/*

  Simple DirectMedia Layer

  Copyright (C) 1997-2012 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"

/* An implementation of mutexes using semaphores */

#include "SDL_thread.h"

#include "SDL_systhread_c.h"

struct SDL_mutex

{

    int recursive;

    SDL_threadID owner;

    SDL_sem *sem;

};

/* Create a mutex */

extern "C"

SDL_mutex *

SDL_CreateMutex(void)

{

    SDL_mutex *mutex;

    /* Allocate mutex memory */

    mutex = (SDL_mutex *) SDL_malloc(sizeof(*mutex));

    if (mutex) {

        /* Create the mutex semaphore, with initial value 1 */

        mutex->sem = SDL_CreateSemaphore(1);

        mutex->recursive = 0;

        mutex->owner = 0;

        if (!mutex->sem) {

            SDL_free(mutex);

            mutex = NULL;

        }

    } else {

        SDL_OutOfMemory();

    }

    return mutex;

}

/* Free the mutex */

extern "C"

void

SDL_DestroyMutex(SDL_mutex * mutex)

{

    if (mutex) {

        if (mutex->sem) {

            SDL_DestroySemaphore(mutex->sem);

        }

        SDL_free(mutex);

    }

}

/* Lock the semaphore */

extern "C"

int

SDL_mutexP(SDL_mutex * mutex)

{

#if SDL_THREADS_DISABLED

    return 0;

#else

    SDL_threadID this_thread;

    if (mutex == NULL) {

        SDL_SetError("Passed a NULL mutex");

        return -1;

    }

    this_thread = SDL_ThreadID();

    if (mutex->owner == this_thread) {

        ++mutex->recursive;

    } else {

        /* The order of operations is important.

           We set the locking thread id after we obtain the lock

           so unlocks from other threads will fail.

         */

        SDL_SemWait(mutex->sem);

        mutex->owner = this_thread;

        mutex->recursive = 0;

    }

    return 0;

#endif /* SDL_THREADS_DISABLED */

}

/* Unlock the mutex */

extern "C"

int

SDL_mutexV(SDL_mutex * mutex)

{

#if SDL_THREADS_DISABLED

    return 0;

#else

    if (mutex == NULL) {

        SDL_SetError("Passed a NULL mutex");

        return -1;

    }

    /* If we don't own the mutex, we can't unlock it */

    if (SDL_ThreadID() != mutex->owner) {

        SDL_SetError("mutex not owned by this thread");

        return -1;

    }

    if (mutex->recursive) {

        --mutex->recursive;

    } else {

        /* The order of operations is important.

           First reset the owner so another thread doesn't lock

           the mutex and set the ownership before we reset it,

           then release the lock semaphore.

         */

        mutex->owner = 0;

        SDL_SemPost(mutex->sem);

    }

    return 0;

#endif /* SDL_THREADS_DISABLED */

}

/* vi: set ts=4 sw=4 expandtab: */