src/thread/pthread/SDL_syssem.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2012 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
*/
#include "SDL_config.h"

#include <pthread.h>
#include <semaphore.h>
#include <errno.h>
#include <sys/time.h>

#include "SDL_thread.h"
#include "SDL_timer.h"

/* Wrapper around POSIX 1003.1b semaphores */

#ifdef __MACOSX__
/* Mac OS X doesn't support sem_getvalue() as of version 10.4 */
#include "../generic/SDL_syssem.c"
#else

struct SDL_semaphore {
	sem_t sem;
};

/* 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 ( sem_init(&sem->sem, 0, initial_value) < 0 ) {
			SDL_SetError("sem_init() failed");
			SDL_free(sem);
			sem = NULL;
		}
	} else {
		SDL_OutOfMemory();
	}
	return sem;
}

void SDL_DestroySemaphore(SDL_sem *sem)
{
	if ( sem ) {
		sem_destroy(&sem->sem);
		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;
	}

	while ( ((retval = sem_wait(&sem->sem)) == -1) && (errno == EINTR) ) {}
	if ( retval < 0 ) {
		SDL_SetError("sem_wait() failed");
	}
	return retval;
}

int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)
{
	int retval;
	struct timeval now;
	struct timespec ts_timeout;

	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);
	}

	/* Setup the timeout. sem_timedwait doesn't wait for
	 * a lapse of time, but until we reach a certain time.
	 * This time is now plus the timeout.
	 */
	gettimeofday(&now, NULL);

	/* Add our timeout to current time */
	now.tv_usec += (timeout % 1000) * 1000;
	now.tv_sec += timeout / 1000;

	/* Wrap the second if needed */
	if ( now.tv_usec >= 1000000 ) {
		now.tv_usec -= 1000000;
		now.tv_sec ++;
	}

	/* Convert to timespec */
	ts_timeout.tv_sec = now.tv_sec;
	ts_timeout.tv_nsec = now.tv_usec * 1000;

	/* Wait. */
	do
		retval = sem_timedwait(&sem->sem, &ts_timeout);
	while (retval == -1 && errno == EINTR);

	if (retval == -1)
		SDL_SetError(strerror(errno));

	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;
}

#endif /* __MACOSX__ */