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1 <HTML
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2 ><HEAD
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3 ><TITLE
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4 >SDL_CreateSemaphore</TITLE
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5 ><META
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6 NAME="GENERATOR"
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.61
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8 "><LINK
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9 REL="HOME"
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10 TITLE="SDL Library Documentation"
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11 HREF="index.html"><LINK
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13 TITLE="Multi-threaded Programming"
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16 TITLE="SDL_mutexV"
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17 HREF="sdlmutexv.html"><LINK
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19 TITLE="SDL_DestroySemaphore"
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20 HREF="sdldestroysemaphore.html"></HEAD
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27 ALINK="#ff0000"
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28 ><DIV
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29 CLASS="NAVHEADER"
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30 ><TABLE
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31 WIDTH="100%"
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34 CELLSPACING="0"
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35 ><TR
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36 ><TH
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37 COLSPAN="3"
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38 ALIGN="center"
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39 >SDL Library Documentation</TH
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40 ></TR
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41 ><TR
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42 ><TD
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43 WIDTH="10%"
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44 ALIGN="left"
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45 VALIGN="bottom"
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46 ><A
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47 HREF="sdlmutexv.html"
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48 >Prev</A
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49 ></TD
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50 ><TD
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51 WIDTH="80%"
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52 ALIGN="center"
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53 VALIGN="bottom"
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54 ></TD
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55 ><TD
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56 WIDTH="10%"
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57 ALIGN="right"
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58 VALIGN="bottom"
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59 ><A
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60 HREF="sdldestroysemaphore.html"
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61 >Next</A
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62 ></TD
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63 ></TR
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64 ></TABLE
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65 ><HR
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66 ALIGN="LEFT"
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67 WIDTH="100%"></DIV
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68 ><H1
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69 ><A
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70 NAME="SDLCREATESEMAPHORE"
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71 >SDL_CreateSemaphore</A
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72 ></H1
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73 ><DIV
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74 CLASS="REFNAMEDIV"
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75 ><A
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76 NAME="AEN7311"
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77 ></A
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78 ><H2
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79 >Name</H2
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80 >SDL_CreateSemaphore -- Creates a new semaphore and assigns an initial value to it.</DIV
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81 ><DIV
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82 CLASS="REFSYNOPSISDIV"
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83 ><A
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84 NAME="AEN7314"
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85 ></A
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86 ><H2
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87 >Synopsis</H2
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88 ><DIV
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89 CLASS="FUNCSYNOPSIS"
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90 ><A
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91 NAME="AEN7315"
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92 ></A
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93 ><P
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94 ></P
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95 ><PRE
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96 CLASS="FUNCSYNOPSISINFO"
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97 >#include "SDL.h"
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98 #include "SDL_thread.h"</PRE
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99 ><P
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100 ><CODE
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101 ><CODE
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102 CLASS="FUNCDEF"
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103 >SDL_sem *<B
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104 CLASS="FSFUNC"
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105 >SDL_CreateSemaphore</B
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106 ></CODE
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107 >(Uint32 initial_value);</CODE
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108 ></P
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109 ><P
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110 ></P
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111 ></DIV
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112 ></DIV
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113 ><DIV
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114 CLASS="REFSECT1"
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115 ><A
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116 NAME="AEN7321"
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117 ></A
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118 ><H2
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119 >Description</H2
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120 ><P
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121 ><TT
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122 CLASS="FUNCTION"
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123 >SDL_CreateSemaphore()</TT
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124 > creates a new semaphore and
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125 initializes it with the value <TT
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126 CLASS="PARAMETER"
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127 ><I
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128 >initial_value</I
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129 ></TT
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130 >.
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131 Each locking operation on the semaphore by
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132 <A
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133 HREF="sdlsemwait.html"
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134 >SDL_SemWait</A
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135 >,
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136 <A
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137 HREF="sdlsemtrywait.html"
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138 >SDL_SemTryWait</A
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139 > or
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140 <A
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141 HREF="sdlsemwaittimeout.html"
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142 >SDL_SemWaitTimeout</A
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143 >
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144 will atomically decrement the semaphore value. The locking operation will be blocked
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145 if the semaphore value is not positive (greater than zero). Each unlock operation by
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146 <A
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147 HREF="sdlsempost.html"
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148 >SDL_SemPost</A
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149 >
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150 will atomically increment the semaphore value.</P
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151 ></DIV
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152 ><DIV
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153 CLASS="REFSECT1"
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154 ><A
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155 NAME="AEN7330"
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156 ></A
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157 ><H2
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158 >Return Value</H2
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159 ><P
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160 >Returns a pointer to an initialized semaphore or
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161 <SPAN
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162 CLASS="RETURNVALUE"
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163 >NULL</SPAN
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164 > if there was an error.</P
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165 ></DIV
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166 ><DIV
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167 CLASS="REFSECT1"
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168 ><A
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169 NAME="AEN7334"
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170 ></A
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171 ><H2
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172 >Examples</H2
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173 ><P
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174 ><PRE
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175 CLASS="PROGRAMLISTING"
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176 >SDL_sem *my_sem;
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177
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178 my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE);
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179
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180 if (my_sem == NULL) {
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181 return CREATE_SEM_FAILED;
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182 }</PRE
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183 ></P
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184 ></DIV
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185 ><DIV
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186 CLASS="REFSECT1"
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187 ><A
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188 NAME="AEN7338"
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189 ></A
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190 ><H2
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191 >See Also</H2
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192 ><P
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193 ><A
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194 HREF="sdldestroysemaphore.html"
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195 ><TT
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196 CLASS="FUNCTION"
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197 >SDL_DestroySemaphore</TT
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198 ></A
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199 >,
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200 <A
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201 HREF="sdlsemwait.html"
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202 ><TT
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203 CLASS="FUNCTION"
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204 >SDL_SemWait</TT
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205 ></A
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206 >,
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207 <A
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208 HREF="sdlsemtrywait.html"
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209 ><TT
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210 CLASS="FUNCTION"
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211 >SDL_SemTryWait</TT
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212 ></A
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213 >,
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214 <A
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215 HREF="sdlsemwaittimeout.html"
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216 ><TT
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217 CLASS="FUNCTION"
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218 >SDL_SemWaitTimeout</TT
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219 ></A
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220 >,
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221 <A
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222 HREF="sdlsempost.html"
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223 ><TT
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224 CLASS="FUNCTION"
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225 >SDL_SemPost</TT
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226 ></A
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227 >,
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228 <A
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229 HREF="sdlsemvalue.html"
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230 ><TT
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231 CLASS="FUNCTION"
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232 >SDL_SemValue</TT
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233 ></A
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234 ></P
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235 ></DIV
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267 HREF="sdldestroysemaphore.html"
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268 >Next</A
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276 >SDL_mutexV</TD
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289 >SDL_DestroySemaphore</TD
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