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58 Building an Application

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1. In xOutEnv BufInitWriteMode buf result ASCII ENCODE buf tSDLTypeInfo amp ySDL Integer void amp yPDP_Sigl S gt Param1 if result 0 handle error result ASCII ENCODE buf tSDLTypeInfo amp ySDL_ Person void amp yPDP_Sigl S gt Param2 if result 0 handle error result ASCII ENCODE buf tSDLTypeInfo amp ySDL_ Boolean void amp yPDP_Sigl S gt Param3 if result 0 handle error BufCloseWriteMode buf Example 421 ASCII encoding of whole signal all signal parameters In SDL SIGNAL Sigl Integer Person Boolean In xOutEnv BufInitWriteMode buf result ASCII_ENCODE buf tSDLTypeInfo amp ySDL Sigl void S if result 0 handle error BufCloseWriteMode buf Note The names of the type nodes in the examples the second parameter in ASCII_ENCODE depend on the settings for generating system interface header files Decoding into signal parameters from a buffer You can use a decode function to decode from a buffer into a signal pa rameter There is one decoding function for each common format For ASCII it is accessed by using the macro ASCII DECODE A decode function has a buffer reference as the first parameter a pointer to a type Telelogic Tau 4 5 User s Manual 2719 Chapter 58 Building an Application node as the second parameter and a pointer to the va
2. phone gt The program is now ready to receive lines printed on the keyboard and messages sent from other programs A Display signal received from an other program is printed as follows display gt the line received in Display signal Where to Find the Example All files concerning this example may be found in the directory lt installation directory gt sdt examples phone Use these files if you only want to look at the source files and if you are using a Sun workstation you could try the executing versions of the pro gram Otherwise you should copy the files to one of your own directo ries Please be sure not to change the original files In the directory you will find the following files File name Purpose Phone sdt The system file Phone ssy Represents the SDL system PhoneB1 sbk Represents the SDL block PhonePr spr Represents the SDL process phone pr The generated PR file after GR to PR phone c The generated C file after C code generation phone ifc The generated ifc file Telelogic Tau 4 5 User s Manual July 2003 July 2003 Example Section File name Purpose PhoneEnv c Contains the environment functions Phone m The make file for HP UX Phone solaris m The make file for SunOS 5 Telelogic Tau 4 5 User s Manual 2735 Chapter 58 Building an Application Appendix A Formats for ASCII 2736 The ASCII encoding function ASCII_E
3. Message Terminate SIGNALLIST FrSocket Message Terminate Term_Com PhoneBl Socket_Com ToTerm FrTerm FrSocket ToSocket Figure 492 The system Phone July 2003 Telelogic Tau 4 5 User s Manual 2747 Chapter 58 Building an Application Block PhoneBI 1 1 Term_Com R1 PhonePr 1 1 R2 Socket_Com ToTerm FrTerm FrSocket ToSocket Figure 493 The block PhoneBl 2748 Telelogic Tau 4 5 User s Manual July 2003 Appendix C The SDL System Process PhonePr ice Terminput Line engt Line gt true ine 1 true DCL Line Charstring ActMessage Charstring XX gt gt Senderld Pid Message ActMessage Senderld Terminate Senderld true true Terminate Self VIA R2 false false Message Senderld ActMessag VIA R2 Senderld false VIAR Message Me Halt Self CODE aan a VIA R2 SDL_Halt qa July 2003 Figure 494 The process PhonePr Telelogic Tau 4 5 User s Manual 2749 Chapter 58 Building an Application Appendix D The Environment Functions This section contains the environment functions included in the exam ple Note that this example is not updated to use the ASCII encoder BRK RR RR KR IK KK KR KK IK KR KR RRR KR IR IKK RR ROR KK IK RK RK KR RK RK 00 sctEnv c for SimplePhoneSys KK IKK KK IRR
4. Chapter 58 Building an Application strlen Connection Socket Addr sun_path 2 In_Socket accept Connection Socket amp Connection_Socket_Addr amp addr_size else PRINTF nError Timed out n SDL Halt else if FD_ISSET Connection Socket amp readfds addr_size strlen Connection_ Socket _Addr sun_path 2 In_Socket accept Connection Socket amp Connection_Socket_Addr amp addr_size FD_ZERO amp readfds FD SET 1 amp readfds if O lt lt select getdtablesize amp readfds Ed_set 0 fd_set 0 amp t if FD_ISSET 1 amp readfds void gets TmpStr sscanf TmpStr Ss TmpStr sprintf Connected_Socket_Addr sun_path tmp Phone s TmpStr Connected _Socket_Addr sun_family PF_UNIX if connect Out _Socket struct sockaddr amp Connected Socket Addr strlen Connected_ Socket _Addr sun_path 2 lt 0 PRINTF Error from connect n SDL Halt else PRINTF nError Timed out n SDL Halt else PRINTF nError Timed out n SDL Halt PRINTF n n x Welcome to SDT Phone System RAKE KKK KEKE DN A PRINTF nphone gt xCloseEnv extern ifndef XNOPROTO void xCloseEnv void else void xCloseEnv endif close Out_Socket close In_ Socket unlink Connected Socket _Addr sun_path unlink Connection _Socket_Addr sun_path PRINTF nCl
5. Packed Encoding Rules is specified in ITU standard X 691 BER and PER are based on ASN 1 specifications of data types and can only be used for types specified in ASN 1 specifications See chapter 59 ASN 1 Encoding and De coding in the SDL Suite and chapter 8 Tutori al Using ASN 1 Data Types ASCII is a format where the data is represented as ASCII characters It is easy to read and analyze The ASCII format is specified in appendix A Example 419 ASCII common format newtype Person struct nm Charstring nr Integer fm Boolean Telelogic Tau 4 5 User s Manual 2717 Chapter 58 Building an Application 2718 endnewtype Person dcl boss Person Joe 5 false ASCII format Joe 5 F The ASCII coder uses the same buffer management and error manage ment as the BER and PER coders see chapter 59 ASN 1 Encoding and De coding in the SDL Suite Type description nodes for SDL types SDL data encoders and data decoders need information about types and signals information that is stored in type descriptions nodes Type de scription nodes for an SDL system are generated if the Generate SDL coder option is selected in the organizer see chapter 2 The Organizer or in the targeting expert see chapter 60 The Targeting Expert Decla rations to access the type nodes are in the system interface header files and in afile with the name lt system_file_name gt _cod h Type nodes can be found in any generate
6. Returns 1 if anything readable can be found in any of the specified file descriptors where a file descriptor can represent a file a socket and the terminal stdin and stdout read write Reads or writes on a file a file descriptor close Closes a file unlink Removes a file If we now look at the code for the environment functions see Appen dix D The Environment Functions on page 2750 we see that xInitEnv mainly performs the following actions e It creates two unnamed sockets one for message in Connection_Socket and one for messages out Out_Socket e It binds connection_Socket to the file system in the tmp direc tory and starts listen for connections e It prints its UNIX process number e Itreads the UNIX process number of the process where to send mes sages e It attempts to connect to the socket of the process where to send messages e It accepts the connection from the process that will send messages here In xCloseEnv the created sockets are closed and removed The xInEnv and xOutEnv functions follow the guidelines for these functions given in the reference section In xInEnv the select function is used to determine if any messages are ready to be received from the terminal stdin or from the incoming socket An available message is then read and the information is converted to an SDL signal which is sent to the SDL system using the SDL_Output
7. Sender env 1 Now 0 0000 Parameter s hello PhonePr 1 x DECISION Value true OUTPUT of Display to env 1 Parameter s hello NEXTSTATE idle Command output via Terminate Parameter 1 pid env Channel name Signal Terminate was sent to PhonePr 1 from env 1 Process scope PhonePr 1 Command next transition TRANSITION START PId PhonePr 1 State idle Input Terminate Sender env 1 Now z 0 0000 Parameter s env 1 DECISION Value false OUTPUT of Terminate to env 1 Parameter s env 1 TASK Halt Example 427 Start program Phone sim sct Command set trace 6 Default trace set to 6 Command next transition TRANSITION START PId PhonePr 1 State start state July 2003 Telelogic Tau 4 5 User s Manual 2729 Chapter 58 Building an Application 2730 Now 0 0000 NEXTSTATE idle Command output via Terminate Parameter 1 pid PhonePr 1 Channel name Signal Terminate was sent to PhonePr 1 from env 1 Process scope PhonePr 1 Command next transition TRANSITION START PId PhonePr 1 State idle Input Terminate Sender env 1 Now 0 0000 Parameter s PhonePr 1 DECISION Value true TASK Halt By running the system with the SDL monitor as in the examples above you may debug the system at the SDL level The overall behavior of the system can thus be tested It is possibl
8. 2 ViaList 0 ViaList 1 ViaList 2 xIdNode xIN_C1 xIdNode xIN_C2 xIdNode 0 The variable ViaList may then be used as a ViaList parameter in a subseque nt call to SDL_Output Guidelines for the xInEnv Function It is more difficult to give a structure for the xInEnv function than for the xout Env function discussed in the previous subsection A xInEnv function will in principle consist of anumber of if statements where the environment is investigated When some information is found that means that a signal is to be sent to the SDL system then the appropriate code to send a signal see above should be executed The structure given in the example below may serve as an idea of how to design Example void the xInEnv function 417 Structure of xInEnv Function xInEnv SDL Time Time_for next event xSignalNode S if Sigl should be sent to the system SDL Output xGetSignal Sigl xNotDefPId if S xGetSignal Sigl xNotDefPId xEnv xEnv xIdNode 0 Sig2 should be sent to the system xPDP_Sig2 S gt Paraml 3 xPDP_Sig2 S gt Param2 SDL True SDL Output S xIdNode 0 and so on This basic structure can be modified to suit your own needs The if state ments could for example be substituted for while statements The sig nal types July 2003 might be sorted in some priority order and a return
