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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) 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) 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) 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). It differs from getcwd(3) 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), 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).
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) and open(2).
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 }[:<portnbr>]", 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) 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.
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)
perl v5.18.2 2013-12-30 ici::doc::pod3::platform(3)