[sdl_omap.git] / docs / html / sdlsemtrywait.html

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>SDL_SemTryWait</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN8069"
></A
><H2
>Name</H2
>SDL_SemTryWait&nbsp;--&nbsp;Attempt to lock a semaphore but don't suspend the thread.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN8072"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN8073"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"
#include "SDL_thread.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_SemTryWait</B
></CODE
>(SDL_sem *sem);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8079"
></A
><H2
>Description</H2
><P
><TT
CLASS="FUNCTION"
>SDL_SemTryWait</TT
> is a non-blocking varient of
<A
HREF="sdlsemwait.html"
><TT
CLASS="FUNCTION"
>SDL_SemWait</TT
></A
>. If the value of the semaphore
pointed to by <TT
CLASS="PARAMETER"
><I
>sem</I
></TT
> is positive it will atomically
decrement the semaphore value and return 0, otherwise it will return
<SPAN
CLASS="RETURNVALUE"
>SDL_MUTEX_TIMEDOUT</SPAN
> instead of suspending the thread.</P
><P
>After <TT
CLASS="FUNCTION"
>SDL_SemTryWait</TT
> is successful, the semaphore
can be released and its count atomically incremented by a successful call to
<A
HREF="sdlsempost.html"
>SDL_SemPost</A
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8090"
></A
><H2
>Return Value</H2
><P
>Returns <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> if the semaphore was successfully locked or
either <SPAN
CLASS="RETURNVALUE"
>SDL_MUTEX_TIMEDOUT</SPAN
> or <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
>
if the thread would have suspended or there was an error, respectivly.</P
><P
>If the semaphore was not successfully locked, the semaphore will be unchanged.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8097"
></A
><H2
>Examples</H2
><P
><PRE
CLASS="PROGRAMLISTING"
>res = SDL_SemTryWait(my_sem);

if (res == SDL_MUTEX_TIMEDOUT) {
        return TRY_AGAIN;
}
if (res == -1) {
        return WAIT_ERROR;
}

...

