits Lcc win32 will accept some other type than int for a bit field but the real type of a bit field will be always either int or unsigned int For example in the following structure we have 3 bit fields with 1 5 and 7 bits struct 4 InG aii in usb 5 TA eens by With Icc win32 the size of this structure will be 4 with no special options With maximum packing Zp1 option the size will be two When you need to leave some space between adjacent bit fields you can use the notation unsigned n For example SEEUCE 5 4 int est cl La 57 unsigned 10 ROUDE Glan ar by Between the bit fields a and b we leave 10 unused bits so that c starts at a 16 bit word bound ary 1 11 20 stdcall Normally the compiler generates assembly code that pushes each argument to the stack exe cutes the call instruction and then adds to the stack the size of the pushed arguments to return the stack pointer to its previous position The stdcall functions however return the stack pointer to its previous position before executing their final return so this stack adjustment is not necessary The reason for this is a smaller code size since the m
506. standard output and the stderr stream to show errors Initially stdin is bound to the keyboard stdout and stderr to the screen 102 C programming with Icc win32 for Int Count 0s cOunr lt Z256sCOouUnEe T 4 if Freguencies count Freguency 0 printf S3c 4d Sd n Freguencies count CharacterValue Frequencies count CharacterValue Freguencies count Frequency Let s look at our main function again ine main int ee OC eC neue Tafgvi Tie Count FILE infile checkargqs aroc argv 7 if infile NULL return 1 Initialize count ProcessFile infile Frequencies felose infile Prtorr 2d ehars i fice Couns gsort Frequencies 256 sizeof CHARS compare DisplayOutput Frequencies Note how much clearer our main function is now Instead of a lot of code without any struc ture we find a much smaller procedure that is constructed from smaller and easily understand able parts Now suppose that we want to handle several files With this organization it is straightforward to arrange for this in a loop ProcessFile receives an open FILE and a Frequencies array both can be easily changed now A modular program is easier to modify than a monolithic one We see too that the function that process the files leaves them open We could streamline more main if we got rid of that in the ProcessFile function but I find it personally better that the same function tha
507. stination buffer Note that we use the strncpy function This standard library function takes an extra parameter a maximum length to copy We do not want to overflow the destination buffer under any circumstances so we only copy a maximum of bufferlen characters minus one to account for the terminating zero of the string We ensure afterwards that the string is zero terminated and we return the result The rest of the program remains the same so it is not shown It is important to remember to prog p get rid of that MessageBox call however 10 We compile the library and we want to test it but we need a test program A library is not an executable by itself Besides this we need a header file that the user of the library will use to get the prototype of our function Its contents are very simple int GetString char prompt char destBuffer int bufferlen and that s all 105 Well this is not great deal we have just to answer YES when it proposes to create the skeleton Libraries 235 Now we have to define a new project that will contain the test code We do that in the same way as we have created the other projects we choose the Create project option in the Project menu bar and we name it appropriately testdialog We do NOT specify a windows application Since our library should be independent whether it is called from a windows program or a console application we should test that now Additional f
508. szTitle General itt Repeat for all pages psp i pszTemplate MAKEINTRESOURCE IDD COMPILER psp 1 etnDlgProc CompilerDig psp i pszTitle Compiler Lt Now that we have filled the property sheet pages we fill the header data First we set it to zero memset amp psh 0 sizeof PROPSHEETHEADER Then we set the size field flags field and the parent window info psh dwSize sizeof PROPSHEETHEADER psh dwFlags PSH PROPSHEETPAGE PSH NOAPPLYNOW psh hwndParent hwndOwner Then the hinst Application instance the caption and the number of pages this property sheet has psh hInstance hInst DehvpszCaption Contiguration psh nPages i Now we link the header data with the array of property sheet pages we filled above psh ppsp LPCPROPSHEETPAGE amp psp I Now we go Propertysheet amp psh 3 21 28 How to tell Windows to run a program during startup You can either place a shortcut to your program in the Windows startup folder or add an entry to the registry for your program If you want to use the shortcut technique then look at the question on how to create a shortcut on the desktop See page 314 You can use the same code but instead of saving the shortcut to the desktop directory save it to the startup directory You can find the startup directory by call ing SHGetSpecialFolderLocation and passing it the CSIDL_ STARTUP flag If you pr
509. t 0 STREAM infile checkargs argc argv if infile NULL return 1 Initialize do count ProcessStream infile Frequencies folose intile Srile infile GetNext infile f while antile l 0 printf sd chars in flile n Count gsort Frequencies 256 sizeof CHARS compare DisplayOutput Frequencies return U 108 C programming with Icc win32 1 23 Improving the design There are several remarks that can be done about our program The first one 1s that the mem ory allocator could very well fail when there is no more memory available When the alloca tor fails it returns NULL Since we never test for this possibility our program would crash in low memory conditions What a shame We arrange for this immediately Instead of using the allocator we will write a function that will call the allocator test the result and call the exit routine if there is no more memory left Continuing processing without more memory is impossible anyway void xmalloc unsigned int size void result malloc size if result NULL fprintf sdterr No more memory left nProcessing stops n lt i ae Ol return result Note that we keep the same signature 1 e the same type of result and the same type of argu ments as the original function we want to replace This is function sub classing Note too that we use fprintf instead of printf Fprintf takes an extra argument a file whe
510. t Pietreck IDG Books Windows Internals Matt Pietreck Addison Wesley This books are source books for understanding how windows works and how it is built Not easy to read for beginners but indispensable for more advanced programmers Introduction 367 Network Programming 4 1 Introduction Network programming under windows started with the windows socket implementation under windows 3 0 That implementation was a port of the sockets implementation of Unix to win dows that added some support for the asynchronous calls under the weak multitasking of the 16 bit windows implementation When windows passed to 32 bits under windows 95 the sockets implementation improved of course since a real multitasking operating system was running Based on the windows sockets implementation Microsoft released first the wininet interface later the winhttp interface The wininet interface is better for people that are concerned with some other protocols as http of course and it is a more low level interface than winhttp Of course low level is here very relative Having implemented a full FTP protocol under win dows 3 1 the wininet interface is kilometer higher than the bare windows sockets interface 4 1 1 What is a network Let s start with a short review of the basic network terminology The figure below demon strates a simple network that you might find in a small business or in the home Each machine has a network adapter th
511. t is a handy way of avoiding writing a lot of boilerplate code But it is obvious that we will need to understand every bit of what the wizard generates We create a new project as usual with the project then Create menu option and we give it the name of winexample The wizard shows us a lot of dialogs with many options that will be explained later so just stick with the defaults Choose a single win dow application ppe of application C Dialog based f Single window ultiple window C Console application DLL After pressing the next button till the dialog boxes disappear we press F9 compile the whole and we run it We see a single white window with a status bar at the bottom a sum 111 In the data processing field we have been always recycling very old ideas as new just improved Object oriented programming was an idea that came from the old days of Simula in the beginning of the seventies but was rediscovered or rather reinvented in the late 80s Garbage collection was standard in lisp systems in the seventies and now has been discovered again by Mr Bill Gates in the next century with his proposal for the C language 112 Remember the basics of Boolean logic a bit ANDed with another will be one only if both bits are 1 A bit Ored with another with return 1 only if one or both of them is 1 A more advanced window 245 mary menu and nothing else Well this is the skel
512. t opens a file closes it too so that the reader can see if the fopen fclose calls match 1 22 Extending a program Let s suppose then that we want to investigate all frequencies of characters in a directory choosing all files that end in a specific extension for instance c In principle this 1s easy we pass to ProcessFile a different open file each time and the same Frequencies array We develop a GetNextFile function that using our c character string will find the first file that meets this name specifications foo c for example and then will find all the other files in the same directory that end with a c extension How do we do this Well looking at the documentation we find that we have two functions that could help us findfirst and findnext The documentation tells us that findfirst has a prototype like this long Findiarst char spec struct Pfinddata rileinto This means that it receives a pointer to a character string and will fill the fileinfo structure with information about the file it finds 1f it finds it Extending a program 103 We can know if findfirst really found something by looking at the return result It will be 1 if there was an error or a unique value otherwise The documentation tell us too that errno the global error variable will be set to ENOENT if there wasn t any file or to EINVAL if the file specification itself contained an error and findfirst couldn
