SDL_syscond.c

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/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2013 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_config.h"

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

#include "SDL_thread.h"
#include "SDL_sysmutex_c.h"

struct SDL_cond
{
    pthread_cond_t cond;
};

/* Create a condition variable */
SDL_cond *
SDL_CreateCond(void)
{
    SDL_cond *cond;

    cond = (SDL_cond *) SDL_malloc(sizeof(SDL_cond));
    if (cond) {
        if (pthread_cond_init(&cond->cond, NULL) < 0) {
            SDL_SetError("pthread_cond_init() failed");
            SDL_free(cond);
            cond = NULL;
        }
    }
    return (cond);
}

/* Destroy a condition variable */
void
SDL_DestroyCond(SDL_cond * cond)
{
    if (cond) {
        pthread_cond_destroy(&cond->cond);
        SDL_free(cond);
    }
}

/* Restart one of the threads that are waiting on the condition variable */
int
SDL_CondSignal(SDL_cond * cond)
{
    int retval;

    if (!cond) {
        return SDL_SetError("Passed a NULL condition variable");
    }

    retval = 0;
    if (pthread_cond_signal(&cond->cond) != 0) {
        return SDL_SetError("pthread_cond_signal() failed");
    }
    return retval;
}

/* Restart all threads that are waiting on the condition variable */
int
SDL_CondBroadcast(SDL_cond * cond)
{
    int retval;

    if (!cond) {
        return SDL_SetError("Passed a NULL condition variable");
    }

    retval = 0;
    if (pthread_cond_broadcast(&cond->cond) != 0) {
        return SDL_SetError("pthread_cond_broadcast() failed");
    }
    return retval;
}

int
SDL_CondWaitTimeout(SDL_cond * cond, SDL_mutex * mutex, Uint32 ms)
{
    int retval;
    struct timeval delta;
    struct timespec abstime;

    if (!cond) {
        return SDL_SetError("Passed a NULL condition variable");
    }

    gettimeofday(&delta, NULL);

    abstime.tv_sec = delta.tv_sec + (ms / 1000);
    abstime.tv_nsec = (delta.tv_usec + (ms % 1000) * 1000) * 1000;
    if (abstime.tv_nsec > 1000000000) {
        abstime.tv_sec += 1;
        abstime.tv_nsec -= 1000000000;
    }

  tryagain:
    retval = pthread_cond_timedwait(&cond->cond, &mutex->id, &abstime);
    switch (retval) {
    case EINTR:
        goto tryagain;
        break;
    case ETIMEDOUT:
        retval = SDL_MUTEX_TIMEDOUT;
        break;
    case 0:
        break;
    default:
        retval = SDL_SetError("pthread_cond_timedwait() failed");
    }
    return retval;
}

/* Wait on the condition variable, unlocking the provided mutex.
   The mutex must be locked before entering this function!
 */
int
SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex)
{
    if (!cond) {
        return SDL_SetError("Passed a NULL condition variable");
    } else if (pthread_cond_wait(&cond->cond, &mutex->id) != 0) {
        return SDL_SetError("pthread_cond_wait() failed");
    }
    return 0;
}

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