--- name: "platform" section: "3" platform: "linux" package: "ion-doc" version: "3.2.1+dfsg-1.1" release: "Debian 9 (Stretch)" platforms: ["linux"] url: "https://new.carta.tech/platform" --- # platform(3) C software portability definitions and functions ## NAME platform - C software portability definitions and functions ## SYNOPSIS ``` #include "platform.h" [see description for available functions] ``` ## DESCRIPTION *platform* is a library of functions that simplify the porting of software written in C. It provides an API that enables application code to access the resources of an abstract POSIX-compliant "least common denominator" operating system -- typically a large subset of the resources of the actual underlying operating system. Most of the functionality provided by the platform library is aimed at making communication code portable: common functions for shared memory, semaphores, and IP sockets are provided. The implementation of the abstract O/S API varies according to the actual operating system on which the application runs, but the API's behavior is always the same; applications that invoke the platform library functions rather than native O/S system calls may forego some O/S-specific capability, but they gain portability at little if any cost in performance. Differences in word size among platforms are implemented by values of the *SPACE\_ORDER* macro. "Space order" is the base 2 log of the number of octets in a word: for 32-bit machines the space order is 2 (2^2 = 4 octets per word), for 64-bit machines it is 3 (2^3 = 8 octets per word). A consistent platform-independent representation of large integers is useful for some applications. For this purpose, *platform* defines new types **vast** and **uvast** (unsigned vast) which are consistently defined to be 64-bit integers regardless of the platform's native word size. The platform.h header file #includes many of the most frequently needed header files: sys/types.h, errno.h, string.h, stdio.h, sys/socket.h, signal.h, dirent.h, netinet/in.h, unistd.h, stdlib.h, sys/time.h, sys/resource.h, malloc.h, sys/param.h, netdb.h, sys/uni.h, and fcntl.h. Beyond this, *platform* attempts to enhance compatibility by providing standard macros, type definitions, external references, or function implementations that are missing from a few supported O/S's but supported by all others. Finally, entirely new, generic functions are provided to establish a common body of functionality that subsumes significantly different O/S-specific capabilities. ### PLATFORM COMPATIBILITY PATCHES The platform library "patches" the APIs of supported O/S's to guarantee that all of the following items may be utilized by application software: ``` The strchr(), strrchr(), strcasecmp(), and strncasecmp() functions. The unlink(), getpid(), and gettimeofday() functions. The select() function. The FD_BITMAP macro (used by select()). The MAXHOSTNAMELEN macro. The NULL macro. The timer_t type definition. ``` ### PLATFORM GENERIC MACROS AND FUNCTIONS The generic macros and functions in this section may be used in place of comparable O/S-specific functions, to enhance the portability of code. (The implementations of these macros and functions are no-ops in environments in which they are inapplicable, so they're always safe to call.) - FDTABLE\_SIZE The FDTABLE\_SIZE macro returns the total number of file descriptors defined for the process (or VxWorks target). - ION\_PATH\_DELIMITER The ION\_PATH\_DELIMITER macro returns the ASCII character -- either '/' or '\\' -- that is used as a directory name delimiter in path names for the file system used by the local platform. - oK(expression) The oK macro simply casts the value of *expression* to void, a way of handling function return codes that are not meaningful in this context. - CHKERR(condition) The CHKERR macro is an "assert" mechanism. It causes the calling function to return -1 immediately if *condition* is false. - CHKZERO(condition) The CHKZERO macro is an "assert" mechanism. It causes the calling function to return 0 immediately if *condition* is false. - CHKNULL(condition) The CHKNULL macro is an "assert" mechanism. It causes the calling function to return NULL immediately if *condition* is false. - CHKVOID(condition) The CHKVOID macro is an "assert" mechanism. It causes the calling function to return immediately if *condition* is false. - void snooze(unsigned int seconds) Suspends execution of the invoking task or process for the indicated number of seconds. - void microsnooze(unsigned int microseconds) Suspends execution of the invoking task or process for the indicated number of microseconds. - void getCurrentTime(struct timeval \*time) Returns the current local time in a timeval structure (see gettimeofday(3C)). - void isprintf(char \*buffer, int bufSize, char \*format, ...) *isprintf()* is a safe, portable implementation of *snprintf()*; see the snprintf(P) man page for details. *isprintf()* differs from *snprintf()* in that it always NULL-terminates the string in *buffer*, even if the length of the composed string would equal or exceed *bufSize*. Buffer overruns are reported by log message; unlike *snprintf()*, *isprintf()* returns void. - size\_t istrlen(const char \*sourceString, size\_t maxlen) *istrlen()* is a safe implementation of *strlen()*; see the [*strlen*(3)](/strlen/3.md) man page for details. *istrlen()* differs from *strlen()* in that it takes a second argument, the maximum valid length of *sourceString*. The function returns the number of non-NULL characters in *sourceString* preceding the first NULL character in *sourceString*, provided that a NULL character appears somewhere within the first *maxlen* characters of *sourceString*; otherwise it returns *maxlen*. - char \*istrcpy(char \*buffer, char \*sourceString, int bufSize) *istrcpy()* is a safe implementation of *strcpy()*; see the [*strcpy*(3)](/strcpy/3.md) man page for details. *istrcpy()* differs from *strcpy()* in that it takes a third argument, the total size of the buffer into which *sourceString* is to be copied. *istrcpy()* always NULL-terminates the string in *buffer*, even if the length of *sourceString* string would equal or exceed *bufSize* (in which case *sourceString* is truncated to fit within the buffer). - char \*istrcat(char \*buffer, char \*sourceString, int bufSize) *istrcat()* is a safe implementation of *strcat()*; see the [*strcat*(3)](/strcat/3.md) man page for details. *istrcat()* differs from *strcat()* in that it takes a third argument, the total size of the buffer for the string that is being aggregated. *istrcat()* always NULL-terminates the string in *buffer*, even if the length of *sourceString* string would equal or exceed the sum of *bufSize* and the length of the string currently occupying the buffer (in which case *sourceString* is truncated to fit within the buffer). - char \*igetcwd(char \*buf, size\_t size) *igetcwd()* is normally just a wrapper around [*getcwd*(3)](/getcwd/3.md). It differs from [*getcwd*(3)](/getcwd/3.md) only when FSWWDNAME is defined, in which case the implementation of *igetcwd()* must be supplied in an included file named "wdname.c"; this adaptation option accommodates flight software environments in which the current working directory name must be configured rather than discovered at run time. - void isignal(int signbr, void (\*handler)(int)) *isignal()* is a portable, simplified interface to signal handling that is functionally indistinguishable from signal(P). It assures that reception of the indicated signal will interrupt system calls in SVR4 fashion, even when running on a FreeBSD platform. - void iblock(int signbr) *iblock()* simply prevents reception of the indicated signal by the calling thread. It provides a means of controlling which of the threads in a process will receive the signal cited in an invocation of *isignal()*. - char \*igets(int fd, char \*buffer, int buflen, int \*lineLen) *igets()* reads a line of text, delimited by a newline character, from *fd* into *buffer* and writes a NULL character at the end of the string. The newline character itself is omitted from the NULL-terminated text line in *buffer*; if the newline is immediately preceded by a carriage return character (i.e., the line is from a DOS text file), then the carriage return character is likewise omitted from the NULL-terminated text line in *buffer*. End of file is interpreted as an implicit newline, terminating the line. If the number of characters preceding the newline is greater than or equal to *buflen*, only the first (*buflen* - 1) characters of the line are written into *buffer*. On error the function sets *\*lineLen* to -1 and returns NULL. On reading end-of-file, the function sets *\*lineLen* to zero and returns NULL. Otherwise the function sets *\*lineLen* to the length of the text line in *buffer*, as if from [*strlen*(3)](/strlen/3.md), and returns *buffer*. - int iputs(int fd, char \*string) *iputs()* writes to *fd* the NULL-terminated character string at *string*. No terminating newline character is appended to *string* by *iputs()*. On error the function returns -1; otherwise the function returns the length of the character string written to *fd*, as if from [*strlen*(3)](/strlen/3.md). - vast strtovast(char \*string) Converts the leading characters of *string*, skipping leading white space and ending at the first subsequent character that can't be interpreted as contributing to a numeric value, to a **vast** integer and returns that integer. - uvast strtouvast(char \*string) Same as *strtovast()* except the result is an unsigned **vast** integer value. - void findToken(char \*\*cursorPtr, char \*\*token) Locates the next non-whitespace lexical token in a character array, starting at *\*cursorPtr*. The function NULL-terminates that token within the array and places a pointer to the token in *\*token*. Also accommodates tokens enclosed within matching single quotes, which may contain embedded spaces and escaped single-quote characters. If no token is found, *\*token* contains NULL on return from this function. - void \*acquireSystemMemory(size\_t size) Uses *memalign()* to allocate a block of system memory of length *size*, starting at an address that is guaranteed to be an integral multiple of the size of a pointer to void, and initializes the entire block to binary zeroes. Returns the starting address of the allocated block on success; returns NULL on any error. - int createFile(const char \*name, int flags) Creates a file of the indicated name, using the indicated file creation flags. This function provides common file creation functionality across VxWorks and Unix platforms, invoking *creat()* under VxWorks and *open()* elsewhere. For return values, see [*creat*(2)](/creat/2.md) and [*open*(2)](/open/2.md). - unsigned int getInternetAddress(char \*hostName) Returns the IP address of the indicated host machine, or zero if the address cannot be determined. - char \*getInternetHostName(unsigned int hostNbr, char \*buffer) Writes the host name of the indicated host machine into *buffer* and returns *buffer*, or returns NULL on any error. The size of *buffer* should be (MAXHOSTNAMELEN + 1). - int getNameOfHost(char \*buffer, int bufferLength) Writes the first (*bufferLength* - 1) characters of the host name of the local machine into *buffer*. Returns 0 on success, -1 on any error. - unsigned int *getAddressOfHost()* Returns the IP address for the host name of the local machine, or 0 on any error. - void parseSocketSpec(char \*socketSpec, unsigned short \*portNbr, unsigned int \*hostNbr) Parses *socketSpec*, extracting host number (IP address) and port number from the string. *socketSpec* is expected to be of the form "{ @ \| hostname }\[:\\]", where @ signifies "the host name of the local machine". If host number can be determined, writes it into *\*hostNbr*; otherwise writes 0 into *\*hostNbr*. If port number is supplied and is in the range 1024 to 65535, writes it into *\*portNbr*; otherwise writes 0 into *\*portNbr*. - void printDottedString(unsigned int hostNbr, char \*buffer) Composes a dotted-string (xxx.xxx.xxx.xxx) representation of the IPv4 address in *hostNbr* and writes that string into *buffer*. The length of *buffer* must be at least 16. - char \*getNameOfUser(char \*buffer) Writes the user name of the invoking task or process into *buffer* and returns *buffer*. The size of *buffer* must be at least *L\_cuserid*, a constant defined in the stdio.h header file. Returns *buffer*. - int reUseAddress(int fd) Makes the address that is bound to the socket identified by *fd* reusable, so that the socket can be closed and immediately reopened and re-bound to the same port number. Returns 0 on success, -1 on any error. - int makeIoNonBlocking(int fd) Makes I/O on the socket identified by *fd* non-blocking; returns -1 on failure. An attempt to read on a non-blocking socket when no data are pending, or to write on it when its output buffer is full, will not block; it will instead return -1 and cause errno to be set to EWOULDBLOCK. - int watchSocket(int fd) Turns on the "linger" and "keepalive" options for the socket identified by *fd*. See [*socket*(2)](/socket/2.md) for details. Returns 0 on success, -1 on any failure. - void closeOnExec(int fd) Ensures that *fd* will NOT be open in any child process *fork()*ed from the invoking process. Has no effect on a VxWorks platform. ### EXCEPTION REPORTING The functions in this section offer platform-independent capabilities for reporting on processing exceptions. The underlying mechanism for ICI's exception reporting is a pair of functions that record error messages in a privately managed pool of static memory. These functions -- *postErrmsg()* and *postSysErrmsg()* -- are designed to return very rapidly with no possibility of failing, themselves. Nonetheless they are not safe to call from an interrupt service routing (ISR). Although each merely copies its text to the next available location in the error message memory pool, that pool is protected by a mutex; multiple processes might be queued up to take that mutex, so the total time to execute the function is non-deterministic. Built on top of *postErrmsg()* and *postSysErrmsg()* are the *putErrmsg()* and *putSysErrmsg()* functions, which may take longer to return. Each one simply calls the corresponding "post" function but then calls the *writeErrmsgMemos()* function, which calls *writeMemo()* to print (or otherwise deliver) each message currently posted to the pool and then destroys all of those posted messages, emptying the pool. Recommended general policy on using the ICI exception