1 /*-
2  * Copyright (c) 1980, 1993
3  *	The Regents of the University of California.  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 University 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 REGENTS 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 REGENTS 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  * @(#)allow.c	8.1 (Berkeley) 5/31/93
30  * $FreeBSD: src/games/backgammon/common_source/allow.c,v 1.4 1999/11/30 03:48:24 billf Exp $
31  * $DragonFly: src/games/backgammon/common_source/allow.c,v 1.3 2006/08/08 16:36:11 pavalos Exp $
32  */
33 
34 #include "back.h"
35 
36 int
37 movallow(void)
38 {
39 	int i, m, iold;
40 	int r;
41 
42 	if (d0)
43 		swap;
44 	m = (D0 == D1 ? 4 : 2);
45 	for (i = 0; i < 4; i++)
46 		p[i] = bar;
47 	i = iold = 0;
48 	while (i < m) {
49 		if (*offptr == 15)
50 			break;
51 		h[i] = 0;
52 		if (board[bar]) {
53 			if (i == 1 || m == 4)
54 				g[i] = bar + cturn * D1;
55 			else
56 				g[i] = bar + cturn * D0;
57 			if ((r = makmove(i)) != 0) {
58 				if (d0 || m == 4)
59 					break;
60 				swap;
61 				movback(i);
62 				if (i > iold)
63 					iold = i;
64 				for (i = 0; i < 4; i++)
65 					p[i] = bar;
66 				i = 0;
67 			} else
68 				i++;
69 			continue;
70 		}
71 		if ((p[i] += cturn) == home) {
72 			if (i > iold)
73 				iold = i;
74 			if (m == 2 && i) {
75 				movback(i);
76 				p[i--] = bar;
77 				if (p[i] != bar)
78 					continue;
79 				else
80 					break;
81 			}
82 			if (d0 || m == 4)
83 				break;
84 			swap;
85 			movback(i);
86 			for (i = 0; i < 4; i++)
87 				p[i] = bar;
88 			i = 0;
89 			continue;
90 		}
91 		if (i == 1 || m == 4)
92 			g[i] = p[i] + cturn * D1;
93 		else
94 			g[i] = p[i] + cturn * D0;
95 		if (g[i] * cturn > home) {
96 			if (*offptr >= 0)
97 				g[i] = home;
98 			else
99 				continue;
100 		}
101 		if (board[p[i]] * cturn > 0 && (r = makmove(i)) == 0)
102 			i++;
103 	}
104 	movback(i);
105 	return (iold > i ? iold : i);
106 }
107