PICA user manual
Contents
1. functions to create operat and destroy mutexes semaphores and new data structures int PICAcreateMutex PICAmutex mut int PICAcreateSemaphore PICAsemaphore p_sem int initial count int max_count CANES Soo CAN int PICAsemaphoreAction int action PICAsemaphore p_sem int count These functions behaviour depends on the value of the action field MUTEX_ACQUIRE or SEMAPHORE ACQUIRE try to acquire the mutex or semaphore if it has just been acquired or the semaphore value is the minimum the calling thread enters the wait state until the object is signalled or the time out interval elapses blocking the call MUTEX_RELEASE or SEMAPHORE _ RELEASE release th mutex or increment the semaphore value MUTEX_ACQO NO_BLOCK or SEMAPHORE _ACQ NO_BLOCK to acquire the mutex if it has just been acquired the function returns immediately int PICAdestroyMutex PICAmutex mut int PICAdestroySemaphore PICAsemaphore p_sem 6 3 The networking management primitives 6 3 1 In order to get information about available devices Each device is identified by a different string depending on the operating system For Windows operating systems a device is identified by a long and cryptic ASC string while in Linux is a string similar to eth wifi ppp etc where in place of there is a number Inter2. value it can be CREATE_CLEAN Creates a new file in read_and write mode If the file exists the function overwrites the file and clears the existing attributes APPEND Open the file called name in read_and_write mode If the file does not exist the function creates a new one ae PICAwriteToFile FDesc file void ES data unsigned oe datasize This function writes the first datasize bytes of information pointed by data on the file identified by file ime PiCAreacialle Dese file void bui int bufrersize amc datasize This function read data of maximum length buffersize from file identified as file and sets datasize as the real length of the data read int PICAcloseFile FDesc file This function closes the file identified by file 6 1 2 Packet buffer management Relatively to memory management PICA s architecture is based on offering the possibility to easily handle a data structure holding queues The purpose was to provide auxiliary functions which could be useful for implementation The user can create as many queues as desired allowing differentiated packet handling The architecture chosen allows using multiple groups of queues each group having a number of queues chosen by the user This following figure shows new data structures definitions typedef struct PICApacket int packet size void data struct PiCApacket next PICA
3. 7 References 1 Carlos Calafate www grc upv es calafate 2 IEEE Portable operating system interface posix part 1 System application programming interface api c language SO IEC 9945 1 1996 3 www winpcap org 4 V Jacobson C Leres and S McCanne The libpcap packet capture library Lawrence Berkeley Laboratory Berkely Ca Available at http www tcpdump org 5 http msdn2 microsoft com en us library aa366071 aspx 6 Martin Hall and Dav Treadwel t al Windows sockets 2 application programming interface August 1997 Available at ftp ftp microsoft com 8 Index of figures EIQuUre 310 PICA aArenrreecthure is wis ersen el ele a Se Gia Be Se eee ol al ears Figura 327 PICA Arent t SGU Ur Seis eea ida E aa lets ane Sita dog ee le ia Figura si PICA internal arcntrect ures a la Bo oe es Figura 6 1 PICApacket structure definition for all platfaorms Figura 6 2 P ICAbuffer structure definition left for windows ELONE ROT Mia Nuss se ois ee ee Cee ie IA ie Ce te ee nae ce Ree ee Figura 6 3 rights Lor L Figura 6 4 9 Index Tabella 4 1 PICApipe structure definition left for Windows TAI e ra ISE DE ic heh DEALS LN SP Seba EAN E tn era A dae NS RTLines structure and RTInfo structure definitions of tables used tods bra ad a a aa a ai eles at ee aia la
4. Packet 32 ActiveSync 82 5 EmbeddedVis ul c 3 0 WINCE 5 0 Linux ActiveSync 4 2 Visual Studio Net 2005 done with tools versions shown in the table pick a different version but results are not The provided PICA package contains these directories Linux Windows WinCe 3 0 WinCe 5 0 is and another on testing PICA This happens inside every Pl In each directory there is one named pica where the PICA library named test where there is an application for test consists in one simple print of what CA procedure 4 1 Windows The Windows version of PICA is the same for Windows XP and Windows 2000 and it was built with Microsoft Visual Studio Net 2003 The library is based on two system libraries Iphlpapi Error No se encuentra el origen de la referencia and WindowsSocket2 5 libraries The first assists network administration of the local computer by enabling applications to retrieve and to modify information about the network configuration on the local computer while the second allows to work with socket features This directory contains two sub directories pica there are PICA library files pica dll and pica lib and two directories named net and pica containing PICA header files test there is Visual studio Net project test application HOW TO USE PICA In order to install Winpcap download Winpcap executer fil
