/*
- Simple DirectMedia Layer
- Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
-
- This software is provided 'as-is', without any express or implied
- warranty. In no event will the authors be held liable for any damages
- arising from the use of this software.
-
- Permission is granted to anyone to use this software for any purpose,
- including commercial applications, and to alter it and redistribute it
- freely, subject to the following restrictions:
-
- 1. The origin of this software must not be misrepresented; you must not
- claim that you wrote the original software. If you use this software
- in a product, an acknowledgment in the product documentation would be
- appreciated but is not required.
- 2. Altered source versions must be plainly marked as such, and must not be
- misrepresented as being the original software.
- 3. This notice may not be removed or altered from any source distribution.
+ 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_internal.h"
+#include "SDL_config.h"
/* An implementation of condition variables using semaphores and mutexes */
/*
struct SDL_cond
{
- SDL_mutex *lock;
- int waiting;
- int signals;
- SDL_sem *wait_sem;
- SDL_sem *wait_done;
+ 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 * 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);
+ 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)
+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);
- }
+ 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)
+int SDL_CondSignal(SDL_cond *cond)
{
- if (!cond) {
- return SDL_SetError("Passed a NULL condition variable");
- }
-
- /* 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;
+ 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)
+int SDL_CondBroadcast(SDL_cond *cond)
{
- if (!cond) {
- return SDL_SetError("Passed a NULL condition variable");
- }
-
- /* 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;
+ 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.
Typical use:
Thread A:
- SDL_LockMutex(lock);
- while ( ! condition ) {
- SDL_CondWait(cond, lock);
- }
- SDL_UnlockMutex(lock);
+ SDL_LockMutex(lock);
+ while ( ! condition ) {
+ SDL_CondWait(cond);
+ }
+ SDL_UnlockMutex(lock);
Thread B:
- SDL_LockMutex(lock);
- ...
- condition = true;
- ...
- SDL_CondSignal(cond);
- SDL_UnlockMutex(lock);
+ SDL_LockMutex(lock);
+ ...
+ condition = true;
+ ...
+ SDL_UnlockMutex(lock);
*/
-int
-SDL_CondWaitTimeout(SDL_cond * cond, SDL_mutex * mutex, Uint32 ms)
+int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms)
{
- int retval;
-
- if (!cond) {
- return SDL_SetError("Passed a NULL condition variable");
- }
-
- /* 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://web.archive.org/web/20010914175514/http://www-classic.be.com/aboutbe/benewsletter/volume_III/Issue40.html#Workshop
- */
- 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;
+ 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)
+int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex)
{
- return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT);
+ return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT);
}
-
-/* vi: set ts=4 sw=4 expandtab: */
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