.TH "SDL_SemTryWait" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" 

.SH "NAME"

SDL_SemTryWait \- Attempt to lock a semaphore but don\&'t suspend the thread\&.

.SH "SYNOPSIS"

.PP

\fB#include "SDL\&.h"

#include "SDL_thread\&.h"

.sp

\fBint \fBSDL_SemTryWait\fP\fR(\fBSDL_sem *sem\fR);

.SH "DESCRIPTION"

.PP

\fBSDL_SemTryWait\fP is a non-blocking varient of \fI\fBSDL_SemWait\fP\fR\&. If the value of the semaphore pointed to by \fBsem\fR is positive it will atomically decrement the semaphore value and return 0, otherwise it will return \fBSDL_MUTEX_TIMEOUT\fR instead of suspending the thread\&.

.PP

After \fBSDL_SemTryWait\fP is successful, the semaphore can be released and its count atomically incremented by a successful call to \fISDL_SemPost\fR\&.

.SH "RETURN VALUE"

.PP

Returns \fB0\fR if the semaphore was successfully locked or either \fBSDL_MUTEX_TIMEOUT\fR or \fB-1\fR if the thread would have suspended or there was an error, respectivly\&.

.PP

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

.SH "EXAMPLES"

.PP

.PP

.nf

\f(CWres = SDL_SemTryWait(my_sem);

if (res == SDL_MUTEX_TIMEOUT) {

        return TRY_AGAIN;

}

if (res == -1) {

        return WAIT_ERROR;

}

\&.\&.\&.

SDL_SemPost(my_sem);\fR

.fi

.PP

.SH "SEE ALSO"

.PP

\fI\fBSDL_CreateSemaphore\fP\fR, \fI\fBSDL_DestroySemaphore\fP\fR, \fI\fBSDL_SemWait\fP\fR, \fI\fBSDL_SemWaitTimeout\fP\fR, \fI\fBSDL_SemPost\fP\fR, \fI\fBSDL_SemValue\fP\fR

...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00