/*
    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
*/

#ifndef _SDL_mutex_h
#define _SDL_mutex_h

/**
 *  \file SDL_mutex.h
 *  
 *  Functions to provide thread synchronization primitives.
 */

#include "SDL_stdinc.h"
#include "SDL_error.h"

#include "begin_code.h"
/* Set up for C function definitions, even when using C++ */
#ifdef __cplusplus
/* *INDENT-OFF* */
extern "C" {
/* *INDENT-ON* */
#endif

/**
 *  Synchronization functions which can time out return this value
 *  if they time out.
 */
#define SDL_MUTEX_TIMEDOUT	1

/**
 *  This is the timeout value which corresponds to never time out.
 */
#define SDL_MUTEX_MAXWAIT	(~(Uint32)0)


/**
 *  \name Mutex functions
 */
/*@{*/

/* The SDL mutex structure, defined in SDL_mutex.c */
struct SDL_mutex;
typedef struct SDL_mutex SDL_mutex;

/**
 *  Create a mutex, initialized unlocked.
 */
extern DECLSPEC SDL_mutex *SDLCALL SDL_CreateMutex(void);

/**
 *  Lock the mutex.
 *  
 *  \return 0, or -1 on error.
 */
#define SDL_LockMutex(m)	SDL_mutexP(m)
extern DECLSPEC int SDLCALL SDL_mutexP(SDL_mutex * mutex);

/**
 *  Unlock the mutex.
 *  
 *  \return 0, or -1 on error.
 *  
 *  \warning It is an error to unlock a mutex that has not been locked by
 *           the current thread, and doing so results in undefined behavior.
 */
#define SDL_UnlockMutex(m)	SDL_mutexV(m)
extern DECLSPEC int SDLCALL SDL_mutexV(SDL_mutex * mutex);

/** 
 *  Destroy a mutex.
 */
extern DECLSPEC void SDLCALL SDL_DestroyMutex(SDL_mutex * mutex);

/*@}*//*Mutex functions*/


/**
 *  \name Semaphore functions
 */
/*@{*/

/* The SDL semaphore structure, defined in SDL_sem.c */
struct SDL_semaphore;
typedef struct SDL_semaphore SDL_sem;

/**
 *  Create a semaphore, initialized with value, returns NULL on failure.
 */
extern DECLSPEC SDL_sem *SDLCALL SDL_CreateSemaphore(Uint32 initial_value);

/**
 *  Destroy a semaphore.
 */
extern DECLSPEC void SDLCALL SDL_DestroySemaphore(SDL_sem * sem);

/**
 *  This function suspends the calling thread until the semaphore pointed 
 *  to by \c sem has a positive count. It then atomically decreases the 
 *  semaphore count.
 */
extern DECLSPEC int SDLCALL SDL_SemWait(SDL_sem * sem);

/**
 *  Non-blocking variant of SDL_SemWait().
 *  
 *  \return 0 if the wait succeeds, ::SDL_MUTEX_TIMEDOUT if the wait would 
 *          block, and -1 on error.
 */
extern DECLSPEC int SDLCALL SDL_SemTryWait(SDL_sem * sem);

/**
 *  Variant of SDL_SemWait() with a timeout in milliseconds.
 *  
 *  \return 0 if the wait succeeds, ::SDL_MUTEX_TIMEDOUT if the wait does not 
 *          succeed in the allotted time, and -1 on error.
 *  
 *  \warning On some platforms this function is implemented by looping with a 
 *           delay of 1 ms, and so should be avoided if possible.
 */
extern DECLSPEC int SDLCALL SDL_SemWaitTimeout(SDL_sem * sem, Uint32 ms);

/**
 *  Atomically increases the semaphore's count (not blocking).
 *  
 *  \return 0, or -1 on error.
 */
extern DECLSPEC int SDLCALL SDL_SemPost(SDL_sem * sem);

/**
 *  Returns the current count of the semaphore.
 */
extern DECLSPEC Uint32 SDLCALL SDL_SemValue(SDL_sem * sem);

/*@}*//*Semaphore functions*/


/**
 *  \name Condition variable functions
 */
/*@{*/

/* The SDL condition variable structure, defined in SDL_cond.c */
struct SDL_cond;
typedef struct SDL_cond SDL_cond;

/**
 *  Create a condition variable.
 *
 *  Typical use of condition variables:
 *
 *  Thread A:
 *    SDL_LockMutex(lock);
 *    while ( ! condition ) {
 *        SDL_CondWait(cond, lock);
 *    }
 *    SDL_UnlockMutex(lock);
 *
 *  Thread B:
 *    SDL_LockMutex(lock);
 *    ...
 *    condition = true;
 *    ...
 *    SDL_CondSignal(cond);
 *    SDL_UnlockMutex(lock);
 *
 *  There is some discussion whether to signal the condition variable
 *  with the mutex locked or not.  There is some potential performance
 *  benefit to unlocking first on some platforms, but there are some
 *  potential race conditions depending on how your code is structured.
 *
 *  In general it's safer to signal the condition variable while the
 *  mutex is locked.
 */
extern DECLSPEC SDL_cond *SDLCALL SDL_CreateCond(void);

/**
 *  Destroy a condition variable.
 */
extern DECLSPEC void SDLCALL SDL_DestroyCond(SDL_cond * cond);

/**
 *  Restart one of the threads that are waiting on the condition variable.
 *  
 *  \return 0 or -1 on error.
 */
extern DECLSPEC int SDLCALL SDL_CondSignal(SDL_cond * cond);

/**
 *  Restart all threads that are waiting on the condition variable.
 *
 *  \return 0 or -1 on error.
 */
extern DECLSPEC int SDLCALL SDL_CondBroadcast(SDL_cond * cond);

/**
 *  Wait on the condition variable, unlocking the provided mutex.
 *  
 *  \warning The mutex must be locked before entering this function!
 *  
 *  The mutex is re-locked once the condition variable is signaled.
 *  
 *  \return 0 when it is signaled, or -1 on error.
 */
extern DECLSPEC int SDLCALL SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex);

/**
 *  Waits for at most \c ms milliseconds, and returns 0 if the condition
 *  variable is signaled, ::SDL_MUTEX_TIMEDOUT if the condition is not
 *  signaled in the allotted time, and -1 on error.
 *
 *  \warning On some platforms this function is implemented by looping with a 
 *           delay of 1 ms, and so should be avoided if possible.
 */
extern DECLSPEC int SDLCALL SDL_CondWaitTimeout(SDL_cond * cond,
                                                SDL_mutex * mutex, Uint32 ms);

/*@}*//*Condition variable functions*/


/* Ends C function definitions when using C++ */
#ifdef __cplusplus
/* *INDENT-OFF* */
}
/* *INDENT-ON* */
#endif
#include "close_code.h"

#endif /* _SDL_mutex_h */

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