9. PId values except SDL_NULL The Symbol Table The symbol table is a tree built up during the initialization phase in the execution of the generated program and contains information about the static structure of the SDL system The symbol table contains for ex ample nodes which represent signal types blocks channels process types and procedures The C type that are used to represent for example signals in the symbol table is given below typedef struct xSignalIdStruct xSignalIdNode typedef struct xSignalIdStruct components xSignalIdRec It is the nodes that represent the signal types for signals sent to and from the environment of the SDL system that are of major interest in connec tion with the environment functions For each signal type there will be a symbol table node That node may be referenced using the name ySigNn_ followed by the signal name with prefix Such references may be used in for example xOut Env to find the signal type of the signal passed as parameter In some cases the symbol table nodes for channels from the environ ment to a block in the system are of interest to refer to In a similar way as for signals such nodes may be referenced using the name yChan_ fol lowed by the channel name with prefix The Environment Functions An SDL system communicates with its environment by sending signals to the environment and by receiving signals from the environment As no information about the environ
10. Real is used to represent the mathematical real values Example 449 Using Real dcl Var_Real Real task Var_Real 1 0 Output to the buffer 1 0000000000000e0 always 13 decimals Signalld Signalld is used to describe the signal ID Signalld is a sequence with characters Example 450 Using Signalld dcl Var _SignalId SignalId task Var _SignalId Sigl Output to the buffer Sig1 Struct Struct can be used to make an aggregate of data that belong together Example 451 Using Struct newtype S struct sl integer s2 integer s3 charstring endnewt ype Telelogic Tau 4 5 User s Manual 2743 Chapter 58 Building an Application dcl Var Struct S task Var Struct 1 2 Telelogic Output to the buffer 1 2 Telelogic 2744 Telelogic Tau 4 5 User s Manual July 2003 Appendix B User defined ASCII encoding and decoding Appendix B User defined ASCII encoding and decoding July 2003 The types CharStar PId UnionC Userdef VoidStar VoidStarStar do not have a natural transformation to ASCII format The desired encod ing probably differs from application to application The ASCII encod ing procedure and the ASCII decoding procedures do not encode or de code these types but they can invoke user written procedures for encod ing and decoding them For threaded integrations the PId value will be encoded decoded by coding the memory address as an integer If you want
11. SDL system void xInEnv SDL _ Time Time_for next event To implement the sending of a signal into the SDL system two func tions are available xGet Signal which is used to obtain a data area suitable to represent the signal and SDL_Output which sends the sig nal to the specified receiver according to the semantic rules of SDL These functions will be described later in this subsection The parameter Time_for_next_event will contain the time for the next event scheduled in the SDL system The parameter will either be 0 which indicates that there is a transition or a timer output that can be executed immediately or be greater than Now indicating that the next event is a timer output scheduled at the specified time or be a very large number indicating that there is no scheduled action in the system that is the system is waiting for an external stimuli This large value can be found in the variable xSysD xMaxTime You should scan the environment perform the current outputs and re turn as fast as possible if Time has past Time_for_next_event If Time has not past Time_for_next_event you have a choice to ei ther return from the xInEnv function at once and have repeated calls of xInEnv or stay in the xInEnv until something triggers a signal output a signal sent to the SDL system or until Time has past Time_for_ next event Note We recommend always to return from the xInEnv function as fast as possible to ensure
12. a decision error that is no path exists for the cur rent decision value the execution of the program will continue in an unpredictable way To avoid these kind of problems you should al ways have else paths in decisions if not all values in the current data type are covered in other paths If the error occurred during an import or view action a data area of the correct size containing zero in all positions is returned No checks of assignment or index out of range will be performed This means that if an array index is out of bounds then the corre sponding C array will be indexed out of its bounds No checks when accessing struct UNION or choice components are performed No checks are performed when de referencing a pointer value Ref generator These operations will just be execut ed Telelogic Tau 4 5 User s Manual July 2003 Example Section e Ifthe dynamic error occurred within an SDL expression the oper ator that found the error will return a default value and the evalua tion of the expression is continued The default values returned de pend on the result type of the operator and are given in the section Default Values on page 2604 in chapter 57 The Cadvanced Cha sic SDL to C Compiler Example Section July 2003 In this section a complete example of an application is presented The application is simple but it still contains most of the problems that arise when the Cadvanced SDL to C Compiler i
13. own communicating over a network with other pro cessors There may of course also be combinations of these cases Let us for the sake of simplicity call the operating system processes or pro cessors for nodes communicating over a network In the case of com municating operating system OS processes the network will be the fa cilities for process communication provided by the OS There are no problems in building an application consisting of several nodes communicating over a network using the Cadvanced SDL to C Compiler However you have to implement the communication be tween the nodes in the environment functions Note All nodes in a network do not need to be programs generated by the Cadvanced SDL to C Compiler from SDL systems As long as a node can communicate with other nodes it might be implemented using any technique Telelogic Tau 4 5 User s Manual 2697 Chapter 58 Building an Application 2698 The Pld values references to process instances are a problem in a dis tributed world containing several communicating SDL systems We still want for example Output To Sender to work even if Sender re fers to a process instance in another SDL system To cope with this kind of problem a global node number has been introduced as a component in a PId value The global node number which is a unique integer value assigned to each node identifies the node where the current process in stance resides while the othe
14. the source code for the run time library in cluded in the Cadvanced SDL to C Compiler and can produce a new object library with the appropriate switches e You can generate a skeleton by using the Generate environment functions option in the Make dialog in the Organizer In very simple cases you might obtain executable env functions by just tuning the macros in this generated file but in the general case you must use it as a Skeleton and edit it Remember then to copy the file so that it is not overwritten when code is generated the next time An advantage with the generated env functions is that the SDL to C Compiler knows about the signal interface to be implemented in the env functions and can therefore insert code or macros for all signals in the interface To calculate this information is not that easy especially if par titioning generating code for a part of a system is used July 2003 Telelogic Tau 4 5 User s Manual 2703 Chapter 58 Building an Application 2704 Note A make template file is generated every time you generate an envi ronment file This file contains make information for the environ ment file and possibly for data encoding and decoding files If you need to change this skeleton file then remember to copy it so it is not overwritten next time an environment file is generated The file can be used as make template in the Organizer s generate options Note that you may have to generate the file first bef
15. to add encoding for these types then do the following steps e Implement a C function for encoding with input and output param eters compatible with tEncodeFunc which is declared in file coderucf h The encode functions in coderascii c can be used as an example e Set static variable AsciiUserEncode to your encode function in xInitEnv If you want to add decoding for these types then do the following steps e Implement a C function for decoding with input and output param eters compatible with tDecodeFunc which is declared in file coderucf h The decode functions in coderascii c can be used as an example e Set static variable AsciiUserDecode to your decode function in xInitEnv Example 452 User defined ASCII encoding int MyAsciiEncoder tBuffer Buf tSDLTypeInfo TypeNode void Value my error handling code for one or more of CharStar PId UnionC Userdef VoidStar VoidStarStar return 1 if it was succesful return 0 if it failed In xInitEnv Telelogic Tau 4 5 User s Manual 2745 Chapter 58 Building an Application AsciiUserEncode MyAsciiEncoder 2746 Telelogic Tau 4 5 User s Manual July 2003 Appendix C The SDL System Appendix C The SDL System System Phone SIGNAL TermInput Charstring Display Charstring Message Charstring Pid Terminate Pid SIGNALLIST ToTerm Display SIGNALLIST FrT erm Terminput SIGNALLIST ToSocket
