.TH "SDL_SemTryWait" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" +
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.SH "NAME"+
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SDL_SemTryWait\- Attempt to lock a semaphore but don\&'t suspend the thread\&.+
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.SH "SYNOPSIS"+
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.PP+
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\fB#include "SDL\&.h"+
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#include "SDL_thread\&.h"+
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.sp+
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\fBint \fBSDL_SemTryWait\fP\fR(\fBSDL_sem *sem\fR);+
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.SH "DESCRIPTION"+
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.PP+
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\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\&.+
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.PP+
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After \fBSDL_SemTryWait\fP is successful, the semaphore can be released and its count atomically incremented by a successful call to \fISDL_SemPost\fR\&.+
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.SH "RETURN VALUE"+
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.PP+
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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\&.+
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.PP+
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If the semaphore was not successfully locked, the semaphore will be unchanged\&.+
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.SH "EXAMPLES"+
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.PP+
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.PP+
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.nf+
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\f(CWres = SDL_SemTryWait(my_sem);+
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+
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if (res == SDL_MUTEX_TIMEOUT) {+
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        return TRY_AGAIN;+
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}+
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if (res == -1) {+
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        return WAIT_ERROR;+
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}+
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+
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\&.\&.\&.+
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+
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SDL_SemPost(my_sem);\fR+
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.fi+
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.PP+
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.SH "SEE ALSO"+
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.PP+
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\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+
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...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00+
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