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[mLib] / hash.c
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03d53b73 1/* -*-c-*-
2 *
b5ea4de3 3 * $Id: hash.c,v 1.3 2000/07/16 12:29:16 mdw Exp $
03d53b73 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 $
b5ea4de3 33 * Revision 1.3 2000/07/16 12:29:16 mdw
34 * Change to arena `realloc' interface, to fix a design bug.
35 *
20eb516f 36 * Revision 1.2 2000/06/17 10:37:39 mdw
37 * Add support for arena management.
38 *
03d53b73 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"
20eb516f 51#include "arena.h"
03d53b73 52#include "bits.h"
53#include "exc.h"
54#include "hash.h"
03d53b73 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
70void hash_create(hash_table *t, size_t n)
71{
72 hash_base **v;
20eb516f 73
74 t->a = arena_global;
75 t->v = x_alloc(t->a, n * sizeof(hash_base *));
03d53b73 76 t->mask = n - 1;
77 for (v = t->v; n; v++, n--)
78 *v = 0;
03d53b73 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
91void hash_destroy(hash_table *t)
92{
20eb516f 93 x_free(t->a, t->v);
03d53b73 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
107hash_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
122int hash_extend(hash_table *t)
123{
124 hash_base **v;
125 uint32 m = t->mask + 1;
126 size_t i;
127
03d53b73 128 /* --- Allocate a new hash bin vector --- */
129
b5ea4de3 130 if ((v = A_REALLOC(t->a, t->v,
131 2 * m * sizeof(hash_base *),
132 m * sizeof(hash_base *))) == 0) {
03d53b73 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
03d53b73 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
172void 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
195void 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
206hash_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 -------------------------------------------------*/