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117 lines
2.6 KiB
C
117 lines
2.6 KiB
C
/*
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Copyright 2005 Allen B. Downey
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This file contains an example program from The Little Book of
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Semaphores, available from Green Tea Press, greenteapress.com
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see http://www.gnu.org/licenses/gpl.html
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or write to the Free Software Foundation, Inc., 51 Franklin St,
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Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/* Code taken from http://greenteapress.com/semaphores/semaphore.c
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* and changed to use libretro-common's mutexes and conditions.
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*/
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#include <stdlib.h>
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#include <rthreads/rthreads.h>
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#include <rthreads/rsemaphore.h>
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struct ssem
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{
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int value;
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int wakeups;
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slock_t *mutex;
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scond_t *cond;
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};
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ssem_t *ssem_new(int value)
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{
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ssem_t *semaphore = (ssem_t*)calloc(1, sizeof(*semaphore));
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if (!semaphore)
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goto error;
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semaphore->value = value;
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semaphore->wakeups = 0;
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semaphore->mutex = slock_new();
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if (!semaphore->mutex)
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goto error;
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semaphore->cond = scond_new();
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if (!semaphore->cond)
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goto error;
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return semaphore;
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error:
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if (semaphore->mutex)
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slock_free(semaphore->mutex);
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semaphore->mutex = NULL;
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if (semaphore)
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free((void*)semaphore);
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return NULL;
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}
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void ssem_free(ssem_t *semaphore)
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{
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if (!semaphore)
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return;
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scond_free(semaphore->cond);
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slock_free(semaphore->mutex);
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free((void*)semaphore);
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}
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void ssem_wait(ssem_t *semaphore)
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{
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if (!semaphore)
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return;
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slock_lock(semaphore->mutex);
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semaphore->value--;
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if (semaphore->value < 0)
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{
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do
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{
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scond_wait(semaphore->cond, semaphore->mutex);
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}while (semaphore->wakeups < 1);
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semaphore->wakeups--;
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}
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slock_unlock(semaphore->mutex);
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}
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void ssem_signal(ssem_t *semaphore)
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{
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if (!semaphore)
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return;
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slock_lock(semaphore->mutex);
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semaphore->value++;
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if (semaphore->value <= 0)
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{
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semaphore->wakeups++;
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scond_signal(semaphore->cond);
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}
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slock_unlock(semaphore->mutex);
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}
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