16. to the buffer Hello world Choice Union Choice represents the ASN 1 concept CHOICE and can also be seen as a C union with an implicit tag field Telelogic Tau 4 5 User s Manual July 2003 Appendix A Formats for ASCII Example 436 Using Choice newtype C Choice cl Character c2 Boolean endnewt ype dcl Var Choice C task Var_Choice c2 true Output to the buffer 1 T where 1 is an implicit tag Duration Time Time is used to denote a point in time and Duration is used to denote a time interval A value of sort Time represents a point of time in the real world The Time unit is usually 1 second Example 437 Using Time dcl Var Time Time task Var_Time 1 Output to the buffer 1 0 The first field is seconds and the second field is nano seconds Enum Enum contains only the values enumerated in a sort Example 438 Using Enum newtype E Enum literals el e2 e3 endnewt ype dcl Var_Enum E task Var_Enum e2 Output to the buffer 1 July 2003 Telelogic Tau 4 5 User s Manual 2739 Chapter 58 Building an Application 2740 Float Float is equivalent to float in C Example 439 Using Float dcl Var Float Float task Var_Float 3 14159 Output to the buffer 3 141590 1e0 always 7 decimals GPowerset Object_Identifier String GPowerset is used as an abstraction of other data types GPowerset takes one generator parameter the item sort Obj
17. used You first simulate each SDL system on its own and can then sim ulate the systems together if you have communicating systems using the facility of communicating simulations After that you probably want to debug the application with the environment functions This may be performed with the library ApplicationDebug You may then generate the application with the library Application The library Validation allows you to build validators from the code gen erated by the Cadvanced SDL to C Compiler A Validator has a user in Telelogic Tau 4 5 User s Manual July 2003 Reference Section terface and executing principles that are similar to a Simulator The technical approach is however different a Validator is based on a tech nique called state space exploration and operates on structures called behavior trees Its purpose is to validate an SDL system in order to find errors and to verify its consistency against Message Sequence Charts Reference Section July 2003 Representation of Signals and Processes In this first section the representation of signals and processes is pre sented The symbol table which is a representation of the static struc ture of the system will also be discussed The information given here will be used in the next part of this section where the environment func tions which should be provided by the user are described Types Representing Signals A signal is represented by a C struct containing ge
18. Chapter 5 S Building an Application This chapter describes how you can use the Cadvanced SDL to C Compiler to generate applications and especially how to design the environment functions These functions allows you connect the SDL system with the environment of the system You should read chapter 57 The Cadvanced Cbasic SDL to C Com piler before reading this chapter to understand the general behav ior of the Cadvanced SDL to C Compiler Much of what you need to know to generate an application may be found there and that in formation is not repeated here July 2003 Telelogic Tau 4 5 User s Manual 2695 Chapter 58 Building an Application Introduction The Basic Idea An application generated with the Cadvanced SDL to C Compiler can be viewed as having three parts e The SDL system e The physical environment of the system e The environment functions where you connect the SDL system with the environment of the system In the SDL system process transitions are executed in priority order signals are sent from one process to another initiating new transitions timer signals are sent and so on These are examples of internal actions that only affect the execution of the SDL system An SDL system com municates with its environment by sending signals to the environment and by receiving signals from the environment The physical environment of an application consists of an operating system a file system the hardware a netwo
19. IR RFK KOK RK KK KR IK OK IK IR IK IR k k k RK KK k k KK include scttypes h include lt stdio h gt include phone ifc include lt sys types h gt include lt sys time h gt include lt sys socket h gt ifdef AIXV3CC include lt sys select h gt endif include lt sys un h gt include lt unistd h gt define getdtablesize int sysconf _SC_OPEN MAX int Out_Socket In_ Socket struct sockaddr un Connection Socket Addr struct sockaddr_un Connected Socket Addr ifdef ULTRIXCC define PRINTF s printf s flush output to get a prompt fflush stdout else define PRINTF s printf s endif ifdef XENV if defined XPMCOMM amp amp defined XENV xGlobalNodeNumber extern Wei EE E ENOS bt Se ee OO EEN ifndef XNOPROTO int xGlobalNodeNumber void else int xGlobalNodeNumber ure static int ProcId 1 if ProcId lt 0 ProcId getpid return ProcId EET 2750 Telelogic Tau 4 5 User s Manual July 2003 July 2003 Appendix D The Environment Functions xInitEnv extern ifndef XNOPROTO void xInitEnv void else void xInitEnv endif fd_set readfds int addr_size int Connection Socket char TmpStr 132 struct timeval t t tv_sec 60 t tv_usec 0 if Connection Socket socket PF_UNIX SOCK _STREAM 0 lt 0 PRINTF nError No Connection
20. NCODE encodes the SDL sig nal parameters and variables as ASCII characters before adding into the buffer The output into the buffer is illustrated with a number of exam ples Braces are used for most data types and show where the data types start and stop Signal parameters start and stop with braces Comma is used to delimit For more information about data types see Using SDL Data Types on page 42 in chapter 2 Data Types Array CArray Array is used to define a fixed number of elements Array takes two generator parameters an index sort and a component sort Example 428 Using Array newtype Al Array b Integer endnewtype dcl Var Array Al task Var Array 3 Output to the buffer 3 3 3 Bag Bag is almost the same as Powerset The only difference is that Bag contains the same value several times Bag can be used as an abstraction of other data types Bag takes one generator parameter the item sort Example 429 Using Bag newtype B1 Bag Integer endnewtype dcl Var_Bag Bl Telelogic Tau 4 5 User s Manual July 2003 Appendix A Formats for ASCII July 2003 task Var_Bag 7 4 7 Output to the buffer 2 7 1 4 Example 430 Using Bag old style SDL operator code generation newtype B1 Bag Integer endnewtype dcl Var_ Bag Bl task Var_Bag Incl 7 Incl 4 Incl 7 Empty j Output to the buffer 2 7 1 4 Bit Bit can only take two values 0 and 1 Ex
21. Octet_String Octet_String represents a sequence of Octet values Telelogic Tau 4 5 User s Manual 2741 Chapter 58 Building an Application 2742 Octet_String always contains an equal number of characters since every octet takes two characters Example 445 Using Octet_String dcl Var _OctetString Octet String task Var _OctetString Mkstring I20 12 Output to the buffer Oc ORef Own Ref ORef Own and Ref are used to define pointer types Example 446 Using Ref newtype R Ref r1 endnewtype dcl Var_Ref R task Var_Ref 1 2 Telelogic Output to the buffer 1 2 Telelogic Powerset Powerset takes one generator parameter the item sort and imple ments a powerset over that sort Powerset can be used as an abstrac tion of other data types Example 447 Using Powerset newtype P Powerset p1 endnewtype dcl Var _Powerset P task Var _Powerset 4 3 Output to the buffer 001 10000000000000000000000000000 The bits are an equal multiple of sizeof unsigned long Example 448 Using Powerset old style SDL operator code generation newtype P Powerset p1 endnewtype Telelogic Tau 4 5 User s Manual July 2003 Appendix A Formats for ASCII July 2003 dcl Var _Powerset P task Var_Powerset Incl 4 Incl 3 Empty Output to the buffer 001 10000000000000000000000000000 The bits are an equal multiple of sizeof unsigned long Real
22. SION Value true DECISION Value false OUTPUT of Message to env 1 Parameter s hello PhonePr 1 NEXTSTATE idle Command output via TermInput Signal TermInput was sent to PhonePr 1 from env 1 Process Scope PhonePr 1 Command next transition TRANSITION START PId PhonePr 1 State idle Input TermInput Sender env 1 Now 0 0000 Parameter s DECISION Value true DECISION Value true OUTPUT of Terminate to env 1 Parameter s PhonePr 1 NEXTSTATE idle ee ee a Command output via Message Parameter 1 charstring hello Parameter 2 pid env Channel name Signal Message was sent to PhonePr 1 from env 1 Process scope PhonePr 1 Command next transition x TRANSITION START PId PhonePr 1 State idle Input Message Sender env 1 Now 0 0000 Parameter s hello env 1 DECISION Value false OUTPUT of Message to env 1 Parameter s hello env 1 OUTPUT of Display to env 1 Parameter s hello e ee FF FF HF HF a 2728 Telelogic Tau 4 5 User s Manual July 2003 Example Section NEXTSTATE idle Command output via Message Parameter 1 charstring hello Parameter 2 pid PhonePr 1 Channel name Signal Message was sent to PhonePr 1 from env 1 Process scope PhonePr 1 Command next transition x TRANSITION START PId PhonePr 1 State idle Input Message
23. Socket available n SDL Halt if Out_Socket socket PF_UNIX SOCK_STREAM 0 lt 0 PRINTF nError No Out Socket available n SDL Halt sprintf Connection Socket Addr sun_path tmp Phone d xGlobalNodeNumber Connection _Socket_Addr sun_family PF_UNIX if 0 gt bind Connection_ Socket amp Connection_ Socket Addr strlen Connection Socket Addr sun_path 2 PRINTF nError Bind did not succeed n SDL Halt listen Connection Socket 3 sprintf TmpStr nMy Pid d n xGlobalNodeNumber PRINTF TmpStr PRINTF nConnect me to FD_ZERO amp readfds FD_SET 1 amp readfds FD_SET Connection Socket amp readfds if 0 lt select getdtablesize amp readfds fd_set 0 fd_set 0 amp t if FD ISSET 1 amp readfds void gets TmpStr sscanf TmpStr Ss TmpStr sprintf Connected _Socket_Addr sun_path tmp Phones s TmpStr Connected _Socket_Addr sun_family PF_UNIX if connect Out Socket struct sockaddr amp Connected_ Socket Addr strlen Connected Socket Addr sun_path 2 lt 0 PRINTF Error from connect n SDL Halt FD_ZERO amp readfds FD_SET Connection Socket amp readfds if 0 lt select getdtablesize amp readfds fd_set 0 fd_set 0 amp t if FD_ISSET Connection Socket amp readfds addr_size Telelogic Tau 4 5 User s Manual 2751
