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1 | /* ternary.c - Ternary Search Trees | |
2 | Copyright (C) 2001 Free Software Foundation, Inc. | |
3 | ||
4 | Contributed by Daniel Berlin (dan@cgsoftware.com) | |
5 | ||
6 | This program is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU General Public License as published by the | |
8 | Free Software Foundation; either version 2, or (at your option) any | |
9 | later version. | |
10 | ||
11 | This program is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | GNU General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU General Public License | |
17 | along with this program; if not, write to the Free Software | |
18 | Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, | |
19 | USA. */ | |
20 | #ifdef HAVE_CONFIG_H | |
21 | #include "config.h" | |
22 | #endif | |
23 | ||
24 | #ifdef HAVE_STDLIB_H | |
25 | #include <stdlib.h> | |
26 | #endif | |
27 | ||
28 | #include <stdio.h> | |
29 | ||
30 | #include "libiberty.h" | |
31 | #include "ternary.h" | |
32 | ||
33 | /* Non-recursive so we don't waste stack space/time on large | |
34 | insertions. */ | |
35 | ||
36 | PTR | |
37 | ternary_insert (ternary_tree *root, const char *s, PTR data, int replace) | |
38 | { | |
39 | int diff; | |
40 | ternary_tree curr, *pcurr; | |
41 | ||
42 | /* Start at the root. */ | |
43 | pcurr = root; | |
44 | /* Loop until we find the right position */ | |
45 | while ((curr = *pcurr)) | |
46 | { | |
47 | /* Calculate the difference */ | |
48 | diff = *s - curr->splitchar; | |
49 | /* Handle current char equal to node splitchar */ | |
50 | if (diff == 0) | |
51 | { | |
52 | /* Handle the case of a string we already have */ | |
53 | if (*s++ == 0) | |
54 | { | |
55 | if (replace) | |
56 | curr->eqkid = (ternary_tree) data; | |
57 | return (PTR) curr->eqkid; | |
58 | } | |
59 | pcurr = &(curr->eqkid); | |
60 | } | |
61 | /* Handle current char less than node splitchar */ | |
62 | else if (diff < 0) | |
63 | { | |
64 | pcurr = &(curr->lokid); | |
65 | } | |
66 | /* Handle current char greater than node splitchar */ | |
67 | else | |
68 | { | |
69 | pcurr = &(curr->hikid); | |
70 | } | |
71 | } | |
72 | /* It's not a duplicate string, and we should insert what's left of | |
73 | the string, into the tree rooted at curr */ | |
74 | for (;;) | |
75 | { | |
76 | /* Allocate the memory for the node, and fill it in */ | |
77 | *pcurr = (ternary_tree) xmalloc (sizeof (ternary_node)); | |
78 | curr = *pcurr; | |
79 | curr->splitchar = *s; | |
80 | curr->lokid = curr->hikid = curr->eqkid = 0; | |
81 | ||
82 | /* Place nodes until we hit the end of the string. | |
83 | When we hit it, place the data in the right place, and | |
84 | return. | |
85 | */ | |
86 | if (*s++ == 0) | |
87 | { | |
88 | curr->eqkid = (ternary_tree) data; | |
89 | return data; | |
90 | } | |
91 | pcurr = &(curr->eqkid); | |
92 | } | |
93 | } | |
94 | ||
95 | /* Free the ternary search tree rooted at p. */ | |
96 | void | |
97 | ternary_cleanup (ternary_tree p) | |
98 | { | |
99 | if (p) | |
100 | { | |
101 | ternary_cleanup (p->lokid); | |
102 | if (p->splitchar) | |
103 | ternary_cleanup (p->eqkid); | |
104 | ternary_cleanup (p->hikid); | |
105 | free (p); | |
106 | } | |
107 | } | |
108 | ||
109 | /* Non-recursive find of a string in the ternary tree */ | |
110 | PTR | |
111 | ternary_search (const ternary_node *p, const char *s) | |
112 | { | |
113 | const ternary_node *curr; | |
114 | int diff, spchar; | |
115 | spchar = *s; | |
116 | curr = p; | |
117 | /* Loop while we haven't hit a NULL node or returned */ | |
118 | while (curr) | |
119 | { | |
120 | /* Calculate the difference */ | |
121 | diff = spchar - curr->splitchar; | |
122 | /* Handle the equal case */ | |
123 | if (diff == 0) | |
124 | { | |
125 | if (spchar == 0) | |
126 | return (PTR) curr->eqkid; | |
127 | spchar = *++s; | |
128 | curr = curr->eqkid; | |
129 | } | |
130 | /* Handle the less than case */ | |
131 | else if (diff < 0) | |
132 | curr = curr->lokid; | |
133 | /* All that's left is greater than */ | |
134 | else | |
135 | curr = curr->hikid; | |
136 | } | |
137 | return NULL; | |
138 | } | |
139 | ||
140 | /* For those who care, the recursive version of the search. Useful if | |
141 | you want a starting point for pmsearch or nearsearch. */ | |
142 | static PTR | |
143 | ternary_recursivesearch (const ternary_node *p, const char *s) | |
144 | { | |
145 | if (!p) | |
146 | return 0; | |
147 | if (*s < p->splitchar) | |
148 | return ternary_recursivesearch (p->lokid, s); | |
149 | else if (*s > p->splitchar) | |
150 | return ternary_recursivesearch (p->hikid, s); | |
151 | else | |
152 | { | |
153 | if (*s == 0) | |
154 | return (PTR) p->eqkid; | |
155 | return ternary_recursivesearch (p->eqkid, ++s); | |
156 | } | |
157 | } |