source: trunk/minix/commands/yap/machine.c@ 10

Last change on this file since 10 was 9, checked in by Mattia Monga, 14 years ago

Minix 3.1.2a
File size: 2.6 KB
Line 
1/* Copyright (c) 1985 Ceriel J.H. Jacobs */
2
3# ifndef lint
4static char rcsid[] = "$Header: /cvsup/minix/src/commands/yap/machine.c,v 1.1.1.1 2005/04/21 14:55:40 beng Exp $";
5# endif
6
7# define _MACHINE_
8
9# include <ctype.h>
10# include "in_all.h"
11# include "machine.h"
12# include "getline.h"
13# include "assert.h"
14
15/*
16 * Add part of finite state machine to recognize the string s.
17 */
18
19STATIC int
20addtomach(s, cnt, list) char *s; struct state **list; {
21
22 register struct state *l;
23 register int i = FSM_OKE; /* Return value */
24 register int j;
25
26 for (;;) {
27 l = *list;
28 if (!l) {
29 /*
30 * Create new list element
31 */
32 *list = l = (struct state *) alloc(sizeof(*l), 0);
33 l->s_char = *s;
34 l->s_endstate = 0;
35 l->s_match = 0;
36 l->s_next = 0;
37 }
38 if (l->s_char == *s) {
39 /*
40 * Continue with next character
41 */
42 if (!*++s) {
43 /*
44 * No next character
45 */
46 j = l->s_endstate;
47 l->s_endstate = 1;
48 if (l->s_match || j) {
49 /*
50 * If the state already was an endstate,
51 * or has a successor, the currently
52 * added string is a prefix of an
53 * already recognized string
54 */
55 return FSM_ISPREFIX;
56 }
57 l->s_cnt = cnt;
58 return i;
59 }
60 if (l->s_endstate) {
61 /*
62 * In this case, the currently added string has
63 * a prefix that is an already recognized
64 * string.
65 */
66 i = FSM_HASPREFIX;
67 }
68 list = &(l->s_match);
69 continue;
70 }
71 list = &(l->s_next);
72 }
73 /* NOTREACHED */
74}
75
76/*
77 * Add a string to the FSM.
78 */
79
80int
81addstring(s,cnt,machine) register char *s; struct state **machine; {
82
83 if (!s || !*s) {
84 return FSM_ISPREFIX;
85 }
86 return addtomach(s,cnt,machine);
87}
88
89/*
90 * Match string s with the finite state machine.
91 * If it matches, the number of characters actually matched is returned,
92 * and the count is put in the word pointed to by i.
93 * If the string is a prefix of a string that could be matched,
94 * FSM_ISPREFIX is returned. Otherwise, 0 is returned.
95 */
96
97int
98match(s,i,mach) char *s; int *i; register struct state *mach; {
99
100 register char *s1 = s; /* Walk through string */
101 register struct state *mach1 = 0;
102 /* Keep track of previous state */
103
104 while (mach && *s1) {
105 if (mach->s_char == *s1) {
106 /*
107 * Current character matches. Carry on with next
108 * character and next state
109 */
110 mach1 = mach;
111 mach = mach->s_match;
112 s1++;
113 continue;
114 }
115 mach = mach->s_next;
116 }
117 if (!mach1) {
118 /*
119 * No characters matched
120 */
121 return 0;
122 }
123 if (mach1->s_endstate) {
124 /*
125 * The string matched
126 */
127 *i = mach1->s_cnt;
128 return s1 - s;
129 }
130 if (!*s1) {
131 /*
132 * The string matched a prefix
133 */
134 return FSM_ISPREFIX;
135 }
136 return 0;
137}
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