Mercurial > sdl-ios-xcode
annotate docs/html/sdlsemvalue.html @ 765:4c2ba6161939
Editors Note: The original patch was modified to use SDL_Delay() instead of
nanosleep because nanosleep may not be portable to all systems
using SDL with the ALSA backend. This may be a moot point with
the switch to blocking writes anyway...
Date: Sat, 27 Dec 2003 21:47:36 +0100
From: Michel Daenzer
To: Debian Bug Tracking System
Subject: [SDL] Bug#225252: [PATCH] ALSA fixes
Package: libsdl1.2debian-all
Version: 1.2.6-2
Severity: normal
Tags: patch
For SDL 1.2.6, the ALSA backend was changed to call snd_pcm_open() with
SND_PCM_NONBLOCK. That's a good idea per se, however, it causes high CPU
usage, interrupted sound and stuttering in some games here. Taking a nanosleep
whenever snd_pcm_writei() returns -EAGAIN fixes this, but I think it's more
efficient to use blocking mode for the actual sound playback. Feedback from the
SDL and ALSA lists appreciated.
The patch also fixes the default ALSA device to be used.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sun, 04 Jan 2004 15:40:50 +0000 |
| parents | e5bc29de3f0a |
| children | 355632dca928 |
| rev | line source |
|---|---|
| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_SemValue</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_SemPost" | |
| 17 HREF="sdlsempost.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_CreateCond" | |
| 20 HREF="sdlcreatecond.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="sdlsempost.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="sdlcreatecond.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="SDLSEMVALUE" | |
| 71 >SDL_SemValue</A | |
| 72 ></H1 | |
| 73 ><DIV | |
| 74 CLASS="REFNAMEDIV" | |
| 75 ><A | |
|
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76 NAME="AEN7830" |
| 0 | 77 ></A |
| 78 ><H2 | |
| 79 >Name</H2 | |
| 80 >SDL_SemValue -- Return the current value of a semaphore.</DIV | |
| 81 ><DIV | |
| 82 CLASS="REFSYNOPSISDIV" | |
| 83 ><A | |
|
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84 NAME="AEN7833" |
| 0 | 85 ></A |
| 86 ><H2 | |
| 87 >Synopsis</H2 | |
| 88 ><DIV | |
| 89 CLASS="FUNCSYNOPSIS" | |
| 90 ><A | |
|
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91 NAME="AEN7834" |
| 0 | 92 ></A |
| 93 ><P | |
| 94 ></P | |
| 95 ><PRE | |
| 96 CLASS="FUNCSYNOPSISINFO" | |
| 97 >#include "SDL.h" | |
| 98 #include "SDL/SDL_thread.h"</PRE | |
| 99 ><P | |
| 100 ><CODE | |
| 101 ><CODE | |
| 102 CLASS="FUNCDEF" | |
| 103 >Uint32 <B | |
| 104 CLASS="FSFUNC" | |
| 105 >SDL_SemValue</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 | |
|
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116 NAME="AEN7840" |
| 0 | 117 ></A |
| 118 ><H2 | |
| 119 >Description</H2 | |
| 120 ><P | |
| 121 ><TT | |
| 122 CLASS="FUNCTION" | |
| 123 >SDL_SemValue()</TT | |
| 124 > returns the current semaphore value from | |
| 125 the semaphore pointed to by <TT | |
| 126 CLASS="PARAMETER" | |
| 127 ><I | |
| 128 >sem</I | |
| 129 ></TT | |
