NAME¶
SDL_SemTryWait - Attempt to lock a semaphore but don't suspend the thread.
SYNOPSIS¶
#include "SDL.h" #include "SDL_thread.h"
int SDL_SemTryWait(
SDL_sem *sem);
DESCRIPTION¶
SDL_SemTryWait is a non-blocking varient of
SDL_SemWait. If the value of the semaphore pointed to by
sem is positive it will atomically decrement the semaphore value and
return 0, otherwise it will return
SDL_MUTEX_TIMEOUT instead of
suspending the thread.
After
SDL_SemTryWait 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 thread would have suspended or
there was an error, respectivly.
If the semaphore was not successfully locked, the semaphore will be unchanged.
EXAMPLES¶
res = SDL_SemTryWait(my_sem);
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_SemWaitTimeout,
SDL_SemPost,
SDL_SemValue