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<HTML><HEAD><TITLE>SDL_CreateSemaphore</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+"><LINKREL="HOME"TITLE="SDL Library Documentation"HREF="index.html"><LINKREL="UP"TITLE="Multi-threaded Programming"HREF="thread.html"><LINKREL="PREVIOUS"TITLE="SDL_mutexV"HREF="sdlmutexv.html"><LINKREL="NEXT"TITLE="SDL_DestroySemaphore"HREF="sdldestroysemaphore.html"></HEAD><BODYCLASS="REFENTRY"BGCOLOR="#FFF8DC"TEXT="#000000"LINK="#0000ee"VLINK="#551a8b"ALINK="#ff0000"><DIVCLASS="NAVHEADER"><TABLESUMMARY="Header navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">SDL Library Documentation</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><AHREF="sdlmutexv.html"ACCESSKEY="P">Prev</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom"></TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="sdldestroysemaphore.html"ACCESSKEY="N">Next</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><H1><ANAME="SDLCREATESEMAPHORE"></A>SDL_CreateSemaphore</H1><DIVCLASS="REFNAMEDIV"><ANAME="AEN7936"></A><H2>Name</H2>SDL_CreateSemaphore -- Creates a new semaphore and assigns an initial value to it.</DIV><DIVCLASS="REFSYNOPSISDIV"><ANAME="AEN7939"></A><H2>Synopsis</H2><DIVCLASS="FUNCSYNOPSIS"><ANAME="AEN7940"></A><P></P><PRECLASS="FUNCSYNOPSISINFO">#include "SDL.h"#include "SDL_thread.h"</PRE><P><CODE><CODECLASS="FUNCDEF">SDL_sem *<BCLASS="FSFUNC">SDL_CreateSemaphore</B></CODE>(Uint32 initial_value);</CODE></P><P></P></DIV></DIV><DIVCLASS="REFSECT1"><ANAME="AEN7946"></A><H2>Description</H2><P><TTCLASS="FUNCTION">SDL_CreateSemaphore()</TT> creates a new semaphore andinitializes it with the value <TTCLASS="PARAMETER"><I>initial_value</I></TT>.Each locking operation on the semaphore by<AHREF="sdlsemwait.html">SDL_SemWait</A>,<AHREF="sdlsemtrywait.html">SDL_SemTryWait</A> or<AHREF="sdlsemwaittimeout.html">SDL_SemWaitTimeout</A>will atomically decrement the semaphore value. The locking operation will be blockedif the semaphore value is not positive (greater than zero). Each unlock operation by<AHREF="sdlsempost.html">SDL_SemPost</A>will atomically increment the semaphore value.</P></DIV><DIVCLASS="REFSECT1"><ANAME="AEN7955"></A><H2>Return Value</H2><P>Returns a pointer to an initialized semaphore or<SPANCLASS="RETURNVALUE">NULL</SPAN> if there was an error.</P></DIV><DIVCLASS="REFSECT1"><ANAME="AEN7959"></A><H2>Examples</H2><P><PRECLASS="PROGRAMLISTING">SDL_sem *my_sem;my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE);if (my_sem == NULL) { return CREATE_SEM_FAILED;}</PRE></P></DIV><DIVCLASS="REFSECT1"><ANAME="AEN7963"></A><H2>See Also</H2><P><AHREF="sdldestroysemaphore.html"><TTCLASS="FUNCTION">SDL_DestroySemaphore</TT></A>,<AHREF="sdlsemwait.html"><TTCLASS="FUNCTION">SDL_SemWait</TT></A>,<AHREF="sdlsemtrywait.html"><TTCLASS="FUNCTION">SDL_SemTryWait</TT></A>,<AHREF="sdlsemwaittimeout.html"><TTCLASS="FUNCTION">SDL_SemWaitTimeout</TT></A>,<AHREF="sdlsempost.html"><TTCLASS="FUNCTION">SDL_SemPost</TT></A>,<AHREF="sdlsemvalue.html"><TTCLASS="FUNCTION">SDL_SemValue</TT></A></P></DIV><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLESUMMARY="Footer navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><AHREF="sdlmutexv.html"ACCESSKEY="P">Prev</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="index.html"ACCESSKEY="H">Home</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><AHREF="sdldestroysemaphore.html"ACCESSKEY="N">Next</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">SDL_mutexV</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="thread.html"ACCESSKEY="U">Up</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">SDL_DestroySemaphore</TD></TR></TABLE></DIV></BODY></HTML>⌨️ 快捷键说明
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