RIOT/sys/net/sixlowpan/semaphore.c

/**
 * Semaphore implemenation 
 *
 * Copyright (C) 2013  INRIA.
 *
 * This file subject to the terms and conditions of the GNU Lesser General
 * Public License. See the file LICENSE in the top level directory for more
 * details.
 *
 * @ingroup sixlowpan
 * @{
 * @file    semaphore.c
 * @brief   Implemntation of semaphores using mutexes
 * @author  Martin Lenders <mlenders@inf.fu-berlin.de>
 * @author  Oliver Hahm <oliver.hahm@inria.fr>
 * @}
 */

#include <mutex.h>

#include "semaphore.h"

void sem_init(sem_t *sem, int8_t value)
{
    sem->value = value;
    mutex_init(&sem->mutex);
    sem->locked = 0;
}

int sem_wait(sem_t *sem)
{
    int res;

    if (--(sem->value) <= 0 && !sem->locked) {
        sem->locked = !(sem->locked);
        res = mutex_lock(&(sem->mutex));

        if (res < 0) {
            return res;
        }
    }

    return 0;
}

int sem_signal(sem_t *sem)
{
    if (++(sem->value) > 0 && sem->locked) {
        sem->locked = !(sem->locked);
        mutex_unlock(&(sem->mutex), 0);
    }

    return 0;
}