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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_SemTryWait</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_SemWait"
17 HREF="sdlsemwait.html"><LINK
18 REL="NEXT"
19 TITLE="SDL_SemWaitTimeout"
20 HREF="sdlsemwaittimeout.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="sdlsemwait.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="sdlsemwaittimeout.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="SDLSEMTRYWAIT"
71 >SDL_SemTryWait</A
72 ></H1
73 ><DIV
74 CLASS="REFNAMEDIV"
75 ><A
76 NAME="AEN7444"
77 ></A
78 ><H2
79 >Name</H2
80 >SDL_SemTryWait&nbsp;--&nbsp;Attempt to lock a semaphore but don't suspend the thread.</DIV
81 ><DIV
82 CLASS="REFSYNOPSISDIV"
83 ><A
84 NAME="AEN7447"
85 ></A
86 ><H2
87 >Synopsis</H2
88 ><DIV
89 CLASS="FUNCSYNOPSIS"
90 ><A
91 NAME="AEN7448"
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_SemTryWait</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="AEN7454"
117 ></A
118 ><H2
119 >Description</H2
120 ><P
121 ><TT
122 CLASS="FUNCTION"
123 >SDL_SemTryWait</TT
124 > is a non-blocking varient of
125 <A
126 HREF="sdlsemwait.html"
127 ><TT
128 CLASS="FUNCTION"
129 >SDL_SemWait</TT
130 ></A
131 >. If the value of the semaphore
132 pointed to by <TT
133 CLASS="PARAMETER"
134 ><I
135 >sem</I
136 ></TT
137 > is positive it will atomically
138 decrement the semaphore value and return 0, otherwise it will return
139 <SPAN
140 CLASS="RETURNVALUE"
141 >SDL_MUTEX_TIMEOUT</SPAN
142 > instead of suspending the thread.</P
143 ><P
144 >After <TT
145 CLASS="FUNCTION"
146 >SDL_SemTryWait</TT
147 > is successful, the semaphore
148 can be released and its count atomically incremented by a successful call to
149 <A
150 HREF="sdlsempost.html"
151 >SDL_SemPost</A
152 >.</P
153 ></DIV
154 ><DIV
155 CLASS="REFSECT1"
156 ><A
157 NAME="AEN7465"
158 ></A
159 ><H2
160 >Return Value</H2
161 ><P
162 >Returns <SPAN
163 CLASS="RETURNVALUE"
164 >0</SPAN
165 > if the semaphore was successfully locked or
166 either <SPAN
167 CLASS="RETURNVALUE"
168 >SDL_MUTEX_TIMEOUT</SPAN
169 > or <SPAN
170 CLASS="RETURNVALUE"
171 >-1</SPAN
172 >
173 if the thread would have suspended or there was an error, respectivly.</P
174 ><P
175 >If the semaphore was not successfully locked, the semaphore will be unchanged.</P
176 ></DIV
177 ><DIV
178 CLASS="REFSECT1"
179 ><A
180 NAME="AEN7472"
181 ></A
182 ><H2
183 >Examples</H2
184 ><P
185 ><PRE
186 CLASS="PROGRAMLISTING"
187 >res = SDL_SemTryWait(my_sem);
188
189 if (res == SDL_MUTEX_TIMEOUT) {
190 return TRY_AGAIN;
191 }
192 if (res == -1) {
193 return WAIT_ERROR;
194 }
195
196 ...
197
198 SDL_SemPost(my_sem);</PRE
199 ></P
200 ></DIV
201 ><DIV
202 CLASS="REFSECT1"
203 ><A
204 NAME="AEN7476"
205 ></A
206 ><H2
207 >See Also</H2
208 ><P
209 ><A
210 HREF="sdlcreatesemaphore.html"
211 ><TT
212 CLASS="FUNCTION"
213 >SDL_CreateSemaphore</TT
214 ></A
215 >,
216 <A
217 HREF="sdldestroysemaphore.html"
218 ><TT
219 CLASS="FUNCTION"
220 >SDL_DestroySemaphore</TT
221 ></A
222 >,
223 <A
224 HREF="sdlsemwait.html"
225 ><TT
226 CLASS="FUNCTION"
227 >SDL_SemWait</TT
228 ></A
229 >,
230 <A
231 HREF="sdlsemwaittimeout.html"
232 ><TT
233 CLASS="FUNCTION"
234 >SDL_SemWaitTimeout</TT
235 ></A
236 >,
237 <A
238 HREF="sdlsempost.html"
239 ><TT
240 CLASS="FUNCTION"
241 >SDL_SemPost</TT
242 ></A
243 >,
244 <A
245 HREF="sdlsemvalue.html"
246 ><TT
247 CLASS="FUNCTION"
248 >SDL_SemValue</TT
249 ></A
250 ></P
251 ></DIV
252 ><DIV
253 CLASS="NAVFOOTER"
254 ><HR
255 ALIGN="LEFT"
256 WIDTH="100%"><TABLE
257 WIDTH="100%"
258 BORDER="0"
259 CELLPADDING="0"
260 CELLSPACING="0"
261 ><TR
262 ><TD
263 WIDTH="33%"
264 ALIGN="left"
265 VALIGN="top"
266 ><A
267 HREF="sdlsemwait.html"
268 >Prev</A
269 ></TD
270 ><TD
271 WIDTH="34%"
272 ALIGN="center"
273 VALIGN="top"
274 ><A
275 HREF="index.html"
276 >Home</A
277 ></TD
278 ><TD
279 WIDTH="33%"
280 ALIGN="right"
281 VALIGN="top"
282 ><A
283 HREF="sdlsemwaittimeout.html"
284 >Next</A
285 ></TD
286 ></TR
287 ><TR
288 ><TD
289 WIDTH="33%"
290 ALIGN="left"
291 VALIGN="top"
292 >SDL_SemWait</TD
293 ><TD
294 WIDTH="34%"
295 ALIGN="center"
296 VALIGN="top"
297 ><A
298 HREF="thread.html"
299 >Up</A
300 ></TD
301 ><TD
302 WIDTH="33%"
303 ALIGN="right"
304 VALIGN="top"
305 >SDL_SemWaitTimeout</TD
306 ></TR
307 ></TABLE
308 ></DIV
309 ></BODY
310 ></HTML
311 >