reporting functions (which the functions in the ION distribution libraries are supposed to adhere to) is as follows: ``` In the implementation of any ION library function or any ION task's top-level driver function, any condition that prevents the function from continuing execution toward producing the effect it is designed to produce is considered an "error". Detection of an error should result in the printing of an error message and, normally, the immediate return of whatever return value is used to indicate the failure of the function in which the error was detected. By convention this value is usually -1, but both zero and NULL are appropriate failure indications under some circumstances such as object creation. The CHKERR, CHKZERO, CHKNULL, and CHKVOID macros are used to implement this behavior in a standard and lexically terse manner. Use of these macros offers an additional feature: for debugging purposes, they can easily be configured to call sm_Abort() to terminate immediately with a core dump instead of returning a error indication. This option is enabled by setting the compiler parameter CORE_FILE_NEEDED to 1 at compilation time. In the absence of either any error, the function returns a value that indicates nominal completion. By convention this value is usually zero, but under some circumstances other values (such as pointers or addresses) are appropriate indications of nominal completion. Any additional information produced by the function, such as an indication of "success", is usually returned as the value of a reference argument. [Note, though, that database management functions and the SDR hash table management functions deviate from this rule: most return 0 to indicate nominal completion but functional failure (e.g., duplicate key or object not found) and return 1 to indicate functional success.] So when returning a value that indicates nominal completion of the function -- even if the result might be interpreted as a failure at a higher level (e.g., an object identified by a given string is not found, through no failure of the search function) -- do NOT invoke putErrmsg(). Use putErrmsg() and putSysErrmsg() only when functions are unable to proceed to nominal completion. Use writeMemo() or writeMemoNote() if you just want to log a message. Whenever returning a value that indicates an error: If the failure is due to the failure of a system call or some other non-ION function, assume that errno has already been set by the function at the lowest layer of the call stack; use putSysErrmsg (or postSysErrmsg if in a hurry) to describe the nature of the activity that failed. The text of the error message should normally start with a capital letter and should NOT end with a period. Otherwise -- i.e., the failure is due to a condition that was detected within ION -- use putErrmsg (or postErrmg if pressed for time) to describe the nature of the failure condition. This will aid in tracing the failure through the function stack in which the failure was detected. The text of the error message should normally start with a capital letter and should end with a period. When a failure in a called function is reported to "driver" code in an application program, before continuing or exiting use writeErrmsgMemos() to empty the message pool and print a simple stack trace identifying the failure. ``` - char \*system\_error\_msg( ) Returns a brief text string describing the current system error, as identified by the current value of errno. - void setLogger(Logger usersLoggerName) Sets the user function to be used for writing messages to a user-defined "log" medium. The logger function's calling sequence must match the following prototype: ``` void usersLoggerName(char *msg); ``` The default Logger function simply writes the message to standard output. - void writeMemo(char \*msg) Writes one log message, using the currently defined message logging function. - void writeMemoNote(char \*msg, char \*note) Writes a log message like *writeMemo()*, accompanied by the user-supplied context-specific text in *note*. - void writeErrMemo(char \*msg) Writes a log message like *writeMemo()*, accompanied by text describing the current system error. - char \*itoa(int value) Returns a string representation of the signed integer in *value*, nominally for immediate use as an argument to *putErrmsg()*. \[Note that the string is constructed in a static buffer; this function is not thread-safe.\] - char \*utoa(unsigned int value) Returns a string representation of the unsigned integer in *value*, nominally for immediate use as an argument to *putErrmsg()*. \[Note that the string is constructed in a static buffer; this function is not thread-safe.