Mercurial > sdl-ios-xcode
annotate docs/html/sdlsemwaittimeout.html @ 773:da0a2ad35bf4
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> |
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date | Mon, 05 Jan 2004 00:57:51 +0000 |
parents | e5bc29de3f0a |
children | 355632dca928 |
rev | line source |
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0 | 1 <HTML |
2 ><HEAD | |
3 ><TITLE | |
4 >SDL_SemWaitTimeout</TITLE | |
5 ><META | |
6 NAME="GENERATOR" | |
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
0 | 8 "><LINK |
9 REL="HOME" | |
10 TITLE="SDL Library Documentation" | |
11 HREF="index.html"><LINK | |
12 REL="UP" | |
13 TITLE="Multi-threaded Programming" | |
14 HREF="thread.html"><LINK | |
15 REL="PREVIOUS" | |
16 TITLE="SDL_SemTryWait" | |
17 HREF="sdlsemtrywait.html"><LINK | |
18 REL="NEXT" | |
19 TITLE="SDL_SemPost" | |
20 HREF="sdlsempost.html"></HEAD | |
21 ><BODY | |
22 CLASS="REFENTRY" | |
23 BGCOLOR="#FFF8DC" | |
24 TEXT="#000000" | |
25 LINK="#0000ee" | |
26 VLINK="#551a8b" | |
27 ALINK="#ff0000" | |
28 ><DIV | |
29 CLASS="NAVHEADER" | |
30 ><TABLE | |
31 WIDTH="100%" | |
32 BORDER="0" | |
33 CELLPADDING="0" | |
34 CELLSPACING="0" | |
35 ><TR | |
36 ><TH | |
37 COLSPAN="3" | |
38 ALIGN="center" | |
39 >SDL Library Documentation</TH | |
40 ></TR | |
41 ><TR | |
42 ><TD | |
43 WIDTH="10%" | |
44 ALIGN="left" | |
45 VALIGN="bottom" | |
46 ><A | |
47 HREF="sdlsemtrywait.html" | |
48 >Prev</A | |
49 ></TD | |
50 ><TD | |
51 WIDTH="80%" | |
52 ALIGN="center" | |
53 VALIGN="bottom" | |
54 ></TD | |
55 ><TD | |
56 WIDTH="10%" | |
57 ALIGN="right" | |
58 VALIGN="bottom" | |
59 ><A | |
60 HREF="sdlsempost.html" | |
61 >Next</A | |
62 ></TD | |
63 ></TR | |
64 ></TABLE | |
65 ><HR | |
66 ALIGN="LEFT" | |
67 WIDTH="100%"></DIV | |
68 ><H1 | |
69 ><A | |
70 NAME="SDLSEMWAITTIMEOUT" | |
71 >SDL_SemWaitTimeout</A | |
72 ></H1 | |
73 ><DIV | |
74 CLASS="REFNAMEDIV" | |
75 ><A | |
181
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76 NAME="AEN7732" |
0 | 77 ></A |
78 ><H2 | |
79 >Name</H2 | |
80 >SDL_SemWaitTimeout -- Lock a semaphore, but only wait up to a specified maximum time.</DIV | |
81 ><DIV | |
82 CLASS="REFSYNOPSISDIV" | |
83 ><A | |
181
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84 NAME="AEN7735" |
0 | 85 ></A |
86 ><H2 | |
87 >Synopsis</H2 | |
88 ><DIV | |
89 CLASS="FUNCSYNOPSIS" | |
90 ><A | |
181
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91 NAME="AEN7736" |
0 | 92 ></A |
93 ><P | |
94 ></P | |
95 ><PRE | |
96 CLASS="FUNCSYNOPSISINFO" | |
97 >#include "SDL.h" | |
98 #include "SDL_thread.h"</PRE | |
99 ><P | |
100 ><CODE | |
101 ><CODE | |
102 CLASS="FUNCDEF" | |
103 >int <B | |
104 CLASS="FSFUNC" | |
105 >SDL_SemWaitTimeout</B | |
106 ></CODE | |
107 >(SDL_sem *sem, Uint32 timeout);</CODE | |
108 ></P | |
109 ><P | |
110 ></P | |
111 ></DIV | |
112 ></DIV | |
113 ><DIV | |
114 CLASS="REFSECT1" | |
115 ><A | |
181
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116 NAME="AEN7742" |
0 | 117 ></A |
118 ><H2 | |
119 >Description</H2 | |
120 ><P | |
121 ><TT | |
122 CLASS="FUNCTION" | |
123 >SDL_SemWaitTimeout()</TT | |
124 > is a varient of | |
125 <A | |
126 HREF="sdlsemwait.html" | |
127 >SDL_SemWait</A | |
128 > | |
129 with a maximum timeout value. | |
130 If the value of the semaphore pointed to by <TT | |
131 CLASS="PARAMETER" | |
132 ><I | |
133 >sem</I | |
134 ></TT | |
135 > is | |
136 positive (greater than zero) it will atomically decrement the semaphore value | |
137 and return 0, otherwise it will wait up to <TT | |
138 CLASS="PARAMETER" | |
139 ><I | |
140 >timeout</I | |
141 ></TT | |
142 > | |
143 milliseconds trying to lock the semaphore. This function is to be avoided if | |
