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

     2 .SH "NAME"

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

     4 .SH "SYNOPSIS"

     5 .PP

     6 \fB#include "SDL\&.h"

     7 #include "SDL_thread\&.h"

     8 .sp

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

    10 .SH "DESCRIPTION"

    11 .PP

    12 \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\&.

    13 .PP

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

    15 .SH "RETURN VALUE"

    16 .PP

    17 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\&.

    18 .PP

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

    20 .SH "EXAMPLES"

    21 .PP

    22 .PP

    23 .nf

    24 \f(CWres = SDL_SemTryWait(my_sem);

    25 

    26 if (res == SDL_MUTEX_TIMEOUT) {

    27         return TRY_AGAIN;

    28 }

    29 if (res == -1) {

    30         return WAIT_ERROR;

    31 }

    32 

    33 \&.\&.\&.

    34 

    35 SDL_SemPost(my_sem);\fR

    36 .fi

    37 .PP

    38 .SH "SEE ALSO"

    39 .PP

    40 \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

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