docs/html/sdlcreatesemaphore.html
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     1 <HTML
       
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     4 >SDL_CreateSemaphore</TITLE
       
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    40 >SDL Library Documentation</TH
       
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    71 ><H1
       
    72 ><A
       
    73 NAME="SDLCREATESEMAPHORE"
       
    74 ></A
       
    75 >SDL_CreateSemaphore</H1
       
    76 ><DIV
       
    77 CLASS="REFNAMEDIV"
       
    78 ><A
       
    79 NAME="AEN7936"
       
    80 ></A
       
    81 ><H2
       
    82 >Name</H2
       
    83 >SDL_CreateSemaphore&nbsp;--&nbsp;Creates a new semaphore and assigns an initial value to it.</DIV
       
    84 ><DIV
       
    85 CLASS="REFSYNOPSISDIV"
       
    86 ><A
       
    87 NAME="AEN7939"
       
    88 ></A
       
    89 ><H2
       
    90 >Synopsis</H2
       
    91 ><DIV
       
    92 CLASS="FUNCSYNOPSIS"
       
    93 ><A
       
    94 NAME="AEN7940"
       
    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 >SDL_sem *<B
       
   107 CLASS="FSFUNC"
       
   108 >SDL_CreateSemaphore</B
       
   109 ></CODE
       
   110 >(Uint32 initial_value);</CODE
       
   111 ></P
       
   112 ><P
       
   113 ></P
       
   114 ></DIV
       
   115 ></DIV
       
   116 ><DIV
       
   117 CLASS="REFSECT1"
       
   118 ><A
       
   119 NAME="AEN7946"
       
   120 ></A
       
   121 ><H2
       
   122 >Description</H2
       
   123 ><P
       
   124 ><TT
       
   125 CLASS="FUNCTION"
       
   126 >SDL_CreateSemaphore()</TT
       
   127 > creates a new semaphore and
       
   128 initializes it with the value <TT
       
   129 CLASS="PARAMETER"
       
   130 ><I
       
   131 >initial_value</I
       
   132 ></TT
       
   133 >.
       
   134 Each locking operation on the semaphore by
       
   135 <A
       
   136 HREF="sdlsemwait.html"
       
   137 >SDL_SemWait</A
       
   138 >,
       
   139 <A
       
   140 HREF="sdlsemtrywait.html"
       
   141 >SDL_SemTryWait</A
       
   142 > or
       
   143 <A
       
   144 HREF="sdlsemwaittimeout.html"
       
   145 >SDL_SemWaitTimeout</A
       
   146 >
       
   147 will atomically decrement the semaphore value. The locking operation will be blocked
       
   148 if the semaphore value is not positive (greater than zero). Each unlock operation by
       
   149 <A
       
   150 HREF="sdlsempost.html"
       
   151 >SDL_SemPost</A
       
   152 >
       
   153 will atomically increment the semaphore value.</P
       
   154 ></DIV
       
   155 ><DIV
       
   156 CLASS="REFSECT1"
       
   157 ><A
       
   158 NAME="AEN7955"
       
   159 ></A
       
   160 ><H2
       
   161 >Return Value</H2
       
   162 ><P
       
   163 >Returns a pointer to an initialized semaphore or
       
   164 <SPAN
       
   165 CLASS="RETURNVALUE"
       
   166 >NULL</SPAN
       
   167 > if there was an error.</P
       
   168 ></DIV
       
   169 ><DIV
       
   170 CLASS="REFSECT1"
       
   171 ><A
       
   172 NAME="AEN7959"
       
   173 ></A
       
   174 ><H2
       
   175 >Examples</H2
       
   176 ><P
       
   177 ><PRE
       
   178 CLASS="PROGRAMLISTING"
       
   179 >SDL_sem *my_sem;
       
   180 
       
   181 my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE);
       
   182 
       
   183 if (my_sem == NULL) {
       
   184         return CREATE_SEM_FAILED;
       
   185 }</PRE
       
   186 ></P
       
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   189 CLASS="REFSECT1"
       
   190 ><A
       
   191 NAME="AEN7963"
       
   192 ></A
       
   193 ><H2
       
   194 >See Also</H2
       
   195 ><P
       
   196 ><A
       
   197 HREF="sdldestroysemaphore.html"
       
   198 ><TT
       
   199 CLASS="FUNCTION"
       
   200 >SDL_DestroySemaphore</TT
       
   201 ></A
       
   202 >,
       
   203 <A
       
   204 HREF="sdlsemwait.html"
       
   205 ><TT
       
   206 CLASS="FUNCTION"
       
   207 >SDL_SemWait</TT
       
   208 ></A
       
   209 >,
       
   210 <A
       
   211 HREF="sdlsemtrywait.html"
       
   212 ><TT
       
   213 CLASS="FUNCTION"
       
   214 >SDL_SemTryWait</TT
       
   215 ></A
       
   216 >,
       
   217 <A
       
   218 HREF="sdlsemwaittimeout.html"
       
   219 ><TT
       
   220 CLASS="FUNCTION"
       
   221 >SDL_SemWaitTimeout</TT
       
   222 ></A
       
   223 >,
       
   224 <A
       
   225 HREF="sdlsempost.html"
       
   226 ><TT
       
   227 CLASS="FUNCTION"
       
   228 >SDL_SemPost</TT
       
   229 ></A
       
   230 >,
       
   231 <A
       
   232 HREF="sdlsemvalue.html"
       
   233 ><TT
       
   234 CLASS="FUNCTION"
       
   235 >SDL_SemValue</TT
       
   236 ></A
       
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