513. t should be avoided A common beginner error 1s char a hello char b world Strcat a b In this case you are adding at the end of the space reserved for the character array hello another character string destroying whatever was stored after the a character array 186 C programming with Icc win32 1 37 12 Indefinite order of evaluation Consider this code fn pointer gt member pointer amp buffer 0 This will work for some compilers gcc lcc win32 and not for others The order of evaluation of arguments in a function call is undefined Keep this in mind If you use a compiler that will evaluate the arguments from left to right you will get a trap or a nonsense result 1 37 13 A local variable shadows a global one Suppose you have a global variable say buf If you declare a local variable of the same name at an inner scope the local variable will take precedence over the global one 1 e when you write unsigned char buf BUFSIZ ine EFEn Lnt a shar burl buf BUFSIZ 1 0 Error the local variable is accessed not the global one Giving the command line option shadows to the compiler will generate a warning when this happens 1 37 14 Careful with integer wraparound Consider this code 8 pool fun Si 7S Cho Lzey 4 if cbSize lt 1024 we never deal with a string trailing null char buf malloc cbSize 1 memset buf 0 cbSize 1
514. t to verify that the exception code is the one we are expecting If another exception had happened that has no parameters or a different set of parameters we would have crashed 1 34 5 5 Catching stack overflow The stack space allocated by windows to a program at start is 4K This stack can grow up to a size of IMB If you go beyond this limit you get a stack overflow exception OxCOOOOOFD This exception will be catched by the structured exception handling framework however and at first it looks like a normal exception Consider this program include lt windows h gt include lt seh h gt include lt stdio h gt include lt intrinsics h gt void StackOverflow int depth char blockdata 30000 prince Overt lows adyn depth StackOverflow depth 1 ine main int arger Char argv for d ey A StackOverflow OQ except EXCEPTION EXECUTE HANDLER Prints Exception handler ik n GethxceptronGode ijy return Oy When run this program will print Overflow 0 Overflow 1 Overflow 2 Overt low 3 Advanced C programming with Icc win32 161 Overt lows Overflow Overflow Overflow Overflow Overflow 9 Overflows 10 Exception handler C00000FD Overflows 0 Overflow Overflow Overflow Overflow Overflow Overflow Overflow Overt Lows Overflow Overflow o Nx D OSB e o o Oy Ol HB UN O We see that the first time the handler is invoked but the
515. t uses them Most of the windows data structures are used this way an opaque HANDLE is given that discloses none of the internals of the object it 1s pointing to 3 12 Filling the blanks Input goes through dialog boxes under windows They are ubiquitous so let s start to fill our skeleton with some flesh Let s suppose for the sake of the example that we want to develop a simple text editor It should read some text draw it in the screen and provide some utilities like search replace etc First we edit our menu and add an edit item We open the directory window and select the inexample_rc menu Dialogs J Icons Menus o LA IDMAINMEND lt lt J Stings Accelerator We arrive at the menu editor If we open each branch of the tree in its left side it looks like this Menu editor File Edt Help IDMAINMENL iNew J amp 0pen BER Menu tem options Disabled Owner drawl Checked raved 5 eparator Fopup options Menu bar break Menu break Apply Edit menu header 121 This type of interface requires an action from the part of the user to indicate when it is finished modifying the name and desires to apply the changes Another possibility would be that the resource editor applies the changes letter by letter as the user types them in as some other editors do This has the advantage of being simpler to use but the disadvantage of being harder t
516. tMargin and yOffsetOfBottomMargin 3 21 7 How do I calcula text Get a bounding rectangle for te the bounding rectangle of a string of a string of text output to a specified coordinate in a DC using the currently selected font NOTE The reference DC must have a True Type font selected BOOL GetTextBoundingRec LPPOINT lpPoaints LPBYTE Jor yoes int i iNumPts t HDC hDC Reference DC Int X X Coordinate ine Ya l1 Y Coordinate LPSTR IpStr The text string to evaluate DWORD dwLen LPRECT prc The bength of the string Holds bounding rectangle Draw the text into a path BeginFath nDC I SetBkMode hDC TextOut hDC x Yy SetBkMode hDC EndPath hDC ie TRANSPARENT lestr dwlen 7 7 l I How many points are in the path GetPath 1 iNumPts if iNumPt aDC NULL NULL return FALSE 0 Allocate room for the points lpPoints it lipPoints re LPPOINT GlobalAlloc GPTR sizeof POINT iNumPts turn FALSE Allocate room for the point types 342 C Tutorial lpTypes GlobalAlloc GPTR iNumPts if lpTypes GlobalFree lpPoints return FALSE Get the points and types from the current path iNumPts GetPath hDC lpPoints lpTypes iNumPts More error checking if i1NumPts 1 GlobalFree lpTypes GlobalFree lpPoints return FALSE Intialize the rectangle SetRect lorc UXFFEFF OXPFREP 0
517. tandard way of windows programming until the C wizards decided that this message pump was too ugly to be shown to programmers and hid it behind an application object Later several years later things changed again and the ATL environment made the famous message pump visible again a Texts started appearing explaining the surprised programmers what was WinMain and that message pump that was again the non plus ultra of modernity 7 Luckily for people pro gramming in C all those fads were invisible Since C programming emphasizes low level knowledge of what is going on the message pump has always been there and we knew about it Messages are sent to window objects that are members of a class of similar objects or window class The procedure SendMessage can also send messages to a window object as if they would have been sent by the system itself We send for instance the message EM SETLIMITTEXT to an entry field to set the maximum number of characters that the entry field will process The system relies on the window procedure passing all messages that it doesn t handle to the default message procedure for that class of objects to maintain a coherent view of the desktop and to avoid unnecessary code duplication at each window We are now ready to start our next project building a real window not just a simple dialog 3 7 Amore advanced window We will create the next example with the wizard too I
518. tatement has the general form while condition statements The loop body will be executed for so long as the condition holds We test at each iteration of the loop if our character is not the special constant EOF End Of File defined in stdio h 9 We increment the counter of the characters If we arrive here it means that the character wasn t the last one so we increase the counter 10 After counting the character we are done with it and we read into the same variable a new character again using the fgetc function 11 If we arrive here it means that we have hit EOF the end of the file We print our count in the screen and exit the program returning zero 1 e all is OK By convention a program 38 There is another construct in this line a comment Commentaries are textual remarks left by the programmer for the benefit of other human readers and are ignored by the compiler We will come back to commentaries in a more formal manner later 24 C programming with Icc win32 returns zero when no errors happened and an error code when something happens that needs to be reported to the calling environment Now we are ready to start our program We compile it link 1t and we call it with he loec examples gt countchars countchars c 288 We have achieved the first step in the development of a program We have a version of it that in some circumstances can fulfil the specifications that we received But what happen
519. tcut 314 Error handling under windows 316 Check the return status of any API call 318 Always check allocations 318 Some Coding Tips 320 Determining which version of Windows is running 320 Translating the value returned by GetLastError into a readable string 320 Clearing the screen in text mode 320 Getting a pointer to the stack 321 Disabling the screen saver from a program 321 Drawing a gradient background 322 Capturing and printing the contents of an entire window 322 Centering a dialog box in the screen 325 Determining the number of visible items in a list box 325 Starting a non modal dialog box 326 Propagating environment variables to the parent environment 326 Restarting the shell under program control 327 Translating client coordinates to screen coordinates 327 Passing an argument to a dialog box procedure 327 Calling printf from a windows application 327 Enabling or disabling a button or control in a dialog box 327 Making a window class available for all applications in the system 328 Accessing the disk drive directly without using a file system 328 Retrieving the Last Write Time 329 Setting the System Time 329 Getting the list of running processes 329 Changing a File Time to the Current Time 331 Converting from GMT UTC time to local time 331 Displaying the amount of disk space for each drive 331 Mounting and unmounting volumes in NTFS 5 0 332 FAQ 334 How do I create a progress report with a Cancel button 334 How do I show in th
520. tePipe LPSECURITY ATTRIBUTES lpsa NULL SECURITY ATTRIBUTES sa Implementation 207 SECURITY DESCRIPTOR sd ThreadParams tparams DWORD Statusi PROCESS_INFORMATION pi char tmpfile tmpnam NULL char cmdline 1024 char arguments 8192 memset cmdline 0 sizeof cmdline memset arguments 0 sizeof arguments Check for quoted file names with spaces in them if Cmdline content 0O Pp strchr Cmdline contenttl Le p 4 Dirt strncpy cmdline Cmdline content p Cmdline content cmdline p Cmdline content 0 strncpy arguments p sizeof arguments 1 else ret rn invalid stringA else strncpy cmdline Cmdline content sizeof cmdline p strchr cmdline ii p 4 so Oy strcpy arguments Cmdline content else arguments 0 0 if IsWindowsNT InitializeSecurityDescriptor amp sd SECURITY DESCRIPTOR REVISION SetSecurityDescriptorDacl amp sd TRUE NULL FALSE Sa nhength Sizeor SECURITY ATTRIBUTES sa bInheritHandle TRUE sa lpSecurityDescriptor amp sd lpsa amp Sa i memset amp StartiInfo 0 sizeof STARTUPINFO startInfo cb sizeof STARTUPINFO tparams file fopen tmpfile wb if tparams file NULL return invalid stringA hWritePipe HANDLE get osfhandle fileno tparams file Startinito dwrlags STARTF USESTDHANDLES STARTF USESHOWWINDOW startInfo wShowWindow SW HIDE startiInfo hStdOutput hWritePip
521. ter Programs normally receive arguments from their environment A very old but still quite effec tive method is to pass a command line to the program 1 e a series of character strings that the program can use Let s see how arguments are passed to a program Fine Lwde lt stalorh 1 ine main int arocs Char targy i 2 Ine Count 3 for count 07 Count x arge countt 4 printf 5 Argument d s n count argv PCOunE 6 return 0 1 We include again stdio h 2 We use a longer definition of the main function as before This one is as standard as the previous one but allows us to pass parameters to the program There are two arguments 24 Here we will only describe the standard way of passing arguments as specified by the ANSI C standard the one Icc win32 uses Under the Windows operating system there is an alternative entry point called WinMain and its arguments are different than those described here See the Windows programming section later in this tutorial 12 C programming with Icc win32 int argc This is an integer that in C is known as int It contains the number of arguments passed to the program plus one char argy This is an array of pointers to characters gt containing the actual arguments given For example if we call our program from the command line with the arguments foo and bar the argv array will contain argv 0 The name of
