472 lines
14 KiB
C
472 lines
14 KiB
C
/*
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Simple DirectMedia Layer
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Copyright (C) 1997-2022 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 new mutex.
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*
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* All newly-created mutexes begin in the _unlocked_ state.
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*
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* Calls to SDL_LockMutex() will not return while the mutex is locked by
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* another thread. See SDL_TryLockMutex() to attempt to lock without blocking.
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*
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* SDL mutexes are reentrant.
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*
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* \returns the initialized and unlocked mutex or NULL on failure; call
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* SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_DestroyMutex
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* \sa SDL_LockMutex
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* \sa SDL_TryLockMutex
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* \sa SDL_UnlockMutex
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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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* This will block until the mutex is available, which is to say it is in the
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* unlocked state and the OS has chosen the caller as the next thread to lock
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* it. Of all threads waiting to lock the mutex, only one may do so at a time.
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*
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* It is legal for the owning thread to lock an already-locked mutex. It must
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* unlock it the same number of times before it is actually made available for
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* other threads in the system (this is known as a "recursive mutex").
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*
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* \param mutex the mutex to lock
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* \return 0, or -1 on error.
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*
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* \since This function is available since SDL 2.0.0.
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*/
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extern DECLSPEC int SDLCALL SDL_LockMutex(SDL_mutex * mutex);
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#define SDL_mutexP(m) SDL_LockMutex(m)
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/**
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* Try to lock a mutex without blocking.
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*
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* This works just like SDL_LockMutex(), but if the mutex is not available,
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* this function returns `SDL_MUTEX_TIMEOUT` immediately.
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*
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* This technique is useful if you need exclusive access to a resource but
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* don't want to wait for it, and will return to it to try again later.
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*
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* \param mutex the mutex to try to lock
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* \returns 0, `SDL_MUTEX_TIMEDOUT`, or -1 on error; call SDL_GetError() for
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* more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateMutex
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* \sa SDL_DestroyMutex
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* \sa SDL_LockMutex
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* \sa SDL_UnlockMutex
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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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* It is legal for the owning thread to lock an already-locked mutex. It must
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* unlock it the same number of times before it is actually made available for
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* other threads in the system (this is known as a "recursive mutex").
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*
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* It is an error to unlock a mutex that has not been locked by the current
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* thread, and doing so results in undefined behavior.
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*
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* It is also an error to unlock a mutex that isn't locked at all.
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*
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* \param mutex the mutex to unlock.
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* \returns 0, or -1 on error.
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*
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* \since This function is available since SDL 2.0.0.
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*/
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extern DECLSPEC int SDLCALL SDL_UnlockMutex(SDL_mutex * mutex);
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#define SDL_mutexV(m) SDL_UnlockMutex(m)
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/**
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* Destroy a mutex created with SDL_CreateMutex().
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*
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* This function must be called on any mutex that is no longer needed. Failure
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* to destroy a mutex will result in a system memory or resource leak. While
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* it is safe to destroy a mutex that is _unlocked_, it is not safe to attempt
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* to destroy a locked mutex, and may result in undefined behavior depending
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* on the platform.
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*
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* \param mutex the mutex to destroy
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateMutex
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* \sa SDL_LockMutex
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* \sa SDL_TryLockMutex
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* \sa SDL_UnlockMutex
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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.
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*
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* This function creates a new semaphore and initializes it with the value
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* `initial_value`. Each wait operation on the semaphore will atomically
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* decrement the semaphore value and potentially block if the semaphore value
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* is 0. Each post operation will atomically increment the semaphore value and
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* wake waiting threads and allow them to retry the wait operation.
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*
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* \param initial_value the starting value of the semaphore
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* \returns a new semaphore or NULL on failure; call SDL_GetError() for more
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* information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_DestroySemaphore
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* \sa SDL_SemPost
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* \sa SDL_SemTryWait
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* \sa SDL_SemValue
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* \sa SDL_SemWait
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* \sa SDL_SemWaitTimeout
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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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* It is not safe to destroy a semaphore if there are threads currently
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* waiting on it.
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*
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* \param sem the semaphore to destroy
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateSemaphore
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* \sa SDL_SemPost
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* \sa SDL_SemTryWait
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* \sa SDL_SemValue
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* \sa SDL_SemWait
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* \sa SDL_SemWaitTimeout
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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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* Wait until a semaphore has a positive value and then decrements it.
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*
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* This function suspends the calling thread until either the semaphore
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* pointed to by `sem` has a positive value or the call is interrupted by a
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* signal or error. If the call is successful it will atomically decrement the
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* semaphore value.
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*
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* This function is the equivalent of calling SDL_SemWaitTimeout() with a time
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* length of `SDL_MUTEX_MAXWAIT`.
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*
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* \param sem the semaphore wait on
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* \returns 0 on success or a negative error code on failure; call
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* SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateSemaphore
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* \sa SDL_DestroySemaphore
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* \sa SDL_SemPost
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* \sa SDL_SemTryWait
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* \sa SDL_SemValue
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* \sa SDL_SemWait
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* \sa SDL_SemWaitTimeout
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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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* See if a semaphore has a positive value and decrement it if it does.
