See if a semaphore has a positive value and decrement it if it does.
Defined in <SDL3/SDL_mutex.h>
| sem | the semaphore to wait on |
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.
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.
This function is available since SDL 3.0.0.
// BEWARE: This code example was migrated from the SDL2 Wiki, by only updating the names.
void add_data_to_queue(void);
void get_data_from_queue(void);
int data_available(void);
void wait_for_threads(void);
SDL_AtomicInt done;
SDL_Semaphore *sem;
SDL_AtomicSet(&done, 0);
sem = SDL_CreateSemaphore(0);
Thread_A:
while (!SDL_AtomicGet(&done)) {
add_data_to_queue();
SDL_PostSemaphore(sem);
}
Thread_B:
while (!SDL_AtomicGet(&done)) {
if (SDL_TryWaitSemaphore(sem) == 0 && data_available()) {
get_data_from_queue();
}
/* do other processing */
}
SDL_AtomicSet(&done, 1);
SDL_PostSemaphore(sem);
wait_for_threads();
SDL_DestroySemaphore(sem);