Mercurial > sdl-ios-xcode
annotate docs/html/sdlsemtrywait.html @ 1157:baf35853ad54
Date: Mon, 10 Oct 2005 13:09:32 +0300
From: Tommi Kyntola <tommi.kyntola@ray.fi>
To: sdl@libsdl.org
Subject: [SDL] [RFC] get_ticks broken on linux
It uses gettimeofday to calculate the timedifference.
Gettimeofday returns current time which is seldom monotonous.
This breaks SDL timer subsystem. (time callbacks and all that
get borked when the time difference ms is suddenly ~ 2^32)
I posted a message about this earlier but got no response.
Some thoughts on this matter would be appreciated.
(Or even an explanation for the lack of interest.)
A patch below would use the posix timers that have been around
since posix 93 and do provide a good source of monotonous time
on linux boxes (and on few others too).
The following patch is also availabe at:
http://www.hut.fi/u/tkyntola/SDL-1.2.9-clockfix.patch
It's against 1.2.9, but I can easily rediffit against
the cvs branch is needed.
cheers,
Tommi Kyntola tommi.kyntola@ray.fi
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Tue, 11 Oct 2005 18:16:12 +0000 |
| parents | 355632dca928 |
| children |
| rev | line source |
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| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_SemTryWait</TITLE | |
| 5 ><META | |
| 6 NAME="GENERATOR" | |
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ |
| 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_SemWait" | |
| 17 HREF="sdlsemwait.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_SemWaitTimeout" | |
| 20 HREF="sdlsemwaittimeout.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 | |
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31 SUMMARY="Header navigation table" |
| 0 | 32 WIDTH="100%" |
| 33 BORDER="0" | |
| 34 CELLPADDING="0" | |
| 35 CELLSPACING="0" | |
| 36 ><TR | |
| 37 ><TH | |
| 38 COLSPAN="3" | |
| 39 ALIGN="center" | |
| 40 >SDL Library Documentation</TH | |
| 41 ></TR | |
| 42 ><TR | |
| 43 ><TD | |
| 44 WIDTH="10%" | |
| 45 ALIGN="left" | |
| 46 VALIGN="bottom" | |
| 47 ><A | |
| 48 HREF="sdlsemwait.html" | |
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49 ACCESSKEY="P" |
| 0 | 50 >Prev</A |
| 51 ></TD | |
| 52 ><TD | |
| 53 WIDTH="80%" | |
| 54 ALIGN="center" | |
| 55 VALIGN="bottom" | |
| 56 ></TD | |
| 57 ><TD | |
| 58 WIDTH="10%" | |
| 59 ALIGN="right" | |
| 60 VALIGN="bottom" | |
| 61 ><A | |
| 62 HREF="sdlsemwaittimeout.html" | |
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63 ACCESSKEY="N" |
| 0 | 64 >Next</A |
| 65 ></TD | |
| 66 ></TR | |
| 67 ></TABLE | |
| 68 ><HR | |
| 69 ALIGN="LEFT" | |
| 70 WIDTH="100%"></DIV | |
| 71 ><H1 | |
| 72 ><A | |
| 73 NAME="SDLSEMTRYWAIT" | |
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74 ></A |
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75 >SDL_SemTryWait</H1 |
| 0 | 76 ><DIV |
| 77 CLASS="REFNAMEDIV" | |
| 78 ><A | |
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79 NAME="AEN8069" |
| 0 | 80 ></A |
| 81 ><H2 | |
| 82 >Name</H2 | |
| 83 >SDL_SemTryWait -- Attempt to lock a semaphore but don't suspend the thread.</DIV | |
| 84 ><DIV | |
| 85 CLASS="REFSYNOPSISDIV" | |
| 86 ><A | |
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87 NAME="AEN8072" |
| 0 | 88 ></A |
| 89 ><H2 | |
| 90 >Synopsis</H2 | |
| 91 ><DIV | |
| 92 CLASS="FUNCSYNOPSIS" | |
| 93 ><A | |
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94 NAME="AEN8073" |
| 0 | 95 ></A |
| 96 ><P | |
| 97 ></P | |
| 98 ><PRE | |
| 99 CLASS="FUNCSYNOPSISINFO" | |
| 100 >#include "SDL.h" | |
| 101 #include "SDL_thread.h"</PRE | |
| 102 ><P | |
| 103 ><CODE | |
| 104 ><CODE | |
| 105 CLASS="FUNCDEF" | |
| 106 >int <B | |
| 107 CLASS="FSFUNC" | |
| 108 >SDL_SemTryWait</B | |
| 109 ></CODE | |
