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lc-switch.h
1 /*
2  * Copyright (c) 2004-2005, Swedish Institute of Computer Science.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  * notice, this list of conditions and the following disclaimer in the
12  * documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the Institute nor the names of its contributors
14  * may be used to endorse or promote products derived from this software
15  * without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * This file is part of the Contiki operating system.
30  *
31  * Author: Adam Dunkels <adam@sics.se>
32  *
33  * $Id: lc-switch.h,v 1.4 2006/06/03 11:29:43 adam Exp $
34  */
35 
36 /*
37  * \file
38  * Implementation of local continuations based on switch() statment
39  * \author Adam Dunkels <adam@sics.se>
40  *
41  * This implementation of local continuations uses the C switch()
42  * statement to resume execution of a function somewhere inside the
43  * function's body. The implementation is based on the fact that
44  * switch() statements are able to jump directly into the bodies of
45  * control structures such as if() or while() statmenets.
46  *
47  * This implementation borrows heavily from Simon Tatham's coroutines
48  * implementation in C:
49  * http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html
50  */
51 
52 #ifndef __LC_SWITCH_H__
53 #define __LC_SWITCH_H__
54 
55 /* WARNING! lc implementation using switch() does not work if an
56  LC_SET() is done within another switch() statement! */
57 
58 /** \hideinitializer */
59 typedef unsigned short lc_t;
60 
61 #define LC_INIT(s) s = 0;
62 
63 #define LC_IS_INITED(s) (s==0)
64 
65 #define LC_RESUME(s) switch(s) { case 0:
66 
67 #define LC_SET(s) s = __LINE__; case __LINE__:
68 
69 #define LC_END(s) }
70 
71 #endif /* __LC_SWITCH_H__ */
72 
73 /** @} */