summaryrefslogtreecommitdiffstatshomepage
path: root/3rdparty/SDL2/src/thread/generic/SDL_syscond.c
diff options
context:
space:
mode:
Diffstat (limited to '3rdparty/SDL2/src/thread/generic/SDL_syscond.c')
-rw-r--r--3rdparty/SDL2/src/thread/generic/SDL_syscond.c220
1 files changed, 220 insertions, 0 deletions
diff --git a/3rdparty/SDL2/src/thread/generic/SDL_syscond.c b/3rdparty/SDL2/src/thread/generic/SDL_syscond.c
new file mode 100644
index 00000000000..e2ccd88ef1a
--- /dev/null
+++ b/3rdparty/SDL2/src/thread/generic/SDL_syscond.c
@@ -0,0 +1,220 @@
+/*
+ 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.
+*/
+#include "../../SDL_internal.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) {
+ 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;
+}
+
+/* Restart all threads that are waiting on the condition variable */
+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;
+}
+
+/* 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, lock);
+ }
+ SDL_UnlockMutex(lock);
+
+Thread B:
+ SDL_LockMutex(lock);
+ ...
+ condition = true;
+ ...
+ SDL_CondSignal(cond);
+ SDL_UnlockMutex(lock);
+ */
+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;
+}
+
+/* Wait on the condition variable forever */
+int
+SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex)
+{
+ return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT);
+}
+
+/* vi: set ts=4 sw=4 expandtab: */