24. ample 431 Using Bit dcl Var Bit Bit task Var_Bit 1 Output to the buffer 1 Bit_String Bit String is used to represent a sequence of bits Example 432 Using Bit_String dcl Var Bit Bit String task Var_Bit Mkstring I20 1101 j Output to the buffer 1101 Boolean Boolean can only take two values False and True Example 433 Using Boolean dcl Var Boolean Boolean Telelogic Tau 4 5 User s Manual 2737 Chapter 58 Building an Application 2738 task Var_Boolean TRUE Output to the buffer T If Var_Boolean is set to FALSE the output to the buffer will be F Character Character is used to represent the ASCII characters Example 434 Using Character dcl Var Character Character task Var_Character M Output to the buffer M CharStar Pld UnionC Userdef VoidStar VoidStarStar The user has to define encoding decoding procedures for these types see Appendix B User defined ASCII encoding and decoding on page 2745 If no encoding decoding procedure is defined then there will be no output to buffer For threaded integrations the PId value will be encoded decoded by coding the memory address as an integer CharString A5String NumericString PrintableString VisibleString These string types are used to represent sequences of characters Example 435 Using Charstring dcl Var _Charstring Charstring task Var _Charstring Hello world Output
25. can be Telelogic Tau 4 5 User s Manual 2715 Chapter 58 Building an Application 2716 introduced last in the if statements This means that only one signal is sent during a xInEnv call which reduces the latency Alternative to OutEnv Directive EXTSIG To speed up an application it is sometimes possible to use the directive EXTSIG instead of the xOut Env function The decision to use EXTSIG or xOutEnv may be taken individually for each signal type The usage of the EXTSIG directive is described in the section Modi fying Outputs Directive HEXTSIG HALT TRANSFER on page 2668 in chapter 57 The Cadvanced Cbhasic SDL to C Compiler This in formation is not repeated here By using the EXTSIG directive the following overhead can be avoided e Calling SDL_Output the library function for outputs e SDL Output determines that the signal is to be sent to the environ ment e SDL Output calls xOutEnv e xOutEnv executes nested if statements to determine the signal type Including the Environment Functions in the SDL System Design Apart from having the environment functions on a file of their own it is of course possible to include these function directly into the system diagram in a CODE directive Example 418 Including Environment Functions in SDL System G COD BODY code for the environment functions A In this case you cannot use the system interfa
26. ce header file but instead you have all the necessary declarations already at your disposal as the functions will be part of the SDL system The only problem you will en counter is the prefixing of SDL names when they are translated to C The SDL directive should be used to handle this problem or the NAME Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section directive see sections Accessing SDL Names in C Code Directive SDL on page 2654 and Specifying Names in Generated Code Di rective NAME on page 2667 in chapter 57 The Cadvanced Cbasic SDL to C Compiler The following table shows how to obtain C names for some SDL objects of interest Synonym name Newtype or syntype name ySigN_ Signal name yPDP_ Signal name yChaN_ Channel name SDL Data Encoding and Decoding ASCII coder Communication between nodes often requires data encoding and de coding between node internal representations and a common format in a protocol buffer The sending node writes information in the common format and the receiving node reads information from the common for mat Data encoding is the transformation from a node internal represen tation into a common format and data decoding is the transformation from a common format into a node internal representation Supported common formats are e BER e PER e ASCII BER Basic Encoding Rules is specified in ITU standard X 690 and PER
27. d c file from a system or a package and also in the lt system_file name gt cod c file A type description node for SDL is implemented as a static variable with the type information The variable can be accessed by using the name ySDL_ lt type_name gt or ySDL_ lt signal_name gt where lt type_name gt and lt signal_name gt are the names used in the interface header file See Names of SDL Objects in C on page 2705 for more information Encoding signal and signal parameters into a buffer You can use an encode function to encode signal parameters into a buff er There is one encoding function for each common format For ASCII it is accessed by using the macro ASCII_ENCODE An encoding func tion has a buffer reference as the first parameter a pointer to a type node as the second parameter and a pointer to the variable to encode as the third The encoding function returns an integer value which is 0 if the encoding was successful and error code if it was not More details about encoding functions the buffer reference type nodes and error codes can be found in chapter 59 ASN 1 Encoding and De coding in the SDL Suite Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section Function declarations are in the file ascii ascii h ascii ascii h on Windows platforms in the coder directory Example 420 ASCII encoding of signal parameters In SDL SIGNAL Sigl Integer Person Boolean
28. der in the struct as the parameters are placed in the signal definition Note There are no generated types for a signal without parameters Types Representing Processes A Pld value is a struct consisting of two components a global node number which is an integer see also Function xGlobalNodeNumber on page 2722 and The Basic Idea on page 2696 and a local PId val ue which is a pointer typedef xLocalPIdRec xLocalPIdNode typedef struct int GlobalNodeNr xLocalPIdNode LocalPId SDL_PId The global node number identifies the SDL system that the process in stance belongs to while the local PId value identifies the process in stance within the system The local PId pointer value should not be ref erenced outside the SDL system where it is defined By introducing a global node number in the PId values these values are possible to interpret throughout an application consisting of several SDL systems You can also define your own Pld values in non SDL de fined parts of the application and still use communication with signals The variable SDL_NULL which represents a null value for PIds and which is defined in the runtime library and available through the file scttypes h contains zero in both the global node number and the lo Telelogic Tau 4 5 User s Manual 2701 Chapter 58 Building an Application 2702 cal PId component Note that the global node number should be greater than zero in all
29. e solved Example 413 Avoiding Name Clashes In an SDL system the following two newtypes are defined NewType s literals red green NewType t literals red yellow As the literal red appears in both newtypes the C code cannot distin guish between them However by using the identifiers in the literals field lit_tn_ s the literals are given the following names lit_red_s lit_red_t Thus we will avoid a possible name clash Telelogic Tau 4 5 User s Manual 2707 Chapter 58 Building an Application 2708 Structure of File for Environment Functions The file containing the environment functions should have the follow ing structure include scttypes h include file with macros for external synonyms include systemfilename ifc void xInitEnv XPP void void xCloseEnv XPP void ifndef XNOPROTO void xOutEnv xSignalNode S else void xOutEnv S xSignalNode S endif ifndef XNOPROTO void xInEnv SDL Time Time_for_ next event else void xInEnv Time_for_ next_event SDL Time Time_for_ next event endif int xGlobalNodeNumber XPP void The last function xGlobalNodeNumber will be discussed later see Function xGlobalNodeNumber on page 2722 The usage of the mac ros XPP and XNOPROTO makes the code possible to compile both with compilers that can handle prototypes and with compilers that cannot If you do not need this portabi
30. e to start two instances of the simulation and have the simu lators communicate with each other Then Message and Terminate sig nals sent to the environment in one of the simulations will appear as sig nals coming from the environment in the other Note Do not forget the monitor command Start SDL Env to make the simulation programs start communicating The Environment In the environment functions we use the socket facility in UNIX to im plement the communication between the executing programs In the current example the implementation is developed for SunOS 5 and HP UX To simplify the example we assume that each instance of the application is started in a window of its own a shell tool window under for instance X Windows where UNIX commands can be entered This means that we will have no problems with the interpretation of stdin and stdout in the programs Telelogic Tau 4 5 User s Manual July 2003 Example Section The name of the socket for incoming messages for a certain instance of the application will be the string Phone concatenated with the UNIX process number for the current program The socket will be created in the directory tmp Each application instance will print this number dur ing the initialization and will then ask for the process number of the ap plication instance where it should send its messages You have to enter these numbers in such a way as to form a ring among the applications The Enviro
31. ect_Identifier is a sequence of Natural values String can be used to build lists of items of the same type String has two generator parameters the component sort and the name of an empty string Example 440 Using GPowerset newtype GP Powerset Integer endnewtype dcl Var_GPowerset GP task Var_GPowerset Incl 7 Incl 4 Empty Output to the buffer 3 4 Object_Identifier and String are used in the same way as GPow erset Inherits Syntype Syntype and Inherits create a new type that has the same properties as an existing type by inheriting the type or make a syntype of the type Example 441 Using Syntype syntype newinteger Integer endsyntype dcl Var _Newinteger newinteger Telelogic Tau 4 5 User s Manual July 2003 July 2003 Appendix A Formats for ASCII task Var _Newinteger 2 Output to the buffer 2 Integer Longint ShortInt UnsignedInt UnsignedLonglInt UnsignedShortint Natural Integer is used to represent mathematical integers Natural is a syntype of Integer Example 442 Using Integer dcl Var_Integer Integer task Var_Integer 1 Output to the buffer 1 Null The sort Null only contains one value Null Example 443 Using Null dcl Var_Null Null task Var_Null Null Output to the buffer 0 Octet Octet is used to represent eight bit values Example 444 Using Octet dcl Var Octet Octet task Var_Octet 120 12 Output to the buffer Oc