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*
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* This function checks to see if the semaphore pointed to by `sem` has a
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* positive value and atomically decrements the semaphore value if it does. If
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* the semaphore doesn't have a positive value, the function immediately
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* returns SDL_MUTEX_TIMEDOUT.
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*
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* \param sem the semaphore to wait on
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* \returns 0 if the wait succeeds, `SDL_MUTEX_TIMEDOUT` if the wait would
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* block, or a negative error code on failure; call SDL_GetError()
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* for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateSemaphore
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* \sa SDL_DestroySemaphore
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* \sa SDL_SemPost
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* \sa SDL_SemValue
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* \sa SDL_SemWait
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* \sa SDL_SemWaitTimeout
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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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* Wait until a semaphore has a positive value and then decrements it.
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*
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* This function suspends the calling thread until either the semaphore
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* pointed to by `sem` has a positive value, the call is interrupted by a
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* signal or error, or the specified time has elapsed. If the call is
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* successful it will atomically decrement the semaphore value.
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*
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* \param sem the semaphore to wait on
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* \param ms the length of the timeout, in milliseconds
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* \returns 0 if the wait succeeds, `SDL_MUTEX_TIMEDOUT` if the wait does not
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* succeed in the allotted time, or a negative error code on failure;
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* call SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateSemaphore
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* \sa SDL_DestroySemaphore
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* \sa SDL_SemPost
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* \sa SDL_SemTryWait
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* \sa SDL_SemValue
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* \sa SDL_SemWait
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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 increment a semaphore's value and wake waiting threads.
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*
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* \param sem the semaphore to increment
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* \returns 0 on success or a negative error code on failure; call
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* SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateSemaphore
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* \sa SDL_DestroySemaphore
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* \sa SDL_SemTryWait
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* \sa SDL_SemValue
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* \sa SDL_SemWait
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* \sa SDL_SemWaitTimeout
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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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* Get the current value of a semaphore.
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*
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* \param sem the semaphore to query
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* \returns the current value of the semaphore.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CreateSemaphore
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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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* \returns a new condition variable or NULL on failure; call SDL_GetError()
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* for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CondBroadcast
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* \sa SDL_CondSignal
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* \sa SDL_CondWait
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* \sa SDL_CondWaitTimeout
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* \sa SDL_DestroyCond
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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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* \param cond the condition variable to destroy
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CondBroadcast
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* \sa SDL_CondSignal
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* \sa SDL_CondWait
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* \sa SDL_CondWaitTimeout
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* \sa SDL_CreateCond
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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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* \param cond the condition variable to signal
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* \returns 0 on success or a negative error code on failure; call
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* SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CondBroadcast
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* \sa SDL_CondWait
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* \sa SDL_CondWaitTimeout
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* \sa SDL_CreateCond
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* \sa SDL_DestroyCond
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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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* \param cond the condition variable to signal
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* \returns 0 on success or a negative error code on failure; call
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* SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CondSignal
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* \sa SDL_CondWait
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* \sa SDL_CondWaitTimeout
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* \sa SDL_CreateCond
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* \sa SDL_DestroyCond
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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 until a condition variable is signaled.
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*
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* This function unlocks the specified `mutex` and waits for another thread to
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* call SDL_CondSignal() or SDL_CondBroadcast() on the condition variable
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* `cond`. Once the condition variable is signaled, the mutex is re-locked and
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* the function returns.
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*
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* The mutex must be locked before calling this function.
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*
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* This function is the equivalent of calling SDL_CondWaitTimeout() with a
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* time length of `SDL_MUTEX_MAXWAIT`.
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*
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* \param cond the condition variable to wait on
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* \param mutex the mutex used to coordinate thread access
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* \returns 0 when it is signaled or a negative error code on failure; call
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* SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CondBroadcast
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* \sa SDL_CondSignal
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* \sa SDL_CondWaitTimeout
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* \sa SDL_CreateCond
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* \sa SDL_DestroyCond
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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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* Wait until a condition variable is signaled or a certain time has passed.
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*
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* This function unlocks the specified `mutex` and waits for another thread to
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* call SDL_CondSignal() or SDL_CondBroadcast() on the condition variable
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* `cond`, or for the specified time to elapse. Once the condition variable is
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* signaled or the time elapsed, the mutex is re-locked and the function
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* returns.
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*
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* The mutex must be locked before calling this function.
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*
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* \param cond the condition variable to wait on
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* \param mutex the mutex used to coordinate thread access
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* \param ms the maximum time to wait, in milliseconds, or `SDL_MUTEX_MAXWAIT`
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* to wait indefinitely
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* \returns 0 if the condition variable is signaled, `SDL_MUTEX_TIMEDOUT` if
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* the condition is not signaled in the allotted time, or a negative
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* error code on failure; call SDL_GetError() for more information.
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*
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* \since This function is available since SDL 2.0.0.
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*
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* \sa SDL_CondBroadcast
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* \sa SDL_CondSignal
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* \sa SDL_CondWait
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* \sa SDL_CreateCond
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* \sa SDL_DestroyCond
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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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