522. ter VERTRES Create the intermediate drawing surface at window resolution hbm Create24BPPDIBSection hdcWindow rc right rc bottom if hbm DeleteDC hdcPrinter ReleaseDC hWnd hdcWindow return FALSE Prepare the surface for drawing hdcMemory CreateCompatibleDC hdcWindow SelectObject hdcMemory hbm Get the current system palette hPal GetSystemPalette If a palette was returned if hPal Apply the palette to the source DC SelectPalette hdcWindow hPal FALSE RealizePalette hdcWindow Apply the palette to the destination DC selectPalette hdcMemory hPal FALSE RealizePalette hdcMemory I Copy the window contents to the memory surface BitBlthdcMemory OU Uy e6srrgnt re botrom hacwindow 0 0 SRCCOPY s Prepare the DOCINFO ZeroMemory amp di sizeof di di cbSize sizeof di di lpszDocName Window Contents Initialize the print job if StartDoc hdcPrinter amp di gt 0 Prepare to send a page if StartPage hdcPrinter gt 0 Some Coding Tips 325 Retrieve the information describing the surface GetObject hbm sizeof DIBSECTION amp ds Print the contents of the surface StretchDIBits hacPrinter Oy Oy Width 1Heighnt O gt Uy PC right re bottom ds dsBm bmBies LPBITMAPINFO amp ds dsBmih DIB RGB COLORS SRCCOPY Let the driver know the page is done EndPage hdcPrinter
523. th 1 e the last directory Why this is so Because the user could choose a path like My documents and in this case we could detect that the user has chosen a standard well known name for the directory But we do not use 312 C Tutorial this feature and just give the shell some place in our result variable Since we overwrite this data later this is harmless and avoids a new variable We set the IpszTitle member to the value we passed in This is a text that will be displayed at the top of the user interface window that appears and should remain the user what kind of folder he she is looking for As flags we just pass BFID USENEWUL meaning that we want the shell to use the improved user interface with drag and drop new folder the possibility of deleting folders whatever And we are done with the filling of the structure We just have to call our famous SHBrowseForFolder and assign the result to ItemIdList Here is an image of the user interface display that appears in a windows 2000 machine in other versions of windows it will look different The user interface is quite sophisticated and it is all at our disposal without writing any code well almost What is better even if we had spent some months developing a similar thing we would have to maintain it test it etc Note that you can transparently browse the network give a symbolic path like My computer or other goodies Pet Desktop a a My Computer
524. the C language without an example like this Exercise 24 C Write a program that counts the words in a given file and reports its result sorted by word frequency OK Suppose you got one assignment like that Suppose also that we use the C language defi nition of a word 1 e an identifier A word is a sequence of letters that begins with an under score or a letter and continues with the same set of characters or digits In principle the solution could look like this 1 Open the file and repeat for each character 2 If the character starts a word scan the word and store it Each word is stored once If it is in the table already the count 1s incremented for that word otherwise it 1s entered in the table 3 Sort the table of words by frequency 4 Print the report We start with an outline of the main procedure The emphasis when developing a program is to avoid getting distracted by the details and keep the main line of the program in your head We ignore all error checking for the time being int main int argc ehar argyll ELGE urs Iie oC f fopen argv 1 r open the input file 6 fogete i jy Read the frrst character while c EOF H Unie Tne ene lt 6 tie Lt eswordStart c 1 77 Starts a word SCanWord c 4 Ti Yes Scan irt c fgetc f Go on with the next character felose f gt Done with the file DoReports argv 1 Print results returno O3 7 RECUR wit
525. the MainWndProc function that is passed as the message handling function when registering the window class The standard version looks like this each event is mapped to a case in a big switch of possible events LRESULT CALLBACK MainWndProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam Switch msg case WM SIZE Windows has been resized Resize any child windows here SendMessage hWndStatusbar msg wParam lParam InitializeStatusBar hWndStatusbar 1 break case WM MENUSELECT The user is browsing the menu Here you can add code to display some text about the menu item being browsed for instance return MsgMenuSelect hwnd msg wParam lParam The WM_COMMAND message reports an item of the menu has been selected case WM COMMAND HANDLE WM COMMAND hwnd wParam 1Param MainWndProc OnCommand break This message reports that the window will be destroyed Close the application now case WM DESTROY PostQuitMessage 0 break All other messages go to the default procedure provided by Windows default return DefWindowProc hwnd msg wParam lParam 113 You may wonder what that variable msg stands for It is a structure of type MSG that is defined in windows h as follows typedef struct tagMSG HWND hwnd UINT message WPARAM wParam LPARAM lParam DWORD time POINT ply MSG PMSG NPMSG LPMSG Note that in C you can append as many names to a pointer to a structure as you like and in windows t
526. the structure the characters in the word and the terminating zero Then we copy the characters from the buffer we got set the count to since we have seen this word at least once and return the result Note that we do not test for failure We rely on more memory to stop the program if there isn t any more memory left since the pro gram can t go on if we have exhausted the machine resources Under windows the implementation of the standard malloc function is very slow To avoid calling malloc too often we devise an intermediate structure that will hold chunks of mem ory calling malloc only when each chunk is exhausted typedef struct memory int used int S176 char memory MEMORY Now we write our memory allocator define MEM ALLOC SIZE Oxffff int memoryused 0 v id more Memory int siz static MEMORY mem void result if mem NULL mem gt usedt siz gt mem gt size mem malloc sizeof mem MEM ALLOC SIZE if mem NULL EDrinti t stderr No more memory at line ed n line exit l 132 C programming with Icc win32 mem gt used 0 memoryused MEM ALLOC SIZE mem gt size MEM ALLOC SIZE result mem gt memory mem gt used mem gt used siz memset result siz 0O memoryused siz return result We use a Static pointer to a MEMORY structure to hold the location of the current memory chunk being used Since it is static it will be initial
527. the test succeeds this means that there is at least a bit set in the lower 16 bits Nothing is done and the program continues to test the lower 16 bits He uses the same reasoning with the 16 bits in x that now contain either the high or the lower word of x 255 is 2 1 This is applied then recursively At each step we test 16 then 8 then 4 then 2 and at the end the last bit 86 This is based in a discussion of comp lang c 184 C programming with Icc win32 int main void Lat Arb a 10 a gt 10 b 20 b 30 Error in this line Drea rT a Dy This will provoke an error If we rewrite the above line like this a gt 10 b 20 b 30 the error disappears Why The explanation 1s that the first line 1s parsed as a gt 10 b 20 b 30 because of the established precedence of the operators The assignment operator is one of the weakest binding operators in C 1 e its precedence 1s very low The correct way to write the expression above is b a lt lQ 2 20 10 1 37 7 Extra Semi colon in Macros The next code fragment illustrates a common error when using the preprocessor to define con stants define MAXVAL 107 7 77 move the semicolon at the end IE cre F if value gt MAXVAL break The compiler will report an error The problem is easily spotted when the macro substitution is performed on the above line Using the definition for MAXVAL the substituted version reads if value gt 10 b
528. ther a left parenthesis appears imme diately after the name of the macro The first form without parenthesis is simply the substitu tion of text An example can be define MAXBUFFERSIZE 9192 This means that whenever the preprocessor find the identifier MAXBUFFERSIZE in the pro gram text it will replace it with the character string 8192 The second form of the preprocessor macros is the following define add a b a b This means that when the preprocessor finds the sequence int m add b it will replace this with Tae m SOC sey Note that the left parenthesis MUST be immediately after the name of the macro without any white space blanks tabs in between It is often said that white space doesn t change the meaning of a C program but that is not always true as you can see now If there is white space between the macro name and the left parenthesis the preprocessor will consider that this is a macro with no arguments whose body starts with a left parentheses If you want to delete the macro from the preprocessor table you use the undef lt macro name gt command This is useful for avoiding name clashes Remember that when you define a macro the name of the macro will take precedence before everything else since the compiler will not even see the identifier that holds the macro This can be the origin of strange bugs like rat Taint a some code If you have the idea of defining a macro like this
529. though 1 An empty string cannot be accessed In traditional C it is possible to write s a even if s is an empty string This destroys the string of course it is no longer zero terminated but no trap occurs at the point of the assignment since s points to valid memory Traps Description 197 occur later when a non zero terminated string destroys the whole program Here any access to an empty string will provoke an exception 2 The syntax s is not supported You can t increment a string structure You can only increment a pointer to a string a Stringp Both types are distinct to the contrary of traditional C where they are both the same 3 You may wonder when you see that this operator returns a naked char pointer Wouldn t this mean that this pointer could be misused in the code using the library Happily for us the compiler dereferences immediately the result of this operator so the pointer can t be used anywhere else or even be assigned to something If you try to write char p s it will provoke a compile time error since you are assigning a char to a pointer to char what is not allowed Is it necessary to do this We could have decided that the user will always use the array notation the but in general it is better to make the string package behave as much as possible but not more as traditional C strings The objective is that people do not have to retrain themselves to use this