\] - void postErrmsg(char \*text, char \*argument) Constructs an error message noting the name of the source file containing the line at which this function was called, the line number, the *text* of the message, and -- if not NULL -- a single textual *argument* that can be used to give more specific information about the nature of the reported failure (such as the value of one of the arguments to the failed function). The error message is appended to the list of messages in a privately managed pool of static memory, ERRMSGS\_BUFSIZE bytes in length. If *text* is NULL or is a string of zero length or begins with a newline character (i.e., *\*text* == '\\0' or '\\n'), the function returns immediately and no error message is recorded. The errmsgs pool is designed to be large enough to contain error messages from all levels of the calling stack at the time that an error is encountered. If the remaining unused space in the pool is less than the size of the new error message, however, the error message is silently omitted. In this case, provided at least two bytes of unused space remain in the pool, a message comprising a single newline character is appended to the list to indicate that a message was omitted due to excessive length. - void postSysErrmsg(char \*text, char \*arg) Like *postErrmsg()* except that the error message constructed by the function additionally contains text describing the current system error. *text* is truncated as necessary to assure that the sum of its length and that of the description of the current system error does not exceed 1021 bytes. - int getErrmsg(char \*buffer) Copies the oldest error message in the message pool into *buffer* and removes that message from the pool, making room for new messages. Returns zero if the message pool cannot be locked for update or there are no more messages in the pool; otherwise returns the length of the message copied into *buffer*. Note that, for safety, the size of *buffer* should be ERRMSGS\_BUFSIZE. Note that a returned error message comprising only a single newline character always signifies an error message that was silently omitted because there wasn't enough space left on the message pool to contain it. - void writeErrmsgMemos( ) Calls *getErrmsg()* repeatedly until the message pool is empty, using *writeMemo()* to log all the messages in the pool. Messages that were omitted due to excessive length are indicated by logged lines of the form "\[message omitted due to excessive length\]". - void putErrmsg(char \*text, char \*argument) The *putErrmsg()* function merely calls *postErrmsg()* and then *writeErrmsgMemos()*. - void putSysErrmsg(char \*text, char \*arg) The *putSysErrmsg()* function merely calls *postSysErrmsg()* and then *writeErrmsgMemos()*. - void discardErrmsgs( ) Calls *getErrmsg()* repeatedly until the message pool is empty, discarding all of the messages. - void printStackTrace( ) On Linux machines only, uses *writeMemo()* to print a trace of the process's current execution stack, starting with the lowest level of the stack and proceeding to the *main()* function of the executable. Note that (a) *printStackTrace()* is **only** implemented for Linux platforms at this time; (b) symbolic names of functions can only be printed if the *-rdynamic* flag was enabled when the executable was linked; (c) only the names of non-static functions will appear in the stack trace. For more complete information about the state of the executable at the time the stack trace snapshot was taken, use the Linux *addr2line* tool. To do this, cd into a directory in which the executable file resides (such as /opt/bin) and submit an addr2line command as follows: addr2line -e *name\_of\_executable* *stack\_frame\_address* where both *name\_of\_executable* and *stack\_frame\_address* are taken from one of the lines of the printed stack trace. addr2line will print the source file name and line number for that stack frame. ### WATCH CHARACTERS The functions in this section offer platform-independent capabilities for recording "watch" characters indicating the occurrence of protocol events. See [*bprc*(5)](/bprc/5.md), [*ltprc*(5)](/ltprc/5.md), [*cfdprc*(5)](/cfdprc/5.md), etc. for details of the watch character production options provided by the protocol packages. - void setWatcher(Watcher usersWatcherName) Sets the user function to be used for recording watch characters to a user-defined "watch" medium. The watcher function's calling sequence must match the following prototype: ``` void usersWatcherName(char token); ``` The default Watcher function simply writes the token to standard output. - void iwatch(char token) Records one "watch" character, using the currently defined watch character recording function. ### SELF-DELIMITING NUMERIC VALUES (SDNV) The functions in this section encode and decode SDNVs, portable variable-length numeric variables that expand to whatever size is necessary to contain the values they contain. SDNVs are used extensively in the BP and LTP libraries. - void encodeSdnv(Sdnv \*sdnvBuffer, uvast