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Initial revision
author Sam Lantinga <slouken@lokigames.com>
date Thu, 26 Apr 2001 16:45:43 +0000
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children 55f1f1b3e27d
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-1:000000000000 0:74212992fb08
1 <HTML
2 ><HEAD
3 ><TITLE
4 >SDL_SemWait</TITLE
5 ><META
6 NAME="GENERATOR"
7 CONTENT="Modular DocBook HTML Stylesheet Version 1.61
8 "><LINK
9 REL="HOME"
10 TITLE="SDL Library Documentation"
11 HREF="index.html"><LINK
12 REL="UP"
13 TITLE="Multi-threaded Programming"
14 HREF="thread.html"><LINK
15 REL="PREVIOUS"
16 TITLE="SDL_DestroySemaphore"
17 HREF="sdldestroysemaphore.html"><LINK
18 REL="NEXT"
19 TITLE="SDL_SemTryWait"
20 HREF="sdlsemtrywait.html"></HEAD
21 ><BODY
22 CLASS="REFENTRY"
23 BGCOLOR="#FFF8DC"
24 TEXT="#000000"
25 LINK="#0000ee"
26 VLINK="#551a8b"
27 ALINK="#ff0000"
28 ><DIV
29 CLASS="NAVHEADER"
30 ><TABLE
31 WIDTH="100%"
32 BORDER="0"
33 CELLPADDING="0"
34 CELLSPACING="0"
35 ><TR
36 ><TH
37 COLSPAN="3"
38 ALIGN="center"
39 >SDL Library Documentation</TH
40 ></TR
41 ><TR
42 ><TD
43 WIDTH="10%"
44 ALIGN="left"
45 VALIGN="bottom"
46 ><A
47 HREF="sdldestroysemaphore.html"
48 >Prev</A
49 ></TD
50 ><TD
51 WIDTH="80%"
52 ALIGN="center"
53 VALIGN="bottom"
54 ></TD
55 ><TD
56 WIDTH="10%"
57 ALIGN="right"
58 VALIGN="bottom"
59 ><A
60 HREF="sdlsemtrywait.html"
61 >Next</A
62 ></TD
63 ></TR
64 ></TABLE
65 ><HR
66 ALIGN="LEFT"
67 WIDTH="100%"></DIV
68 ><H1
69 ><A
70 NAME="SDLSEMWAIT"
71 >SDL_SemWait</A
72 ></H1
73 ><DIV
74 CLASS="REFNAMEDIV"
75 ><A
76 NAME="AEN7398"
77 ></A
78 ><H2
79 >Name</H2
80 >SDL_SemWait&nbsp;--&nbsp;Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV
81 ><DIV
82 CLASS="REFSYNOPSISDIV"
83 ><A
84 NAME="AEN7401"
85 ></A
86 ><H2
87 >Synopsis</H2
88 ><DIV
89 CLASS="FUNCSYNOPSIS"
90 ><A
91 NAME="AEN7402"
92 ></A
93 ><P
94 ></P
95 ><PRE
96 CLASS="FUNCSYNOPSISINFO"
97 >#include "SDL.h"
98 #include "SDL_thread.h"</PRE
99 ><P
100 ><CODE
101 ><CODE
102 CLASS="FUNCDEF"
103 >int <B
104 CLASS="FSFUNC"
105 >SDL_SemWait</B
106 ></CODE
107 >(SDL_sem *sem);</CODE
108 ></P
109 ><P
110 ></P
111 ></DIV
112 ></DIV
113 ><DIV
114 CLASS="REFSECT1"
115 ><A
116 NAME="AEN7408"
117 ></A
118 ><H2
119 >Description</H2
120 ><P
121 ><TT
122 CLASS="FUNCTION"
123 >SDL_SemWait()</TT
124 > suspends the calling thread until either
125 the semaphore pointed to by <TT
126 CLASS="PARAMETER"
127 ><I
128 >sem</I
129 ></TT
130 > has a positive value,
131 the call is interrupted by a signal or error. If the call is successful it
132 will atomically decrement the semaphore value.</P
133 ><P
134 >After <TT
135 CLASS="FUNCTION"
136 >SDL_SemWait()</TT
137 > is successful, the semaphore
138 can be released and its count atomically incremented by a successful call to
139 <A
140 HREF="sdlsempost.html"
141 >SDL_SemPost</A
142 >.</P
143 ></DIV
144 ><DIV
145 CLASS="REFSECT1"
146 ><A
147 NAME="AEN7416"
148 ></A
149 ><H2
150 >Return Value</H2
151 ><P
152 >Returns <SPAN
153 CLASS="RETURNVALUE"
154 >0</SPAN
155 > if successful or
156 <SPAN
157 CLASS="RETURNVALUE"
158 >-1</SPAN
159 > if there was an error (leaving the semaphore unchanged).</P
160 ></DIV
161 ><DIV
162 CLASS="REFSECT1"
163 ><A
164 NAME="AEN7421"
165 ></A
166 ><H2
167 >Examples</H2
168 ><P
169 ><PRE
170 CLASS="PROGRAMLISTING"
171 >if (SDL_SemWait(my_sem) == -1) {
172 return WAIT_FAILED;
173 }
174
175 ...
