docs/html/sdlsemwaittimeout.html

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  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&nbsp;--&nbsp;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
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