focal (3) SDL_SemTryWait.3.gz

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