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      1 /*
      2     SDL - Simple DirectMedia Layer
      3     Copyright (C) 1997-2012 Sam Lantinga
      4 
      5     This library is free software; you can redistribute it and/or
      6     modify it under the terms of the GNU Lesser General Public
      7     License as published by the Free Software Foundation; either
      8     version 2.1 of the License, or (at your option) any later version.
      9 
     10     This library is distributed in the hope that it will be useful,
     11     but WITHOUT ANY WARRANTY; without even the implied warranty of
     12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     13     Lesser General Public License for more details.
     14 
     15     You should have received a copy of the GNU Lesser General Public
     16     License along with this library; if not, write to the Free Software
     17     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
     18 
     19     Sam Lantinga
     20     slouken (at) libsdl.org
     21 */
     22 
     23 #ifndef _SDL_mutex_h
     24 #define _SDL_mutex_h
     25 
     26 /** @file SDL_mutex.h
     27  *  Functions to provide thread synchronization primitives
     28  *
     29  *  @note These are independent of the other SDL routines.
     30  */
     31 
     32 #include "SDL_stdinc.h"
     33 #include "SDL_error.h"
     34 
     35 #include "begin_code.h"
     36 /* Set up for C function definitions, even when using C++ */
     37 #ifdef __cplusplus
     38 extern "C" {
     39 #endif
     40 
     41 /** Synchronization functions which can time out return this value
     42  *  if they time out.
     43  */
     44 #define SDL_MUTEX_TIMEDOUT	1
     45 
     46 /** This is the timeout value which corresponds to never time out */
     47 #define SDL_MUTEX_MAXWAIT	(~(Uint32)0)
     48 
     49 
     50 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
     51 /** @name Mutex functions                                        */ /*@{*/
     52 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
     53 
     54 /** The SDL mutex structure, defined in SDL_mutex.c */
     55 struct SDL_mutex;
     56 typedef struct SDL_mutex SDL_mutex;
     57 
     58 /** Create a mutex, initialized unlocked */
     59 extern DECLSPEC SDL_mutex * SDLCALL SDL_CreateMutex(void);
     60 
     61 #define SDL_LockMutex(m)	SDL_mutexP(m)
     62 /** Lock the mutex
     63  *  @return 0, or -1 on error
     64  */
     65 extern DECLSPEC int SDLCALL SDL_mutexP(SDL_mutex *mutex);
     66 
     67 #define SDL_UnlockMutex(m)	SDL_mutexV(m)
     68 /** Unlock the mutex
     69  *  @return 0, or -1 on error
     70  *
     71  *  It is an error to unlock a mutex that has not been locked by
     72  *  the current thread, and doing so results in undefined behavior.
     73  */
     74 extern DECLSPEC int SDLCALL SDL_mutexV(SDL_mutex *mutex);
     75 
     76 /** Destroy a mutex */
     77 extern DECLSPEC void SDLCALL SDL_DestroyMutex(SDL_mutex *mutex);
     78 
     79 /*@}*/
     80 
     81 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
     82 /** @name Semaphore functions                                    */ /*@{*/
     83 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
     84 
     85 /** The SDL semaphore structure, defined in SDL_sem.c */
     86 struct SDL_semaphore;
     87 typedef struct SDL_semaphore SDL_sem;
     88 
     89 /** Create a semaphore, initialized with value, returns NULL on failure. */
     90 extern DECLSPEC SDL_sem * SDLCALL SDL_CreateSemaphore(Uint32 initial_value);
     91 
     92 /** Destroy a semaphore */
     93 extern DECLSPEC void SDLCALL SDL_DestroySemaphore(SDL_sem *sem);
     94 
     95 /**
     96  * This function suspends the calling thread until the semaphore pointed
     97  * to by sem has a positive count. It then atomically decreases the semaphore
     98  * count.
     99  */
    100 extern DECLSPEC int SDLCALL SDL_SemWait(SDL_sem *sem);
    101 
    102 /** Non-blocking variant of SDL_SemWait().
    103  *  @return 0 if the wait succeeds,
    104  *  SDL_MUTEX_TIMEDOUT if the wait would block, and -1 on error.
    105  */
    106 extern DECLSPEC int SDLCALL SDL_SemTryWait(SDL_sem *sem);
    107 
    108 /** Variant of SDL_SemWait() with a timeout in milliseconds, returns 0 if
    109  *  the wait succeeds, SDL_MUTEX_TIMEDOUT if the wait does not succeed in
    110  *  the allotted time, and -1 on error.
    111  *
    112  *  On some platforms this function is implemented by looping with a delay
    113  *  of 1 ms, and so should be avoided if possible.
    114  */
    115 extern DECLSPEC int SDLCALL SDL_SemWaitTimeout(SDL_sem *sem, Uint32 ms);
    116 
    117 /** Atomically increases the semaphore's count (not blocking).
    118  *  @return 0, or -1 on error.
    119  */
    120 extern DECLSPEC int SDLCALL SDL_SemPost(SDL_sem *sem);
    121 
    122 /** Returns the current count of the semaphore */
    123 extern DECLSPEC Uint32 SDLCALL SDL_SemValue(SDL_sem *sem);
    124 
    125 /*@}*/
    126 
    127 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
    128 /** @name Condition_variable_functions                           */ /*@{*/
    129 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
    130 
    131 /*@{*/
    132 /** The SDL condition variable structure, defined in SDL_cond.c */
    133 struct SDL_cond;
    134 typedef struct SDL_cond SDL_cond;
    135 /*@}*/
    136 
    137 /** Create a condition variable */
    138 extern DECLSPEC SDL_cond * SDLCALL SDL_CreateCond(void);
    139 
    140 /** Destroy a condition variable */
    141 extern DECLSPEC void SDLCALL SDL_DestroyCond(SDL_cond *cond);
    142 
    143 /** Restart one of the threads that are waiting on the condition variable,
    144  *  @return 0 or -1 on error.
    145  */
    146 extern DECLSPEC int SDLCALL SDL_CondSignal(SDL_cond *cond);
    147 
    148 /** Restart all threads that are waiting on the condition variable,
    149  *  @return 0 or -1 on error.
    150  */
    151 extern DECLSPEC int SDLCALL SDL_CondBroadcast(SDL_cond *cond);
    152 
    153 /** Wait on the condition variable, unlocking the provided mutex.
    154  *  The mutex must be locked before entering this function!
    155  *  The mutex is re-locked once the condition variable is signaled.
    156  *  @return 0 when it is signaled, or -1 on error.
    157  */
    158 extern DECLSPEC int SDLCALL SDL_CondWait(SDL_cond *cond, SDL_mutex *mut);
    159 
    160 /** Waits for at most 'ms' milliseconds, and returns 0 if the condition
    161  *  variable is signaled, SDL_MUTEX_TIMEDOUT if the condition is not
    162  *  signaled in the allotted time, and -1 on error.
    163  *  On some platforms this function is implemented by looping with a delay
    164  *  of 1 ms, and so should be avoided if possible.
    165  */
    166 extern DECLSPEC int SDLCALL SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms);
    167 
    168 /*@}*/
    169 
    170 /* Ends C function definitions when using C++ */
    171 #ifdef __cplusplus
    172 }
    173 #endif
    174 #include "close_code.h"
    175 
    176 #endif /* _SDL_mutex_h */
    177 
    178