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| ><H1 |
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| NAME="SDLSEMWAIT" |
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| >SDL_SemWait</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN8023" |
| ></A |
| ><H2 |
| >Name</H2 |
| >SDL_SemWait -- Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN8026" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><A |
| NAME="AEN8027" |
| ></A |
| ><P |
| ></P |
| ><PRE |
| CLASS="FUNCSYNOPSISINFO" |
| >#include "SDL.h" |
| #include "SDL_thread.h"</PRE |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >int <B |
| CLASS="FSFUNC" |
| >SDL_SemWait</B |
| ></CODE |
| >(SDL_sem *sem);</CODE |
| ></P |
| ><P |
| ></P |
| ></DIV |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8033" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemWait()</TT |
| > suspends the calling thread until either |
| the semaphore pointed to by <TT |
| CLASS="PARAMETER" |
| ><I |
| >sem</I |
| ></TT |
| > has a positive value, |
| the call is interrupted by a signal or error. If the call is successful it |
| will atomically decrement the semaphore value.</P |
| ><P |
| >After <TT |
| CLASS="FUNCTION" |
| >SDL_SemWait()</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="AEN8041" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >Returns <SPAN |
| CLASS="RETURNVALUE" |
| >0</SPAN |
| > if successful or |
| <SPAN |
| CLASS="RETURNVALUE" |
| >-1</SPAN |
| > if there was an error (leaving the semaphore unchanged).</P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8046" |
| ></A |
| ><H2 |
| >Examples</H2 |
| ><P |
| ><PRE |
| CLASS="PROGRAMLISTING" |
| >if (SDL_SemWait(my_sem) == -1) { |
| return WAIT_FAILED; |
| } |
| |
| ... |
| |
| SDL_SemPost(my_sem);</PRE |
| ></P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8050" |
| ></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="sdlsemtrywait.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_SemTryWait</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 |
| ></P |
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