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SDL_SemWaitTimeout

Wait until a semaphore has a positive value and then decrements it.

Syntax

int SDL_SemWaitTimeout(SDL_sem * sem, Uint32 ms);

Function Parameters

sem

the semaphore to wait on

ms

the length of the timeout, in milliseconds

Return Value

Returns 0 if the wait succeeds, SDL_MUTEX_TIMEDOUT if the wait does not succeed in the allotted time, or a negative error code on failure; call SDL_GetError() for more information.

Remarks

This function suspends the calling thread until either the semaphore pointed to by sem has a positive value, the call is interrupted by a signal or error, or the specified time has elapsed. If the call is successful it will atomically decrement the semaphore value.

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:
    const Uint32 timeout = 1000; /* wake up every second */

    while (!SDL_AtomicGet(&done)) {
        if (SDL_SemWaitTimeout(sem, timeout) == 0 && data_available()) {
            get_data_from_queue();
        }
        ... do other processing
    }
.
.
SDL_AtomicSet(&done, 1);
SDL_SemPost(sem);
wait_for_threads();
SDL_DestroySemaphore(sem);
SDL_CreateSemaphore
SDL_DestroySemaphore
SDL_SemPost
SDL_SemTryWait
SDL_SemValue
SDL_SemWait

CategoryAPI, CategoryMutex


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