SDL_SemPost(my_sem);</PRE
></P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN8101"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlcreatesemaphore.html"
><TT
CLASS="FUNCTION"
>SDL_CreateSemaphore</TT
></A
>,
<A
HREF="sdldestroysemaphore.html"
><TT
CLASS="FUNCTION"
>SDL_DestroySemaphore</TT
></A
>,
<A
HREF="sdlsemwait.html"
><TT
CLASS="FUNCTION"
>SDL_SemWait</TT
></A
>,
<A
HREF="sdlsemwaittimeout.html"
><TT
CLASS="FUNCTION"
>SDL_SemWaitTimeout</TT
></A
>,
<A
HREF="sdlsempost.html"
><TT
CLASS="FUNCTION"
>SDL_SemPost</TT
></A
>,
<A
HREF="sdlsemvalue.html"
><TT
CLASS="FUNCTION"
>SDL_SemValue</TT
></A
></P
></DIV
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>
Commit	Line	Data
e14743d1	1	<HTML
	2	><HEAD
	3	><TITLE
	4	>SDL_SemTryWait</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_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"
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	39	ALIGN="center"
	40	>SDL Library Documentation</TH
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	42	><TR
	43	><TD
	44	WIDTH="10%"
	45	ALIGN="left"
	46	VALIGN="bottom"
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	64	>Next</A
65	></TD
66	></TR
67	></TABLE
68	><HR
69	ALIGN="LEFT"
70	WIDTH="100%"></DIV
71	><H1
72	><A
73	NAME="SDLSEMTRYWAIT"
74	></A
75	>SDL_SemTryWait</H1
76	><DIV
77	CLASS="REFNAMEDIV"
78	><A
79	NAME="AEN8069"
80	></A
81	><H2
82	>Name</H2
83	>SDL_SemTryWait -- Attempt to lock a semaphore but don't suspend the thread.</DIV
84	><DIV
85	CLASS="REFSYNOPSISDIV"
86	><A
87	NAME="AEN8072"
88	></A
89	><H2
90	>Synopsis</H2
91	><DIV
92	CLASS="FUNCSYNOPSIS"
93	><A
94	NAME="AEN8073"
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_SemTryWait</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="AEN8079"
120	></A
121	><H2
122	>Description</H2
123	><P
124	><TT
125	CLASS="FUNCTION"
126	>SDL_SemTryWait</TT
127	> is a non-blocking varient of
128	<A
129	HREF="sdlsemwait.html"
130	><TT
131	CLASS="FUNCTION"
132	>SDL_SemWait</TT
133	></A
134	>. If the value of the semaphore
135	pointed to by <TT
136	CLASS="PARAMETER"
137	><I
138	>sem</I
139	></TT
140	> is positive it will atomically
141	decrement the semaphore value and return 0, otherwise it will return
142	<SPAN
143	CLASS="RETURNVALUE"
144	>SDL_MUTEX_TIMEDOUT</SPAN
145	> instead of suspending the thread.</P
146	><P
147	>After <TT
148	CLASS="FUNCTION"
149	>SDL_SemTryWait</TT
150	> is successful, the semaphore
151	can be released and its count atomically incremented by a successful call to
152	<A
153	HREF="sdlsempost.html"
154	>SDL_SemPost</A
155	>.</P
156	></DIV
157	><DIV
158	CLASS="REFSECT1"
159	><A
160	NAME="AEN8090"
161	></A
162	><H2
163	>Return Value</H2
164	><P
165	>Returns <SPAN
166	CLASS="RETURNVALUE"
167	>0</SPAN
168	> if the semaphore was successfully locked or
169	either <SPAN
170	CLASS="RETURNVALUE"
171	>SDL_MUTEX_TIMEDOUT</SPAN
172	> or <SPAN
173	CLASS="RETURNVALUE"
174	>-1</SPAN
175	>
176	if the thread would have suspended or there was an error, respectivly.</P
177	><P
178	>If the semaphore was not successfully locked, the semaphore will be unchanged.</P
179	></DIV
180	><DIV
181	CLASS="REFSECT1"
182	><A
183	NAME="AEN8097"
184	></A
185	><H2
186	>Examples</H2
187	><P
188	><PRE
189	CLASS="PROGRAMLISTING"
190	>res = SDL_SemTryWait(my_sem);
191
192	if (res == SDL_MUTEX_TIMEDOUT) {
193	return TRY_AGAIN;
194	}
195	if (res == -1) {
196	return WAIT_ERROR;
197	}
198
199	...
200
201	SDL_SemPost(my_sem);</PRE
202	></P
203	></DIV
204	><DIV
205	CLASS="REFSECT1"
206	><A
207	NAME="AEN8101"
208	></A
209	><H2
210	>See Also</H2
211	><P
212	><A
213	HREF="sdlcreatesemaphore.html"
214	><TT
215	CLASS="FUNCTION"
216	>SDL_CreateSemaphore</TT
217	></A
218	>,
219	<A
220	HREF="sdldestroysemaphore.html"
221	><TT
222	CLASS="FUNCTION"
223	>SDL_DestroySemaphore</TT
224	></A
225	>,
226	<A
227	HREF="sdlsemwait.html"
228	><TT
229	CLASS="FUNCTION"
230	>SDL_SemWait</TT
231	></A
232	>,
233	<A
234	HREF="sdlsemwaittimeout.html"
235	><TT
236	CLASS="FUNCTION"
237	>SDL_SemWaitTimeout</TT
238	></A
239	>,
240	<A
241	HREF="sdlsempost.html"
242	><TT
243	CLASS="FUNCTION"
244	>SDL_SemPost</TT
245	></A
246	>,
247	<A
248	HREF="sdlsemvalue.html"
249	><TT
250	CLASS="FUNCTION"
251	>SDL_SemValue</TT
252	></A
253	></P
254	></DIV
255	><DIV
256	CLASS="NAVFOOTER"
257	><HR
258	ALIGN="LEFT"
259	WIDTH="100%"><TABLE
260	SUMMARY="Footer navigation table"
261	WIDTH="100%"
262	BORDER="0"
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264	CELLSPACING="0"
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267	WIDTH="33%"
268	ALIGN="left"
269	VALIGN="top"
270	><A
271	HREF="sdlsemwait.html"
272	ACCESSKEY="P"
273	>Prev</A
274	></TD
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276	WIDTH="34%"
277	ALIGN="center"
278	VALIGN="top"
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280	HREF="index.html"
281	ACCESSKEY="H"
282	>Home</A
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284	><TD
285	WIDTH="33%"
286	ALIGN="right"
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291	>Next</A
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297	ALIGN="left"
298	VALIGN="top"
299	>SDL_SemWait</TD
300	><TD
301	WIDTH="34%"
302	ALIGN="center"
303	VALIGN="top"
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305	HREF="thread.html"
306	ACCESSKEY="U"
307	>Up</A
308	></TD
309	><TD
310	WIDTH="33%"
311	ALIGN="right"
312	VALIGN="top"
313	>SDL_SemWaitTimeout</TD
314	></TR
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318	></HTML
319	>