530. ties part that allows you to change things like the element s text or other simple properties and a part that is visible only when you have selected the C code generation That part 1s normally labeled events and appears at the right That label tells us which kind of events the framework supports window messages There are many events that can possibly happen of course but the framework handles only those Push button 1 x Froperties LoginDlgIdok MS Sans Serif We see at the right tab a typical messages part We have some buttons to choose the mes sages we want to handle the function name prefix we want for all callback procedures for this element and other things like the font we want to use when the elements are displayed We see again that Dlg400 but this allows us to explain how those names are generated actually The names of the generated functions are built from the prefix of the dialog box then the prefix for the element and then a fixed part that corresponds to the event name We edit the prefix again following this convention Froperties Events LoginDlgIdok MS Sans Serif The Selected message is on so the framework will generate a call to a function called Dlg SearchOnOkSeelected Happily for us we do not have to type those names our selves Without changing anything else we close the button properties and save our work We open the c source file generated by the editor
531. tion failed this module will not work The rest of the software could go on run ning however and it would be too drastic to stop the functioning of the whole software because of a small failure in a routine that could be maybe optional Why the registration of our class could fail One of the obvious reasons 1s that the class 1s already registered 1 e that our calling program has already loaded the DLL and it is loading it again Since we do not unregister our class this would provoke that we try to register the class a second time For the time being we need to handle only the event when the DLL is loaded or unloaded We do two things when we receive the DLL PROCESS ATACH message we store away in our global variable the instance of the DLL and then we register our string dialog box class We could have just done it in the LibMain function but is clearer to put that code in its own rou tine We write then Static void DoRegisterClass void Dynamically linked libraries DLLs 239 WNDCLASS wc memset amp wc 0 sizeof wc we lpfnWndProc DefDlgProc wce cboWndExtra DLGWINDOWEXTRA wc hInstance hinst we hCursor LoadCursor NULL IDC ARROW wc hbrBackground HBRUSH COLOR WINDOW 1 we LpszClassName dialog RegisterClass amp wc You see that the code is the same as the code we had originally in WinMain then in our Get String procedure etc To finish LibMain we handle the message DLL PR
532. tionHigh unsigned Exponent 15 unsigned sign 1 The bias for the exponent is 16383 and the formula is 1 s x 7 16383 x 1 f The range of this format is from 7ffe ffffffff ffffffff to 0001 80000000 00000000 or in decimal notation from 1 18973149535723176505e 4932 to 3 36210314311209350626e 4932 Quite enough to represent the number of atoms in the whole known universe Those numbers are defined as LDBL MAX and LDBL MIN in float h The number of significant digits is 18 defined as LDBL_DIG Note that even if the number of bits of the long double representation is 80 or ten bytes sizeof long dou ble 1s 12 and not 10 The reason for this is the alignment of this numbers in memory To avoid having numbers not aligned at addresses that are not multiple of four two bytes of pad ding are left empty 1 35 1 4 The qfloat format This format is specific to Icc win32 and was designed by Stephen Moshier the author of the Cephes mathematical library that lcc win32 uses internally Its description is as follows define NQ 12 Struct GELOarroOrman 4 unsigned int sign int exponent unsigned int mantissa NO Iy bog This is defined in the qfloat h header file It provides 104 significant digits a fraction of 352 bits one word 1s left empty for technical reasons and a biased exponent of 32 bits The bias uses Ox8001 or 32769 1 35 1 5 Special numbers All the floating point representations include two numbers
533. to the lt nth gt element stored before the one the pointer is pointing to Id we have a pointer to int with a value of 0x4202604 making pae means that we subtract 4 from the value of the pointer to make it point to the integer stored at address 0x4202600 the previous one 1 13 1 2 Subtraction The subtraction of two pointers means the distance that separates two objects of the same type This distance is not expressed in terms of memory locations but in terms of the size of the objects For instance the distance between two consecutive objects is always one and not the number of memory locations that separates the start addresses of the two objects The type of the result is an integer but it is implementation defined exactly which short int long etc To make things portable the standard has defined a special typedef ptrdiff t that encapsulates this result type Under Icc win32 this is an int but under other versions of Icc win32 in 64 bit architectures for instance it could be something else setjmp and longjmp 65 1 13 1 3 Relational operators Pointers can be compared for equality with the operator The meaning of this operation is to find out 1f the contents of two pointers are the same 1 e if they point to the same object The other relational operators are allowed too and the result allows to know which pointer appears before or later in the linear memory space Obviously this comparisons will fail if the memor
534. torage Our function cleans the buffer before using it and then calls one of the workhorses of the dia log procedures the API GetDlgItemText This versatile procedure will put in the designated buffer the text in a control window in this case the text in the entry field We again indicate to the API which control we are interested in by using its numerical ID Note that GetDlgItem Text returns the number of characters read from the control If there isn t anything the user pressed OK without entering any text GetDlgItemText returns zero The first time that we do that we will surely will want to verify that the text we are getting is the one we entered To do this we use the API MessageBox that puts up a message in the screen without forcing us to register a window class define yet another window procedure etc We add then to our window procedure the following lines case IDOK if ReadText hwndDlg MessageBox hwndDlg buffer DEX GnLered MB OK EndDialog hwndDlg 1 j return 1 MessageBox takes a parent window handle in this case the handle of the dialog box proce dure a buffer of text a title of the message box window and several predefined integer con stants that indicate which buttons it should show We want just one button called OK so we pass that constant 226 C Tutorial Note too that if the user entered no text we do NOT call the EndDialog API so the dialog box will refuse to close even if w
535. torical accidents that make little sense now Let s look at the gory details int APIENTRY WinMain HINSTANCE hinst HINSTANCE hinstPrev LPSTR lpCmdLine int nCmdShow This is a function that returns an int uses the stdcall calling convention denoted by APIEN TRY and that receives from the system 4 parameters hinst a HANDLE to an instance of the program This will always be 0x400000 in hexadec imal and is never used But many window functions need it so better store it away 92 This has only historical reasons from the good old days of windows 2 0 or even earlier You can use main as the entry point and your program will run as you expect but traditionally the entry point is called WinMain and we will stick to that for now 93 A calling convention refers to the way the caller and the called function agrees as to who is going to adjust the stack after the call Parameters are passed to functions by pushing them into the system stack Normally it is the caller that adjusts the stack after the call returns With the stdcall calling convention it is the called function that does this It is slightly more efficient and contributes to keeping the code size small 94 API means Application Programmer Interface i e entry points into the windows system for use by the programmers like you and me Introduction 217 hinstPrev Again this is a mysterious HANDLE to a previous instance of the program Agai
536. tryFieldMessages Its code is int EntryFieldMessages HWND hDlg WPARAM wParam HWND hIdOk GetDlgItem hDlg IDOK Switch HIWORD wParam case EN CHANGE iE GetDlgitemText hDlg IDENTRYFIELD buffrer sizeof butter There is some text in the entry field Enable the IDOK button FnableWindow hidOk 1 else no text disable the IDOK button FnableWindow hIidOk 0 break return 1 Let s look at this more in detail Our switch statement uses the HIWORD of the first message parameter This message carries different information in the upper 16 bits the HIWORD than in the lower 16 bits LOWORD In the lower part of wParam we find the ID of the control that sent the message in this case IDENTRYFIELD and in the higher 16 bits we find which sub message of WM COMMAND the control is sending to us in this case EN CHANGE 1 e a change in the text of the edit field There are many other notifications this small window is sending to us When the user leaves the edit field and sets the focus with the mouse somewhere else we are notified etc But all of those notifications follow the same pattern they are sub messages of WM COMMAND and their code is sent in the upper 16 bits of the wParam message parameter Continuing the analysis of EntryFieldMessages we just use our friend GetDlgItemText to get the length of the text in the edit field If there is some text we enable the IDOK button w
537. tup A splash screen is usually used when it is known that an application will take more than a sec ond or two to display its first UI elements The splash screen gives the user visual feedback that the application is starting If a splash screen is not used the user may assume that the start command was not run properly and the user may try to start the application again To display a splash window create an overlapped window In the WndProc for this window intercept the WM NCCALCSIZE message and return NULL instead of the DefWindowProc function which prevents Microsoft Windows from redefining the window s maximum default full screen client area size to accommodate borders and caption bar This window can be created before the main application initializes The main application can send messages to this window to display its initialization information or a bitmap The following code shows one way to implement a splash screen window define SZ INIT TEXT In traliz ng appl cationes define SZ LOAD TEXT Loading resources define SZ CLOSE TEXT Closing splash window define SZ SPLASH TEXT Splash window define ID TIMER CLOSEOx1111 define ID TIMER INITOx1112 define ID TIMER LOADOx1113 define ID TIMER DONEOx1114 ATOM MyRegisterClass HINSTANCE hiInstance BOOL InitInstance HINSTANCE hiInstance int nCmdShow LRESULT CALLBACK WndProc HWND hWnd UINT message WPARAM wParam LPARAM lParam HINSTANCE hInst N