32. enced by the variable P the code will be xSignalNode OutputSignal local variable OutputSignal xGetSignal S2 P xEnv yPDP_S2 OutputSignal gt Param1 yPDP_S2 OutputSignal gt Param2 1 2 SDL _Output OutputSignal xIdNode 0 For the details of how to reference the parameters of a signal see the subsection Types Representing Signals on page 2699 To introduce a via list in the output requires a variable which should be an array of xIdNode that contains references to the symbol table nodes representing the current channels or signal routes in the via list In more detail we need a variable ViaList xIdNode N where N should be replaced by the length of the longest via list we want to represent plus one The components in the variable should then be given appropriate values such that component 0 is a reference to the first channel its symbol table node in the via list component 1 is a ref erence to the second channel and so on The last component with a ref erence to a channel must be followed by a component containing a null pointer the value xIdNode 0 Components after the null pointer will not be referenced Below is an example of how to create a via list of two channels C1 and C2 2714 Telelogic Tau 4 5 User s Manual July 2003 Example Reference Section 416 Via List of two Channels ViaList xIdNode 4 longest via has length 3 this via has length
33. ess instance e NameNode This component is a pointer to the node in the symbol table that represents the signal type The symbol table is a tree with information about the SDL system and contains among other things one node for each signal type that is defined within the SDL system e prio This component represents the priority of the signal and is used in connection with continuous signals In the generated code there will be types to represent the parameters of the signals according to the following example Example 410 Generated C Code for Signal Definition Assume the following signal definitions in SDL SIGNAL S1 Integer S2 S3 Integer Boolean OwnType then the C code below will be generated typedef struct SIGNAL VARS SDL Integer Paraml yPDef_z0f_S1 typedef yPDef zO0f S1 yPDP_ zOf S1 typedef struct SIGNAL VARS SDL Integer Paraml SDL Boolean Param2 Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section z09_ OwnType Param3 yPDef_z0h_S3 typedef yPDef z0h_S3 yPDP z0h S3 where SIGNAL VARS is a macro defined in scttypes h that is expand ed to the common components in a signal struct For each signal with parameters there are two generated types a struct type and a pointer type The struct type contains one component for each parameter in the signal definition and the components will be named Param1 Param2 and so on The components will be placed in the same or
34. function In xOutEnv a test on the NameNode in the signal is used to determine the signal type Depending on the signal type the appropriate information is written ei ther on the outgoing socket or on the terminal stdout Telelogic Tau 4 5 User s Manual July 2003 July 2003 Example Section Debugging The first part of the debugging activity is of course when the SDL sys tem is simulated and examined through the monitor system Now we also want to include the environment functions during debugging The intention of the library ApplicationDebug is to use the monitor and the environment functions together When the environment functions xInEnv read information from the keyboard there is however a problem in using xInEnv together with the monitor In our system for instance a line typed on the keyboard may either be a monitor command or a line typed to the SDL system As both the monitor and xInEnv are polling for lines from stdin the in terpretation of a typed line depends on which one first finds the line A better way is to eliminate this indeterministic behavior by not polling for typed lines in xInEnv Instead you may use the monitor command Output Via TermInput the line to simulate a line typed on the keyboard In this way all the other parts of the environment functions can be tested under the monitor If you en close the sections in xInEnv handling keyboard polling between ifndef XMONITOR and end
35. have to map the global node number to the current OS process or processor to be able to transmit signals addressed to non lo 2722 Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section cal PIds to the correct OS process or processor This will be part of the xOutEnv function Program Structure The generated code will contain two important types of functions the initialization functions and the PAD functions The PAD functions im plement the actions performed by processes during transitions There will be one initialization function in each generated c file In the file that represents the system this function will have the name yInit Each process in the system will be represented by a PAD function which is called when a process instance of the current instance set is to execute a transition The example below shows the structure of the main MainInit and MainLoop functions Example 425 Start up structure void main void xMainInit xMainLoop void xMainInit void xInitEnv Init of internal data structures in the runtime library yInit void xMainLoop void while 1 xInEnv if Timer output is possible SDL_OutputTimerSignal else if Process transition is possible Call appropriate PAD function The function xMainLoop contains an endless loop The appropriate way to stop the execution of the program is to call the runtime library func tio
36. if this code is removed when the moni tor is used that is if the library ApplicationDebug is used see the code for xInEnv in Appendix D The Environment Functions on page 2750 A C source code debugger is of course also useful when debugging the environment functions The initialization phase xInitEnv is probably the most difficult part to get working correctly in our system All the source code for this function is available and a C debugger can be used While debugging generated code from SDL at the C level it is always easy to find the currently executing SDL symbol by using the SDT ref erences see Syntax on page 911 in chapter 19 SDT References in the C code and the Go To Source menu choice in the Edit menu in the Organizer For more details please see Go To Source on page 99 in chapter 2 The Organizer Running the Application To have an application of the Phone system you now only need to make a new executing program with the library Application Telelogic Tau 4 5 User s Manual 2733 Chapter 58 Building an Application 2734 When you run the Phone system start the program from two or more shell tools on UNIX Each instance of the program will then print My Pid 2311 Connect me to You should answer these questions in such a way that a ring is formed by the programs When the initialization is completed for a program it prints kekkkKKK Welcome to SDT Phone System x
37. l 2721 Chapter 58 Building an Application Buf CloseWriteMode buf In xInEnv void xInEnv SDL Time Time for next _event char SId 100 Buf InitReadMode buf decode signal id result ASCII _DECODE buf tSDLTypeInfo amp ySDL_Signalld SId if result 0 handle error signal Sigl in buffer if stremp SId Sig1 S xGetSignal Sigl1 xNotDefPId xEnv result ASCII _DECODE buf tSDLTypeInfo amp ySDL Sigl void S if result 0 handle error SDL Output S xIdNode 0 BufCloseReadMode buf Function xGlobalNodeNumber You should also provide a function x lobalNodeNumber with no pa rameters which returns an integer that is unique for each executing sys tem int xGlobalNodeNumber void The returned integer should be greater than zero and should be unique among the communicating SDL systems that constitutes an application If the application consists of only one application then this number is of minor interest it still has to be set The global node number is used in Pld values to identify the node OS process processor that the process instance belongs to PId values are thereby universally accessible and you may for example in a simple way make Output To Sender work between processes in different SDL systems OS processes proces sors When an application consisting of several communicating SDL systems is designed you
38. l procedure in SDL to establish direct communication Sender Sender should either be a PId value representing a process instance in the environment of the current SDL system or the value xEnv xEnv is a PId value that refers to an environment process in stance which is used to represent the general concept of the SDL environment without specifying an explicit process instance in the environment The function SDL_Output takes a reference to a signal instance and outputs the signal according to the rules of SDL void SDL Output xSignalNode S xIdNode ViaList s This parameter should be a reference to a signal instance with all components filled in ViaList This parameter is used to specify if a VIA clause is or is not part of the output statement The value xIdNode o a null pointer is used to represent that no VIA clause is present For in formation about how to build a via list please see below Telelogic Tau 4 5 User s Manual 2713 Chapter 58 Building an Application We now have enough information to be able to write the code to send a signal Suppose we want to send a signal S1 without parameters from xEnv into the system without an explicit receiver without TO The code will then be Example 415 C Code to Send a Signal to the Environment SDL Output xGetSignal S1 xNotDefPId xEnv xIdNode 0 If S2 with two integer parameters should be sent from xEnv to the pro cess instance refer
39. lity you can reduce the complexity of the function headings somewhat In the minor examples in the remaining part of this section only versions with prototypes are shown Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section Functions xlnitEnv and xCloseEnv There are two functions among the environment functions that handle initialization and termination of the environment These functions as well as the other environment functions should be provided by the user void xInitEnv void void xCloseEnv void In the implementation of these functions you can place the appropriate code needed to initialize and terminate the software and the hardware The function xInitEnv will be called during the start up of the program as first action while the xCloseEnv will be called in the function SDL_Halt Calling SDL_Halt is the appropriate way to terminate the program The easiest way to call SDL Halt is to include the call ina CODE directive ina TASK SDL_Halt is part of the runtime library and has the following definition void SDL Halt void Note xInitEnv will be called before the SDL system is initialized which means that no references to the SDL system are allowed in this func tion To for example send signals into the system during the initial ization phase the MAIN directive should be used see Initializa tion Directive MAIN on page 2668 in chapter 57 The Cad vanced Cba
