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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.
WATCH CHARACTERS
The functions in this section offer platform-independent capabilities for recording
"watch" characters indicating the occurrence of protocol events. See bprc(5), ltprc(5),
cfdprc(5), 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)