538. type 45 n in response to the first scanf The 45 is copied into variable n When the program encounters the next scanf the remaining n is quickly copied into the variable c The fix is to put explicitely a n like this scanf Sd n amp 1 62 C programming with Icc win32 1 13 Pointers Pointers are one of the great ideas in C but it is one that is difficult to grasp at the beginning All objects integers structures any data reside in RAM Conceptually memory is organized in a linear sequence of locations numbered from 0 upwards Pointers allow you to pass the location of the data instead of the data itself To make things explicit suppose you have some structure like this define MAXNAME 128 SELUCE Person char Name MAXNAME int Age bool Sex double Weight be Instead of passing all the data to a function that works with this data you just pass the address where it starts What is this address We can print it out Consider this simple program L 4eanelude lt stdio h gt 2 include lt stdbool h gt 3 define MAXNAME 128 4 struct person 5 char Name MAXNAME 6 int Age a bool Sex 8 double Weight Qh 10 struct person Joe 11 int main void LO 4 13 pPrintt 0z t an A Joer sSize0f Struct person 14 The address of operator in line 13 returns the index of the memory location where the Joe structure starts In my machine this prints 0x402004 144 The memory loc
539. u when you click the compile button This can go wrong if there is not enough space in the disk to compile or the installation of lcc win32 went wrong and Wedit can t find the compiler executable or many other reasons If you see an error message please do not panic and try to correct the error the message is pointing you to A common failure happens when you install an older version of Wedit in a directory that has spaces in it Even if there is an explicit warning that you should NOT install it there most people are used to just press return at those warnings without reading them Then Icc win32 doesn t work and they complain to me I have improved this in later versions but still problems can arise 18 For understanding the rest of the output see the technical notes below 6 C programming with Icc win32 Prine Hero vn it means that the address of the first element is passed to printf not a copy of the whole character array This is of course more efficient than making a copy but there is no free lunch The cost is that the array can be modified by the function you are calling More about this later 1 2 3 Console mode programs and windows programs Windows makes a difference between text mode programs and windows programs In the first part of this book we will use console programs 1 e programs that run in a text mode window receiving only textual input and producing text output Those are simpler to build than t
540. u assign a character in the string with suol Ars Now the string contains Abc Note that mathematical operations with characters are not supported You can t write s1 0 2 Wrong The rationale behind this decision is that characters are characters and not numbers You can of course do it 1f you do hie 3S SLOT CG 25 s Q c Note that pointer notation is not supported The construct Pek Sars is no longer valid It must be replaced with SiO Sars 2 2 3 1 Comparing strings You can compare two strings with the sign or with the Strcmp function Strcmp returns the lexicographical order alphabet order for the given strings The equals sign just compares if the strings are equal Both types of comparison are case sensitive To use a case insesitive comparison use Strempi Note that this implementation doesn t support the case insesitive wide char comparison yet 2 2 3 2 Relational operators The relational operators can be defined like this int Operator const SELLING string const String amp String 2 Lt ESsNulLlStrang StringZ amp amp TSeNuUlLUString scring return 1 Lt reNnulistring string 2Z I teNullisrring string return O struct Exception exc GetAnExceptionStructure PRECONDITION Stirvalid stringl S6 Strvalrd string iy exc it scringl count J stringZ count Yeturn 0F return memcmp stringl content string2 content stringl count We check fo
541. u receive the machine address of the start of an integer array where are stored the start addresses of character strings containing the actual arguments In the first position for example we will find an integer that contains the start position in RAM of a sequence of characters containing the name of the program We will see this in more detail when we handle pointers later on 26 Local variables are declared as any other variables with lt type gt identifier For instance int a double b char c Arrays are declared in the same fashion but followed by their size in square brackets int a 23 double b 45 char c 890 Passing arguments to a program 13 Argument d s n count argv count Printf will scan its first argument It distinguishes directives introduced with a per cent sign from normal text that is outputted without any modification We have in the character string passed two directives a d and a s The first one a d means that printf will introduce at this position the character representation of a number that should also be passed as an argument Since the next argument after the string is the integer count its value will be displayed at this point The second one a s means that a character string should be introduced at this point Since the next argument is argv count the character string at the position count in the argv array will be passed to printf that will display it at
542. ucture Fields are declared as all other declarations are done Note that a structure declaration is just that a dec laration and it reserves no actual storage anywhere After declaring a structure we can use this new type to declare variables or other objects of this type SLCUCE coordinate Coords 4 23 T8 F Here we have declared a variable called Coords that is a structure of type coordinate 1 e hav ing two fields of integer type called x and y In the same statement we initialize the struc ture to a concrete point the point 23 78 The compiler when processing this declaration will assign to the first field the first number 1 e to the field x will be assigned the value 23 and to the field y will be assigned the number 78 Note that the data that will initialize the structure is enclosed in curly braces Structures can be recursive 1 e they can contain pointers to themselves This comes handy to define structures like lists for instance Struct List 4 SErUCE Last NEXU int Data by Here we have defined a structure that in its first field contains a pointer to the same structure and in its second field contains an integer Please note that we are defining a pointer to an iden tical structure not the structure itself what 1s impossible A structure can t contain itself Double linked list can be defined as follows Struct di list 4 struct dl list Next struct dl list Previous int
543. unction that returns an int and that takes as arguments a void 1 e a pointer to some unspecified object that can t be changed within that function const This is maybe quite difficult to write but quite a powerful feature Functions can be passed as arguments to other functions in C They are first class objects that can be used to specify a function to call Why does qsort need this Well since the qsort function is completely general it needs a helper function that will tell it when an element of the array is smaller than the other Since qsort doesn t have any a priori knowledge of the types of the elements of the passed array it needs a helper function that returns an integer smaller than zero if the first element is smaller than the next one zero if the elements are equal or bigger than zero if the elements are bigger Let s apply this to a smaller example so that the usage of qsort is clear before we apply it to our frequencies problem inclu e lt stdlib hHn gt 53 Finding out where is something defined can be quite a difficult task The easiest way is to use the IDE of Icc win32 right click in the identifier and choose goto definition If that doesn t work you can use grep to search in a set of files 82 C programming with Icc win32 include lt string h gt 1 Finclude lt stdio h gt int COmoare Const void argl const void argz 2 Compare all of both strings 3 retu
544. upport the latest ANSI standard however so they have been rewritten in a static library libc lib which is used by the linker That 1s why the size of your code can grow suddenly by several kilobytes when you add just one single line to your program source 20 The result of this process can be seen if you call the compiler with the E flag For instance to see what is the result of pre processing the hello c file you call the compiler in a command shell window with the command line lec E hello c The resulting file is called hello i 21 Again you can see the intermediate code of lcc by calling the compiler with lcc z hello c This will produce an intermediate language file called he 110 1311 that contains the intermediate language statements 22 Assembly code can be generated with the lcc S hello c command and the generated assembly file will be called hello asm The generated file contains a listing of the C source and the corresponding translation into assembly language 8 C programming with Icc win32 2 Size of initialized data This is the number of bytes that the tables constants and other initial data use In this case we see that besides the character string hello we have many other constants added to the program by the C library 3 Uninitialized data This is the part of your program that reserves space for variables that will be zeroed by the system at the start 4 Size of image This the place the whole will take in
545. ur famous qsort function We use the following call expression SOCCI VOLd argy size targos zeo Char yCOMpare 7 The first argument of qsort is a void Since our array argv is a char we transform it into the required type by using a cast expression void argv The second argument is the number of elements in our array Since we need a size t and we have argc that is an integer variable we use again a cast expression to transform our int into a size_t Note that typedefs are accepted as casts The third argument should be the size of each element of our array We use the built in pseudo function sizeof which returns the size in bytes of its argument This is a pseudo function because there is no such a function actually The compiler will replace this expression with an integer that it calculates from its internal tables We have here an array of char so we just tell the compiler to write that number in there The fourth argument is our comparison function We just write it like that No casts are needed since we were careful to define our comparison function exactly as qsort expects To output the already sorted array we use again a for loop Note that the index of the loop is declared at the initialization of the for construct This is one of the new specifications of the C99 language standard that lcc win32 follows You can declare variables at any statement and within for constructs too Note that the