40. ly 2003 Reference Section Note The names of the type nodes in the examples the second parameter in ASCII_DECODE depend on the settings for generating system interface header files Encoding and decoding signal identifier for ASCII encoding When sending signals between nodes it is often important to put a signal identifier first in the buffer The signal identifier must be a unique iden tifier of the signal in the distributed system Decoding is then a two step process first decode signal identifier and find signal information and second decode signal parameters You can use any representation of signal identifiers in the environment functions For SDL types there is a special signal id type node that supports char acter string signal ids The type node can be used for ASCII encoding Example 424 Using signal identifier In SDL SIGNAL Sigl Integer In xOutEnv void xOutEnv xSignalNode S char signalld BufInitWriteMode buf if S gt NameNode Sigl encode signal id into buffer signalId Sigl1 result ASCII_ENCODE buf tSDLInfo amp ySDL_ SignallId void signalId if result 0 handle error encode signal parameter result ASCII_ENCODE buf tSDLTypeInfo amp ySDL_ Sigl1 void S if result 0 handle error send buffer using protocol release memory xReleaseSignal S return Telelogic Tau 4 5 User s Manua
41. m diagram there will be an ex tern definition for the xSignalIdRec variable representing the sig nal e For each signal with parameters defined in the system diagram there will be definitions of the types yPDef_SignalName and yPDP_SignalName i e of the types used to represent a signal e For each remote procedure that can be sent to or from the environ ment code will be generated exactly as for two signals named pCALL_procedurename and pREPLY_procedurename e For each channel defined in the system diagram there will be extern definitions for the xchannelIdRec representing the channel Together with these definitions macros that simplify the translation of SDL names to C names are also be generated Names of SDL Objects in C Due to differences in naming rules in SDL and C prefixing is used to make C identifiers unique see section Names and Prefixes in Gener ated Code on page 2663 in chapter 57 The Cadvanced Cbasic SDL to C Compiler These prefixes however may change when you update your SDL diagrams and cannot be predicted Therefore you should not use the prefixed object names in the environment functions Instead macros generated in the system interface header file assist you by map ping static names to the prefixed names This means that you must re generate the system interface header file each time you regenerate code for the system The good part is that you do not have to make any chang es in the environmen
42. ment is given in the SDL system the Cadvanced SDL to C Compiler cannot generate the actions that should be performed when for instance a signal is sent to the environment In stead you have to provide a function that performs this mapping be tween a signal sent to the environment and the actions that then should be performed Examples of such actions are writing a bit pattern on a port sending information over a network to another computer and send ing information to another OS process using some OS primitive Telelogic Tau 4 5 User s Manual July 2003 Reference Section You should provide the following functions to represent the environ ment of the SDL system e xInitEnv and xCloseEnv which are called during initialization and termination of the application e xOutEnv which should treat signals sent to the environment e xInEnv which should treat signals sent into the SDL system from the environment There are two ways to get a skeleton for the env functions e You can copy the file sctenv c from the directory lt installation directory gt sdt sdtdir lt machine depen dent dir gt INCLUDE where lt machine dependent dir gt is for example sunos5sdtdir on SunOS 5 hppasdtdir on HP and wini386 in Windows In Win dows should be replaced by in the path above This file also contains some trace mechanisms that may be used to trace the execution in a target computer This trace can however only be used if you have
43. n SDL_Halt The call of this C function should normally be included in an appropriate task using the directive CODE SDL_Halt which has the following structure Telelogic Tau 4 5 User s Manual 2723 Chapter 58 Building an Application 2724 void SDL Halt void xCloseEnv exit 0 To complete this overview which emphasizes the usage of the environ ment functions we have to deal with the xOutEnv function Within PAD functions the runtime library function SDL Output is called to implement outputs of signals When SDL _ Output identifies the receiver of a signal to be a process instance that is not part of the current SDL system SDL_Output will call the xoutEnv function Dynamic Errors In the library for applications SDL runtime errors will not be reported The application will just perform some appropriate actions and continue to execute These actions are in almost all cases the same as the actions at dynamic errors described in the Dynamic Errors on page 2121 in chapter 50 The SDL Simulator Output warnings If a signal is sent to NULL or to a stopped pro cess instance or if no receiver is found in an output without a to clause the signal will not be sent that is the output statement is a null action If a signal is sent to a process instance and there is no path between the sender and the receiver the signal will be sent any way actually no check will be performed If the error was
44. n the same SDL system Receiver will refer to the process xEnv if the PId expression in an output TO refers to xEnv or if the signal was sent in an output without a TO clause and the environment was selected as receiver in the scan for re ceivers Remote procedure calls to or from the environment should in the envi ronment functions be treated a two signals a pCALL_procedurename and a pREPLY_procedurename signal Recommended Siructure of the xOutEnv Function You can of course write the xOutEnv function as you wish the struc ture discussed below may be seen as an example but also as a guide line of how to design xOutEnv functions Example 414 Structure of xOutEnv Function void xOutEnv xSignalNode S if S gt NameNode Sigl perform appropriate actions xReleaseSignal S return if S gt NameNode Sig2 perform appropriate actions xReleaseSignal S return and so on Telelogic Tau 4 5 User s Manual 2711 Chapter 58 Building an Application 2712 Function xInEnv To make it possible to receive signals from the environment and to send them into the SDL system the user provided function xInEnv is repeat edly called during the execution of the system see section Program Structure on page 2723 During such a call you should scan the envi ronment to see if anything has occurred which should trigger a signal to be sent to a process within the
45. neral information about the signal followed by the parameters carried by the signal xSignalNode Pre Reference xSignalNode Suc to signal SDL PId Receiver SDL _PId Sender xIdNode NameNode int Prio first signal parameter second signal parameter Figure 491 Data structure representing a signal A general typedef xSignalRec for a signal without parameters and for a pointer to such a signal xSignalNode are given below These types may be found in the file sct types h These types may be used for type casting of any signal to access the general components typedef struct xSignalRec xSignalNode typedef struct xSignalRec xSignalNode Pre xSignalNode Suc SDL_PId Receiver SDL_PId Sender xIdNode NameNode Telelogic Tau 4 5 User s Manual 2699 Chapter 58 Building an Application 2700 int Prio xSignalRec A xSignalRec contains the following components e Pre and Suc These components are used to link the signal in the in put port list of the receiving process instance The input port is im plemented as a double linked list When a signal has been consumed and the information contained in the signal is no longer needed the signal will be returned to an avail list to be re used in future outputs The component Suc is used to link the signal into the avail list while Pre will be xSignalNode 0 as long as the signal is in the avail list e Receiver The receiving process instance e Sender The sending proc
46. nment Functions The environment functions which may be found in the file PhoneEnv c are shown in section Appendix D The Environment Functions on page 2750 The file is developed according to the struc ture discussed in the previous part of this chapter and uses the system interface header file generated from the SDL system As the PhoneEnv c file includes scttypes h and uses some C mac ros it should be compiled using the same compiler options as the C file for the SDL system For information about how to extend the generated make file to handle also non generated files please see Makefile Op tions on page 122 in chapter 2 The Organizer In the code for the environment functions a number of UNIX functions are used Their basic behavior is described below For any details please see the UNIX manuals available from Sun Microsystems Function name Functionality getpid Returns the UNIX process number for the current program socket Returns a new unnamed socket bind Binds a socket to a name in the file system listen Starts listen for other programs trying to connect to this socket connect Should be called by other programs that want to establish a connection to the current socket accept Accepts a connection request July 2003 Telelogic Tau 4 5 User s Manual 2731 Chapter 58 Building an Application 2732 Function name Functionality select
