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2 ><HEAD |
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4 >SDL_SemWait</TITLE |
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16 TITLE="SDL_DestroySemaphore" |
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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="sdldestroysemaphore.html" |
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49 ACCESSKEY="P" |
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50 >Prev</A |
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61 ><A |
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62 HREF="sdlsemtrywait.html" |
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63 ACCESSKEY="N" |
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64 >Next</A |
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65 ></TD |
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66 ></TR |
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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="SDLSEMWAIT" |
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74 ></A |
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75 >SDL_SemWait</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="AEN8023" |
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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_SemWait -- Lock a semaphore and suspend the thread if the semaphore value is zero.</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="AEN8026" |
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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="AEN8027" |
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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_SemWait</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="AEN8033" |
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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_SemWait()</TT |
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127 > suspends the calling thread until either |
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128 the semaphore pointed to by <TT |
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129 CLASS="PARAMETER" |
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130 ><I |
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131 >sem</I |
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132 ></TT |
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133 > has a positive value, |
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134 the call is interrupted by a signal or error. If the call is successful it |
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135 will atomically decrement the semaphore value.</P |
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136 ><P |
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137 >After <TT |
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138 CLASS="FUNCTION" |
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139 >SDL_SemWait()</TT |
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140 > is successful, the semaphore |
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141 can be released and its count atomically incremented by a successful call to |
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142 <A |
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143 HREF="sdlsempost.html" |
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144 >SDL_SemPost</A |
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145 >.</P |
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146 ></DIV |
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147 ><DIV |
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148 CLASS="REFSECT1" |
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149 ><A |
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150 NAME="AEN8041" |
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151 ></A |
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152 ><H2 |
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153 >Return Value</H2 |
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154 ><P |
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155 >Returns <SPAN |
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156 CLASS="RETURNVALUE" |
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157 >0</SPAN |
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158 > if successful or |
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159 <SPAN |
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160 CLASS="RETURNVALUE" |
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161 >-1</SPAN |
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162 > if there was an error (leaving the semaphore unchanged).</P |
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163 ></DIV |
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164 ><DIV |
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165 CLASS="REFSECT1" |
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166 ><A |
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167 NAME="AEN8046" |
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168 ></A |
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169 ><H2 |
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170 >Examples</H2 |
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171 ><P |
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172 ><PRE |
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173 CLASS="PROGRAMLISTING" |
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174 >if (SDL_SemWait(my_sem) == -1) { |
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175 return WAIT_FAILED; |
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176 } |
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177 |
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178 ... |
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179 |
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180 SDL_SemPost(my_sem);</PRE |
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181 ></P |
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182 ></DIV |
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183 ><DIV |
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184 CLASS="REFSECT1" |
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185 ><A |
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186 NAME="AEN8050" |
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187 ></A |
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188 ><H2 |
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189 >See Also</H2 |
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190 ><P |
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191 ><A |
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192 HREF="sdlcreatesemaphore.html" |
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193 ><TT |
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194 CLASS="FUNCTION" |
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195 >SDL_CreateSemaphore</TT |
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196 ></A |
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197 >, |
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198 <A |
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199 HREF="sdldestroysemaphore.html" |
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200 ><TT |
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201 CLASS="FUNCTION" |
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202 >SDL_DestroySemaphore</TT |
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203 ></A |
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204 >, |
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205 <A |
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206 HREF="sdlsemtrywait.html" |
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207 ><TT |
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208 CLASS="FUNCTION" |
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209 >SDL_SemTryWait</TT |
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210 ></A |
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211 >, |
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212 <A |
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213 HREF="sdlsemwaittimeout.html" |
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214 ><TT |
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215 CLASS="FUNCTION" |
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216 >SDL_SemWaitTimeout</TT |
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217 ></A |
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218 >, |
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219 <A |
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220 HREF="sdlsempost.html" |
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221 ><TT |
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222 CLASS="FUNCTION" |
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223 >SDL_SemPost</TT |
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224 ></A |
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225 >, |
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226 <A |
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227 HREF="sdlsemvalue.html" |
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228 ><TT |
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229 CLASS="FUNCTION" |
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230 >SDL_SemValue</TT |
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231 ></A |
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232 ></P |
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278 >SDL_DestroySemaphore</TD |
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