| 110 >(SDL_sem *sem);</CODE | |
| 111 ></P | |
| 112 ><P | |
| 113 ></P | |
| 114 ></DIV | |
| 115 ></DIV | |
| 116 ><DIV | |
| 117 CLASS="REFSECT1" | |
| 118 ><A | |
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119 NAME="AEN8079" |
| 0 | 120 ></A |
| 121 ><H2 | |
| 122 >Description</H2 | |
| 123 ><P | |
| 124 ><TT | |
| 125 CLASS="FUNCTION" | |
| 126 >SDL_SemTryWait</TT | |
| 127 > is a non-blocking varient of | |
| 128 <A | |
| 129 HREF="sdlsemwait.html" | |
| 130 ><TT | |
| 131 CLASS="FUNCTION" | |
| 132 >SDL_SemWait</TT | |
| 133 ></A | |
| 134 >. If the value of the semaphore | |
| 135 pointed to by <TT | |
| 136 CLASS="PARAMETER" | |
| 137 ><I | |
| 138 >sem</I | |
| 139 ></TT | |
| 140 > is positive it will atomically | |
| 141 decrement the semaphore value and return 0, otherwise it will return | |
| 142 <SPAN | |
| 143 CLASS="RETURNVALUE" | |
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144 >SDL_MUTEX_TIMEDOUT</SPAN |
| 0 | 145 > instead of suspending the thread.</P |
| 146 ><P | |
| 147 >After <TT | |
| 148 CLASS="FUNCTION" | |
| 149 >SDL_SemTryWait</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 | |
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160 NAME="AEN8090" |
| 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" | |
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171 >SDL_MUTEX_TIMEDOUT</SPAN |
| 0 | 172 > or <SPAN |
| 173 CLASS="RETURNVALUE" | |
| 174 >-1</SPAN | |
| 175 > | |
| 176 if the thread would have suspended 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 | |
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183 NAME="AEN8097" |
| 0 | 184 ></A |
| 185 ><H2 | |
| 186 >Examples</H2 | |
| 187 ><P | |
| 188 ><PRE | |
| 189 CLASS="PROGRAMLISTING" | |
| 190 >res = SDL_SemTryWait(my_sem); | |
| 191 | |
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192 if (res == SDL_MUTEX_TIMEDOUT) { |
| 0 | 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 | |
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207 NAME="AEN8101" |
| 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="sdlsemwaittimeout.html" | |
| 235 ><TT | |
| 236 CLASS="FUNCTION" | |
| 237 >SDL_SemWaitTimeout</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 | |
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260 SUMMARY="Footer navigation table" |
| 0 | 261 WIDTH="100%" |
| 262 BORDER="0" | |
| 263 CELLPADDING="0" | |
| 264 CELLSPACING="0" | |
| 265 ><TR | |
| 266 ><TD | |
| 267 WIDTH="33%" | |
| 268 ALIGN="left" | |
| 269 VALIGN="top" | |
| 270 ><A | |
| 271 HREF="sdlsemwait.html" | |
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272 ACCESSKEY="P" |
| 0 | 273 >Prev</A |
| 274 ></TD | |
| 275 ><TD | |
| 276 WIDTH="34%" | |
| 277 ALIGN="center" | |
| 278 VALIGN="top" | |
| 279 ><A | |
| 280 HREF="index.html" | |
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281 ACCESSKEY="H" |
| 0 | 282 >Home</A |
| 283 ></TD | |
| 284 ><TD | |
| 285 WIDTH="33%" | |
| 286 ALIGN="right" | |
| 287 VALIGN="top" | |
| 288 ><A | |
| 289 HREF="sdlsemwaittimeout.html" | |
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290 ACCESSKEY="N" |
| 0 | 291 >Next</A |
| 292 ></TD | |
| 293 ></TR | |
| 294 ><TR | |
| 295 ><TD | |
| 296 WIDTH="33%" | |
| 297 ALIGN="left" | |
| 298 VALIGN="top" | |
| 299 >SDL_SemWait</TD | |
| 300 ><TD | |
| 301 WIDTH="34%" | |
| 302 ALIGN="center" | |
| 303 VALIGN="top" | |
| 304 ><A | |
| 305 HREF="thread.html" | |
|
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306 ACCESSKEY="U" |
| 0 | 307 >Up</A |
| 308 ></TD | |
| 309 ><TD | |
| 310 WIDTH="33%" | |
| 311 ALIGN="right" | |
| 312 VALIGN="top" | |
| 313 >SDL_SemWaitTimeout</TD | |
| 314 ></TR | |
| 315 ></TABLE | |
| 316 ></DIV | |
| 317 ></BODY | |
| 318 ></HTML | |
| 319 > |