docs/html/sdlsemwait.html
changeset 3352 6dc250ebdd80
parent 3351 8e0182c236d8
child 3353 6b14223dd5c7
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3351:8e0182c236d8 3352:6dc250ebdd80
     1 <HTML
       
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     3 ><TITLE
       
     4 >SDL_SemWait</TITLE
       
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    40 >SDL Library Documentation</TH
       
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    43 ><TD
       
    44 WIDTH="10%"
       
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    48 HREF="sdldestroysemaphore.html"
       
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    68 ><HR
       
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    70 WIDTH="100%"></DIV
       
    71 ><H1
       
    72 ><A
       
    73 NAME="SDLSEMWAIT"
       
    74 ></A
       
    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"
       
    88 ></A
       
    89 ><H2
       
    90 >Synopsis</H2
       
    91 ><DIV
       
    92 CLASS="FUNCSYNOPSIS"
       
    93 ><A
       
    94 NAME="AEN8027"
       
    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_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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