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| NAME="SDLSEMTRYWAIT" |
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| >SDL_SemTryWait</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN8069" |
| ></A |
| ><H2 |
| >Name</H2 |
| >SDL_SemTryWait -- Attempt to lock a semaphore but don't suspend the thread.</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN8072" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><A |
| NAME="AEN8073" |
| ></A |
| ><P |
| ></P |
| ><PRE |
| CLASS="FUNCSYNOPSISINFO" |
| >#include "SDL.h" |
| #include "SDL_thread.h"</PRE |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int <B |
| CLASS="FSFUNC" |
| >SDL_SemTryWait</B |
| ></CODE |
| >(SDL_sem *sem);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8079" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemTryWait</TT |
| > is a non-blocking varient of |
| <A |
| HREF="sdlsemwait.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemWait</TT |
| ></A |
| >. If the value of the semaphore |
| pointed to by <TT |
| CLASS="PARAMETER" |
| ><I |
| >sem</I |
| ></TT |
| > is positive it will atomically |
| decrement the semaphore value and return 0, otherwise it will return |
| <SPAN |
| CLASS="RETURNVALUE" |
| >SDL_MUTEX_TIMEDOUT</SPAN |
| > instead of suspending the thread.</P |
| ><P |
| >After <TT |
| CLASS="FUNCTION" |
| >SDL_SemTryWait</TT |
| > is successful, the semaphore |
| can be released and its count atomically incremented by a successful call to |
| <A |
| HREF="sdlsempost.html" |
| >SDL_SemPost</A |
| >.</P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8090" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >Returns <SPAN |
| CLASS="RETURNVALUE" |
| >0</SPAN |
| > if the semaphore was successfully locked or |
| either <SPAN |
| CLASS="RETURNVALUE" |
| >SDL_MUTEX_TIMEDOUT</SPAN |
| > or <SPAN |
| CLASS="RETURNVALUE" |
| >-1</SPAN |
| > |
| if the thread would have suspended or there was an error, respectivly.</P |
| ><P |
| >If the semaphore was not successfully locked, the semaphore will be unchanged.</P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8097" |
| ></A |
| ><H2 |
| >Examples</H2 |
| ><P |
| ><PRE |
| CLASS="PROGRAMLISTING" |
| >res = SDL_SemTryWait(my_sem); |
| |
| if (res == SDL_MUTEX_TIMEDOUT) { |
| return TRY_AGAIN; |
| } |
| if (res == -1) { |
| return WAIT_ERROR; |
| } |
| |
| ... |
| |
| SDL_SemPost(my_sem);</PRE |
| ></P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8101" |
| ></A |
| ><H2 |
| >See Also</H2 |
| ><P |
| ><A |
| HREF="sdlcreatesemaphore.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_CreateSemaphore</TT |
| ></A |
| >, |
| <A |
| HREF="sdldestroysemaphore.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_DestroySemaphore</TT |
| ></A |
| >, |
| <A |
| HREF="sdlsemwait.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemWait</TT |
| ></A |
| >, |
| <A |
| HREF="sdlsemwaittimeout.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemWaitTimeout</TT |
| ></A |
| >, |
| <A |
| HREF="sdlsempost.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemPost</TT |
| ></A |
| >, |
| <A |
| HREF="sdlsemvalue.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemValue</TT |
| ></A |
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