5. design to provide dynamic connectivity For example in OLSRvl In order to transform IP addresses from dotnotation format to bit string it is possible to use in Windows and in Linux The data structures used in Windows and Linux are different Therefore PICA used the following typedef struct RTLines typedef struct RTInfo UINT32 dest int entry count UINT32 mask RTLines lines UINT32 gw RTInto int metric char device struct RTLines next RTLines Figura 6 4 RTLines structure and RTInfo structure definitions RTLines represents an entry in routing table specifying the adapter to which related RTInfo represents routing table with entry_count entries number and lines is a pointer to a list of all entries int PICAaddRoute UINT32 dest UINT32 mask UINT32 gateway int metric Char device This function adds a route in device s routing table with destination dest mask mask gateway gateway and metric metric int PICAdelRoute UINT32 dest UINT32 mask UINT32 gateway char dev iee This function deletes a route from device s route table with destination dest mask mask gateway gateway and metric metric int PICAgetRoutingTable RTInfo rti This function gives routing table information stored in the routing table structure RTInfo pointed by rti 6 3 5 Socket management These functions allow the user to open
6. possible to obtain a description and a code number for the last error that occurred by calling the PICAgetLastError function see paragraph 6 4 for more details Managed errors are almost same in Windows and Linux some pica functions depend only on system calls hence th returned error can differ both in message description and in the error number as returned by a function Section 6 4 presents primitives for PICA library management Moreover it is important to notice that in Windows the special features like pipe mutex and semaphore used for inter process communication are defined inheritable in order to allow threads to communicate with main application 6 1 System management primitives 6 1 1 In order to write log file In order to unify file descriptor PICA uses FDesc that in windows is defined as type HANDLE while in Linux it is defined as type int iim PICACoeMle MDeESse file Cla eie meme amit read melee ame flags Depending on read_write and flags parameters values this function opens or creates a file called name in read only mode or read and write mode The read_write parameter Can take the following values READF the file name is open in read mode if it doesn t exit the function creates a new one With this value the function ignores the flag parameter value WRITEF in this case the functions behaviour depends on flag
7. In order to compile your application do gcc lt your stuff gt lpica 5 PICA library s internal structure This paragraph shows the internal structure of the PICA project and PICA s available features The PICA project consists of eleven files of code and each of them includes a header file Figura 5 1 shows the internal structure of Windows PICA project and the relationships between header files Linux s PICA project has the same internal structure but without the reference to the Winpcap library pica timer Devs Iphfwd manager sock thr mem log packet user picaSpec Figura 5 1 PICA internal architecture In this figure one blank rectangle is a single PICA header file while the yellow one is the libpcap or its porting header file Arrows are used as follow In this case File 2 h includes File 1 h with the directive include File_1 h 6 PICA s primitives This paragraph shows and describes PICA s primitives divided in three logical groups process management primitives memory management primitives communication management In each of them PICA S primitives are separated by their function PICA provides a good error management each function returns O if an error is occurred or 1 otherwise in the first case it is
8. and applications to the device In order to use PICA in a project to install necessaries libraries download them from http www winpcap org install default htmt The download consists in a zip file that contains a project developed with Microsoft Embedded Visual Studio c This solution contains three projects named DDL Driver Sample Apply While the first two projects consist of code to allow direct interaction with the network interface the third one is a small application that illustrates the behaviour of the first two libraries In order to obtain the Packet32 library you must build the DLL project and download it on the PocketPc since the Driver project is also required you must perform the same action on it Notice that their output files are packet32 dll for DLL and pktdrv dll for Driver Since Winpcap developers do not guarantee its correct functioning it is advisable to execute SampleApply to verify if the driver is suitable for using with the PocketPC when creating a new project enable the socket option That way the tool initializes the right libraries and the right code for socket use in your project Copy the following files and directories contained in the ARMDbg directory of Packet32 s project in the new project s folder Packet32 dll packet32 lib PktDrv dll PktDrv lib MSInclude Add the content of PICA s directory