value) Determines the number of octets of SDNV text needed to contain the value, places that number in the *length* field of the SDNV buffer, and encodes the value in SDNV format into the first *length* octets of the *text* field of the SDNV buffer. - int decodeSdnv(uvast \*value, unsigned char \*sdnvText) Determines the length of the SDNV located at *sdnvText* and returns this number after extracting the SDNV's value from those octets and storing it in *value*. Returns 0 if the encoded number value will not fit into an unsigned vast integer. ### ARITHMETIC ON LARGE INTEGERS (SCALARS) The functions in this section perform simple arithmetic operations on unsigned Scalar objects -- structures encapsulating large positive integers in a machine-independent way. Each Scalar comprises two integers, a count of units \[ranging from 0 to (2^30 - 1), i.e., up to 1 gig\] and a count of gigs \[ranging from 0 to (2^31 -1)\]. A Scalar can represent a numeric value up to 2 billion billions, i.e., 2 million trillions. - void loadScalar(Scalar \*scalar, signed int value) Sets the value of *scalar* to the absolute value of *value*. - void increaseScalar(Scalar \*scalar, signed int value) Adds to *scalar* the absolute value of *value*. - void reduceScalar(Scalar \*scalar, signed int value) Adds to *scalar* the absolute value of *value*. - void multiplyScalar(Scalar \*scalar, signed int value) Multiplies *scalar* by the absolute value of *value*. - void divideScalar(Scalar \*scalar, signed int value) Divides *scalar* by the absolute value of *value*. - void copyScalar(Scalar \*to, Scalar \*from) Copies the value of *from* into *to*. - void addToScalar(Scalar \*scalar, Scalar \*increment) Adds *increment* (a Scalar rather than a C integer) to *scalar*. - void subtractFromScalar(Scalar \*scalar, Scalar \*decrement) Subtracts *decrement* (a Scalar rather than a C integer) from *scalar*. - int scalarIsValid(Scalar \*scalar) Returns 1 if the arithmetic performed on *scalar* has not resulted in overflow or underflow. - int scalarToSdnv(Sdnv \*sdnv, Scalar \*scalar) If *scalar* points to a valid Scalar, stores the value of *scalar* in *sdnv*; otherwise sets the length of *sdnv* to zero. - int sdnvToScalar(Scalar \*scalar, unsigned char \*sdnvText) If *sdnvText* points to a sequence of bytes that, when interpreted as the text of an Sdnv, has a value that can be represented in a 61-bit unsigned binary integer, then this function stores that value in *scalar* and returns the detected Sdnv length. Otherwise returns zero. Note that Scalars and Sdnvs are both representations of potentially large unsigned integer values. Any Scalar can alternatively be represented as an Sdnv. However, it is possible for a valid Sdnv to be too large to represent in a Scalar. ### PRIVATE MUTEXES The functions in this section provide platform-independent management of mutexes for synchronizing operations of threads or tasks in a common private address space. - int initResourceLock(ResourceLock \*lock) Establishes an inter-thread lock for use in locking some resource. Returns 0 if successful, -1 if not. - void killResourceLock(ResourceLock \*lock) Deletes the resource lock referred to by *lock*. - void lockResource(ResourceLock \*lock) Checks the state of *lock*. If the lock is already owned by a different thread, the call blocks until the other thread relinquishes the lock. If the lock is unowned, it is given to the current thread and the lock count is set to 1. If the lock is already owned by this thread, the lock count is incremented by 1. - void unlockResource(ResourceLock \*lock) If called by the current owner of *lock*, decrements *lock*'s lock count by 1; if zero, relinquishes the lock so it may be taken by other threads. Care must be taken to make sure that one, and only one, *unlockResource()* call is issued for each *lockResource()* call issued on a given resource lock. ### SHARED MEMORY IPC DEVICES The functions in this section provide platform-independent management of IPC mechanisms for synchronizing operations of threads, tasks, or processes that may occupy different address spaces but share access to a common system (nominally, processor) memory. *NOTE* that this is distinct from the VxWorks "VxMP" capability enabling tasks to share access to bus memory or dual-ported board memory from multiple processors. The "platform" system will support IPC devices that utilize this capability at some time in the future, but that support is not yet implemented. - int sm\_ipc\_init( ) Acquires and initializes shared-memory IPC management resources. Must be called before any other shared-memory IPC function is called. Returns 0 on success, -1 on any failure. - void sm\_ipc\_stop( ) Releases shared-memory IPC management resources, disabling the shared-memory IPC functions until *sm\_ipc\_init()* is called again. - int sm\_GetUniqueKey( ) Some of the "sm\_" (shared