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4 >SDL_CreateSemaphore</TITLE |
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62 HREF="sdldestroysemaphore.html" |
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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="SDLCREATESEMAPHORE" |
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74 ></A |
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75 >SDL_CreateSemaphore</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="AEN7936" |
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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_CreateSemaphore -- Creates a new semaphore and assigns an initial value to it.</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="AEN7939" |
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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="AEN7940" |
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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 >SDL_sem *<B |
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107 CLASS="FSFUNC" |
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108 >SDL_CreateSemaphore</B |
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109 ></CODE |
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110 >(Uint32 initial_value);</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="AEN7946" |
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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_CreateSemaphore()</TT |
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127 > creates a new semaphore and |
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128 initializes it with the value <TT |
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129 CLASS="PARAMETER" |
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130 ><I |
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131 >initial_value</I |
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132 ></TT |
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133 >. |
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134 Each locking operation on the semaphore by |
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135 <A |
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136 HREF="sdlsemwait.html" |
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137 >SDL_SemWait</A |
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138 >, |
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139 <A |
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140 HREF="sdlsemtrywait.html" |
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141 >SDL_SemTryWait</A |
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142 > or |
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143 <A |
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144 HREF="sdlsemwaittimeout.html" |
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145 >SDL_SemWaitTimeout</A |
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146 > |
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147 will atomically decrement the semaphore value. The locking operation will be blocked |
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148 if the semaphore value is not positive (greater than zero). Each unlock operation by |
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149 <A |
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150 HREF="sdlsempost.html" |
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151 >SDL_SemPost</A |
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152 > |
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153 will atomically increment the semaphore value.</P |
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154 ></DIV |
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155 ><DIV |
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156 CLASS="REFSECT1" |
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157 ><A |
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158 NAME="AEN7955" |
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159 ></A |
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160 ><H2 |
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161 >Return Value</H2 |
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162 ><P |
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163 >Returns a pointer to an initialized semaphore or |
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164 <SPAN |
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165 CLASS="RETURNVALUE" |
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166 >NULL</SPAN |
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167 > if there was an error.</P |
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168 ></DIV |
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169 ><DIV |
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170 CLASS="REFSECT1" |
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171 ><A |
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172 NAME="AEN7959" |
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173 ></A |
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174 ><H2 |
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175 >Examples</H2 |
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176 ><P |
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177 ><PRE |
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178 CLASS="PROGRAMLISTING" |
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179 >SDL_sem *my_sem; |
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180 |
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181 my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE); |
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182 |
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183 if (my_sem == NULL) { |
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184 return CREATE_SEM_FAILED; |
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185 }</PRE |
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186 ></P |
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187 ></DIV |
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188 ><DIV |
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189 CLASS="REFSECT1" |
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190 ><A |
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191 NAME="AEN7963" |
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192 ></A |
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193 ><H2 |
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194 >See Also</H2 |
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195 ><P |
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196 ><A |
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197 HREF="sdldestroysemaphore.html" |
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198 ><TT |
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199 CLASS="FUNCTION" |
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200 >SDL_DestroySemaphore</TT |
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201 ></A |
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202 >, |
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203 <A |
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204 HREF="sdlsemwait.html" |
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205 ><TT |
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206 CLASS="FUNCTION" |
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207 >SDL_SemWait</TT |
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208 ></A |
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209 >, |
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210 <A |
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211 HREF="sdlsemtrywait.html" |
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212 ><TT |
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213 CLASS="FUNCTION" |
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214 >SDL_SemTryWait</TT |
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215 ></A |
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216 >, |
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217 <A |
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218 HREF="sdlsemwaittimeout.html" |
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219 ><TT |
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220 CLASS="FUNCTION" |
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221 >SDL_SemWaitTimeout</TT |
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222 ></A |
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223 >, |
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224 <A |
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225 HREF="sdlsempost.html" |
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226 ><TT |
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227 CLASS="FUNCTION" |
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228 >SDL_SemPost</TT |
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229 ></A |
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230 >, |
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231 <A |
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232 HREF="sdlsemvalue.html" |
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233 ><TT |
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234 CLASS="FUNCTION" |
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235 >SDL_SemValue</TT |
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236 ></A |
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237 ></P |
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