9. iodev of size packetsize read value states how many bytes are actually read It is important to point out that data to be sent has to conform to the packet format of a MAC frame Many network adapters use Ethernet as packet format It includes many fields but the user must create a data stream with only these ones Destination and source MAC addresses Ethernet type length and Payload since the remaining ones are set by network adapter LANE PICAcreatePacket char acele unsigned ehai cata LDE datasize unsigned char packet int packetsize This function creates an Ethernet packet with the destination address indicated by addr a string with dot notation and sets the packet data field with the data pointed by data This function requires data to be already in the hexadecimal format datasize is the length of the data parameter Parameter packet will point to the packet just created and packetsize is its size This function does not requir the source address because th network adapter sets it in each packet before sending int PICAcloseDevice PICA_IO_DEVICE iodev Close the device identified by iodev 6 3 4 Routing management These functions allow the user to add and remov entries in the forwarding table and reading such table They are not frequented used but we found that they are sometimes useful in protocol
10. CApipe HANDLE pipe HANDLE event PICApipe Figura 6 3 PICApipe structure definition left for Windows right for Linux Despite Windows pipe declaration uses an event the communication between the pipe writing thread and pipe reading thread is transparent to the PICA user To learn about how to use PICA s pipe functionalities see the test application On Windows and Linux reads and writes to anonymous pipes are always blocking In other words a read from an empty pipe will block in the call until ither one or more bytes arrive or the pipe is closed and an end of file is sent Likewise a write to a full pipe will block the call until space becomes available to store the data being written Reads may return with less than the number of bytes requested otherwise known as a short read int PICAmakePipe PICApipe in PICApipe out This function creates a pipe the in parameter is used to put data while out one to get data on the same pipe dim PUCASSmcltoPijoSs PICAS QUE Wwolc dera imi size ame written This function allows to write data pointed by data of size size on pipe The write value states how many bytes are actually written lime PICAGetlrombPlipwe PICADige im vola lu me OE S E me datasize This function allows to read bufsize bytes from the pipe and put them in buf The datasize value states how many bytes are act
11. ICA 2 Terminology Since the biggest difference between operating systems are between Linux and Windows families in this document the word Windows is to be interpreted as the Windows operating system family In case it is necessary to b mor precise w will state the exact version of Windows being used 3 Overall architecture The PICA library is an adaptation layer between the users and the kernel space as shown in figure Figure 3 1 and offers specialized functions that aid the programming activity when creating networking solution Application PICA library Figure 3 1 PICA architecture PICA library is based on Winpcap 2 the porting of the Packet Capture Library Libpcap jError No se encuentra el origen de la referencia work by Van Jacobson to the Windows operating system Both Libpcap and its port Winpcap consist of drivers which extend the operating system to provide low level network access They also include a library that offers easy access the low level network layers Libpcap allows applications to capture and transmit network packets bypassing the protocol stack and has additional useful features including kernel level packet filtering a network statistics engine and support for remote packet capture Unfortunately the port of Winpcap to the Windows CE 5 0 platform is not yet available but the lack of Winpcap s port to WinCE 5 0
12. PICA user manual This document presents and describes PICA a library designed specifically for the implementation of network protocols which aims at reducing the production cycle duration for MANET s communication protocols Nevertheless it can also be used to write applications that need Operating system features like thread socket timer etc avoiding having to port them to different platforms It also explains how to install and use PICA on different platforms Windows 2000 Windows XP Linux Windows CE 3 0 and Sa 0 Index Bb W N Be D ICA user manual 1 Introduction 3 Terminology 3 Overall architecture 9 Installation 7 4 1 Windows 8 62 gt WindowsCE 3 0 8 woo Windows CE 5 0 10 4 Linux 10 PICA library s internal structure 11 PICA s primitives 12 jes System management primitives 13 6 1 1 In order to write log file 13 6 1 2 Packet buffer management 14 6 1 3 Pipe management 16 Process management primitives 17 6 2 1 Timer management La 6 2 2 Thread management 18 6 2 3 Mutex management 21 fous The networking management primitives 22 6 3 1 In order to get information about available devices 22 6 3 2 Management forwarding information 23 6 3 3 24 6 3 4 Frame sending and receiving 24 6 3 5 Routing management 25 6 3 6 Socket management 26 4 gt In order to manage PICA library 27 1 Introduction The PICA library wa
13. and close a socket lime PICACTScitesocien PICASOCKkSet se imc GClomeadin iinet Eye mt ISEOQEOCOL lime loloelk in order to understand the possible values of domain type and protocol parameters see documentation of Windows and Linux socket function 5 while the parameter block can take values BLOCK in order to create a blocking socket meaning that the application waits for the socket until it receives something NO BLOCK ehterwise int PICAcloseSocket PICAsocket sd This function closes socket sd In order to get user information int PICALSAci MLinaLgiciceicor int true false This function sets variable true false to IS_ADM if the process is executing with administrator privileges or sets it to IS_NOT_ADM otherwise 6 4 In order to manage PICA library ine PICAstartcupl lint flage This function is essential to use PICA since it initialises PICA library and all necessary data structures Therefore it has to be the first PICA function called int PICAcleanup void This function cleans up the PICA library and it must be executed before the application exits Lack of such call can generate an error ime PIrCAgetlastircror Char err int Code y This is a useful function that allows to debug applications based on PICA it puts in err a concise error description and in code its error number code
