252 lines
6.5 KiB
C
252 lines
6.5 KiB
C
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/*
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Simple DirectMedia Layer
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Copyright (C) 1997-2019 Sam Lantinga <slouken@libsdl.org>
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#ifndef SDL_mutex_h_
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#define SDL_mutex_h_
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/**
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* \file SDL_mutex.h
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*
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* Functions to provide thread synchronization primitives.
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*/
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#include "SDL_stdinc.h"
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#include "SDL_error.h"
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#include "begin_code.h"
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/* Set up for C function definitions, even when using C++ */
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* Synchronization functions which can time out return this value
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* if they time out.
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*/
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#define SDL_MUTEX_TIMEDOUT 1
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/**
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* This is the timeout value which corresponds to never time out.
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*/
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#define SDL_MUTEX_MAXWAIT (~(Uint32)0)
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/**
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* \name Mutex functions
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*/
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/* @{ */
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/* The SDL mutex structure, defined in SDL_sysmutex.c */
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struct SDL_mutex;
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typedef struct SDL_mutex SDL_mutex;
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/**
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* Create a mutex, initialized unlocked.
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*/
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extern DECLSPEC SDL_mutex *SDLCALL SDL_CreateMutex(void);
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/**
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* Lock the mutex.
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*
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* \return 0, or -1 on error.
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*/
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#define SDL_mutexP(m) SDL_LockMutex(m)
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extern DECLSPEC int SDLCALL SDL_LockMutex(SDL_mutex * mutex);
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/**
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* Try to lock the mutex
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*
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* \return 0, SDL_MUTEX_TIMEDOUT, or -1 on error
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*/
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extern DECLSPEC int SDLCALL SDL_TryLockMutex(SDL_mutex * mutex);
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/**
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* Unlock the mutex.
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*
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* \return 0, or -1 on error.
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*
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* \warning It is an error to unlock a mutex that has not been locked by
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* the current thread, and doing so results in undefined behavior.
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*/
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#define SDL_mutexV(m) SDL_UnlockMutex(m)
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extern DECLSPEC int SDLCALL SDL_UnlockMutex(SDL_mutex * mutex);
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/**
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* Destroy a mutex.
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*/
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extern DECLSPEC void SDLCALL SDL_DestroyMutex(SDL_mutex * mutex);
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/* @} *//* Mutex functions */
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/**
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* \name Semaphore functions
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*/
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/* @{ */
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/* The SDL semaphore structure, defined in SDL_syssem.c */
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struct SDL_semaphore;
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typedef struct SDL_semaphore SDL_sem;
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/**
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* Create a semaphore, initialized with value, returns NULL on failure.
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*/
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extern DECLSPEC SDL_sem *SDLCALL SDL_CreateSemaphore(Uint32 initial_value);
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/**
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* Destroy a semaphore.
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*/
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extern DECLSPEC void SDLCALL SDL_DestroySemaphore(SDL_sem * sem);
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/**
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* This function suspends the calling thread until the semaphore pointed
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* to by \c sem has a positive count. It then atomically decreases the
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* semaphore count.
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*/
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extern DECLSPEC int SDLCALL SDL_SemWait(SDL_sem * sem);
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/**
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* Non-blocking variant of SDL_SemWait().
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*
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* \return 0 if the wait succeeds, ::SDL_MUTEX_TIMEDOUT if the wait would
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* block, and -1 on error.
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*/
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extern DECLSPEC int SDLCALL SDL_SemTryWait(SDL_sem * sem);
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/**
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* Variant of SDL_SemWait() with a timeout in milliseconds.
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*
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* \return 0 if the wait succeeds, ::SDL_MUTEX_TIMEDOUT if the wait does not
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* succeed in the allotted time, and -1 on error.
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*
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* \warning On some platforms this function is implemented by looping with a
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* delay of 1 ms, and so should be avoided if possible.
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*/
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extern DECLSPEC int SDLCALL SDL_SemWaitTimeout(SDL_sem * sem, Uint32 ms);
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/**
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* Atomically increases the semaphore's count (not blocking).
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*
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* \return 0, or -1 on error.
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*/
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extern DECLSPEC int SDLCALL SDL_SemPost(SDL_sem * sem);
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/**
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* Returns the current count of the semaphore.
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*/
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extern DECLSPEC Uint32 SDLCALL SDL_SemValue(SDL_sem * sem);
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/* @} *//* Semaphore functions */
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/**
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* \name Condition variable functions
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*/
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/* @{ */
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/* The SDL condition variable structure, defined in SDL_syscond.c */
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struct SDL_cond;
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typedef struct SDL_cond SDL_cond;
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/**
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* Create a condition variable.
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*
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* Typical use of condition variables:
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*
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* Thread A:
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* SDL_LockMutex(lock);
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* while ( ! condition ) {
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* SDL_CondWait(cond, lock);
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* }
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* SDL_UnlockMutex(lock);
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*
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* Thread B:
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* SDL_LockMutex(lock);
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* ...
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* condition = true;
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* ...
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* SDL_CondSignal(cond);
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* SDL_UnlockMutex(lock);
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*
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* There is some discussion whether to signal the condition variable
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* with the mutex locked or not. There is some potential performance
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* benefit to unlocking first on some platforms, but there are some
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* potential race conditions depending on how your code is structured.
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*
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* In general it's safer to signal the condition variable while the
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* mutex is locked.
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*/
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extern DECLSPEC SDL_cond *SDLCALL SDL_CreateCond(void);
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/**
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* Destroy a condition variable.
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*/
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extern DECLSPEC void SDLCALL SDL_DestroyCond(SDL_cond * cond);
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/**
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* Restart one of the threads that are waiting on the condition variable.
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*
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* \return 0 or -1 on error.
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*/
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extern DECLSPEC int SDLCALL SDL_CondSignal(SDL_cond * cond);
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/**
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* Restart all threads that are waiting on the condition variable.
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*
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* \return 0 or -1 on error.
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*/
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extern DECLSPEC int SDLCALL SDL_CondBroadcast(SDL_cond * cond);
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/**
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* Wait on the condition variable, unlocking the provided mutex.
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*
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* \warning The mutex must be locked before entering this function!
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*
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* The mutex is re-locked once the condition variable is signaled.
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*
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* \return 0 when it is signaled, or -1 on error.
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*/
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extern DECLSPEC int SDLCALL SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex);
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/**
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* Waits for at most \c ms milliseconds, and returns 0 if the condition
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* variable is signaled, ::SDL_MUTEX_TIMEDOUT if the condition is not
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* signaled in the allotted time, and -1 on error.
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*
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* \warning On some platforms this function is implemented by looping with a
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* delay of 1 ms, and so should be avoided if possible.
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*/
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extern DECLSPEC int SDLCALL SDL_CondWaitTimeout(SDL_cond * cond,
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SDL_mutex * mutex, Uint32 ms);
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/* @} *//* Condition variable functions */
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/* Ends C function definitions when using C++ */
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#ifdef __cplusplus
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}
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#endif
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#include "close_code.h"
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#endif /* SDL_mutex_h_ */
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/* vi: set ts=4 sw=4 expandtab: */
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