127 lines
2.9 KiB
C
127 lines
2.9 KiB
C
/*
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SST_Semaphore_POSIX.c
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Author: Patrick Baggett <ptbaggett@762studios.com>
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Created: 12/20/2011
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Purpose:
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libsst-concurrency semaphore functions for POSIX platforms
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License:
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This program is free software. It comes without any warranty, to
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the extent permitted by applicable law. You can redistribute it
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and/or modify it under the terms of the Do What The Fuck You Want
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To Public License, Version 2, as published by Sam Hocevar. See
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http://sam.zoy.org/wtfpl/COPYING for more details.
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*/
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#include <SST/SST_Concurrency.h>
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#include <SST/SST_Semaphore.h>
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#include <semaphore.h> /* POSIX semaphores */
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#include <time.h>
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#include <stdlib.h> /* malloc()/free() */
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#include <errno.h> /* errno */
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#include "timespecadd.h"
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/******************************************************************************/
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SST_Semaphore SST_Concurrency_CreateSemaphore(uint32_t _initialCount)
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{
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sem_t* sema;
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sema = (sem_t*)malloc(sizeof(sem_t));
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if(sema)
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{
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sem_init(sema, 0, (unsigned int)_initialCount);
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}
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return (SST_Semaphore)sema;
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}
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/******************************************************************************/
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void SST_Concurrency_DestroySemaphore(SST_Semaphore _sema)
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{
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sem_t* sema = (sem_t*)_sema;
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sem_destroy(sema);
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free(sema);
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}
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/******************************************************************************/
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void SST_Concurrency_PostSemaphore(SST_Semaphore _sema, uint32_t _count)
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{
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sem_t* sema = (sem_t*)_sema;
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while(_count)
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{
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/* The Open Group doesn't define a sem_post() that allows
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larger than incrementing by 1, so loop. */
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sem_post(sema);
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_count--;
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}
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}
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/******************************************************************************/
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int SST_Concurrency_WaitSemaphore(SST_Semaphore _sema, uint32_t _ticks)
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{
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int result = 0;
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sem_t* sema = (sem_t*)_sema;
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int ok;
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/* Infinite wait */
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if(_ticks == SST_WAIT_INFINITE)
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{
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/* Wait in a loop until we get a value OTHER than EINTR,
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or the function succeeds.
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Basically, EINTR means a signal interrupted this function,
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so we can retry the wait */
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do
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{
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ok = sem_wait(sema);
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if(ok == 0)
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break;
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} while(errno == EINTR);
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/* sem_wait() returns 0 on success, so see if successful */
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result = (ok == 0);
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}
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else /* Maximum wait measured in milliseconds */
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{
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struct timespec ts, tswait;
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clock_gettime(CLOCK_REALTIME, &ts);
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tswait.tv_sec = (_ticks / 1000);
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tswait.tv_nsec = (_ticks % 1000) * 1000 * 1000;
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_sst_add_timespec(&ts, &tswait);
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/* EINTER = signal interrupted the function. Loop until we get
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something other than a signal interruption */
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do
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{
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ok = sem_timedwait(sema, &ts);
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if(ok == 0)
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break;
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} while(errno == EINTR);
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/* Either success or timeout, trap legitimate errors (which
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are due to invalid conditions -> bug) */
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if(ok < 0 && errno != ETIMEDOUT)
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{
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result = 0;
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}
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else
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{
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/* If this returned success, then save that result
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as TRUE */
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result = (ok == 0);
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}
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}
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return result;
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}
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