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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: hash.c,v 1.3 2000/07/16 12:29:16 mdw Exp $ |
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4 | * |
5 | * General hashtable infrastructure |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of the mLib utilities library. |
13 | * |
14 | * mLib is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * mLib is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with mLib; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: hash.c,v $ |
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33 | * Revision 1.3 2000/07/16 12:29:16 mdw |
34 | * Change to arena `realloc' interface, to fix a design bug. |
35 | * |
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36 | * Revision 1.2 2000/06/17 10:37:39 mdw |
37 | * Add support for arena management. |
38 | * |
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39 | * Revision 1.1 1999/08/02 14:45:48 mdw |
40 | * Break low-level hashtable code out from sym. |
41 | * |
42 | */ |
43 | |
44 | /*----- Header files ------------------------------------------------------*/ |
45 | |
46 | #include <stdio.h> |
47 | #include <stdlib.h> |
48 | #include <string.h> |
49 | |
50 | #include "alloc.h" |
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51 | #include "arena.h" |
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52 | #include "bits.h" |
53 | #include "exc.h" |
54 | #include "hash.h" |
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55 | |
56 | /*----- Main code ---------------------------------------------------------*/ |
57 | |
58 | /* --- @hash_create@ --- * |
59 | * |
60 | * Arguments: @hash_table *t@ = pointer to hashtable to initialize |
61 | * @size_t n@ = number of bins to allocate (zero initially) |
62 | * |
63 | * Returns: --- |
64 | * |
65 | * Use: Initializes a hashtable with a given number of bins. The |
66 | * bins are initially empty. The number of bins must be a power |
67 | * of two. This is not checked. |
68 | */ |
69 | |
70 | void hash_create(hash_table *t, size_t n) |
71 | { |
72 | hash_base **v; |
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73 | |
74 | t->a = arena_global; |
75 | t->v = x_alloc(t->a, n * sizeof(hash_base *)); |
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76 | t->mask = n - 1; |
77 | for (v = t->v; n; v++, n--) |
78 | *v = 0; |
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79 | } |
80 | |
81 | /* --- @hash_destroy@ --- * |
82 | * |
83 | * Arguments: @hash_table *t@ = pointer to hashtable to destroy |
84 | * |
85 | * Returns: --- |
86 | * |
87 | * Use: Frees a hashtable. The items are not freed: they are the |
88 | * responsibility of the implementation. |
89 | */ |
90 | |
91 | void hash_destroy(hash_table *t) |
92 | { |
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93 | x_free(t->a, t->v); |
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94 | } |
95 | |
96 | /* --- @hash_bin@ --- * |
97 | * |
98 | * Arguments: @hash_table *t@ = pointer to hashtable |
99 | * @uint32 hash@ = hash value to look up |
100 | * |
101 | * Returns: Pointer to the bin's list head. |
102 | * |
103 | * Use: Given a hash value return the address of the appropriate list |
104 | * head. It is safe to remove the current entry from the table. |
105 | */ |
106 | |
107 | hash_base **hash_bin(hash_table *t, uint32 hash) |
108 | { |
109 | return (HASH_BIN(t, hash)); |
110 | } |
111 | |
112 | /* --- @hash_extend@ --- * |
113 | * |
114 | * Arguments: @hash_table *t@ = pointer to hashtable to extend |
115 | * |
116 | * Returns: Nonzero if extension was successful. |
117 | * |
118 | * Use: Extends a hashtable. The number of bins is doubled and the |
119 | * entries are redistributed. |
120 | */ |
121 | |
122 | int hash_extend(hash_table *t) |
123 | { |
124 | hash_base **v; |
125 | uint32 m = t->mask + 1; |
126 | size_t i; |
127 | |
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128 | /* --- Allocate a new hash bin vector --- */ |
129 | |
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130 | if ((v = A_REALLOC(t->a, t->v, |
131 | 2 * m * sizeof(hash_base *), |
132 | m * sizeof(hash_base *))) == 0) { |
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133 | return (0); |
134 | } |
135 | t->v = v; |
136 | t->mask = (m * 2) - 1; |
137 | |
138 | /* --- Wander through the table rehashing things --- */ |
139 | |
140 | for (i = 0; i < m; i++) { |
141 | hash_base **p = v + i; |
142 | hash_base **q = p + m; |
143 | |
144 | while (*p) { |
145 | if (!((*p)->hash & m)) |
146 | p = &(*p)->next; |
147 | else { |
148 | *q = *p; |
149 | q = &(*q)->next; |
150 | *p = (*p)->next; |
151 | } |
152 | } |
153 | *p = 0; |
154 | *q = 0; |
155 | } |
156 | |
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157 | return (1); |
158 | } |
159 | |
160 | /* --- @hash_remove@ --- * |
161 | * |
162 | * Arguments: @hash_table *t@ = pointer to hashtable |
163 | * @hash_base *p@ = pointer to item to remove |
164 | * |
165 | * Returns: --- |
166 | * |
167 | * Use: Removes an item from a hashtable. The item itself is not |
168 | * freed, although it is removed from the data structure and is |
169 | * safe to free. |
170 | */ |
171 | |
172 | void hash_remove(hash_table *t, hash_base *p) |
173 | { |
174 | hash_base **b = HASH_BIN(t, p->hash); |
175 | while (*b) { |
176 | if (*b == p) { |
177 | *b = p->next; |
178 | return; |
179 | } |
180 | b = &(*b)->next; |
181 | } |
182 | return; |
183 | } |
184 | |
185 | /* --- @hash_mkiter@ --- * |
186 | * |
187 | * Arguments: @hash_iter *i@ = pointer to iterator to create |
188 | * @hash_table *t@ = pointer to hashtable to iterate |
189 | * |
190 | * Returns: --- |
191 | * |
192 | * Use: Initializes a hashtable iterator. |
193 | */ |
194 | |
195 | void hash_mkiter(hash_iter *i, hash_table *t) { HASH_MKITER(i, t); } |
196 | |
197 | /* --- @hash_next@ --- * |
198 | * |
199 | * Arguments: @hash_iter *i@ = pointer to iterator |
200 | * |
201 | * Returns: Pointer to the next hashtable entry found, or null. |
202 | * |
203 | * Use: Returns the next entry from the hashtable. |
204 | */ |
205 | |
206 | hash_base *hash_next(hash_iter *i) |
207 | { |
208 | hash_base *b; |
209 | HASH_NEXT(i, b); |
210 | return (b); |
211 | } |
212 | |
213 | /*----- That's all, folks -------------------------------------------------*/ |