| 130 >.</P | |
| 131 ></DIV | |
| 132 ><DIV | |
| 133 CLASS="REFSECT1" | |
| 134 ><A | |
|
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135 NAME="AEN7845" |
| 0 | 136 ></A |
| 137 ><H2 | |
| 138 >Return Value</H2 | |
| 139 ><P | |
| 140 >Returns current value of the semaphore.</P | |
| 141 ></DIV | |
| 142 ><DIV | |
| 143 CLASS="REFSECT1" | |
| 144 ><A | |
|
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145 NAME="AEN7848" |
| 0 | 146 ></A |
| 147 ><H2 | |
| 148 >Examples</H2 | |
| 149 ><P | |
| 150 ><PRE | |
| 151 CLASS="PROGRAMLISTING" | |
| 152 > sem_value = SDL_SemValue(my_sem);</PRE | |
| 153 ></P | |
| 154 ></DIV | |
| 155 ><DIV | |
| 156 CLASS="REFSECT1" | |
| 157 ><A | |
|
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158 NAME="AEN7852" |
| 0 | 159 ></A |
| 160 ><H2 | |
| 161 >See Also</H2 | |
| 162 ><P | |
| 163 ><A | |
| 164 HREF="sdlcreatesemaphore.html" | |
| 165 ><TT | |
| 166 CLASS="FUNCTION" | |
| 167 >SDL_CreateSemaphore</TT | |
| 168 ></A | |
| 169 >, | |
| 170 <A | |
| 171 HREF="sdldestroysemaphore.html" | |
| 172 ><TT | |
| 173 CLASS="FUNCTION" | |
| 174 >SDL_DestroySemaphore</TT | |
| 175 ></A | |
| 176 >, | |
| 177 <A | |
| 178 HREF="sdlsemwait.html" | |
| 179 ><TT | |
| 180 CLASS="FUNCTION" | |
| 181 >SDL_SemWait</TT | |
| 182 ></A | |
| 183 >, | |
| 184 <A | |
| 185 HREF="sdlsemtrywait.html" | |
| 186 ><TT | |
| 187 CLASS="FUNCTION" | |
| 188 >SDL_SemTryWait</TT | |
| 189 ></A | |
| 190 >, | |
| 191 <A | |
| 192 HREF="sdlsemwaittimeout.html" | |
| 193 ><TT | |
| 194 CLASS="FUNCTION" | |
| 195 >SDL_SemWaitTimeout</TT | |
| 196 ></A | |
| 197 >, | |
| 198 <A | |
| 199 HREF="sdlsempost.html" | |
| 200 ><TT | |
| 201 CLASS="FUNCTION" | |
| 202 >SDL_SemPost</TT | |
| 203 ></A | |
| 204 ></P | |
| 205 ></DIV | |
| 206 ><DIV | |
| 207 CLASS="NAVFOOTER" | |
| 208 ><HR | |
| 209 ALIGN="LEFT" | |
| 210 WIDTH="100%"><TABLE | |
| 211 WIDTH="100%" | |
| 212 BORDER="0" | |
| 213 CELLPADDING="0" | |
| 214 CELLSPACING="0" | |
| 215 ><TR | |
| 216 ><TD | |
| 217 WIDTH="33%" | |
| 218 ALIGN="left" | |
| 219 VALIGN="top" | |
| 220 ><A | |
| 221 HREF="sdlsempost.html" | |
| 222 >Prev</A | |
| 223 ></TD | |
| 224 ><TD | |
| 225 WIDTH="34%" | |
| 226 ALIGN="center" | |
| 227 VALIGN="top" | |
| 228 ><A | |
| 229 HREF="index.html" | |
| 230 >Home</A | |
| 231 ></TD | |
| 232 ><TD | |
| 233 WIDTH="33%" | |
| 234 ALIGN="right" | |
| 235 VALIGN="top" | |
| 236 ><A | |
| 237 HREF="sdlcreatecond.html" | |
| 238 >Next</A | |
| 239 ></TD | |
| 240 ></TR | |
| 241 ><TR | |
| 242 ><TD | |
| 243 WIDTH="33%" | |
| 244 ALIGN="left" | |
| 245 VALIGN="top" | |
| 246 >SDL_SemPost</TD | |
| 247 ><TD | |
| 248 WIDTH="34%" | |
| 249 ALIGN="center" | |
| 250 VALIGN="top" | |
| 251 ><A | |
| 252 HREF="thread.html" | |
| 253 >Up</A | |
| 254 ></TD | |
| 255 ><TD | |
| 256 WIDTH="33%" | |
| 257 ALIGN="right" | |
| 258 VALIGN="top" | |
| 259 >SDL_CreateCond</TD | |
| 260 ></TR | |
| 261 ></TABLE | |
| 262 ></DIV | |
| 263 ></BODY | |
| 264 ></HTML | |
| 265 > |