docs/html/sdlsemwait.html

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  73 NAME="SDLSEMWAIT"
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  75 >SDL_SemWait</H1
  76 ><DIV
  77 CLASS="REFNAMEDIV"
  78 ><A
  79 NAME="AEN8023"
  80 ></A
  81 ><H2
  82 >Name</H2
  83 >SDL_SemWait&nbsp;--&nbsp;Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV
  84 ><DIV
  85 CLASS="REFSYNOPSISDIV"
  86 ><A
  87 NAME="AEN8026"
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  89 ><H2
  90 >Synopsis</H2
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  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_SemWait</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
 119 NAME="AEN8033"
 120 ></A
 121 ><H2
 122 >Description</H2
 123 ><P
 124 ><TT
 125 CLASS="FUNCTION"
 126 >SDL_SemWait()</TT
 127 > suspends the calling thread until either
 128 the semaphore pointed to by <TT
 129 CLASS="PARAMETER"
 130 ><I
 131 >sem</I
 132 ></TT
 133 > has a positive value,
 134 the call is interrupted by a signal or error. If the call is successful it
 135 will atomically decrement the semaphore value.</P
 136 ><P
 137 >After <TT
 138 CLASS="FUNCTION"
 139 >SDL_SemWait()</TT
 140 > is successful, the semaphore
 141 can be released and its count atomically incremented by a successful call to
 142 <A
 143 HREF="sdlsempost.html"
 144 >SDL_SemPost</A
 145 >.</P
 146 ></DIV
 147 ><DIV
 148 CLASS="REFSECT1"
 149 ><A
 150 NAME="AEN8041"
 151 ></A
 152 ><H2
 153 >Return Value</H2
 154 ><P
 155 >Returns <SPAN
 156 CLASS="RETURNVALUE"
 157 >0</SPAN
 158 > if successful or
 159 <SPAN
 160 CLASS="RETURNVALUE"
 161 >-1</SPAN
 162 > if there was an error (leaving the semaphore unchanged).</P
 163 ></DIV
 164 ><DIV
 165 CLASS="REFSECT1"
 166 ><A
 167 NAME="AEN8046"
 168 ></A
 169 ><H2
 170 >Examples</H2
 171 ><P
 172 ><PRE
 173 CLASS="PROGRAMLISTING"
 174 >if (SDL_SemWait(my_sem) == -1) {
 175         return WAIT_FAILED;
 176 }
 177
 178 ...
 179
 180 SDL_SemPost(my_sem);</PRE
 181 ></P
 182 ></DIV
 183 ><DIV
 184 CLASS="REFSECT1"
 185 ><A
 186 NAME="AEN8050"
 187 ></A
 188 ><H2
 189 >See Also</H2
 190 ><P
 191 ><A
 192 HREF="sdlcreatesemaphore.html"
 193 ><TT
 194 CLASS="FUNCTION"
 195 >SDL_CreateSemaphore</TT
 196 ></A
 197 >,
 198 <A
 199 HREF="sdldestroysemaphore.html"
 200 ><TT
 201 CLASS="FUNCTION"
 202 >SDL_DestroySemaphore</TT
 203 ></A
 204 >,
 205 <A
 206 HREF="sdlsemtrywait.html"
 207 ><TT
 208 CLASS="FUNCTION"
 209 >SDL_SemTryWait</TT
 210 ></A
 211 >,
 212 <A
 213 HREF="sdlsemwaittimeout.html"
 214 ><TT
 215 CLASS="FUNCTION"
 216 >SDL_SemWaitTimeout</TT
 217 ></A
 218 >,
 219 <A
 220 HREF="sdlsempost.html"
 221 ><TT
 222 CLASS="FUNCTION"
 223 >SDL_SemPost</TT
 224 ></A
 225 >,
 226 <A
 227 HREF="sdlsemvalue.html"
 228 ><TT
 229 CLASS="FUNCTION"
 230 >SDL_SemValue</TT
 231 ></A
 232 ></P
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