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Fixed SDL 1.2 compatibility problem. The API specifies that SDL_OpenAudio() will fill out the 'desired' audio spec with the correct samples and size set by the driver. This value is important since it may be used by applications that size audio buffers, etc. However, we want to allow advanced applications to call SDL_OpenAudioDevice() which gets passed a const 'desired' parameter, and have the correct data filled into the 'obtained' parameter, possibly allowing or not allowing format changes. So... 'obtained' becomes the audio format the user callback is expected to use, and we add flags to allow the application to specify which format changes are allowed. Note: We really need to add a way to query the 'obtained' audio spec.
author Sam Lantinga <slouken@libsdl.org>
date Sat, 13 Dec 2008 06:36:47 +0000
parents 355632dca928
children
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<HTML
><HEAD
><TITLE
>SDL_SemWaitTimeout</TITLE
><META
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><H1
><A
NAME="SDLSEMWAITTIMEOUT"
></A
>SDL_SemWaitTimeout</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN8120"
></A
><H2
>Name</H2
>SDL_SemWaitTimeout&nbsp;--&nbsp;Lock a semaphore, but only wait up to a specified maximum time.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN8123"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN8124"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"
#include "SDL_thread.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_SemWaitTimeout</B
></CODE
>(SDL_sem *sem, Uint32 timeout);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8130"
></A
><H2
>Description</H2
><P
><TT
CLASS="FUNCTION"
>SDL_SemWaitTimeout()</TT
> is a varient of
<A
HREF="sdlsemwait.html"
>SDL_SemWait</A
>
with a maximum timeout value.
If the value of the semaphore pointed to by <TT
CLASS="PARAMETER"
><I
>sem</I
></TT
> is
positive (greater than zero) it will atomically decrement the semaphore value
and return 0, otherwise it will wait up to <TT
CLASS="PARAMETER"
><I
>timeout</I
></TT
>
milliseconds trying to lock the semaphore. This function is to be avoided if
possible since on some platforms it is implemented by polling the semaphore
every millisecond in a busy loop.</P
><P
>After <TT
CLASS="FUNCTION"
>SDL_SemWaitTimeout()</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="AEN8140"
></A
><H2
>Return Value</H2
><P
>Returns <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> if the semaphore was successfully locked or
either <SPAN
CLASS="RETURNVALUE"
>SDL_MUTEX_TIMEDOUT</SPAN
> or <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
>
if the timeout period was exceeded or there was an error, respectivly.</P
><P
>If the semaphore was not successfully locked, the semaphore will be unchanged.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8147"
></A
><H2
>Examples</H2
><P
><PRE
CLASS="PROGRAMLISTING"
>res = SDL_SemWaitTimeout(my_sem, WAIT_TIMEOUT_MILLISEC);

if (res == SDL_MUTEX_TIMEDOUT) {
        return TRY_AGAIN;
}
if (res == -1) {
        return WAIT_ERROR;
}

...

SDL_SemPost(my_sem);</PRE
></P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8151"
></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="sdlsemwait.html"
><TT
CLASS="FUNCTION"
>SDL_SemWait</TT
></A
>,
<A
HREF="sdlsemtrywait.html"
><TT
CLASS="FUNCTION"
>SDL_SemTryWait</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
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