SDL_syssem.c
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/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2006 Sam Lantinga
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Sam Lantinga
slouken@libsdl.org
*/
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#include "SDL_config.h"
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#include <pthread.h>
#include <semaphore.h>
#include "SDL_thread.h"
#include "SDL_timer.h"
/* Wrapper around POSIX 1003.1b semaphores */
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#ifdef __MACOSX__
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#define USE_NAMED_SEMAPHORES 1
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struct SDL_semaphore {
sem_t *sem;
#if !USE_NAMED_SEMAPHORES
sem_t sem_data;
#endif
};
/* Create a semaphore, initialized with value */
SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)
{
SDL_sem *sem = (SDL_sem *) SDL_malloc(sizeof(SDL_sem));
if ( sem ) {
#if USE_NAMED_SEMAPHORES
static int semnum = 0;
char name[32];
SDL_snprintf(name, SDL_arraysize(name), "/SDL_sem-%d-%4.4d", getpid(), semnum++);
sem->sem = sem_open(name, O_CREAT, 0600, initial_value);
if ( sem->sem == (sem_t *)SEM_FAILED ) {
SDL_SetError("sem_open(%s) failed", name);
SDL_free(sem);
sem = NULL;
} else {
sem_unlink(name);
}
#else
if ( sem_init(&sem->sem_data, 0, initial_value) < 0 ) {
SDL_SetError("sem_init() failed");
SDL_free(sem);
sem = NULL;
} else {
sem->sem = &sem->sem_data;
}
#endif /* USE_NAMED_SEMAPHORES */
} else {
SDL_OutOfMemory();
}
return sem;
}
void SDL_DestroySemaphore(SDL_sem *sem)
{
if ( sem ) {
#if USE_NAMED_SEMAPHORES
sem_close(sem->sem);
#else
sem_destroy(sem->sem);
#endif
SDL_free(sem);
}
}
int SDL_SemTryWait(SDL_sem *sem)
{
int retval;
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
retval = SDL_MUTEX_TIMEDOUT;
if ( sem_trywait(sem->sem) == 0 ) {
retval = 0;
}
return retval;
}
int SDL_SemWait(SDL_sem *sem)
{
int retval;
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
retval = sem_wait(sem->sem);
if ( retval < 0 ) {
SDL_SetError("sem_wait() failed");
}
return retval;
}
int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
{
int retval;
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
/* Try the easy cases first */
if ( timeout == 0 ) {
return SDL_SemTryWait(sem);
}
if ( timeout == SDL_MUTEX_MAXWAIT ) {
return SDL_SemWait(sem);
}
/* Ack! We have to busy wait... */
timeout += SDL_GetTicks();
do {
retval = SDL_SemTryWait(sem);
if ( retval == 0 ) {
break;
}
SDL_Delay(1);
} while ( SDL_GetTicks() < timeout );
return retval;
}
Uint32 SDL_SemValue(SDL_sem *sem)
{
int ret = 0;
if ( sem ) {
sem_getvalue(sem->sem, &ret);
if ( ret < 0 ) {
ret = 0;
}
}
return (Uint32)ret;
}
int SDL_SemPost(SDL_sem *sem)
{
int retval;
if ( ! sem ) {
SDL_SetError("Passed a NULL semaphore");
return -1;
}
retval = sem_post(sem->sem);
if ( retval < 0 ) {
SDL_SetError("sem_post() failed");
}
return retval;
}