47. obalNodeNr amp yPDP_Message OUTSIGNAL DATA PTR gt Param2 LocalPId amp NrOfReadChars xAss_ SDL Charstring amp yPDP_ Message OUTSIGNAL DATA PTR gt Paraml1 Instr NrOfReadChars 2 XASS Telelogic Tau 4 5 User s Manual 2753 Chapter 58 Building an Application SDL_Output yOutputSignal xIdNode NIL else if SignalName T SDL signal Terminate yOutputSignal xGetSignal Terminate xNotDefPId xEnv sscanf Instr 1 Sq Sx amp yPDP_Terminate OUTSIGNAL DATA PTR gt Paraml1 GlobalNodeNr amp yPDP_Terminate OUTSIGNAL DATA PTR gt Paraml1 LocalPId SDL_Output yOutputSignal xIdNode 0 xFree void amp Instr xOutEnv extern Sfiwo ce Ceo ese eee ce eee gece ees este etek ee eae sce eee ifndef XNOPROTO void xOutEnv xSignalNode S else void xOutEnv S xSignalNode S endif char Outstr 150 SDL signal Message if S gt NameNode Message sprintf Outstr M d Sx S s yPDP_Message S yPDP_Message S strlen yPDP_ Message S gt Param1 yPDP_Message S gt Param1 write Out_Socket Outstr strlen Outstr 1 xReleaseSignal S return gt Param2 GlobalNodeNr gt Param2 LocalPId SDL signal Terminate if S gt NameNode Terminate sprintf Outst
48. ore you can select it in the Organizer The env functions are thoroughly discussed below but first we will in troduce the system interface header file which considerably simplifies writing the environment functions System Interface Header File The system interface header file contains code for objects that are de fined in the system diagram Included are all type definitions and other external definitions that are needed in order to implement external C code These object definitions simplify the implementation of the envi ronment functions Therefore the system interface header file is also known the environment header file This file is generated if e Code is generated for the complete system e The Generate environment header file option is selected in the Make dialog in the Organizer see Code Generation Options on page 120 in chapter 2 The Organizer The default name of the generated interface header file is lt system_ file name gt ifc The system interface header file has the following structure e Macros for all synonyms that are translated to macros e All type definitions generated from newtypes and syntypes This in cludes TYPE and HEADING sections in ADT directives and in CODE directives e External definitions of variables for all synonyms that are translated to variables Telelogic Tau 4 5 User s Manual July 2003 Reference Section e For each signal defined in the syste
49. osing this session n 2752 Telelogic Tau 4 5 User s Manual July 2003 Appendix D The Environment Functions xInEnv extern ifndef XNOPROTO void xInEnv SDL Time Time_for_ next event else void xInEnv Time for next event SDL Time Time for next event endif f struct timeval t fd_set readfds char Instr int NrOfReadChars char SignalName 0 xSignalNode yOutputSignal int i 0 char chr 0 t tv_sec 0 t tv_usec 1000 FD_ZERO amp readfds ifndef XMONITOR FD_SET 1 amp readfds endif FD_SET In _ Socket amp readfds if select getdtablesize amp readfds 0 0 amp t gt 0 ifndef XMONITOR SDL signal TermInput if FD_ISSET 1 amp readfds Instr char xAlloc 132 Instr 0 L Instr void gets Instr yOutputSignal xGetSignal TermInput xNotDefPId xEnv xAss_ SDL Charstring amp yPDP_TermInput OUTSIGNAL DATA PTR gt Param1 Instr XASS SDL_Output yOutputSignal xIdNode NIL xFree void amp Instr endif if FD_ISSET In Socket amp readfds Instr char xAlloc 151 do read In_ Socket amp chr 1 Instr i chr while chr 0 sscanf Instr sc amp SignalName if SignalName M SDL signal Message yOutputSignal xGetSignal Message xNotDefPId xEnv sscanf Instr 1 Sd Sx n amp yPDP_Message OUTSIGNAL DATA PTR gt Param2 Gl
50. r e If Message with a PId parameter equal to the receiving process is sent to the system it should respond by just sending a Display signal to the environment with the received line as parameter e If Terminate with a PId parameter not equal to the receiving pro cess is sent to the system it should respond by sending a copy of the Terminate signal to the environment The execution of the pro gram should then terminate e If Terminate with a PId parameter equal to the receiving process is sent to the system the program should just stop executing Let us now verify that the SDL system behaves according to this In the two executions of the simulation shown below the cases described above are tested in the same order as they are listed Example 426 Execution Trace of Generated Application Start program Phone sim sct Command set trace 6 Default trace set to 6 Command next transition x x TRANSITION START PId PhonePr 1 State start state Now 0 0000 NEXTSTATE idle Command output via Signal name TermInput Parameter 1 charstring hello Channel name Signal TermInput was sent to PhonePr 1 from env 1 Process scope PhonePr 1 Telelogic Tau 4 5 User s Manual 2727 Chapter 58 Building an Application Command next transition TRANSITION START PId PhonePr 1 State idle Input TermInput Sender env 1 Now 0 0000 Parameter s hello DECI
51. r T Sd Sx yPDP_Terminate S gt Paraml GlobalNodeNr yPDP_Terminate S gt Paraml LocalPId write Out Socket Outstr strlen Outstr 1 xReleaseSignal S return SDL signal Display if S gt NameNode Display sprintf Outstr ndisplay gt s strlen yPDP_ Display S gt Param1 yPDP_Display S gt Param1 1 PRINTF Outstr PRINTF nphone gt xReleaseSignal S return endif 2754 Telelogic Tau 4 5 User s Manual July 2003
52. r component in the PId value is a local identification of the process instance within the node SDL system The partitioning of an application into an SDL system and the environ ment functions has additional advantages It separates external actions into the logical decision to perform the action the decision to send a signal to the environment and the implementation details of the action treating the signal in the environment functions This kind of separa tion reduces the complexity of the problem and allows separate testing It also allows parallel development of the logic the SDL system and the interface towards the environment the environment functions When the signal interface between the SDL system and its environment is settled it is possible to continue both the activities in parallel Libraries Two libraries Application and ApplicationDebug are provided to gen erate applications Both use real time see Time on page 2576 in chapter 57 The Cadvanced Cbasic SDL to C Compiler and perform calls to environment functions see section The Environment Func tions on page 2702 The difference is that ApplicationDebug includes the monitor system while Application does not include the monitor sys tem When an application is developed it is usually appropriate to first sim ulate and debug the SDL system or systems without its environment One of the libraries Simulation or RealTimeSimulation may then be
53. riable to decode as the third The decoding function returns an integer value which is 0 if the decoding was successful and an error code if it was not More details about decoding functions the buffer reference type nodes and error codes can be found in chapter 59 ASN 1 Encoding and De coding in the SDL Suite Function declarations are in the file ascii ascii h ascii ascii h on Windows platforms in the coder directory Example 422 ASCII decoding into signal parameters In SDL SIGNAL Sigl Integer Person Boolean In xInEnv Buf InitReadMode buf result ASCII_DECODE buf tSDLTypeInfo amp ySDL_ Integer void amp yPDP_Sigl S gt Param1 if result 0 handle error result ASCII _DECODE buf tSDLTypeInfo amp ySDL_ Person void amp yPDP_Sigl S gt Param2 if result 0 handle error result ASCII _DECODE buf tSDLTypeInfo amp ySDL_ Boolean void amp yPDP_Sigl S gt Param3 if result 0 handle error BufCloseReadMode buf Example 423 ASCII decoding of whole signal all signal parameters In SDL SIGNAL Sigil Integer Person Boolean In xInEnv Buf InitReadMode buf result ASCII_DECODE buf tSDLTypeInfo amp ySDL Sigl void S if result 0 handle error BufCloseReadMode buf 2720 Telelogic Tau 4 5 User s Manual July 2003 Ju
54. rk of computers and so on In this world other actions than just signal sending are required Exam ples of actions that an application wants to perform are e To read or to write on a file e To send or receive messages over a network e To respond on interrupts e To read and to write information on hardware ports or on sockets The environment functions are the place where the two worlds the SDL system and the physical environment meet Here signals sent from the SDL system to the environment can induce all kinds of events in the physical environment and events in the environment might cause sig nals to be sent into the SDL system You have to provide the environ ment functions as the Cadvanced SDL to C Compiler has no knowl edge of the actions that should be performed 2696 Telelogic Tau 4 5 User s Manual July 2003 Introduction July 2003 Environment Functions Physical Environment SDL signal interface Interface containing Read and write on files Read and write on ports Read and write on sockets Communication over network Handling of interrupts and so on Figure 490 Structure of an application In a distributed system an application might consist of several commu nicating SDL systems Each SDL system will become one executable program It might execute either as an operating system process com municating with other operating system processes or it might execute in a processor of its
55. s in the system interface header file you must define static unambiguous names Using the Env Header File Generation tab in the Targeting Ex pert you can do this by using available general identifiers The identi fiers are e n This identifier is the SDL name e zs This identifier is the SDL name of the scope e sdlobject In order to identify the type of object you can type the object name as a prefix e g signal literal etc Any combination of the identifiers can be used and they are all optional However in order to create a useful system interface header file it is recommended that the vn identifier is always included Leaving the field empty means that no objects of that type is included in the system interface header file at all Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section Note If you select to include all objects and use the n identifier only the system interface header file will become compatible with earlier versions Example 412 Name Mapping in an system interface header file If the signal Signa11 is in the system System2 you should type the fol lowing in the Signal field in the TAEX sig sn _ s The result in the system interface header file will be sig Signall System2 This approach helps you to avoid name clashes in the ifc file Literals for example are often given the same name when defined in different types The following example shows how this can b
