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SDL_SemTryWait

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