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Size: 1550
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← Revision 9 as of 2013-10-05 19:37:56 ⇥
Size: 1553
Comment: Corrected description, see SGFunctions page.
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| Use this function see if a semaphore has a positive value and decrement it if it does. | Use this function to see if a semaphore has a positive value and decrement it if it does. |
SDL_SemTryWait
Use this function to see if a semaphore has a positive value and decrement it if it does.
Contents
Syntax
int SDL_SemTryWait(SDL_sem* sem)
Function Parameters
sem |
the semaphore to wait on |
Return Value
Returns 0 if the wait succeeds, SDL_MUTEX_TIMEDOUT if the wait would block, or a negative error code on failure; call SDL_GetError() for more information.
Code Examples
SDL_atomic_t done;
SDL_sem *sem;
SDL_AtomicSet(&done, 0);
sem = SDL_CreateSemaphore(0);
.
.
Thread A:
while (!SDL_AtomicGet(&done)) {
add_data_to_queue();
SDL_SemPost(sem);
}
Thread B:
while (!SDL_AtomicGet(&done)) {
if (SDL_SemTryWait(sem) == 0 && data_available()) {
get_data_from_queue();
}
... do other processing
}
.
.
SDL_AtomicSet(&done, 1);
SDL_SemPost(sem);
wait_for_threads();
SDL_DestroySemaphore(sem);
Remarks
This function checks to see if the semaphore pointed to by sem has a positive value and atomically decrements the semaphore value if it does. If the semaphore doesn't have a positive value, the function immediately returns SDL_MUTEX_TIMEDOUT.
