SDL_syscond.c
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/*
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"
#if SDL_THREAD_PSP
/* 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://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);
}
#endif /* SDL_THREAD_PSP */
/* vi: set ts=4 sw=4 expandtab: */
SDL_LockMutex
#define SDL_LockMutex
Definition: SDL_dynapi_overrides.h:266
Uint32
uint32_t Uint32
An unsigned 32-bit integer type.
Definition: SDL_stdinc.h:155
SDL_CondWait
int SDL_CondWait(SDL_cond *cond, SDL_mutex *mutex)
Definition: SDL_syscond.c:215
SDL_CreateSemaphore
#define SDL_CreateSemaphore
Definition: SDL_dynapi_overrides.h:270
SDL_cond::lock
SDL_mutex * lock
Definition: SDL_syscond.c:33
SDL_CreateMutex
#define SDL_CreateMutex
Definition: SDL_dynapi_overrides.h:265
SDL_cond::waiting
int waiting
Definition: SDL_syscond.c:34
mutex
static SDL_mutex * mutex
Definition: testlock.c:23
SDL_cond
Definition: SDL_syscond.c:31
SDL_thread.h
SDL_SemPost
#define SDL_SemPost
Definition: SDL_dynapi_overrides.h:275
SDL_mutex
Definition: SDL_sysmutex.c:29
SDL_CreateCond
SDL_cond * SDL_CreateCond(void)
Definition: SDL_syscond.c:42
retval
SDL_bool retval
Definition: testgamecontroller.c:65
SDL_SemWaitTimeout
#define SDL_SemWaitTimeout
Definition: SDL_dynapi_overrides.h:274
SDL_MUTEX_MAXWAIT
#define SDL_MUTEX_MAXWAIT
Definition: SDL_mutex.h:49
SDL_free
void SDL_free(void *mem)
SDL_cond::cond
pthread_cond_t cond
Definition: SDL_syscond.c:34
SDL_cond::signals
int signals
Definition: SDL_syscond.c:35
i
return Display return Display Bool Bool int int int return Display XEvent Bool(*) XPointer return Display return Display Drawable _Xconst char unsigned int unsigned int return Display Pixmap Pixmap XColor XColor unsigned int unsigned int return Display _Xconst char char int char return Display Visual unsigned int int int char unsigned int unsigned int in i)
Definition: SDL_x11sym.h:42
NULL
#define NULL
Definition: begin_code.h:143
SDL_OutOfMemory
#define SDL_OutOfMemory()
Definition: SDL_error.h:52
SDL_CondWaitTimeout
int SDL_CondWaitTimeout(SDL_cond *cond, SDL_mutex *mutex, Uint32 ms)
Definition: SDL_syscond.c:160
SDL_SetError
#define SDL_SetError
Definition: SDL_dynapi_overrides.h:36
SDL_DestroyMutex
#define SDL_DestroyMutex
Definition: SDL_dynapi_overrides.h:269
SDL_cond::wait_done
SDL_sem * wait_done
Definition: SDL_syscond.c:37
SDL_SemWait
#define SDL_SemWait
Definition: SDL_dynapi_overrides.h:272
SDL_DestroySemaphore
#define SDL_DestroySemaphore
Definition: SDL_dynapi_overrides.h:271
SDL_cond::wait_sem
SDL_sem * wait_sem
Definition: SDL_syscond.c:36
SDL_UnlockMutex
#define SDL_UnlockMutex
Definition: SDL_dynapi_overrides.h:268
SDL_malloc
#define SDL_malloc
Definition: SDL_dynapi_overrides.h:380
SDL_CondBroadcast
int SDL_CondBroadcast(SDL_cond *cond)
Definition: SDL_syscond.c:106
SDL_CondSignal
int SDL_CondSignal(SDL_cond *cond)
Definition: SDL_syscond.c:82
SDL_DestroyCond
void SDL_DestroyCond(SDL_cond *cond)
Definition: SDL_syscond.c:64