e14743d1 |
1 | <HTML |
2 | ><HEAD |
3 | ><TITLE |
4 | >SDL_SemWait</TITLE |
5 | ><META |
6 | NAME="GENERATOR" |
7 | CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ |
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 | SUMMARY="Header navigation table" |
32 | WIDTH="100%" |
33 | BORDER="0" |
34 | CELLPADDING="0" |
35 | CELLSPACING="0" |
36 | ><TR |
37 | ><TH |
38 | COLSPAN="3" |
39 | ALIGN="center" |
40 | >SDL Library Documentation</TH |
41 | ></TR |
42 | ><TR |
43 | ><TD |
44 | WIDTH="10%" |
45 | ALIGN="left" |
46 | VALIGN="bottom" |
47 | ><A |
48 | HREF="sdldestroysemaphore.html" |
49 | ACCESSKEY="P" |
50 | >Prev</A |
51 | ></TD |
52 | ><TD |
53 | WIDTH="80%" |
54 | ALIGN="center" |
55 | VALIGN="bottom" |
56 | ></TD |
57 | ><TD |
58 | WIDTH="10%" |
59 | ALIGN="right" |
60 | VALIGN="bottom" |
61 | ><A |
62 | HREF="sdlsemtrywait.html" |
63 | ACCESSKEY="N" |
64 | >Next</A |
65 | ></TD |
66 | ></TR |
67 | ></TABLE |
68 | ><HR |
69 | ALIGN="LEFT" |
70 | WIDTH="100%"></DIV |
71 | ><H1 |
72 | ><A |
73 | NAME="SDLSEMWAIT" |
74 | ></A |
75 | >SDL_SemWait</H1 |
76 | ><DIV |
77 | CLASS="REFNAMEDIV" |
78 | ><A |
79 | NAME="AEN8023" |
80 | ></A |
81 | ><H2 |
82 | >Name</H2 |
83 | >SDL_SemWait -- Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV |
84 | ><DIV |
85 | CLASS="REFSYNOPSISDIV" |
86 | ><A |
87 | NAME="AEN8026" |
88 | ></A |
89 | ><H2 |
90 | >Synopsis</H2 |
91 | ><DIV |
92 | CLASS="FUNCSYNOPSIS" |
93 | ><A |
94 | NAME="AEN8027" |
95 | ></A |
96 | ><P |
97 | ></P |
98 | ><PRE |
99 | CLASS="FUNCSYNOPSISINFO" |
100 | >#include "SDL.h" |
101 | #include "SDL_thread.h"</PRE |
102 | ><P |
103 | ><CODE |
104 | ><CODE |
105 | CLASS="FUNCDEF" |
106 | >int <B |
107 | CLASS="FSFUNC" |
108 | >SDL_SemWait</B |
109 | ></CODE |
110 | >(SDL_sem *sem);</CODE |
111 | ></P |
112 | ><P |
113 | ></P |
114 | ></DIV |
115 | ></DIV |
116 | ><DIV |
117 | CLASS="REFSECT1" |
118 | ><A |
119 | NAME="AEN8033" |
120 | ></A |
121 | ><H2 |
122 | >Description</H2 |
123 | ><P |
124 | ><TT |
125 | CLASS="FUNCTION" |
126 | >SDL_SemWait()</TT |
127 | > suspends the calling thread until either |
128 | the semaphore pointed to by <TT |
129 | CLASS="PARAMETER" |
130 | ><I |
131 | >sem</I |
132 | ></TT |
133 | > has a positive value, |
134 | the call is interrupted by a signal or error. If the call is successful it |
135 | will atomically decrement the semaphore value.</P |
136 | ><P |
137 | >After <TT |
138 | CLASS="FUNCTION" |
139 | >SDL_SemWait()</TT |
140 | > is successful, the semaphore |
141 | can be released and its count atomically incremented by a successful call to |
142 | <A |
143 | HREF="sdlsempost.html" |
144 | >SDL_SemPost</A |
145 | >.</P |
146 | ></DIV |
147 | ><DIV |
148 | CLASS="REFSECT1" |
149 | ><A |
150 | NAME="AEN8041" |
151 | ></A |
152 | ><H2 |
153 | >Return Value</H2 |
154 | ><P |