176
177 SDL_SemPost(my_sem);</PRE
178 ></P
179 ></DIV
180 ><DIV
181 CLASS="REFSECT1"
182 ><A
183 NAME="AEN7425"
184 ></A
185 ><H2
186 >See Also</H2
187 ><P
188 ><A
189 HREF="sdlcreatesemaphore.html"
190 ><TT
191 CLASS="FUNCTION"
192 >SDL_CreateSemaphore</TT
193 ></A
194 >,
195 <A
196 HREF="sdldestroysemaphore.html"
197 ><TT
198 CLASS="FUNCTION"
199 >SDL_DestroySemaphore</TT
200 ></A
201 >,
202 <A
203 HREF="sdlsemtrywait.html"
204 ><TT
205 CLASS="FUNCTION"
206 >SDL_SemTryWait</TT
207 ></A
208 >,
209 <A
210 HREF="sdlsemwaittimeout.html"
211 ><TT
212 CLASS="FUNCTION"
213 >SDL_SemWaitTimeout</TT
214 ></A
215 >,
216 <A
217 HREF="sdlsempost.html"
218 ><TT
219 CLASS="FUNCTION"
220 >SDL_SemPost</TT
221 ></A
222 >,
223 <A
224 HREF="sdlsemvalue.html"
225 ><TT
226 CLASS="FUNCTION"
227 >SDL_SemValue</TT
228 ></A
229 ></P
230 ></DIV
231 ><DIV
232 CLASS="NAVFOOTER"
233 ><HR
234 ALIGN="LEFT"
235 WIDTH="100%"><TABLE
236 WIDTH="100%"
237 BORDER="0"
238 CELLPADDING="0"
239 CELLSPACING="0"
240 ><TR
241 ><TD
242 WIDTH="33%"
243 ALIGN="left"
244 VALIGN="top"
245 ><A
246 HREF="sdldestroysemaphore.html"
247 >Prev</A
248 ></TD
249 ><TD
250 WIDTH="34%"
251 ALIGN="center"
252 VALIGN="top"
253 ><A
254 HREF="index.html"
255 >Home</A
256 ></TD
257 ><TD
258 WIDTH="33%"
259 ALIGN="right"
260 VALIGN="top"
261 ><A
262 HREF="sdlsemtrywait.html"
263 >Next</A
264 ></TD
265 ></TR
266 ><TR
267 ><TD
268 WIDTH="33%"
269 ALIGN="left"
270 VALIGN="top"
271 >SDL_DestroySemaphore</TD
272 ><TD
273 WIDTH="34%"
274 ALIGN="center"
275 VALIGN="top"
276 ><A
277 HREF="thread.html"
278 >Up</A
279 ></TD
280 ><TD
281 WIDTH="33%"
282 ALIGN="right"
283 VALIGN="top"
284 >SDL_SemTryWait</TD
285 ></TR
286 ></TABLE
287 ></DIV
288 ></BODY
289 ></HTML
290 >