Mercurial > sdl-ios-xcode
annotate docs/html/sdlsemwait.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_SemWait</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_DestroySemaphore" | |
17 HREF="sdldestroysemaphore.html"><LINK | |
18 REL="NEXT" | |
19 TITLE="SDL_SemTryWait" | |
20 HREF="sdlsemtrywait.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="sdldestroysemaphore.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="sdlsemtrywait.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="SDLSEMWAIT" | |
71 >SDL_SemWait</A | |
72 ></H1 | |
73 ><DIV | |
74 CLASS="REFNAMEDIV" | |
75 ><A | |
181
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76 NAME="AEN7635" |
0 | 77 ></A |
78 ><H2 | |
79 >Name</H2 | |
80 >SDL_SemWait -- Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV | |
81 ><DIV | |
82 CLASS="REFSYNOPSISDIV" | |
83 ><A | |
181
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84 NAME="AEN7638" |
0 | 85 ></A |
86 ><H2 | |
87 >Synopsis</H2 | |
88 ><DIV | |
89 CLASS="FUNCSYNOPSIS" | |
90 ><A | |
181
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91 NAME="AEN7639" |
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_SemWait</B | |
106 ></CODE | |
107 >(SDL_sem *sem);</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="AEN7645" |
0 | 117 ></A |
118 ><H2 | |
119 >Description</H2 | |
120 ><P | |
121 ><TT | |
122 CLASS="FUNCTION" | |
123 >SDL_SemWait()</TT | |
124 > suspends the calling thread until either | |
125 the semaphore pointed to by <TT | |
126 CLASS="PARAMETER" | |
127 ><I | |
128 >sem</I | |
129 ></TT | |
130 > has a positive value, | |
131 the call is interrupted by a signal or error. If the call is successful it | |
132 will atomically decrement the semaphore value.</P | |
133 ><P | |
134 >After <TT | |
135 CLASS="FUNCTION" | |
136 >SDL_SemWait()</TT | |
137 > is successful, the semaphore | |
138 can be released and its count atomically incremented by a successful call to | |
139 <A | |
140 HREF="sdlsempost.html" | |
141 >SDL_SemPost</A | |
142 >.</P | |
143 ></DIV | |
144 ><DIV | |
145 CLASS="REFSECT1" | |
146 ><A | |
181
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147 NAME="AEN7653" |
0 | 148 ></A |
149 ><H2 | |
150 >Return Value</H2 | |
151 ><P | |
152 >Returns <SPAN | |
153 CLASS="RETURNVALUE" | |
154 >0</SPAN | |
155 > if successful or | |
156 <SPAN | |
157 CLASS="RETURNVALUE" | |
158 >-1</SPAN | |
159 > if there was an error (leaving the semaphore unchanged).</P | |
160 ></DIV | |
161 ><DIV | |
162 CLASS="REFSECT1" | |
163 ><A | |
181
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164 NAME="AEN7658" |
0 | 165 ></A |
166 ><H2 | |
167 >Examples</H2 | |
168 ><P | |
169 ><PRE | |
170 CLASS="PROGRAMLISTING" | |
171 >if (SDL_SemWait(my_sem) == -1) { | |
172 return WAIT_FAILED; | |
173 } | |
174 | |
175 ... | |
176 | |
177 SDL_SemPost(my_sem);</PRE | |
178 ></P | |
179 ></DIV | |
180 ><DIV | |
181 CLASS="REFSECT1" | |
182 ><A | |
181
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183 NAME="AEN7662" |
0 | 184 ></A |
185 ><H2 | |
186 >See Also</H2 | |
187 ><P | |
188 ><A | |
189 HREF="sdlcreatesemaphore.html" | |
190 ><TT | |
191 CLASS="FUNCTION" | |
192 >SDL_CreateSemaphore</TT | |
193 ></A | |
194 >, | |
195 <A | |
196 HREF="sdldestroysemaphore.html" | |
197 ><TT | |
198 CLASS="FUNCTION" | |
199 >SDL_DestroySemaphore</TT | |
200 ></A | |
201 >, | |
202 <A | |
203 HREF="sdlsemtrywait.html" | |
204 ><TT | |
205 CLASS="FUNCTION" | |
206 >SDL_SemTryWait</TT | |
207 ></A | |
208 >, | |
209 <A | |
210 HREF="sdlsemwaittimeout.html" | |
211 ><TT | |
212 CLASS="FUNCTION" | |
213 >SDL_SemWaitTimeout</TT | |
214 ></A | |
215 >, | |
216 <A | |
217 HREF="sdlsempost.html" | |
218 ><TT | |
219 CLASS="FUNCTION" | |
220 >SDL_SemPost</TT | |
221 ></A | |
222 >, | |
223 <A | |
224 HREF="sdlsemvalue.html" | |
225 ><TT | |
226 CLASS="FUNCTION" | |
227 >SDL_SemValue</TT | |
228 ></A | |
229 ></P | |
230 ></DIV | |
231 ><DIV | |
232 CLASS="NAVFOOTER" | |
233 ><HR | |
234 ALIGN="LEFT" | |
235 WIDTH="100%"><TABLE | |
236 WIDTH="100%" | |
237 BORDER="0" | |
238 CELLPADDING="0" | |
239 CELLSPACING="0" | |
240 ><TR | |
241 ><TD | |
242 WIDTH="33%" | |
243 ALIGN="left" | |
244 VALIGN="top" | |
245 ><A | |
246 HREF="sdldestroysemaphore.html" | |
247 >Prev</A | |
248 ></TD | |
249 ><TD | |
250 WIDTH="34%" | |
251 ALIGN="center" | |
252 VALIGN="top" | |
253 ><A | |
254 HREF="index.html" | |
255 >Home</A | |
256 ></TD | |
257 ><TD | |
258 WIDTH="33%" | |
259 ALIGN="right" | |
260 VALIGN="top" | |
261 ><A | |
262 HREF="sdlsemtrywait.html" | |
263 >Next</A | |
264 ></TD | |
265 ></TR | |
266 ><TR | |
267 ><TD | |
268 WIDTH="33%" | |
269 ALIGN="left" | |
270 VALIGN="top" | |
271 >SDL_DestroySemaphore</TD | |
272 ><TD | |
273 WIDTH="34%" | |
274 ALIGN="center" | |
275 VALIGN="top" | |
276 ><A | |
277 HREF="thread.html" | |
278 >Up</A | |
279 ></TD | |
280 ><TD | |
281 WIDTH="33%" | |
282 ALIGN="right" | |
283 VALIGN="top" | |
284 >SDL_SemTryWait</TD | |
285 ></TR | |
286 ></TABLE | |
287 ></DIV | |
288 ></BODY | |
289 ></HTML | |
290 > |