serenity/Userland/Libraries/LibPthread/semaphore.cpp

/*
 * Copyright (c) 2021, the SerenityOS developers.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <AK/Assertions.h>
#include <errno.h>
#include <semaphore.h>

int sem_close(sem_t*)
{
    errno = ENOSYS;
    return -1;
}

int sem_destroy(sem_t* sem)
{
    auto rc = pthread_mutex_destroy(&sem->mtx);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    rc = pthread_cond_destroy(&sem->cv);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    return 0;
}

int sem_getvalue(sem_t* sem, int* sval)
{
    auto rc = pthread_mutex_trylock(&sem->mtx);

    if (rc == EBUSY) {
        *sval = 0;
        return 0;
    }

    if (rc != 0) {
        errno = rc;
        return -1;
    }

    *sval = sem->value;

    pthread_mutex_unlock(&sem->mtx);

    return 0;
}

int sem_init(sem_t* sem, int shared, unsigned int value)
{
    if (shared) {
        errno = ENOSYS;
        return -1;
    }

    if (value > SEM_VALUE_MAX) {
        errno = EINVAL;
        return -1;
    }

    auto rc = pthread_mutex_init(&sem->mtx, nullptr);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    rc = pthread_cond_init(&sem->cv, nullptr);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    sem->value = value;

    return 0;
}

sem_t* sem_open(const char*, int, ...)
{
    errno = ENOSYS;
    return nullptr;
}

int sem_post(sem_t* sem)
{
    auto rc = pthread_mutex_lock(&sem->mtx);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    if (sem->value == SEM_VALUE_MAX) {
        pthread_mutex_unlock(&sem->mtx);
        errno = EOVERFLOW;
        return -1;
    }

    sem->value++;

    rc = pthread_cond_signal(&sem->cv);
    if (rc != 0) {
        pthread_mutex_unlock(&sem->mtx);
        errno = rc;
        return -1;
    }

    rc = pthread_mutex_unlock(&sem->mtx);
    if (errno != 0) {
        errno = rc;
        return -1;
    }

    return 0;
}

int sem_trywait(sem_t* sem)
{
    auto rc = pthread_mutex_lock(&sem->mtx);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    if (sem->value == 0) {
        pthread_mutex_unlock(&sem->mtx);
        errno = EAGAIN;
        return -1;
    }

    sem->value--;

    rc = pthread_mutex_unlock(&sem->mtx);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    return 0;
}

int sem_unlink(const char*)
{
    errno = ENOSYS;
    return -1;
}

int sem_wait(sem_t* sem)
{
    auto rc = pthread_mutex_lock(&sem->mtx);
    if (errno != 0) {
        errno = rc;
        return -1;
    }

    while (sem->value == 0) {
        rc = pthread_cond_wait(&sem->cv, &sem->mtx);
        if (rc != 0) {
            pthread_mutex_unlock(&sem->mtx);
            errno = rc;
            return -1;
        }
    }

    sem->value--;

    rc = pthread_mutex_unlock(&sem->mtx);
    if (rc != 0) {
        errno = rc;
        return -1;
    }

    return 0;
}