144 possible since on some platforms it is implemented by polling the semaphore | |
145 every millisecond in a busy loop.</P | |
146 ><P | |
147 >After <TT | |
148 CLASS="FUNCTION" | |
149 >SDL_SemWaitTimeout()</TT | |
150 > is successful, the semaphore | |
151 can be released and its count atomically incremented by a successful call to | |
152 <A | |
153 HREF="sdlsempost.html" | |
154 >SDL_SemPost</A | |
155 >.</P | |
156 ></DIV | |
157 ><DIV | |
158 CLASS="REFSECT1" | |
159 ><A | |
181
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160 NAME="AEN7752" |
0 | 161 ></A |
162 ><H2 | |
163 >Return Value</H2 | |
164 ><P | |
165 >Returns <SPAN | |
166 CLASS="RETURNVALUE" | |
167 >0</SPAN | |
168 > if the semaphore was successfully locked or | |
169 either <SPAN | |
170 CLASS="RETURNVALUE" | |
171 >SDL_MUTEX_TIMEOUT</SPAN | |
172 > or <SPAN | |
173 CLASS="RETURNVALUE" | |
174 >-1</SPAN | |
175 > | |
176 if the timeout period was exceeded or there was an error, respectivly.</P | |
177 ><P | |
178 >If the semaphore was not successfully locked, the semaphore will be unchanged.</P | |
179 ></DIV | |
180 ><DIV | |
181 CLASS="REFSECT1" | |
182 ><A | |
181
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183 NAME="AEN7759" |
0 | 184 ></A |
185 ><H2 | |
186 >Examples</H2 | |
187 ><P | |
188 ><PRE | |
189 CLASS="PROGRAMLISTING" | |
190 >res = SDL_SemWaitTimeout(my_sem, WAIT_TIMEOUT_MILLISEC); | |
191 | |
192 if (res == SDL_MUTEX_TIMEOUT) { | |
193 return TRY_AGAIN; | |
194 } | |
195 if (res == -1) { | |
196 return WAIT_ERROR; | |
197 } | |
198 | |
199 ... | |
200 | |
201 SDL_SemPost(my_sem);</PRE | |
202 ></P | |
203 ></DIV | |
204 ><DIV | |
205 CLASS="REFSECT1" | |
206 ><A | |
181
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207 NAME="AEN7763" |
0 | 208 ></A |
209 ><H2 | |
210 >See Also</H2 | |
211 ><P | |
212 ><A | |
213 HREF="sdlcreatesemaphore.html" | |
214 ><TT | |
215 CLASS="FUNCTION" | |
216 >SDL_CreateSemaphore</TT | |
217 ></A | |
218 >, | |
219 <A | |
220 HREF="sdldestroysemaphore.html" | |
221 ><TT | |
222 CLASS="FUNCTION" | |
223 >SDL_DestroySemaphore</TT | |
224 ></A | |
225 >, | |
226 <A | |
227 HREF="sdlsemwait.html" | |
228 ><TT | |
229 CLASS="FUNCTION" | |
230 >SDL_SemWait</TT | |
231 ></A | |
232 >, | |
233 <A | |
234 HREF="sdlsemtrywait.html" | |
235 ><TT | |
236 CLASS="FUNCTION" | |
237 >SDL_SemTryWait</TT | |
238 ></A | |
239 >, | |
240 <A | |
241 HREF="sdlsempost.html" | |
242 ><TT | |
243 CLASS="FUNCTION" | |
244 >SDL_SemPost</TT | |
245 ></A | |
246 >, | |
247 <A | |
248 HREF="sdlsemvalue.html" | |
249 ><TT | |
250 CLASS="FUNCTION" | |
251 >SDL_SemValue</TT | |
252 ></A | |
253 ></P | |
254 ></DIV | |
255 ><DIV | |
256 CLASS="NAVFOOTER" | |
257 ><HR | |
258 ALIGN="LEFT" | |
259 WIDTH="100%"><TABLE | |
260 WIDTH="100%" | |
261 BORDER="0" | |
262 CELLPADDING="0" | |
263 CELLSPACING="0" | |
264 ><TR | |
265 ><TD | |
266 WIDTH="33%" | |
267 ALIGN="left" | |
268 VALIGN="top" | |
269 ><A | |
270 HREF="sdlsemtrywait.html" | |
271 >Prev</A | |
272 ></TD | |
273 ><TD | |
274 WIDTH="34%" | |
275 ALIGN="center" | |
276 VALIGN="top" | |
277 ><A | |
278 HREF="index.html" | |
279 >Home</A | |
280 ></TD | |
281 ><TD | |
282 WIDTH="33%" | |
283 ALIGN="right" | |
284 VALIGN="top" | |
285 ><A | |
286 HREF="sdlsempost.html" | |
287 >Next</A | |
288 ></TD | |
289 ></TR | |
290 ><TR | |
291 ><TD | |
292 WIDTH="33%" | |
293 ALIGN="left" | |
294 VALIGN="top" | |
295 >SDL_SemTryWait</TD | |
296 ><TD | |
297 WIDTH="34%" | |
298 ALIGN="center" | |
299 VALIGN="top" | |
300 ><A | |
301 HREF="thread.html" | |
302 >Up</A | |
303 ></TD | |
304 ><TD | |
305 WIDTH="33%" | |
306 ALIGN="right" | |
307 VALIGN="top" | |
308 >SDL_SemPost</TD | |
309 ></TR | |
310 ></TABLE | |
311 ></DIV | |
312 ></BODY | |
313 ></HTML | |
314 > |