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1 <HTML |
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2 ><HEAD |
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3 ><TITLE |
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4 >SDL_SemTryWait</TITLE |
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40 >SDL Library Documentation</TH |
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42 ><TR |
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43 ><TD |
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44 WIDTH="10%" |
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45 ALIGN="left" |
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46 VALIGN="bottom" |
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47 ><A |
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48 HREF="sdlsemwait.html" |
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49 ACCESSKEY="P" |
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50 >Prev</A |
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62 HREF="sdlsemwaittimeout.html" |
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63 ACCESSKEY="N" |
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64 >Next</A |
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67 ></TABLE |
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68 ><HR |
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69 ALIGN="LEFT" |
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70 WIDTH="100%"></DIV |
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71 ><H1 |
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72 ><A |
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73 NAME="SDLSEMTRYWAIT" |
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74 ></A |
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75 >SDL_SemTryWait</H1 |
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76 ><DIV |
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77 CLASS="REFNAMEDIV" |
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78 ><A |
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79 NAME="AEN8069" |
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80 ></A |
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81 ><H2 |
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82 >Name</H2 |
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83 >SDL_SemTryWait -- Attempt to lock a semaphore but don't suspend the thread.</DIV |
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84 ><DIV |
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85 CLASS="REFSYNOPSISDIV" |
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86 ><A |
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87 NAME="AEN8072" |
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88 ></A |
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89 ><H2 |
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90 >Synopsis</H2 |
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91 ><DIV |
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92 CLASS="FUNCSYNOPSIS" |
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93 ><A |
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94 NAME="AEN8073" |
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95 ></A |
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96 ><P |
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97 ></P |
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98 ><PRE |
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99 CLASS="FUNCSYNOPSISINFO" |
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100 >#include "SDL.h" |
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101 #include "SDL_thread.h"</PRE |
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102 ><P |
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103 ><CODE |
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104 ><CODE |
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105 CLASS="FUNCDEF" |
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106 >int <B |
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107 CLASS="FSFUNC" |
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108 >SDL_SemTryWait</B |
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109 ></CODE |
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110 >(SDL_sem *sem);</CODE |
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111 ></P |
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112 ><P |
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113 ></P |
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114 ></DIV |
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115 ></DIV |
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116 ><DIV |
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117 CLASS="REFSECT1" |
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118 ><A |
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119 NAME="AEN8079" |
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120 ></A |
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121 ><H2 |
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122 >Description</H2 |
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123 ><P |
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124 ><TT |
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125 CLASS="FUNCTION" |
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126 >SDL_SemTryWait</TT |
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127 > is a non-blocking varient of |
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128 <A |
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129 HREF="sdlsemwait.html" |
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130 ><TT |
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131 CLASS="FUNCTION" |
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132 >SDL_SemWait</TT |
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133 ></A |
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134 >. If the value of the semaphore |
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135 pointed to by <TT |
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136 CLASS="PARAMETER" |
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137 ><I |
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138 >sem</I |
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139 ></TT |
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140 > is positive it will atomically |
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141 decrement the semaphore value and return 0, otherwise it will return |
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142 <SPAN |
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143 CLASS="RETURNVALUE" |
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144 >SDL_MUTEX_TIMEDOUT</SPAN |
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145 > instead of suspending the thread.</P |
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146 ><P |
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147 >After <TT |
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148 CLASS="FUNCTION" |
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149 >SDL_SemTryWait</TT |
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150 > is successful, the semaphore |
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151 can be released and its count atomically incremented by a successful call to |
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152 <A |
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153 HREF="sdlsempost.html" |
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154 >SDL_SemPost</A |
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155 >.</P |
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156 ></DIV |
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157 ><DIV |
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158 CLASS="REFSECT1" |
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159 ><A |
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160 NAME="AEN8090" |
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161 ></A |
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162 ><H2 |
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163 >Return Value</H2 |
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164 ><P |
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165 >Returns <SPAN |
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166 CLASS="RETURNVALUE" |
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167 >0</SPAN |
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168 > if the semaphore was successfully locked or |
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169 either <SPAN |
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170 CLASS="RETURNVALUE" |
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171 >SDL_MUTEX_TIMEDOUT</SPAN |
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172 > or <SPAN |
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173 CLASS="RETURNVALUE" |
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174 >-1</SPAN |
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175 > |
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176 if the thread would have suspended or there was an error, respectivly.</P |
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177 ><P |
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178 >If the semaphore was not successfully locked, the semaphore will be unchanged.</P |
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179 ></DIV |
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180 ><DIV |
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181 CLASS="REFSECT1" |
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182 ><A |
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183 NAME="AEN8097" |
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184 ></A |
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185 ><H2 |
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186 >Examples</H2 |
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187 ><P |
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188 ><PRE |
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189 CLASS="PROGRAMLISTING" |
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190 >res = SDL_SemTryWait(my_sem); |
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191 |
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192 if (res == SDL_MUTEX_TIMEDOUT) { |
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193 return TRY_AGAIN; |
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194 } |
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195 if (res == -1) { |
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196 return WAIT_ERROR; |
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197 } |
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198 |
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199 ... |
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200 |
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201 SDL_SemPost(my_sem);</PRE |
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202 ></P |
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203 ></DIV |
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204 ><DIV |
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205 CLASS="REFSECT1" |
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206 ><A |
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207 NAME="AEN8101" |
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208 ></A |
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209 ><H2 |
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210 >See Also</H2 |
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211 ><P |
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212 ><A |
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213 HREF="sdlcreatesemaphore.html" |
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214 ><TT |
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215 CLASS="FUNCTION" |
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216 >SDL_CreateSemaphore</TT |
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217 ></A |
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218 >, |
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219 <A |
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220 HREF="sdldestroysemaphore.html" |
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221 ><TT |
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222 CLASS="FUNCTION" |
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223 >SDL_DestroySemaphore</TT |
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224 ></A |
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225 >, |
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226 <A |
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227 HREF="sdlsemwait.html" |
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228 ><TT |
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229 CLASS="FUNCTION" |
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230 >SDL_SemWait</TT |
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231 ></A |
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232 >, |
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233 <A |
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234 HREF="sdlsemwaittimeout.html" |
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235 ><TT |
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236 CLASS="FUNCTION" |
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237 >SDL_SemWaitTimeout</TT |
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238 ></A |
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239 >, |
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240 <A |
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241 HREF="sdlsempost.html" |
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242 ><TT |
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243 CLASS="FUNCTION" |
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244 >SDL_SemPost</TT |
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245 ></A |
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246 >, |
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247 <A |
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248 HREF="sdlsemvalue.html" |
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249 ><TT |
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250 CLASS="FUNCTION" |
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251 >SDL_SemValue</TT |
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252 ></A |
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253 ></P |
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254 ></DIV |
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298 VALIGN="top" |
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299 >SDL_SemWait</TD |
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319 > |