memory) functions described below associate new communication objects with *key* values that uniquely identify them, so that different processes can access them independently. Key values are typically defined as constants in application code. However, when a new communication object is required for which no specific need was anticipated in the application, the *sm\_GetUniqueKey()* function can be invoked to obtain a new, arbitrary key value that is known not to be already in use. - sm\_SemId sm\_SemCreate(int key, int semType) Creates a shared-memory semaphore that can be used to synchronize activity among tasks or processes residing in a common system memory but possibly multiple address spaces; returns a reference handle for that semaphore, or SM\_SEM\_NONE on any failure. If *key* refers to an existing semaphore, returns the handle of that semaphore. If *key* is the constant value SM\_NO\_KEY, automatically obtains an unused key. On VxWorks platforms, *semType* determines the order in which the semaphore is given to multiple tasks that attempt to take it while it is already taken: if set to SM\_SEM\_PRIORITY then the semaphore is given to tasks in task priority sequence (i.e., the highest-priority task waiting for it receives it when it is released), while otherwise (SM\_SEM\_FIFO) the semaphore is given to tasks in the order in which they attempted to take it. On all other platforms, only SM\_SEM\_FIFO behavior is supported and *semType* is ignored. - int sm\_SemTake(sm\_SemId semId) Blocks until the indicated semaphore is no longer taken by any other task or process, then takes it. Return 0 on success, -1 on any error. - void sm\_SemGive(sm\_SemId semId) Gives the indicated semaphore, so that another task or process can take it. - void sm\_SemEnd(sm\_SemId semId) This function is used to pass a termination signal to whatever task is currently blocked on taking the indicated semaphore, if any. It sets to 1 the "ended" flag associated with this semaphore, so that a test for *sm\_SemEnded()* will return 1, and it gives the semaphore so that the blocked task will have an opportunity to test that flag. - int sm\_SemEnded(sm\_SemId semId) This function returns 1 if the "ended" flag associated with the indicated semaphore has been set to 1; returns zero otherwise. When the function returns 1 it also gives the semaphore so that any other tasks that might be pended on the same semaphore are also given an opportunity to test it and discover that it has been ended. - void sm\_SemUnend(sm\_SemId semId) This function is used to reset an ended semaphore, so that a restarted subsystem can reuse that semaphore rather than delete it and allocate a new one. - int sm\_SemUnwedge(sm\_SemId semId, int timeoutSeconds) Used to release semaphores that have been taken but never released, possibly because the tasks or processes that took them crashed before releasing them. Attempts to take the semaphore; if this attempt does not succeed within *timeoutSeconds* seconds (providing time for normal processing to be completed, in the event that the semaphore is legitimately and temporarily locked by some task), the semaphore is assumed to be wedged. In any case, the semaphore is then released. Returns 0 on success, -1 on any error. - void sm\_SemDelete(sm\_SemId semId) Destroys the indicated semaphore. - sm\_SemId sm\_GetTaskSemaphore(int taskId) Returns the ID of the semaphore that is dedicated to the private use of the indicated task, or SM\_SEM\_NONE on any error. This function implements the concept that for each task there can always be one dedicated semaphore, which the task can always use for its own purposes, whose key value may be known a priori because the key of the semaphore is based on the task's ID. The design of the function rests on the assumption that each task's ID, whether a VxWorks task ID or a Unix process ID, maps to a number that is out of the range of all possible key values that are arbitrarily produced by *sm\_GetUniqueKey()*. For VxWorks, we assume this to be true because task ID is a pointer to task state in memory which we assume not to exceed 2GB; the unique key counter starts at 2GB. For Unix, we assume this to be true because process ID is an index into a process table whose size is less than 64K; unique keys are formed by shifting process ID left 16 bits and adding the value of an incremented counter which is always greater than zero. - int sm\_ShmAttach(int key, int size, char \*\*shmPtr, int \*id) Attaches to a segment of memory to which tasks or processes residing in a common system memory, but possibly multiple address spaces, all have access. This function registers the invoking task or process as a user of the shared memory segment identified by *key*. If *key* is the constant value SM\_NO\_KEY, automatically sets *key* to some unused key value. If a shared memory segment identified