546. urn 1 2 3 10 Joining strings To join a string to another there are several functions described below Note that the operator is not used for joining strings The reasoning behind this is that the addition of strings in the sense used here is non commutative abc dce give abcdce but dce abc gives dceabc what is quite different An overloading of the operation is not warranted Strings are not numbers and if we did this overloading we could come to the interesting conclusion tat Im a MI a Function Description Joins two strings changing the first Joins up to n characters from the second argument to the first Strchcat Inserts a character at the end of the string Joins several C strings into a single String Given the string Sl abcde The call Strcae Si Fons will modify the contents of S1 that will after the call contain abcdefgh It is possible that no resize operation is necessary if the capacity of S1 was already big enough to accomodate both strings Otherwise the library resizes S1 210 C programming with Icc win32 Resizing operations are expensive when done frequently To avoid them it is better to resize the string before doing the joining in such a way that the resize operation is done once instead of several times 2 3 10 1 Strncat Dool EXPORT over loaded StrmcatA Strings S TOS CEIngA lt rom size t elements to cart if Strvali
547. ut expecting J 1 errors U warnings Well this is at least a clear error message More difficult 1s the case of forgetting to put the semi colon after the declaration of count in the line 3 in the program above D lcc examples gt lcc args c Brror argo 6 Syntax error found Tor expecting 7 ELOY arge xcs 6 Skipping Eor Error args Cs 6 Syntax error found yT expecting JS Warning args c 6 Statement has no effect Error args 6 Syntax error found J expecting yS Error args c 6 illegal statement termination Error arGesCs 6 Skipping 3 6 errors 1 warnings D lcc examples gt We see here a chain of errors provoked by the first The compiler tries to arrange things by skipping text but this produces more errors since the whole for construct is not understood Error recovering 1s quite a difficult undertaking and Icc win32 isn t very good at it So the best thing is to look at the first error and in many cases the rest of the error messages are just consequences of it Another type of errors can appear when we forget to include the corresponding header file If we erase the include lt stdio h gt line in the args program the display looks like this Di Lec examplessLce args Warning args c 7 Missing prototype Lor printi O errors 1 warnings This is a warning The printf function will be assumed to return an integer what in this case is a good assumption We can link the program
548. value w H Equivalent to Expression expression 1 Decrement expression before using it Return the machine address of object The type of T the result is a pointer to object Access the contents at the machine address stored in the pointer See Indirection on page 53 Subtract expression from zero 1 e change the sign Bitwise complement expression Change all 1 bitsto 0 and all 0 bits to 1 j Negate expression if expression is zero expression becomes one if expression is different than zero it becomes zero Return the size in bytes of expr see sizeof on sizeof a page 45 Change the type of expression to the given type This is called a cast The expression can be a Ze UO w ct w TAE Fra literal expression enclosed in braces as in a structure initialization Shift left expr1 expr2 bits a ssb Shift right expr1 expr2 bits a gt gt b 1 if expr1 is smaller than expr2 zero otherwise 1 if expr1 is smaller or equal than expr2 zero otherwise a b a b asb atb a lt b a lt b 1 if expr1 is greater or equal than expr2 zero otherwise 1 if expr2 is greater than expr2 zero otherwise a gt b a gt b 34 C programming with Icc win32 exprl expr2 1 if exprl is equal to expr2 zero otherwise ean exprl expr2 1 if expr1 is different from expr2 zero otherwise aen Bitwise AND expr1 with expr2 See Bitwise operators on pag
549. variable as a program global for us to use Note that we give the initial dimensions of the control as zero width and zero height This is not so catastrophic as it seems since we are relying in the fact that after the creation message the main window procedure will receive aWM SIZE message and we will handle the sizing 119 In page 218 Published by St Martin s Press 1990 ISBN 0 312 06179 X pbk 260 C Tutorial of the tree control there This has the advantage that it will work when the user resizes the main window too 3 10 2 Moving and resizing the child windows We add code to the WM SIZE message that Wedit already had there to handle the resizing of the status bar at the bottom of the window LRESULT CALLBACK MainWndProc HWND hwnd UINT msg WPARAM wParam LPARAM lParam Static HWND hwndTree RECT Teepe ocaeus Switch msg Case WM CREATE hwndTree CreateTree hwnd IDTREEWINDOW break case WM SIZE SendMessage hWndStatusbar msg wParam lParam InitializeStatusBar hWndStatusbar 1 GetClientRect hwnd amp rc GetWindowRect hWndStatusbar amp rcStatus ro bottom 1reotatlus DOECOM TrCotaltus Top MoveWindow hwndTree 0 0 rc right rc bottom L break We ask windows the current size of the main window with GetClientRect This proce dure will fill the rectangle passed to it with the width and height of the client area 1 e not con sidering the borders title menu or other parts of the
550. variable to the rest of the system use the following registry key HKEY CURRENT USER Environment You can modify system environment variables by editing the following registry key HKEY LOCAL MACHINE Dio aM CurrentControlSset COnCrol Session Manager Environment A Note that any environment variable that needs to be expanded for example when you use SYSTEM must be stored in the registry asa REG EXPAND SZ registry value Any val ues of type REG_ SZ will not be expanded when read from the registry The problem with this method however is that changes will be effective only after the next logoff probably not exactly what you want To effect these changes without having to log off broadcast a WM SETTINGCHANGE mes sage to all windows in the system so that any applicable applications such as Program Man ager Task Manager Control Panel etc can perform an update SendMessageTimeout HWND BROADCAST WM SETTINGCHANGE 0 LPARAM Environment SMTO_ ABORTIFHUNG 5000 amp dwReturnValue In theory this will work but there is a problem with Windows 95 Under that system there is no other way to set those variables than rebooting the system Some Coding Tips 327 3 20 12 Restarting the shell under program control In many cases it can be necessary to restart the shell To do this find the window of the Explorer send it a quit message and restart it The following code snippet will work HWND hwndSh
551. veral lines below The DefDlgProc needs a procedure to call when something important happens in the dialog box a button has been pushed an edit field receives input etc Ok this closes the call of the DialogBox API and we are done with WinMain It will return the result of the DialogBox function We will see later how to set that result within our Dialog box procedure 3 1 2 Resources We mentioned before that there is a compiler for a small resource language that describes our dialog boxes Let s look at that with a little bit more detail before we go to our dialog proce dure 97 Open that file that should be called dialog rc if you gave the project the dialog name and look at this lines IDD MAINDIALOG DIALOG ey Oy L95 OS 1 STYLE DS MODALFRAME WS POPUP WS VISIBLE WS CAPTION WS SYSMENU 2 CAPTION diralog 3 FONT 6 Helaz 4 BEGIN DEFPUSHBUTTON TOK EDOR L49 Gp AULA 5 PUSHBUTTON Cancel DCANCE Ls T49 y 235 Ay 14 6 END We see that all those statements concern the dialog box its appearance the position of its child windows etc Let s go statement by statement 1 We find here the same identifier IDD MAINDIALOG and then the DIALOG statement together with some coordinates Those coordinates are expressed in Dialog Units not in pixels The motivation behind this is to make dialog boxes that will look similar at all resolutions and with different screen sizes The units are base
552. viders in a notebook or the labels in a file cabinet By using a tab control an application can define multiple pages for the same area of a window or dialog box Each page consists of a certain type of information or a group of controls that the application displays when the user selects the corresponding tab The notifications specific to this control use the TCN XXX pre fix Trackbar control A trackbar is a window that contains a slider and optional tick marks When the user moves the slider using either the mouse or the direc tion keys the trackbar sends notification messages to indicate the change The notifications used are only the NM CUSTOMDRAW and the NM REALEASEDCAPTURE messages Tree views A tree view control is a window that displays a hierarchical list of items such as the headings in a document the entries in an index or the files and directories on a disk Each item consists of a label and an optional bitmapped image and each item can have a list of sub items associated with it By clicking an item the user can expand or collapse the associated list of subitems The notifications sent use the TVN XXX prefix Up down control An up down control is a pair of arrow buttons that the user can click to increment or decrement a value such as a scroll position or a num ber displayed in a companion control The value associated with an up down control is called its current position An up down control is most often used with a c
553. vious contents set our data and we are done 3 17 2 Serial communications You use the same primitives that you use for files to open a communications port Here is the code to open COM 1 for instance HANDLE hComm Char GSZPort COM hComm CreateFile gszPort GENERIC READ GENERIC WRITE 0 0 OPEN EXISTING FILE FLAG OVERLAPPED 0 You use that handle to call ReadFile and WriteFile APIs Communications events are handled by SetCommMask that defines the events that you want to be informed about break clear to send ring rxchar and others You can change the baud rate managing the device control block SetCommState etc As with network interfaces serial line programming 1s a black art 3 17 3 Files Besides the classical functions we have discussed in the examples Windows offers you more detailed file control for accessing file properties using asynchronous file input or output for managing directories controlling file access locking etc In a nutshell you open a file with CreateFile read from it with ReadFile write to it with WriteFile close the connection to it with CloseHandle and access its properties with GetFileAttributes Compared with the simple functions of the standard library those functions are more difficult to use since they require more parameters but they allow you a much finer control Here is a very small list of some of the file functions provided For more information read the associated
