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Date: Sun, 4 Jan 2004 23:48:19 +0100
From: Max Horn
Subject: Re: Again Audio CD patch
Am 04.01.2004 um 22:38 schrieb Sam Lantinga:
>
> Okay, I fixed the buffering problems by simply using a 4 second buffer
> instead of a 1 second buffer. However, using your code I can't play an
> entire CD - the playback stops after the first song.
>
Found the problem: FSReadFork returns eofErr when the file is finished.
However, we check its return value for errors, and if anything but
noErr occurs, the reader thread aborts its current iteration. That is
bad, because it aborts before it can ever set the flag which tells that
the file is over (also, any remaining data which FSRead did return is
lost - so you'd not hear about to 4 seconds from the end of the file.
Furthermore, the computed data size was 8 bytes to high (I forgot to
account for the fact that the size of an (A)IFF chunk always contains
the chunk header & size fields, too). This is enough to make it work.
However, the end condition is rather fragile, so I tuned some other
things to be pessimistic (check for <= 0 instead of == 0, when eofErr
is encountered enforce mReadFilePosition == mFileLength). You never
know...
The attached patch fixes the issue for me.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Mon, 05 Jan 2004 00:57:51 +0000 |
parents | e5bc29de3f0a |
children | 355632dca928 |
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<HTML ><HEAD ><TITLE >Multi-threaded Programming</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.64 "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="SDL Reference" HREF="reference.html"><LINK REL="PREVIOUS" TITLE="SDL_CDtrack" HREF="sdlcdtrack.html"><LINK REL="NEXT" TITLE="SDL_CreateThread" HREF="sdlcreatethread.html"><META NAME="KEYWORD" CONTENT="threads"><META NAME="KEYWORD" CONTENT="function"></HEAD ><BODY CLASS="CHAPTER" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><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="sdlcdtrack.html" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdlcreatethread.html" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="THREAD" >Chapter 12. Multi-threaded Programming</A ></H1 ><DIV CLASS="TOC" ><DL ><DT ><B >Table of Contents</B ></DT ><DT ><A HREF="sdlcreatethread.html" >SDL_CreateThread</A > — Creates a new thread of execution that shares its parent's properties.</DT ><DT ><A HREF="sdlthreadid.html" >SDL_ThreadID</A > — Get the 32-bit thread identifier for the current thread.</DT ><DT ><A HREF="sdlgetthreadid.html" >SDL_GetThreadID</A > — Get the SDL thread ID of a SDL_Thread</DT ><DT ><A HREF="sdlwaitthread.html" >SDL_WaitThread</A > — Wait for a thread to finish.</DT ><DT ><A HREF="sdlkillthread.html" >SDL_KillThread</A > — Gracelessly terminates the thread.</DT ><DT ><A HREF="sdlcreatemutex.html" >SDL_CreateMutex</A > — Create a mutex</DT ><DT ><A HREF="sdldestroymutex.html" >SDL_DestroyMutex</A > — Destroy a mutex</DT ><DT ><A HREF="sdlmutexp.html" >SDL_mutexP</A > — Lock a mutex</DT ><DT ><A HREF="sdlmutexv.html" >SDL_mutexV</A > — Unlock a mutex</DT ><DT ><A HREF="sdlcreatesemaphore.html" >SDL_CreateSemaphore</A > — Creates a new semaphore and assigns an initial value to it.</DT ><DT ><A HREF="sdldestroysemaphore.html" >SDL_DestroySemaphore</A > — Destroys a semaphore that was created by <A HREF="sdlcreatesemaphore.html" >SDL_CreateSemaphore</A >.</DT ><DT ><A HREF="sdlsemwait.html" >SDL_SemWait</A > — Lock a semaphore and suspend the thread if the semaphore value is zero.</DT ><DT ><A HREF="sdlsemtrywait.html" >SDL_SemTryWait</A > — Attempt to lock a semaphore but don't suspend the thread.</DT ><DT ><A HREF="sdlsemwaittimeout.html" >SDL_SemWaitTimeout</A > — Lock a semaphore, but only wait up to a specified maximum time.</DT ><DT ><A HREF="sdlsempost.html" >SDL_SemPost</A > — Unlock a semaphore.</DT ><DT ><A HREF="sdlsemvalue.html" >SDL_SemValue</A > — Return the current value of a semaphore.</DT ><DT ><A HREF="sdlcreatecond.html" >SDL_CreateCond</A > — Create a condition variable</DT ><DT ><A HREF="sdldestroycond.html" >SDL_DestroyCond</A > — Destroy a condition variable</DT ><DT ><A HREF="sdlcondsignal.html" >SDL_CondSignal</A > — Restart a thread wait on a condition variable</DT ><DT ><A HREF="sdlcondbroadcast.html" >SDL_CondBroadcast</A > — Restart all threads waiting on a condition variable</DT ><DT ><A HREF="sdlcondwait.html" >SDL_CondWait</A > — Wait on a condition variable</DT ><DT ><A HREF="sdlcondwaittimeout.html" >SDL_CondWaitTimeout</A > — Wait on a condition variable, with timeout</DT ></DL ></DIV ><P >SDL provides functions for creating threads, mutexes, semphores and condition variables.</P ><P >In general, you must be very aware of concurrency and data integrity issues when writing multi-threaded programs. Some good guidelines include: <P ></P ><UL ><LI ><P >Don't call SDL video/event functions from separate threads</P ></LI ><LI ><P >Don't use any library functions in separate threads</P ></LI ><LI ><P >Don't perform any memory management in separate threads</P ></LI ><LI ><P >Lock global variables which may be accessed by multiple threads</P ></LI ><LI ><P >Never terminate threads, always set a flag and wait for them to quit</P ></LI ><LI ><P >Think very carefully about all possible ways your code may interact</P ></LI ></UL ></P ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B >SDL's threading is not implemented on MacOS, due to that lack of preemptive thread support (MacOS X dos nt suffer from this problem)</P ></BLOCKQUOTE ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlcdtrack.html" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdlcreatethread.html" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_CDtrack</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="reference.html" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_CreateThread</TD ></TR ></TABLE ></DIV ></BODY ></HTML >