by *key* already exists, then *size* may be zero and the value of *\*shmPtr* is ignored. Otherwise the size of the shared memory segment must be provided in *size* and a new shared memory segment is created in a manner that is dependent on *\*shmPtr*: if *\*shmPtr* is NULL then *size* bytes of shared memory are dynamically acquired, allocated, and assigned to the newly created shared memory segment; otherwise the memory located at *shmPtr* is assumed to have been pre-allocated and is merely assigned to the newly created shared memory segment. On success, stores the unique shared memory ID of the segment in *\*id* for possible future destruction, stores a pointer to the segment's assigned memory in *\*shmPtr*, and returns 1 (if the segment is newly created) or 0 (otherwise). Returns -1 on any error. - void sm\_ShmDetach(char \*shmPtr) Unregisters the invoking task or process as a user of the shared memory starting at *shmPtr*. - void sm\_ShmDestroy(int id) Destroys the shared memory segment identified by *id*, releasing any memory that was allocated when the segment was created. ### PORTABLE MULTI-TASKING - int sm\_TaskIdSelf( ) Returns the unique identifying number of the invoking task or process. - int sm\_TaskExists(int taskId) Returns non-zero if a task or process identified by *taskId* is currently running on the local processor, zero otherwise. - void \*sm\_TaskVar(void \*\*arg) Posts or retrieves the value of the "task variable" belonging to the invoking task. Each task has access to a single task variable, initialized to NULL, that resides in the task's private state; this can be convenient for passing task-specific information to a signal handler, for example. If *arg* is non-NULL, then *\*arg* is posted as the new value of the task's private task variable. In any case, the value of that task variable is returned. - void sm\_TaskSuspend( ) Indefinitely suspends execution of the invoking task or process. Helpful if you want to freeze an application at the point at which an error is detected, then use a debugger to examine its state. - void sm\_TaskDelay(int seconds) Same as *snooze*(3). - void sm\_TaskYield( ) Relinquishes CPU temporarily for use by other tasks. - int sm\_TaskSpawn(char \*name, char \*arg1, char \*arg2, char \*arg3, char \*arg4, char \*arg5, char \*arg6, char \*arg7, char \*arg8, char \*arg9, char \*arg10, int priority, int stackSize) Spawns/forks a new task/process, passing it up to ten command-line arguments. *name* is the name of the function (VxWorks) or executable image (UNIX) to be executed in the new task/process. For UNIX, *name* must be the name of some executable program in the `$PATH` of the invoking process. For VxWorks, *name* must be the name of some function named in an application-defined private symbol table (if PRIVATE\_SYMTAB is defined) or the system symbol table (otherwise). If PRIVATE\_SYMTAB is defined, the application must provide a suitable adaptation of the symtab.c source file, which implements the private symbol table. "priority" and "stackSize" are ignored under UNIX. Under VxWorks, if zero they default to the values in the application-defined private symbol table if provided, or otherwise to ICI\_PRIORITY (nominally 100) and 32768 respectively. Returns the task/process ID of the new task/process on success, or -1 on any error. - void sm\_TaskKill(int taskId, int sigNbr) Sends the indicated signal to the indicated task or process. - void sm\_TaskDelete(int taskId) Terminates the indicated task or process. - void *sm\_Abort()* Terminates the calling task or process. If not called while ION is in flight configuration, a stack trace is printed or a core file is written. - int pseudoshell(char \*script) Parses *script* into a command name and up to 10 arguments, then passes the command name and arguments to *sm\_TaskSpawn()* for execution. The *sm\_TaskSpawn()* function is invoked with priority and stack size both set to zero, causing default values (possibly from an application-defined private symbol table) to be used. Tokens in *script* are normally whitespace-delimited, but a token that is enclosed in single-quote characters (') may contain embedded whitespace and may contain escaped single-quote characters ("\\'"). On any parsing failure returns -1; otherwise returns the value returned by *sm\_TaskSpawn()*. ## USER'S GUIDE - Compiling an application that uses "platform": Just be sure to "#include "platform.h"" at the top of each source file that includes any platform function calls. - Linking/loading an application that uses "platform": ``` a. In a Solaris environment, link with these libraries: -lplatform -socket -nsl -posix4 -c b. In a Linux environment, simply link with platform: -lplatform c. In a VxWorks environment, use ld 1, 0, "libplatform.o" to load platform on the target before loading applications. ``` ## SEE ALSO gettimeofday(3C)