14. can lead to a deadlock if the calling thread tries to obtain a synchronization object owned by a suspended thread To avoid this situation a thread within an application that is not a debugger should signal the other thread to suspend itself The target thread must be designed to watch for this signal and respond appropriately Lime PICAS are Wace acl UINRUUD tlie voldel Eiae woilel eG This function creates a thread identified by thr that executes la function func with parameters arg int PICAsuspendThread THRID thr This function suspends the thread identified by thr int PICAresumeThread THRID thr This function resumes the thread identified by thr ine PICAkilLThreac THRID thr p This function kills the thread identified by thr int PICAselect int time PICAdescList dl PICAselResult res This function emulates the behaviour of Linux s select function Linux s select function is used to wait for events associated with any kind of descriptor descriptors ar represented by integers values However in Windows operating systems descriptors are generally represented by a specific data type called HANDLE while integers are only used for sockets Windows select function is only available for sockets while for others events we have to use a function of the WaitFor family The PICA library obviates this problem by emulating the Linux behaviour and
15. does not render PICA unusable since applications can still receive and transmit packets through sockets but they are mandatory processed by the operating system For example OLSR version 1 and version 2 implementations use PICA without resorting to the Libpcap Winpcap libraries PICA as shown in following figure does not completely cover underling layers Depending on the needs of protocol being designed programmers can use PICA s interface the Libpcap Winpcap library or kernel procedures PICA library Figura 3 2 PICA architecture The use of Libpcap library does not compromise inter platform compatibility since there is a version of Libpcap for almost all operating systems By using kernel specific functions though the source code will loose its compatibility between platforms requiring porting and extra effort on the developer s side 4 Installation This paragraph explains how to create a new application based on PICA and which external libraries ar ssential PICA is provided with a sample test application showing the PICA procedures used The following tabl resumes necessary PICA libraries and tools used to implement the test application Win2000 2 XP Library Winpcap Microsof t Visual Tool Studio Net 2003 Tabella 4 1 used tools Tests on PICA were above the user Can guaranteed WINCE 3 0
16. e from www winpcap org install default htm and install it following instructions on that web page In order to use pica in a project copy the following files and directories into your project s folder pica dll pica lib net and pica Add to your project dependencies pica lib Insert include lt PICA pica h gt in new code 4 2 WindowsCE 3 0 PICA s WinCE 3 0 version was built with Embedded Visual studio C 3 0 and it can operate with a WinCE3 0 PocketPC It downloads all output files and necessary libraries on PocketPc but it is necessary to make sure that all of them are downloaded in the same directory the default one is windows Start In order to use ip routing functionalities it is necessary to change HKEY_LOCAL_MACHINE Comm Tcpip Parms IpEnableRouter registry value from 0 to 1 and perform a soft reset This change can be done by an utility similar to Windows s RegEdit suitable for PocketPc WindowsCE 3 0 directory contains two sub directories pica there are PICA library files pica dll and pica lib and two directories named MSInclude and pica containing PICA header files test there is an Embedded Visual Studio project test application HOW USE PICA It is important that your device is connected with your PC through the ActiveSync program in order to allow downloading libraries
17. er PICAbuffer ibuf int num_queues This function initializes a PICAbuffer structure with num_queues queues and num_queues mutex ine PIUCAACCIIOBWiIEESIc PICNowiEteic lu ime Gueme_icl volel elena ae dacar Size This function creates a new packet with information pointed by data and size of data_size Afterwards it puts each packet at the end of queue number queue_id It important to notice that the queue number starts at 0 LANE PICAgetFromBuffer PICAbuffer IE y LDE queue_id LDE num _ packets PICApacket packets int avail_packets This function gives the first num_packet of queue number queue_id of buffer buf Avail_packet contains the real number of packet retrieved from the queue int PICAkil1 Buffer PICAbuffer buf This function frees the memory allocated for the PICAbuffer buf 6 1 3 Pipe management A pipe is a useful inter process communication tool Since pipes are considered as a file under both Linux and Windows it is represented with a different type in Linux with the integer type while in Windows with HANDLE type Moreover in Windows the programmer has to signal pipe writing to the reading thread Therefore PICA provides a pipe data structure and primitives to manage it in order to cope with this difference Figura 6 3 shows the definitions of PICApipe in Linux and Windows typedef struct PICApipe typedef int PI
