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author | Ryan C. Gordon <icculus@icculus.org> |
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date | Sun, 12 Nov 2006 21:23:57 +0000 |
parents | 355632dca928 |
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<HTML ><HEAD ><TITLE >SDL_CreateSemaphore</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Multi-threaded Programming" HREF="thread.html"><LINK REL="PREVIOUS" TITLE="SDL_mutexV" HREF="sdlmutexv.html"><LINK REL="NEXT" TITLE="SDL_DestroySemaphore" HREF="sdldestroysemaphore.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="sdlmutexv.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdldestroysemaphore.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLCREATESEMAPHORE" ></A >SDL_CreateSemaphore</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN7936" ></A ><H2 >Name</H2 >SDL_CreateSemaphore -- Creates a new semaphore and assigns an initial value to it.</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN7939" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN7940" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h" #include "SDL_thread.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >SDL_sem *<B CLASS="FSFUNC" >SDL_CreateSemaphore</B ></CODE >(Uint32 initial_value);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7946" ></A ><H2 >Description</H2 ><P ><TT CLASS="FUNCTION" >SDL_CreateSemaphore()</TT > creates a new semaphore and initializes it with the value <TT CLASS="PARAMETER" ><I >initial_value</I ></TT >. Each locking operation on the semaphore by <A HREF="sdlsemwait.html" >SDL_SemWait</A >, <A HREF="sdlsemtrywait.html" >SDL_SemTryWait</A > or <A HREF="sdlsemwaittimeout.html" >SDL_SemWaitTimeout</A > will atomically decrement the semaphore value. The locking operation will be blocked if the semaphore value is not positive (greater than zero). Each unlock operation by <A HREF="sdlsempost.html" >SDL_SemPost</A > will atomically increment the semaphore value.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7955" ></A ><H2 >Return Value</H2 ><P >Returns a pointer to an initialized semaphore or <SPAN CLASS="RETURNVALUE" >NULL</SPAN > if there was an error.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7959" ></A ><H2 >Examples</H2 ><P ><PRE CLASS="PROGRAMLISTING" >SDL_sem *my_sem; my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE); if (my_sem == NULL) { return CREATE_SEM_FAILED; }</PRE ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN7963" ></A ><H2 >See Also</H2 ><P ><A HREF="sdldestroysemaphore.html" ><TT CLASS="FUNCTION" >SDL_DestroySemaphore</TT ></A >, <A HREF="sdlsemwait.html" ><TT CLASS="FUNCTION" >SDL_SemWait</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 ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlmutexv.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdldestroysemaphore.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_mutexV</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="thread.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_DestroySemaphore</TD ></TR ></TABLE ></DIV ></BODY ></HTML >