554. w the dialog box with controls and all that in the resource editor and then open it as a result of a menu option for instance You would use DialogBox that handy primitive explained in detail in the docs to fire up your dialog 6 You have to write the procedure to handle the dialog box s messages first You can start the dialog box in a non modal mode with the CreateDialog API To make this a bit more explicit let s imagine you have defined your dialog under the name of IDD ASK PARAMS in the resource editor You add a menu item corresponding to the dia log in the menu editor one that will return IDM PARAMETERS say You add then in the func tion MainWndProc OnCommand code like this case I DM PARAME TERS c Die Locbox hins 115 Go to help then click in Win32 API get to the index and write the name of that function 116 Again this is the defined identifier of the dialog not the dialog s title 117 The registry has been criticized because it represents a single point of failure for the whole system That is obviously true but it provides as a redeeming value a standard way of storing and retrieving configuration data and options It allows your application to use the same interface for storing this data instead of having to devise a schema of files for each application The software is greatly simplified by this even if it is risky as a general principle 252 C Tutorial MAKE INTRESOURCE IDD ASK PARAM
555. ways dereferenced when used When you declare a reference you must declare immediately the object they point to There are no invalid references since they can t be assigned Once a reference is declared and initialized you can t reassign them to another object They are safer pointers than normal pointers since they are guaranteed correct unless the object they point to is destroyed of course References are initialized with the construct int a int amp pa a The pa variable is a reference to an integer an int amp and it is immediately initialized to point to the integer a Note that you do not have to take the address of a but just put its name The compiler takes the address Again here is a short pointer only A complete description is found in the user manual 1 34 3 Generic functions You can declare a function that receives several types of arguments 1 e a generic function by using the overloaded keyword Suppose a function that receives as arguments a qfloat or a double int overloaded docalcs qfloat pq int overloaded docalcs double pd gt This function can receive either a qfloat number or a double number as input The compiler notices the type of argument passed in the call and arranges for calling the right function Notice that you define two internally different functions and that the decision of which one will be called will be done according to the type o
556. we ve successfully copied the source if 0 11SrcFileSize QuadPart FResult SUCCESS goto DONE ii Map the source file into memory We receive from the OS a HANDLE that corresponds to the opened mapping object I hSrcMap CreateFileMapping hSrcFile 0 PAGE READONLY 0 0 0 if hSrcMap printr couldn t map source filen goto DONE Advanced windows techniques 309 i Now we create a file mapping for the destination file using the size parameters we got above I hDstMap CreateFileMapping hDstFile 0 PAGE READWRITE 1liSrcFileSize HighPart 1liSrcFileSize LowPart U 1f hDstMap DEBUG PRINT couldn t map destination file n goto DONE Now that we have the source and destination mapping objects we build two map views of the source and destination files and do the file copy To minimize the amount of memory consumed for large files and make it possible to copy files that couldn t be mapped into our virtual address space entirely those over 2GB we limit the source and destination views to the smaller of the file size or a specified maximum view size MAX_VIEW_SIZE which is 96K If the size of file is smaller than the max view size we ll just map and copy it Otherwise we ll map a portion of the file copy it then map the next portion copy it etc until the entire file is copied MAP_ SIZE is 32 bits because MapViewOfFile requires a 32 bit value for the size of the view This makes
557. we want to display the 8 following characters only we pass a width argument to the s directive of printf As you know s is a directive that instructs printf to display a character string Since we give it a maximum width of 8 only the first 8 chars will be displayed We see here the construct expr vall val2 This construct evaluates first the expression in this case tstruct dstflag If the value is different than zero the return value of the expression will be the first value in this case the character string YES If the expression evaluates to zero the second value will be chosen in this case the character string NO The result of this is passed to printf as an argument The Windows system too has a lot of time related functions Here is a handy list of the most important Note that file times are kept using 64 bits in modern versions of windows 1 e the numbers represent the number of 100 nanosecond intervals since January first 1601 G 74 Ihope this happens to you too Time and Date functions 137 To convert from the ANSI C time format to the Windows time format you can use the follow FileTimeToLocalFileTime Converts a file time based on the Coordinated Universal Time UTC to a local file time FileTimeToSystemTime Converts a 64 bit file time to system time format ae Retrieves the date and time that a file was created last accessed and GetFileTime last modified GetLocalTime Retriev
558. when a SIGSEGV is raised void traphandler int s printf Illegal address exception n exit 1 int main void char p NULL Set the function to handle SIGSEGV Signal SIGSEGV traphandler 0 0 return 0 This will produce the following output De iec test gt tsignal Illegal address exception To make it easy to understand the code above doesn t test the result of setting the signal han dler A more robust version looks like this include lt signal h gt include lt stdio h gt include lt stdlib h gt For exit snip for brevity int main void char p NULL void oldhandler int oldhandler signal SIGSEGV traphandler if oldhandler SIG ERR printf Impossible to establish a signal handler n exit 1 164 C programming with Icc win32 kry 0e p 0 signal SIGSEGV oldhandler return U This code tests 1f the return value of the signal call is OK Besides before the function exists the old handler will be restored The software signals that Icc win32 supports are described in the standard header file lt sig nal h gt They include SIGSEGV for illegal addresses SIGFPE floating point exceptions and others In general the signal mechanism is barely supported by the operating system under Windows 1 34 6 2 Using the signal mechanism What can we do within our rescue function Not much We can t call any library functions since
559. windows that this window is updated To draw text you use TextOut or DrawText Note that under windows there is no auto matic scrolling You have to program that yourself or use a multi line edit control 3 8 4 Initializing or cleaning up You can write your initialization code when handling the WM CREATE message This mes sage is sent only once when the window is created To cleanup you can rely on the WM CLOSE message or better the WM DESTROY message Those will be sent when the window is closed destroyed Note that you are not forced to close the window when you receive the WM CLOSE message Even if this is not recommended you can handle this mes sage and avoid passing it to the DefWndProc procedure In this case the window is not destroyed Another thing is when you receive the WM DESTROY message There you are just being informed that your window is going to be destroyed anyway 3 8 5 Getting mouse input You can handle the WM LBUTTONDOWN or WM RBUTTONDOWN messages To follow the mouse you handle the WM MOUSEMOVE messages In the information passed with those mes sage parameters you have the exact position of the mouse in pixel coordinates Customizing the wizard generated sample code 253 Double click in left mouse button WM_LBUTTONDOWN Left mouse button click For the middle and right button the We ERUTIONU messages used use the letters M and R instead of L here WM MOUSEWHEEL The mouse wheel has been u
560. x DLG 1000 7 Dialog Title Dialog 1000 Ty EH FF el it ah E ed H SO a al a E Dialog Title l Ei Near the top left border you see a button like this If you click in that button the controls palette opens 98 Why should introductory texts be clear Why not make obfuscated sentences There is even an obfuscated C contest Who writes the most incomprehensible program Quite a challenge With the documentation you can do even better you write docs that are so incomprehensible that nobody reads them 222 C Tutorial Controls palette The whole operation of the editor is quite simple The smaller T window represents all the controls that you can put in a dialog PENTE x box entry fields buttons checkboxes and several others You contrals A select one button with the mouse and drag it to your dialog box Tst Text label There you drop it at the right position To add an entry field then ed Edit field we just push the edit field icon the third one from the left in the Group box upper row of icons and drag it to our dialog box in the main ok Push button wedit window After doing this it will look like this wv Check box Radio button Z Combe box List box e Horizontal scroll a HH Vertical scroll Rectangle E Filed rectangle Our entry field becomes the selected item hence the red handles around it After resizing if necessary we need to enter its identi Q Ico
561. xing checks The most frequently used function of this library are strlen that returns an integer containing the length of the string Example int len strlen Some character string Note that the length of the string is the number of characters without counting the trailing zero The physical length of the string includes this zero byte however and this has been and will be the source of an infinite number of bugs strcmp that compares two strings If the strings are equal it returns zero If the first is greater in the lexicographical sense than the second it returns a value greater than zero If the first string is less than the second it returns some value less than zero The order for the strings 1s based in the ASCII character set stremp a b 0 irempta b Z0 strompla b gt 0 strcpy copies one string into another strcpy dst src copies the src string into the dst string This means it will start copying characters from the beginning of the src location to the dst location until it finds a zero byte in the src string No checks are ever done and it is assumed that the dst string contains sufficient space to hold the src string 110 C programming with Icc win32 If not the whole program will be destroyed One of the most common errors in C program ming is forgetting these facts strcat appends a character string to another streat src app will add all the char acters of app at the end of the
