| 1 | <HTML |
| 2 | ><HEAD |
| 3 | ><TITLE |
| 4 | >SDL_CreateSemaphore</TITLE |
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| 19 | TITLE="SDL_DestroySemaphore" |
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| 39 | ALIGN="center" |
| 40 | >SDL Library Documentation</TH |
| 41 | ></TR |
| 42 | ><TR |
| 43 | ><TD |
| 44 | WIDTH="10%" |
| 45 | ALIGN="left" |
| 46 | VALIGN="bottom" |
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| 48 | HREF="sdlmutexv.html" |
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| 50 | >Prev</A |
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| 60 | VALIGN="bottom" |
| 61 | ><A |
| 62 | HREF="sdldestroysemaphore.html" |
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| 64 | >Next</A |
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| 68 | ><HR |
| 69 | ALIGN="LEFT" |
| 70 | WIDTH="100%"></DIV |
| 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 -- 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 |
| 187 | ></DIV |
| 188 | ><DIV |
| 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 |
| 237 | ></P |
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