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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_CreateSemaphore</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_mutexV"
17 HREF="sdlmutexv.html"><LINK
18 REL="NEXT"
19 TITLE="SDL_DestroySemaphore"
20 HREF="sdldestroysemaphore.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="sdlmutexv.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="sdldestroysemaphore.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="SDLCREATESEMAPHORE"
71 >SDL_CreateSemaphore</A
72 ></H1
73 ><DIV
74 CLASS="REFNAMEDIV"
75 ><A
76 NAME="AEN7311"
77 ></A
78 ><H2
79 >Name</H2
80 >SDL_CreateSemaphore&nbsp;--&nbsp;Creates a new semaphore and assigns an initial value to it.</DIV
81 ><DIV
82 CLASS="REFSYNOPSISDIV"
83 ><A
84 NAME="AEN7314"
85 ></A
86 ><H2
87 >Synopsis</H2
88 ><DIV
89 CLASS="FUNCSYNOPSIS"
90 ><A
91 NAME="AEN7315"
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 >SDL_sem *<B
104 CLASS="FSFUNC"
105 >SDL_CreateSemaphore</B
106 ></CODE
107 >(Uint32 initial_value);</CODE
108 ></P
109 ><P
110 ></P
111 ></DIV
112 ></DIV
113 ><DIV
114 CLASS="REFSECT1"
115 ><A
116 NAME="AEN7321"
117 ></A
118 ><H2
119 >Description</H2
120 ><P
121 ><TT
122 CLASS="FUNCTION"
123 >SDL_CreateSemaphore()</TT
124 > creates a new semaphore and
125 initializes it with the value <TT
126 CLASS="PARAMETER"
127 ><I
128 >initial_value</I
129 ></TT
130 >.
131 Each locking operation on the semaphore by
132 <A
133 HREF="sdlsemwait.html"
134 >SDL_SemWait</A
135 >,
136 <A
137 HREF="sdlsemtrywait.html"
138 >SDL_SemTryWait</A
139 > or
140 <A
141 HREF="sdlsemwaittimeout.html"
142 >SDL_SemWaitTimeout</A
143 >
144 will atomically decrement the semaphore value. The locking operation will be blocked
145 if the semaphore value is not positive (greater than zero). Each unlock operation by
146 <A
147 HREF="sdlsempost.html"
148 >SDL_SemPost</A
149 >
150 will atomically increment the semaphore value.</P
151 ></DIV
152 ><DIV
153 CLASS="REFSECT1"
154 ><A
155 NAME="AEN7330"
156 ></A
157 ><H2
158 >Return Value</H2
159 ><P
160 >Returns a pointer to an initialized semaphore or
161 <SPAN
162 CLASS="RETURNVALUE"
163 >NULL</SPAN
164 > if there was an error.</P
165 ></DIV
166 ><DIV
167 CLASS="REFSECT1"
168 ><A
169 NAME="AEN7334"
170 ></A
171 ><H2
172 >Examples</H2
173 ><P
174 ><PRE
175 CLASS="PROGRAMLISTING"
176 >SDL_sem *my_sem;
177
178 my_sem = SDL_CreateSemaphore(INITIAL_SEM_VALUE);
179
180 if (my_sem == NULL) {
181 return CREATE_SEM_FAILED;
182 }</PRE
183 ></P
184 ></DIV
185 ><DIV
186 CLASS="REFSECT1"
187 ><A
188 NAME="AEN7338"
189 ></A
190 ><H2
191 >See Also</H2
192 ><P
193 ><A
194 HREF="sdldestroysemaphore.html"
195 ><TT
196 CLASS="FUNCTION"
197 >SDL_DestroySemaphore</TT
198 ></A
199 >,
200 <A
201 HREF="sdlsemwait.html"
202 ><TT
203 CLASS="FUNCTION"
204 >SDL_SemWait</TT
205 ></A
206 >,
207 <A
208 HREF="sdlsemtrywait.html"
209 ><TT
210 CLASS="FUNCTION"
211 >SDL_SemTryWait</TT
212 ></A
213 >,
214 <A
215 HREF="sdlsemwaittimeout.html"
216 ><TT
217 CLASS="FUNCTION"
218 >SDL_SemWaitTimeout</TT
219 ></A
220 >,
221 <A
222 HREF="sdlsempost.html"
223 ><TT
224 CLASS="FUNCTION"
225 >SDL_SemPost</TT
226 ></A
227 >,
228 <A
229 HREF="sdlsemvalue.html"
230 ><TT
231 CLASS="FUNCTION"
232 >SDL_SemValue</TT
233 ></A
234 ></P
235 ></DIV
236 ><DIV
237 CLASS="NAVFOOTER"
238 ><HR
239 ALIGN="LEFT"
240 WIDTH="100%"><TABLE
241 WIDTH="100%"
242 BORDER="0"
243 CELLPADDING="0"
244 CELLSPACING="0"
245 ><TR
246 ><TD
247 WIDTH="33%"
248 ALIGN="left"
249 VALIGN="top"
250 ><A
251 HREF="sdlmutexv.html"
252 >Prev</A
253 ></TD
254 ><TD
255 WIDTH="34%"
256 ALIGN="center"
257 VALIGN="top"
258 ><A
259 HREF="index.html"
260 >Home</A
261 ></TD
262 ><TD
263 WIDTH="33%"
264 ALIGN="right"
265 VALIGN="top"
266 ><A
267 HREF="sdldestroysemaphore.html"
268 >Next</A
269 ></TD
270 ></TR
271 ><TR
272 ><TD
273 WIDTH="33%"
274 ALIGN="left"
275 VALIGN="top"
276 >SDL_mutexV</TD
277 ><TD
278 WIDTH="34%"
279 ALIGN="center"
280 VALIGN="top"
281 ><A
282 HREF="thread.html"
283 >Up</A
284 ></TD
285 ><TD
286 WIDTH="33%"
287 ALIGN="right"
288 VALIGN="top"
289 >SDL_DestroySemaphore</TD
290 ></TR
291 ></TABLE
292 ></DIV
293 ></BODY
294 ></HTML
295 >