18. esting information about a device are its MAC net mask and IP addresses In order to store this information PICA uses two data structures typedef struct Devattrs unsigned char ha 6 UINT32 ip_addr Devittrs typedef struct DEVLIST int num devices char dev_names MAXDEVS MAXDEVSIZE DEVLIST The DEVLIST structure represents a device set containing num_devices devices and their identification name PICA supports a maximum of 128 network adapters on each DevAttrs structure is used to store the IP and MAC address of a device int PICAgetAvailableDevices DEVLIST devs This function allows to obtain the number and names of all available devices in devs see paragraph PICA data structures Appendix A ine PICAGSEDSYILCSATERS char dev DevaArers artis This function sets in attr the MAC net mask and IP addresses of devices identified by dev see paragraph PICA data structures pag 14 6 3 2 Management forwarding information These functions provide information about forwarding and allow to change its state dao PICA si ormervccias bate 5 Expte false This function gives information about the forwarding status set true false true if computer forwards packets false otherwise int PICAsetForwarding int on_off This function sets forwarding on if on_off s value is FWD_ON off if _off s va
19. lue is FWD_OFF other values are not admitted ine PicAde famille 11 iaa set get int CEL This function sets or gets the TTL s value depending on value of set get If its value is TTL_SET then this function sets the TTL with value pointed by ttl If its value is TTL_GET then this function gets the system s value for the time to live It should be noticed that the TTL value affected is the global system s TTL Lowering this value too much might cause loss of connectivity to other networks e g Internet For a per socket definition of this value the appropriate socket option available in most systems should be used 6 3 3 Frame sending and receiving Lim PICACOSINDEWiLCS Clacic ceyics PICA 10 DawviCia ioclewy 7 This function makes the device identified by name device ready to get and put data in the network After this call in order to send and receive a packet it is necessary refer to it through the iodev value dime PIC Arcs amie mocie PICA 10 Davyicia iocew WoOlde PDAcikel aime packetsize int read This function allows to send and receive packets on device iodev If the mode value is PICA_SEND th device sends data pointed by packet of size packetsize In this case parameter read is not used PICA RECEIVE the device receives data from device
20. packet Figura 6 1 PICApacket structure definition for all platfaorms typedef struct _PICAbuffer typedef struct _PICAbuffer int tot_queues int tot_queues HANDLE buf mut pthread_mutex_t buf_mut struct PICApacket packet queues struct _PICApacket packet_queues PICAbuffer PICAbuffer Figura 6 2 PICAbuffer structure definition left for windows right for Linux The first represents the information unit to store in the buffer Each packet can have a different size PICAbuffer is a data structure that contains one or more queues each of them is a linked list of packets In order to guarantee data coherence to multi threaded applications PICA s buffer structure has a set of mutexes Each mutex is used to control the access to each queue so that for example distinct threads can read and write to different queues even though these queues belong to the same group The mutex set is obtained by using a dynamic array with a number of elements equal to the tot queues field This guarantees data coherence to multi threaded applications hence two or more threads can access different queues in parallel or to the same queue avoiding the concurrent access problem It is relevant to point out that in order not to generate meaningful delays these routines do not perform any kind of buffer duplication having the sole task of managing pointers to data int PICAinitBuff
21. s created by Carlos Calafate 1 in order to provide a multi platform intuitive API for communication protocols designers The objective was to accelerate the prototyping phase to provide users with a stable solution whose source code can compile directly on distinct platforms However PICA is very flexible allowing users to choose whether to use PICA s or platform s features The PICA architecture tries to be efficient in terms of code size and speed making the differences in performance when compared to a customized solution minimal The PICA library was developed in ANSI C language and is available as dynamic link library d11 file for Windows operating systems and as a shared object so file for Linux based operating systems PICA is released under the GNU General Public Licence Error No se encuentra el origen de la referencia This manual is divided in four chapters in the first there is a brief explication about PICA s overall architecture in the second there are instructions to install PICA on each platform for which it is available The third chapter explains PICA functionalities if a function uses a particular data structure or defines a new type it is explained in function description At the end of this manual there are a table summarizing all data structures and a list of constants provided by P
