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#ifndef GC_DARWIN_SEMAPHORE_H

#define GC_DARWIN_SEMAPHORE_H

#if !defined(GC_DARWIN_THREADS)

#error darwin_semaphore.h included with GC_DARWIN_THREADS not defined

#endif

/*

   This is a very simple semaphore implementation for darwin. It

   is implemented in terms of pthreads calls so it isn't async signal

   safe. This isn't a problem because signals aren't used to

   suspend threads on darwin.

*/

typedef struct {

    pthread_mutex_t mutex;

    pthread_cond_t cond;

    int value;

} sem_t;

static int sem_init(sem_t *sem, int pshared, int value) {

    int ret;

    if(pshared)

        GC_abort("sem_init with pshared set");

    sem->value = value;

    ret = pthread_mutex_init(&sem->mutex,NULL);

    if(ret < 0) return -1;

    ret = pthread_cond_init(&sem->cond,NULL);

    if(ret < 0) return -1;

    return 0;

}

static int sem_post(sem_t *sem) {

    if(pthread_mutex_lock(&sem->mutex) < 0)

        return -1;

    sem->value++;

    if(pthread_cond_signal(&sem->cond) < 0) {

        pthread_mutex_unlock(&sem->mutex);

        return -1;

    }

    if(pthread_mutex_unlock(&sem->mutex) < 0)

        return -1;

    return 0;

}

static int sem_wait(sem_t *sem) {

    if(pthread_mutex_lock(&sem->mutex) < 0)

        return -1;

    while(sem->value == 0) {

        pthread_cond_wait(&sem->cond,&sem->mutex);

    }

    sem->value--;

    if(pthread_mutex_unlock(&sem->mutex) < 0)

        return -1;

    return 0;

}

static int sem_destroy(sem_t *sem) {

    int ret;

    ret = pthread_cond_destroy(&sem->cond);

    if(ret < 0) return -1;

    ret = pthread_mutex_destroy(&sem->mutex);

    if(ret < 0) return -1;

    return 0;

}

#endif