1 <HTML 2 ><HEAD 3 ><TITLE 4 >SDL_SemWaitTimeout</TITLE 5 ><META 6 NAME="GENERATOR" 7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ 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 SUMMARY="Header navigation table" 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="sdlsemtrywait.html" 49 ACCESSKEY="P" 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="sdlsempost.html" 63 ACCESSKEY="N" 64 >Next</A 65 ></TD 66 ></TR 67 ></TABLE 68 ><HR 69 ALIGN="LEFT" 70 WIDTH="100%"></DIV 71 ><H1 72 ><A 73 NAME="SDLSEMWAITTIMEOUT" 74 ></A 75 >SDL_SemWaitTimeout</H1 76 ><DIV 77 CLASS="REFNAMEDIV" 78 ><A 79 NAME="AEN8120" 80 ></A 81 ><H2 82 >Name</H2 83 >SDL_SemWaitTimeout -- Lock a semaphore, but only wait up to a specified maximum time.</DIV 84 ><DIV 85 CLASS="REFSYNOPSISDIV" 86 ><A 87 NAME="AEN8123" 88 ></A 89 ><H2 90 >Synopsis</H2 91 ><DIV 92 CLASS="FUNCSYNOPSIS" 93 ><A 94 NAME="AEN8124" 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_SemWaitTimeout</B 109 ></CODE 110 >(SDL_sem *sem, Uint32 timeout);</CODE 111 ></P 112 ><P 113 ></P 114 ></DIV 115 ></DIV 116 ><DIV 117 CLASS="REFSECT1" 118 ><A 119 NAME="AEN8130" 120 ></A 121 ><H2 122 >Description</H2 123 ><P 124 ><TT 125 CLASS="FUNCTION" 126 >SDL_SemWaitTimeout()</TT 127 > is a varient of 128 <A 129 HREF="sdlsemwait.html" 130 >SDL_SemWait</A 131 > 132 with a maximum timeout value. 133 If the value of the semaphore pointed to by <TT 134 CLASS="PARAMETER" 135 ><I 136 >sem</I 137 ></TT 138 > is 139 positive (greater than zero) it will atomically decrement the semaphore value 140 and return 0, otherwise it will wait up to <TT 141 CLASS="PARAMETER" 142 ><I 143 >timeout</I 144 ></TT 145 > 146 milliseconds trying to lock the semaphore. This function is to be avoided if 147 possible since on some platforms it is implemented by polling the semaphore 148 every millisecond in a busy loop.</P 149 ><P 150 >After <TT 151 CLASS="FUNCTION" 152 >SDL_SemWaitTimeout()</TT 153 > is successful, the semaphore 154 can be released and its count atomically incremented by a successful call to 155 <A 156 HREF="sdlsempost.html" 157 >SDL_SemPost</A 158 >.</P 159 ></DIV 160 ><DIV 161 CLASS="REFSECT1" 162 ><A 163 NAME="AEN8140" 164 ></A 165 ><H2 166 >Return Value</H2 167 ><P 168 >Returns <SPAN 169 CLASS="RETURNVALUE" 170 >0</SPAN 171 > if the semaphore was successfully locked or 172 either <SPAN 173 CLASS="RETURNVALUE" 174 >SDL_MUTEX_TIMEDOUT</SPAN 175 > or <SPAN 176 CLASS="RETURNVALUE" 177 >-1</SPAN 178 > 179 if the timeout period was exceeded or there was an error, respectivly.</P 180 ><P 181 >If the semaphore was not successfully locked, the semaphore will be unchanged.</P 182 ></DIV 183 ><DIV 184 CLASS="REFSECT1" 185 ><A 186 NAME="AEN8147" 187 ></A 188 ><H2 189 >Examples</H2 190 ><P 191 ><PRE 192 CLASS="PROGRAMLISTING" 193 >res = SDL_SemWaitTimeout(my_sem, WAIT_TIMEOUT_MILLISEC); 194 195 if (res == SDL_MUTEX_TIMEDOUT) { 196 return TRY_AGAIN; 197 } 198 if (res == -1) { 199 return WAIT_ERROR; 200 } 201 202 ... 203 204 SDL_SemPost(my_sem);</PRE 205 ></P 206 ></DIV 207 ><DIV 208 CLASS="REFSECT1" 209 ><A 210 NAME="AEN8151" 211 ></A 212 ><H2 213 >See Also</H2 214 ><P 215 ><A 216 HREF="sdlcreatesemaphore.html" 217 ><TT 218 CLASS="FUNCTION" 219 >SDL_CreateSemaphore</TT 220 ></A 221 >, 222 <A 223 HREF="sdldestroysemaphore.html" 224 ><TT 225 CLASS="FUNCTION" 226 >SDL_DestroySemaphore</TT 227 ></A 228 >, 229 <A 230 HREF="sdlsemwait.html" 231 ><TT 232 CLASS="FUNCTION" 233 >SDL_SemWait</TT 234 ></A 235 >, 236 <A 237 HREF="sdlsemtrywait.html" 238 ><TT 239 CLASS="FUNCTION" 240 >SDL_SemTryWait</TT 241 ></A 242 >, 243 <A 244 HREF="sdlsempost.html" 245 ><TT 246 CLASS="FUNCTION" 247 >SDL_SemPost</TT 248 ></A 249 >, 250 <A 251 HREF="sdlsemvalue.html" 252 ><TT 253 CLASS="FUNCTION" 254 >SDL_SemValue</TT 255 ></A 256 ></P 257 ></DIV 258 ><DIV 259 CLASS="NAVFOOTER" 260 ><HR 261 ALIGN="LEFT" 262 WIDTH="100%"><TABLE 263 SUMMARY="Footer navigation table" 264 WIDTH="100%" 265 BORDER="0" 266 CELLPADDING="0" 267 CELLSPACING="0" 268 ><TR 269 ><TD 270 WIDTH="33%" 271 ALIGN="left" 272 VALIGN="top" 273 ><A 274 HREF="sdlsemtrywait.html" 275 ACCESSKEY="P" 276 >Prev</A 277 ></TD 278 ><TD 279 WIDTH="34%" 280 ALIGN="center" 281 VALIGN="top" 282 ><A 283 HREF="index.html" 284 ACCESSKEY="H" 285 >Home</A 286 ></TD 287 ><TD 288 WIDTH="33%" 289 ALIGN="right" 290 VALIGN="top" 291 ><A 292 HREF="sdlsempost.html" 293 ACCESSKEY="N" 294 >Next</A 295 ></TD 296 ></TR 297 ><TR 298 ><TD 299 WIDTH="33%" 300 ALIGN="left" 301 VALIGN="top" 302 >SDL_SemTryWait</TD 303 ><TD 304 WIDTH="34%" 305 ALIGN="center" 306 VALIGN="top" 307 ><A 308 HREF="thread.html" 309 ACCESSKEY="U" 310 >Up</A 311 ></TD 312 ><TD 313 WIDTH="33%" 314 ALIGN="right" 315 VALIGN="top" 316 >SDL_SemPost</TD 317 ></TR 318 ></TABLE 319 ></DIV 320 ></BODY 321 ></HTML 322 >
