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Adjusted default choice of audio driver. If a driver can definitely see available devices, it is chosen. Otherwise, we'll take the first driver that initializes but saw no devices...this might be because it can't enumerate them, or there really aren't any available. This prevents the dsp driver from hogging control when there are no /dev/dsp* nodes (for example, on a Linux box with ALSA and no OSS emulation).
author Ryan C. Gordon <icculus@icculus.org>
date Thu, 01 Jan 2009 07:54:58 +0000
parents 355632dca928
children
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<HTML
><HEAD
><TITLE
>SDL_CreateSemaphore</TITLE
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><H1
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>SDL_CreateSemaphore</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN7936"
></A
><H2
>Name</H2
>SDL_CreateSemaphore&nbsp;--&nbsp;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
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><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
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