155 | >Returns <SPAN |
156 | CLASS="RETURNVALUE" |
157 | >0</SPAN |
158 | > if successful or |
159 | <SPAN |
160 | CLASS="RETURNVALUE" |
161 | >-1</SPAN |
162 | > if there was an error (leaving the semaphore unchanged).</P |
163 | ></DIV |
164 | ><DIV |
165 | CLASS="REFSECT1" |
166 | ><A |
167 | NAME="AEN8046" |
168 | ></A |
169 | ><H2 |
170 | >Examples</H2 |
171 | ><P |
172 | ><PRE |
173 | CLASS="PROGRAMLISTING" |
174 | >if (SDL_SemWait(my_sem) == -1) { |
175 | return WAIT_FAILED; |
176 | } |
177 | |
178 | ... |
179 | |
180 | SDL_SemPost(my_sem);</PRE |
181 | ></P |
182 | ></DIV |
183 | ><DIV |
184 | CLASS="REFSECT1" |
185 | ><A |
186 | NAME="AEN8050" |
187 | ></A |
188 | ><H2 |
189 | >See Also</H2 |
190 | ><P |
191 | ><A |
192 | HREF="sdlcreatesemaphore.html" |
193 | ><TT |
194 | CLASS="FUNCTION" |
195 | >SDL_CreateSemaphore</TT |
196 | ></A |
197 | >, |
198 | <A |
199 | HREF="sdldestroysemaphore.html" |
200 | ><TT |
201 | CLASS="FUNCTION" |
202 | >SDL_DestroySemaphore</TT |
203 | ></A |
204 | >, |
205 | <A |
206 | HREF="sdlsemtrywait.html" |
207 | ><TT |
208 | CLASS="FUNCTION" |
209 | >SDL_SemTryWait</TT |
210 | ></A |
211 | >, |
212 | <A |
213 | HREF="sdlsemwaittimeout.html" |
214 | ><TT |
215 | CLASS="FUNCTION" |
216 | >SDL_SemWaitTimeout</TT |
217 | ></A |
218 | >, |
219 | <A |
220 | HREF="sdlsempost.html" |
221 | ><TT |
222 | CLASS="FUNCTION" |
223 | >SDL_SemPost</TT |
224 | ></A |
225 | >, |
226 | <A |
227 | HREF="sdlsemvalue.html" |
228 | ><TT |
229 | CLASS="FUNCTION" |
230 | >SDL_SemValue</TT |
231 | ></A |
232 | ></P |
233 | ></DIV |
234 | ><DIV |
235 | CLASS="NAVFOOTER" |
236 | ><HR |
237 | ALIGN="LEFT" |
238 | WIDTH="100%"><TABLE |
239 | SUMMARY="Footer navigation table" |
240 | WIDTH="100%" |
241 | BORDER="0" |
242 | CELLPADDING="0" |
243 | CELLSPACING="0" |
244 | ><TR |
245 | ><TD |
246 | WIDTH="33%" |
247 | ALIGN="left" |
248 | VALIGN="top" |
249 | ><A |
250 | HREF="sdldestroysemaphore.html" |
251 | ACCESSKEY="P" |
252 | >Prev</A |
253 | ></TD |
254 | ><TD |
255 | WIDTH="34%" |
256 | ALIGN="center" |
257 | VALIGN="top" |
258 | ><A |
259 | HREF="index.html" |
260 | ACCESSKEY="H" |
261 | >Home</A |
262 | ></TD |
263 | ><TD |
264 | WIDTH="33%" |
265 | ALIGN="right" |
266 | VALIGN="top" |
267 | ><A |
268 | HREF="sdlsemtrywait.html" |
269 | ACCESSKEY="N" |
270 | >Next</A |
271 | ></TD |
272 | ></TR |
273 | ><TR |
274 | ><TD |
275 | WIDTH="33%" |
276 | ALIGN="left" |
277 | VALIGN="top" |
278 | >SDL_DestroySemaphore</TD |
279 | ><TD |
280 | WIDTH="34%" |
281 | ALIGN="center" |
282 | VALIGN="top" |
283 | ><A |
284 | HREF="thread.html" |
285 | ACCESSKEY="U" |
286 | >Up</A |
287 | ></TD |
288 | ><TD |
289 | WIDTH="33%" |
290 | ALIGN="right" |
291 | VALIGN="top" |
292 | >SDL_SemTryWait</TD |
293 | ></TR |
294 | ></TABLE |
295 | ></DIV |
296 | ></BODY |
297 | ></HTML |
298 | > |