diff options
Diffstat (limited to 'distrib/sdl-1.2.15/src/thread/dc/SDL_syscond.c')
| -rw-r--r-- | distrib/sdl-1.2.15/src/thread/dc/SDL_syscond.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/distrib/sdl-1.2.15/src/thread/dc/SDL_syscond.c b/distrib/sdl-1.2.15/src/thread/dc/SDL_syscond.c new file mode 100644 index 0000000..f6e7223 --- /dev/null +++ b/distrib/sdl-1.2.15/src/thread/dc/SDL_syscond.c @@ -0,0 +1,215 @@ +/* + SDL - Simple DirectMedia Layer + Copyright (C) 1997-2012 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_config.h" + +/* An implementation of condition variables using semaphores and mutexes */ +/* + This implementation borrows heavily from the BeOS condition variable + implementation, written by Christopher Tate and Owen Smith. Thanks! + */ + +#include "SDL_thread.h" + +struct SDL_cond +{ + SDL_mutex *lock; + int waiting; + int signals; + SDL_sem *wait_sem; + SDL_sem *wait_done; +}; + +/* Create a condition variable */ +SDL_cond * SDL_CreateCond(void) +{ + SDL_cond *cond; + + cond = (SDL_cond *) SDL_malloc(sizeof(SDL_cond)); + if ( cond ) { + cond->lock = SDL_CreateMutex(); + cond->wait_sem = SDL_CreateSemaphore(0); + cond->wait_done = SDL_CreateSemaphore(0); + cond->waiting = cond->signals = 0; + if ( ! cond->lock || ! cond->wait_sem || ! cond->wait_done ) { + SDL_DestroyCond(cond); + cond = NULL; + } + } else { + SDL_OutOfMemory(); + } + return(cond); +} + +/* Destroy a condition variable */ +void SDL_DestroyCond(SDL_cond *cond) +{ + if ( cond ) { + if ( cond->wait_sem ) { + SDL_DestroySemaphore(cond->wait_sem); + } + if ( cond->wait_done ) { + SDL_DestroySemaphore(cond->wait_done); + } + if ( cond->lock ) { + SDL_DestroyMutex(cond->lock); + } + SDL_free(cond); + } +} + +/* Restart one of the threads that are waiting on the condition variable */ +int SDL_CondSignal(SDL_cond *cond) +{ + if ( ! cond ) { + SDL_SetError("Passed a NULL condition variable"); + return -1; + } + + /* If there are waiting threads not already signalled, then + signal the condition and wait for the thread to respond. + */ + SDL_LockMutex(cond->lock); + if ( cond->waiting > cond->signals ) { + ++cond->signals; + SDL_SemPost(cond->wait_sem); + SDL_UnlockMutex(cond->lock); + SDL_SemWait(cond->wait_done); + } else { + SDL_UnlockMutex(cond->lock); + } + + return 0; +} + +/* Restart all threads that are waiting on the condition variable */ +int SDL_CondBroadcast(SDL_cond *cond) +{ + if ( ! cond ) { + SDL_SetError("Passed a NULL condition variable"); + return -1; + } + + /* If there are waiting threads not already signalled, then + signal the condition and wait for the thread to respond. + */ + SDL_LockMutex(cond->lock); + if ( cond->waiting > cond->signals ) { + int i, num_waiting; + + num_waiting = (cond->waiting - cond->signals); + cond->signals = cond->waiting; + for ( i=0; i<num_waiting; ++i ) { + SDL_SemPost(cond->wait_sem); + } + /* Now all released threads are blocked here, waiting for us. + Collect them all (and win fabulous prizes!) :-) + */ + SDL_UnlockMutex(cond->lock); + for ( i=0; i<num_waiting; ++i ) { + SDL_SemWait(cond->wait_done); + } + } else { + SDL_UnlockMutex(cond->lock); + } + + return 0; +} + +/* Wait on the condition variable for at most 'ms' milliseconds. + The mutex must be locked before entering this function! + The mutex is unlocked during the wait, and locked again after the wait. + +Typical use: + +Thread A: + SDL_LockMutex(lock); + while ( ! condition ) { + SDL_CondWait(cond); + } + SDL_UnlockMutex(lock); + +Thread B: + SDL_LockMutex(lock); + ... + condition = true; + ... + SDL_UnlockMutex(lock); + */ +int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms) +{ + int retval; + + if ( ! cond ) { + SDL_SetError("Passed a NULL condition variable"); + return -1; + } + + /* Obtain the protection mutex, and increment the number of waiters. + This allows the signal mechanism to only perform a signal if there + are waiting threads. + */ + SDL_LockMutex(cond->lock); + ++cond->waiting; + SDL_UnlockMutex(cond->lock); + + /* Unlock the mutex, as is required by condition variable semantics */ + SDL_UnlockMutex(mutex); + + /* Wait for a signal */ + if ( ms == SDL_MUTEX_MAXWAIT ) { + retval = SDL_SemWait(cond->wait_sem); + } else { + retval = SDL_SemWaitTimeout(cond->wait_sem, ms); + } + + /* Let the signaler know we have completed the wait, otherwise + the signaler can race ahead and get the condition semaphore + if we are stopped between the mutex unlock and semaphore wait, + giving a deadlock. See the following URL for details: + http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html + */ + SDL_LockMutex(cond->lock); + if ( cond->signals > 0 ) { + /* If we timed out, we need to eat a condition signal */ + if ( retval > 0 ) { + SDL_SemWait(cond->wait_sem); + } + /* We always notify the signal thread that we are done */ + SDL_SemPost(cond->wait_done); + + /* Signal handshake complete */ + --cond->signals; + } + --cond->waiting; + SDL_UnlockMutex(cond->lock); + + /* Lock the mutex, as is required by condition variable semantics */ + SDL_LockMutex(mutex); + + return retval; +} + +/* Wait on the condition variable forever */ +int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex) +{ + return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT); +} |