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1 <HTML
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2 ><HEAD
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3 ><TITLE
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4 >SDL_SemWait</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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12 REL="UP"
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13 TITLE="Multi-threaded Programming"
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14 HREF="thread.html"><LINK
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15 REL="PREVIOUS"
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16 TITLE="SDL_DestroySemaphore"
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17 HREF="sdldestroysemaphore.html"><LINK
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18 REL="NEXT"
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19 TITLE="SDL_SemTryWait"
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20 HREF="sdlsemtrywait.html"></HEAD
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21 ><BODY
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22 CLASS="REFENTRY"
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23 BGCOLOR="#FFF8DC"
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24 TEXT="#000000"
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25 LINK="#0000ee"
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26 VLINK="#551a8b"
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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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32 BORDER="0"
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33 CELLPADDING="0"
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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="sdldestroysemaphore.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="sdlsemtrywait.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="SDLSEMWAIT"
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71 >SDL_SemWait</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="AEN7398"
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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_SemWait -- Lock a semaphore and suspend the thread if the semaphore value is zero.</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="AEN7401"
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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="AEN7402"
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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 >int <B
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104 CLASS="FSFUNC"
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105 >SDL_SemWait</B
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106 ></CODE
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107 >(SDL_sem *sem);</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="AEN7408"
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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_SemWait()</TT
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124 > suspends the calling thread until either
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125 the semaphore pointed to by <TT
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126 CLASS="PARAMETER"
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127 ><I
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128 >sem</I
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129 ></TT
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130 > has a positive value,
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131 the call is interrupted by a signal or error. If the call is successful it
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132 will atomically decrement the semaphore value.</P
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133 ><P
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134 >After <TT
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135 CLASS="FUNCTION"
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136 >SDL_SemWait()</TT
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137 > is successful, the semaphore
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138 can be released and its count atomically incremented by a successful call to
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139 <A
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140 HREF="sdlsempost.html"
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141 >SDL_SemPost</A
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142 >.</P
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143 ></DIV
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144 ><DIV
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145 CLASS="REFSECT1"
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146 ><A
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147 NAME="AEN7416"
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148 ></A
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149 ><H2
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150 >Return Value</H2
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151 ><P
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152 >Returns <SPAN
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153 CLASS="RETURNVALUE"
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154 >0</SPAN
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155 > if successful or
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156 <SPAN
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157 CLASS="RETURNVALUE"
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158 >-1</SPAN
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159 > if there was an error (leaving the semaphore unchanged).</P
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160 ></DIV
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161 ><DIV
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162 CLASS="REFSECT1"
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163 ><A
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164 NAME="AEN7421"
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165 ></A
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166 ><H2
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167 >Examples</H2
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168 ><P
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169 ><PRE
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170 CLASS="PROGRAMLISTING"
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171 >if (SDL_SemWait(my_sem) == -1) {
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172 return WAIT_FAILED;
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173 }
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174
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175 ...
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176
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177 SDL_SemPost(my_sem);</PRE
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178 ></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="AEN7425"
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184 ></A
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185 ><H2
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186 >See Also</H2
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187 ><P
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188 ><A
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189 HREF="sdlcreatesemaphore.html"
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190 ><TT
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191 CLASS="FUNCTION"
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192 >SDL_CreateSemaphore</TT
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193 ></A
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194 >,
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195 <A
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196 HREF="sdldestroysemaphore.html"
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197 ><TT
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198 CLASS="FUNCTION"
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199 >SDL_DestroySemaphore</TT
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200 ></A
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201 >,
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202 <A
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203 HREF="sdlsemtrywait.html"
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204 ><TT
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205 CLASS="FUNCTION"
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206 >SDL_SemTryWait</TT
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207 ></A
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208 >,
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209 <A
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210 HREF="sdlsemwaittimeout.html"
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211 ><TT
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212 CLASS="FUNCTION"
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213 >SDL_SemWaitTimeout</TT
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214 ></A
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215 >,
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216 <A
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217 HREF="sdlsempost.html"
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218 ><TT
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219 CLASS="FUNCTION"
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220 >SDL_SemPost</TT
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221 ></A
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222 >,
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223 <A
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224 HREF="sdlsemvalue.html"
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225 ><TT
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226 CLASS="FUNCTION"
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227 >SDL_SemValue</TT
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228 ></A
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229 ></P
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230 ></DIV
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231 ><DIV
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232 CLASS="NAVFOOTER"
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233 ><HR
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234 ALIGN="LEFT"
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235 WIDTH="100%"><TABLE
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236 WIDTH="100%"
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237 BORDER="0"
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238 CELLPADDING="0"
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239 CELLSPACING="0"
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240 ><TR
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241 ><TD
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242 WIDTH="33%"
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243 ALIGN="left"
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244 VALIGN="top"
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245 ><A
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246 HREF="sdldestroysemaphore.html"
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247 >Prev</A
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248 ></TD
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249 ><TD
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250 WIDTH="34%"
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251 ALIGN="center"
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252 VALIGN="top"
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253 ><A
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254 HREF="index.html"
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255 >Home</A
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256 ></TD
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257 ><TD
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258 WIDTH="33%"
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259 ALIGN="right"
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260 VALIGN="top"
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261 ><A
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262 HREF="sdlsemtrywait.html"
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263 >Next</A
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264 ></TD
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265 ></TR
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266 ><TR
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267 ><TD
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268 WIDTH="33%"
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269 ALIGN="left"
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270 VALIGN="top"
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271 >SDL_DestroySemaphore</TD
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272 ><TD
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273 WIDTH="34%"
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274 ALIGN="center"
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275 VALIGN="top"
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276 ><A
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277 HREF="thread.html"
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278 >Up</A
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279 ></TD
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280 ><TD
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281 WIDTH="33%"
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282 ALIGN="right"
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283 VALIGN="top"
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284 >SDL_SemTryWait</TD
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285 ></TR
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286 ></TABLE
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287 ></DIV
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288 ></BODY
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289 ></HTML
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290 > |