22. s the timer for the function therefore deleting the element representing it from the timer queue The element to remove is identified by both time and function or by one of them T KILL terminates the thread created and resets the timer 6 2 2 Thread management The fork call is of common use in Unix environments to manage processes Windows OS though do not offer this function PICA adopts a combination of the threads approximation with the semaphore and mutex abstractions as an alternative to processes without generating too much extra code Although the Posix standard doesn t allow thread suspension and resuming the PICA library allows using such functions in the Linux operating system by means of the SIGUSR1 and SIGUSR2 signals This solution tries to cope with the differences with respect to the windows kernel where such functions exist Th recommended practice is anyway to avoid such calls because they can produce unpredictable results in critical sections of code Also the Posix standard does not allow setting the maximum value of a semaphore which PICA makes available by introducing a little overhead PICASuspendThread and PICAResumeThread are primarily designed for use by debuggers They are not intended to be used for thread synchronization Calling PICASuspendThread on a thread that owns a synchronization object such as a mutex or critical section
23. to the project s folder Add as to the project s dependencies PICA 1ib Insert include lt PICA pica h gt in new code 4 3 Windows CE 5 0 Since Libpcap porting on wince 5 0 is not available PICA library does not offer functionalities of sending and receiving packets bypassing the protocol stack The instructions to install and use PICA are the same ones as for the Wince 3 0 platform but the tool used is Microsoft Visual Studio 2005 since it allows to operate with Wince5 0 PocketPc and obviously it is not necessary to add references to the Packet32 library 4 4 Linux In Linux environments it is necessary to execute all PICA based applications with root privileges This directory contains two sub directories pica source code includes all the files for PICA test there is a simple project that shows how pica works HOW TO USE PICA In this paragraph you can find a simple instruction to follow for installing and then using pica Install PICA Run make Change to superuser with command su Run make install The library will be copied to usr local lib and the headers to usr include PICA Change the makefile if you wish to use different paths for the installation In order to develop applications make sure to insert include lt PICA PICA h gt in your code
24. ually read iat PICAGLOSSPijoSs PICASiljoS pie 5 This function frees pipe space 6 2 Process management primitives 6 2 1 Timer management Windows and Linux represent time in different ways and from different dates Windows operating system uses intervals of 100 nanosecond intervals since January 1 1601 while Linux uses a more complex data structure to represent the time expired since January 1 1970 In order to unify time representation PICA represents time values by number milliseconds intervals since January 1 1970 using UNIT64 type UINT64 PICAgetCurrTime void This function returns current time ime PiCAcamer int accion UNTSA time volea itumeiciom woud gt data This function s behaviour depends on action Its admitted values are T_STARTUP initializes timer it is necessary to have done just this action before taking the following actions T_SET sets the function and its data in the timer s queue in such a way that all its precedent lements have a timeout value lower that its own while the next elements have a greater timeout value Afterwards it updates the timer to the value of the most recent event It is important to point out that it is possible to insert two or more elements with a same timer value and that they will be executed at almost the same time T_STOP remove
25. using new data structures PICAdescList and PICAselResult typedef struct PiICAdescList typedef struct PICAselResult int type int type int mode void desc void desc PICAselResult struct _PiCAdescList next PICAdescList These data structures are necessary in Windows because as referred above it uses different data types to identify descriptor resources Therefore these structures allow identifying type descriptors through the type field Types admitted are PICA PIPE TYPE PICA_TIMEOUT_TYPE PICA _OTHER_TYPE see PICAselect function PICAdescList represents a list of all descriptors on which to wait for an event PICAselResult corresponds to PICAselect result it contains the selected resource descriptor and its type which is the type of resource it refers to ine PiCAsccDese PICACSSChigst Gil inte Eve ine moce voici asian Add a new file descriptor whose type is type and whose mode is mode It is associated with a event described by desc 6 2 3 Mutex management Windows and Linux Unix systems manage Mutexes and semaphores in different ways Besides having different types for mutex and semaphore descriptors Linux does not allow setting the maximum value of a semaphore which is a feature available in Windows PICA provides this functionality In order to cope with the differences PICA provides the following
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