562. xt char txt MessageBox NULL Text to search txt MB OK Jy return 1 We just show the text to search Not very interesting but 278 C Tutorial We compile link the main application window appears we select the Search menu and we See FF Oye 2 oye 7 Ope pe Oe 2 ye 7 pe pe IAA 2 Ze 2 2 2 2 2 2 2 eZ 2 77 ZZ yz 7 oy ES Text to searc is Well we have inverted the parameters to the MessageBox procedure but that s surely not the point Why is the dammed dialog box not showing 123 Well here we need a debugger We need to know what is happening when we call the dia log box We press F5 and we start a debugging session The debugger stops at WinMain bee wedit winexample winexample c El File Edit Search Project Resources Debug Utils Modules Window Help x caze WH DESTROY PostQuitMessagelUi break default return DetWindowProcthwnd mag wParam 1Param ei 5 E return l H 002 00 int WINAPI WinMain t HINSTANCE hinstance HINSTANCE hPrevinst MSG mag HANDLE h ccelTable hInst hlnstance 1f lInitApplicationft i return OU h AccelTable pa ete ae ee eee en ec 1 thwndMain CreatewinexanpleWndClassWnd i HWHD el return OU LreatesBarlhwndMain Ready 1 ShowWindowlhwndMain SW SHOW hilnstance yoid x hPrevyinstance yoid Uxnld4d1lesd IlpUmdLine Uxldsaal ff 20 nomdShow 4210720 hinast void
563. y space is not linear as is the case in segmented architectures where a pointer belongs to a memory region or segment and inter segment comparisons are not meaningful 1 13 2 Null pointers A pointer should either contain a valid address or be empty The empty value of a pointer is defined as the NULL pointer value and it is usually zero Using an empty pointer is usually a bad idea since it provokes a trap immediately under lcc win32 unless there is some __try __ except construct enclosing the expression where that hap pens The address zero is specifically not mapped to real addresses to provoke an immediate crash of the program 1 14 setjmp and longjmp 1 14 1 General usage This two functions implement a jump across function calls to a defined place in your program You define a place where it would be wise to come back to if an error appears in any of the procedures below this one For instance you will engage in the preparation of a buffer to send to the database or some other lengthy operation that can fail Memory can be exhausted the disk can be full yes that can still arrive specially when you get a program stuck in an infinite write loop or the user can become fed up with the waiting and closes the window etc For all those cases you devise an exit with longjmp into a previously saved context The clas sical example is given by Harbison and Steele include lt setjmp h gt jmp buf ErrorEnv int
564. y Char targy Lit Count FILE ata bes Lie yey LE arga s 2 A printf Usage countchars lt file name gt n exit 1 infile fopen argv 1 rb if infile NULL printf File s doesn t exist n argv 1 exit l for int i 0 i lt 256 i Fregquencies i CharacterValue i 96 We transformed our integer array Frequencies into a CHARS array with very few changes just the declaration Note that the array is still accessed as a normal array would By the way it C programming with Icc win32 Cum EGS CC CLI tLe ue while c EOF count t LE GC eS 7 3 Freguencies c Frequencytt c fgetc infile felose infile Printi 2d chars in fale n count gsort Frequencies 256 sizeof CHARS compare for count 0 count lt 256 count 7 1f Freguencies count Freguency 0 4 printf S3c 4d Sd n Freguencies count CharacterValue Frequencies count CharacterValue Freguencies count Fregquency return QO is a normal array We changed our compare function too obviously since we are now comparing two CHARS structures and not just two integers We have to cast our arguments into pointers to CHARS and I decided that using two temporary variables would be clearer than a complicated expres sion that would eliminate those The initialization of the CharacterValue field is trivially done in a loop just before we start counting ch
565. y complex We just count the new line characters The output of our program 1s far from perfect It would be better if we justify the columns To do that we have to just count the length of each word and keep a counter to the longest word we find Another nice thing to have would be a count of how many words with character we find how many with two etc In the Appendix you will find the complete source code containing the answers to this prob lem 1 30 Time and Date functions The C library offers a lot of functions for working with dates and time The first of them is the time function that returns the number of seconds that have passed since January first 1970 at midnight fe Several structures are defined that hold time information The most important from them are the tm structure and the timeb structure struct tm 4 int tm sec int tm min int tm hour 73 This clock will overflow in something like 2 000 years so be prepared for windows 4 000 int int int Lit int ine E struct t E include include include include include void mal char tmobur ilz3 Icine time Time and Date functions 135 tm mday tm mon tm year tm wday tm yday tm 1Ssdst The fields are self explanatory The structure timeb is defined in the directory include sys as follows imeb time t time short padi Long lLpadv short millitm short padl unsigned long lpad1
566. yBezierTo Same as PolyB zier but updates the current position PolyDraw Draws a set of line segments and Bezier curves Draws a series of line segments by connecting the points PolyLine in the specified array PolyLineTo Updates current position after doing the same as PolyLine PolyPolyLine Draws multiple series of connected line segments Sets the drawing direction to be used for arc and rectangle SetArcDirection functions There are many other functions for setting color working with rectangles drawing text TextOut etc Explaining all that is not the point here and you are invited to read the docu mentation Summary C converts integer and other numbers to double precision when used in a double precision expression This will be done too when an argument is passed to a function When the function expects a double and you pass it an int or even a char it will be con verted to double precision by the compiler All functions that return a double result must declare their prototype to the compiler so that the right code will be generated for them An unprototyped function returning a double will surely result in incorrect results Opaque data structures are hidden from client code code that uses them by providing just a void pointer to them This way the client code is not bound to the internal form of the Filling the blanks 273 structure and the designers of the system can modify it without affecting any code tha
567. ynonyms for some functions or other advanced stuff 240 C Tutorial 3 5 Using a DLL To use our newly developed DLL we just plug in the older test program we had done for our static library The interface is the same nothing has changed from the user code of our library The only thing that we must do differently is the link step since now we do not need to add the resource file to our program Wedit leaves our DLL in the lcc directory under the project main directory We just recompile our testdialog c program that we had before Here 1s the code for testdialog c again extern int APIENTRY GetString char prompt char buffer int len int main int argc char argy Char buffer 1024 if GetString Enter a string buffer sizeof buffer printf String is 350 burier else printf User cancelled n return 0 We compile this in the directory of the project without bothering to create a project Suppose that our project is in he lec ero7ects dialag and the dll is in he VbeGe pre ecrs didlog icc We compile with the command lec testdialog then we link with the command leclnk testdialog obj lcec dialog lib Perfect We now type the name of the program to test our dll testdialog but instead of the execution of the program we see a dialog box like this testdialog exe Unable To Locate DLL x The dynamic link librar dialog dil could not be found in the specified path DS loc examples dialog C
568. ype If both are structures the result is a structure If both are void the result is void These expressions can be nested int a c 66 534 698 the integer a will be assigned 534 if c 1s equal to 66 698 otherwise struct b bb bstruct NULL 7 NULL b Snext If bstruct is different than NULL the pointer bb will receive the next field of the structure otherwise bb will be set to NULL 1 11 9 struct A structure or a union can t contain another structure that hasn t been fully specified but they can contain a pointer to such a structure since the size of any pointer is always fixed To build recursive structures like list you should specify a pointer to the structure see Lists on page 138 For a detailed description of this keyword see Structures on page 88 1 11 10 union You can store several values in a single memory location or a group of memory locations with the proviso that they can t be accessed at the same time of course This allows you to reduce the memory requirements of a structure or to interpret a sequence of bits in a different fash ion For a detailed discussion see Unions on page 93 1 11 11 typedef The typedef keyword defines a name that can be used as a synonym for a type or derived type In contrast to the struct union and enum declarations typedef declarations doesn t introduce new types it introduces new names for existing types 1 11 12 register
569. ysis 101 Following our analysis of main we see that the next steps are the processing of the opened file We read a character and we update the Frequencies array Well this is a single task that can be delegated to a function a function that would need the opened file handle to read from and a Frequencies array pointer to be updated We develop a ProcessFile function as follows int ProcessFile FILE infile CHARS Frequencies int Count U7 inie G fgetc infile while c EOF count t LE o SS Tir Freguencies c Frequencytt c fgetc infile return count The interface with the rest of the software for this function looks like this count ProcessFile infile Frequencies We could have avoided passing the Frequencies array to ProcessFile since it is a global vari able Its scope is valid when we are defining ProcessFile and we could use that array directly But there are good reasons to avoid that Our global array can become a bottleneck if we decide later to process more than one file and store the results of several files maybe combin ing them and adding up their frequencies Another reason to explicitly pass the Frequencies array as a parameter is of course clarity The Frequencies array is a parameter of this function since this function modifies it Pass ing it explicitly to a routine that modifies it makes the software clearer and this 1s worth the few cycles the machine need

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