SDL Library Documentation
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# SDL_SemWaitTimeout

## Name

SDL_SemWaitTimeout -- Lock a semaphore, but only wait up to a specified maximum time.

## Synopsis

    #include "SDL.h"
    #include "SDL_thread.h"

``int SDL_SemWaitTimeout`(SDL_sem *sem, Uint32 timeout);`

## Description

`SDL_SemWaitTimeout()` is a varient of SDL_SemWait with a maximum timeout value. If the value of the semaphore pointed to by `sem` is positive (greater than zero) it will atomically decrement the semaphore value and return 0, otherwise it will wait up to `timeout` milliseconds trying to lock the semaphore. This function is to be avoided if possible since on some platforms it is implemented by polling the semaphore every millisecond in a busy loop.

After `SDL_SemWaitTimeout()` is successful, the semaphore can be released and its count atomically incremented by a successful call to SDL_SemPost.

## Return Value

Returns 0 if the semaphore was successfully locked or either SDL_MUTEX_TIMEOUT or -1 if the timeout period was exceeded or there was an error, respectivly.

If the semaphore was not successfully locked, the semaphore will be unchanged.

## Examples

    res = SDL_SemWaitTimeout(my_sem, WAIT_TIMEOUT_MILLISEC);

    if (res == SDL_MUTEX_TIMEOUT) {
            return TRY_AGAIN;
    }
    if (res == -1) {
            return WAIT_ERROR;
    }

    ...

    SDL_SemPost(my_sem);

## See Also

`SDL_CreateSemaphore`, `SDL_DestroySemaphore`, `SDL_SemWait`, `SDL_SemTryWait`, `SDL_SemPost`, `SDL_SemValue`

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