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sdlcreatesemaphore.html

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<HTML
><HEAD
><TITLE
>SDL_CreateSemaphore</TITLE
><META
NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
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"><LINK
REL="HOME"
TITLE="SDL Library Documentation"
HREF="index.html"><LINK
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HREF="sdldestroysemaphore.html"></HEAD
><BODY
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><TR
><TH
COLSPAN="3"
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>SDL Library Documentation</TH
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><TR
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ALIGN="left"
VALIGN="bottom"
><A
HREF="sdlmutexv.html"
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>Prev</A
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><HR
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WIDTH="100%"></DIV
><H1
><A
NAME="SDLCREATESEMAPHORE"
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></A
>SDL_CreateSemaphore</H1
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><DIV
CLASS="REFNAMEDIV"
><A
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></A
><H2
>Name</H2
>SDL_CreateSemaphore&nbsp;--&nbsp;Creates a new semaphore and assigns an initial value to it.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
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></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
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></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
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></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
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></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
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></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
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></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"
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><TR
><TD
WIDTH="33%"
ALIGN="left"
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><A
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>Prev</A
></TD
><TD
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>Home</A
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>Next</A
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><TR
><TD
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>SDL_mutexV</TD
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><A
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>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
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>SDL_DestroySemaphore</TD
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>