/*

  SDL - Simple DirectMedia Layer

  Copyright (C) 1997-2010 Sam Lantinga

  This library is free software; you can redistribute it and/or

  modify it under the terms of the GNU Lesser General Public

  License as published by the Free Software Foundation; either

  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public

  License along with this library; if not, write to the Free Software

  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

  Sam Lantinga

  slouken@libsdl.org

*/

#include "SDL_stdinc.h"

#include "SDL_atomic.h"

#include "SDL_timer.h"

/* Don't do the check for Visual Studio 2005, it's safe here */

#ifdef __WIN32__

#include "../core/windows/SDL_windows.h"

#endif

/* This function is where all the magic happens... */

SDL_bool

SDL_AtomicTryLock(SDL_SpinLock *lock)

{

#if defined(_MSC_VER)

    SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));

    return (InterlockedExchange((long*)lock, 1) == 0);

#elif defined(__MACOSX__)

    return OSAtomicCompareAndSwap32Barrier(0, 1, lock);

#elif defined(HAVE_GCC_ATOMICS) || defined(HAVE_GCC_SYNC_LOCK_TEST_AND_SET)

    return (__sync_lock_test_and_set(lock, 1) == 0);

#elif defined(__GNUC__) && defined(__arm__) && defined(__ARM_ARCH_5__)

    int result;

    __asm__ __volatile__ (

        "swp %0, %1, [%2]\n"

        : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");

    return (result == 0);

#elif defined(__GNUC__) && defined(__arm__)

    int result;

    __asm__ __volatile__ (

        "ldrex %0, [%2]\nteq   %0, #0\nstrexeq %0, %1, [%2]"

        : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");

    return (result == 0);

#else

    /* Need CPU instructions for spinlock here! */

    __need_spinlock_implementation__

#endif

}

void

SDL_AtomicLock(SDL_SpinLock *lock)

{

    /* FIXME: Should we have an eventual timeout? */

    while (!SDL_AtomicTryLock(lock)) {

        SDL_Delay(0);

    }

}

void

SDL_AtomicUnlock(SDL_SpinLock *lock)

{

    /* Assuming atomic assignment operation and full memory barrier in lock */

    *lock = 0;

}

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