56. s parameter The diagrams for the SDL system may be found in Appendix C The SDL System on page 2747 In the section Where to Find the Exam ple on page 2734 references to where to find the source code for this example are given Simulating the Behavior At this stage of the development of the application when the SDL sys tem is completed but the environment functions are not implemented it is time to simulate the SDL system to debug it at the SDL level The runtime library Simulation is appropriate in this case for simulation There are six cases that should be tested e If TermInput with a line not starting with a period is sent to the system it should respond by sending a Message signal to the envi ronment The first parameter in this signal should be equal to the pa Telelogic Tau 4 5 User s Manual July 2003 July 2003 Example Section rameter in the received TermInput signal The second parameter should be the PId value of the sending process e If TermInput with a line starting with a period is sent to the sys tem it should respond by sending a Terminate signal to the environ ment The parameter should be the PId value of the sending process e If Message with a PId parameter not equal to the receiving process is sent to the system it should respond by sending a copy of the Message signal to the environment It should also send Display to the environment with the received line as paramete
57. s used to generate applica tions All source code for this example together with the running appli cation are delivered with the runtime libraries for application genera tion Note that the example is developed for SunOS 5 and HP UX The example is not updated to use encoding and decoding support The Example We want to develop an application that consists of several communicat ing UNIX processes Each UNIX process should also be connected to the keyboard and the screen When a complete line is typed on the key board when lt Return gt is pressed in one of the UNIX processes that line should be sent to and printed by all the UNIX processes including the one where the line was entered If a line starting with the character is entered in any UNIX process then all the UNIX processes should terminate immediately There are some observations we can make from this short description e Firstly all the UNIX processes should behave exactly the same which means that the behavior can be described in one SDL system and one application can be generated This application should be able to communicate with other instances of itself and should simul taneously be started in as many instances as we want communicat ing UNIX processes e Secondly each UNIX process needs access to the terminal To sim plify the connection between a UNIX process and the terminal we assume that each instance of the application is started from its own windo
58. seSignal S before returning from xOutEnv The xReleaseSignal function is de fined as follows void xReleaseSignal xSignalNode S j In the function xOutEnv you may use the information in the signal that is passed as parameters to the function First it is usually suitable to de termine the signal type of the signal This is best performed by if state ments containing expressions of the following form assuming the use of the system interface header file and that the signal has the name Sig1 in SDL S gt NameNode Sigl Suitable expressions to reach the Receiver the Sender and the signal parameters are S gt Receiver S gt Sender yPDP_Sigl S gt Param yPDP_Sigl S gt Param2 and so on Sender will always refer to the sending process instance while Receiver is either a reference to a process in the environment or the value xEnv xEnv is a PId value that refers to an environment process instance which is used to represent the general concept of environment without specifying an explicit process instance in the environment 2710 Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section Note It is not possible to calculate the PId value for a process in the envi ronment the value has to be taken from an incoming signal sender or signal parameter This is the normal procedure in SDL to estab lish direct communication between two processes i
59. sic SDL to C Compiler This directive code can be used after the initialization of the SDL system but before any transitions are executed Function xOutEnv Each time a signal is sent from the SDL system to the environment of the system the function xOutEnv will be called void xOutEnv xSignalNode S The xout Env function will have the current signal as parameter so you have all the information contained in the signal at your disposal when you implement the actions that should be performed The signal con tains the signal type the sending and receiving process instance and the parameters of the signal For more information about the types used to represent signals and processes see section Types Representing Sig nals on page 2699 and Types Representing Processes on page 2701 Telelogic Tau 4 5 User s Manual 2709 Chapter 58 Building an Application Note that the parameter of xOut Env is an address to xSignalNode that is an address to a pointer to a struct representing the signal The reason for this is that the signal that is given as parameter to xOutEnv should be returned to the pool of available memory before return is made from the xOutEnv function This is made by calling the function xReleaseSignal which takes an address to an xSignalNode as pa rameter returns the signal to the pool of available memory and assigns 0 to the xSignalNode parameter Thus there should be a call xRelea
60. t functions as the interface names are static Example 411 Macro in the system interface header file Ifan SDL signal called Sig1 is defined in the system the following mac ro is created extern XCONST struct xSignalIdStruct ySigR_z5 Sigl ifndef Sigl define Sigl amp ySigR_z5 Sigl endif This macro allows you to refer to the xIdNode by using the static name Sig1 rather than the prefixed name ySigR_z5_Sigl July 2003 Telelogic Tau 4 5 User s Manual 2705 Chapter 58 Building an Application 2706 Macros generate static names for the following SDL types e Synonyms both translated to macros and variables e Newtypes and Syntypes If the newtype is translated to an enumer ation type all the literals are available directly in C using their SDL names e xSignalIdNode representing signals No ySigN_ prefix e xChannelIdNode representing channels Use prefix xIN_ or xOUT_ to access the incoming or outgoing direction of the channel e The yPDP_SignalName pointer type This type may be referred to using the name yPDP_SignalName where SignalName is the SDL name Note You must always generate the system interface header file before editing or generating the environment functions Avoiding name clashes In SDL it is allowed to give the same name to different objects This is not allowed in C For instance in SDL you can give a signal and a New type the same name In order to distinguish between the name
61. that it will work appropriately together with the monitor during debugging Otherwise the keyboard polling that is typing lt RETURN gt in order to interrupt the execution will not work The function xGet Signal which is one of the service functions suit able to use when a signal should be sent returns a pointer to a data area Telelogic Tau 4 5 User s Manual July 2003 July 2003 Reference Section that represents a signal instance of the type specified by the first param eter xSignalNode xGetSignal xSignalIdNode SType SDL_PId Receiver SDL _PId Sender The components Receiver and Sender in the signal instance will also be given the values of the corresponding parameters SType This parameter should be a reference to the symbol table node that represents the current signal type Using the system inter face header file such a symbol table node may be referenced using the signal name directly Receiver This parameter should either be a PId value for a process instance within the system or the value xNotDefPId The value xNotDef PId is used to indicate that the signal should be sent as an output without TO clause while if a PId value is given the output it is treated as an output with TO clause Note that PId values for process instances in an SDL system cannot be calculated but have to be captured from the information sender or parameter carried by signals coming from the system This is the norma
62. w its own shell tool In this way the underlying window manager will solve the problem of directing input typed on the key Telelogic Tau 4 5 User s Manual 2725 Chapter 58 Building an Application 2726 board to the correct application as well as making it possible for you to distinguish between output from different applications e Thirdly the UNIX processes have to be connected so they can com municate with each other We have decided to use sockets as com munication media and to let the UNIX processes form a ring This means that when a UNIX process receives a message containing a line it should print the line and send the message on to the next UNIX process in the ring if it did not itself originally send the line message The SDL System The SDL system with a behavior as outlined above is very simple It contains for example only one process The system can receive three types of signals TermInput from the terminal and Message and Terminate from the SDL system that is the previous node in the ring The system will respond by sending Display to the terminal and Message and Terminate to the SDL system next in the ring The signals TermInput and Display take a line which is read from the terminal or should be printed on the terminal as parameter The signal Message takes a line and a PId value the original sender in the ring as parame ter while the signal Terminate takes a PId value the original sender in the ring a

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