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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: hash.c,v 1.4 2004/04/08 01:36:11 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 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <stdio.h> |
33 | #include <stdlib.h> |
34 | #include <string.h> |
35 | |
36 | #include "alloc.h" |
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37 | #include "arena.h" |
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38 | #include "bits.h" |
39 | #include "exc.h" |
40 | #include "hash.h" |
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41 | |
42 | /*----- Main code ---------------------------------------------------------*/ |
43 | |
44 | /* --- @hash_create@ --- * |
45 | * |
46 | * Arguments: @hash_table *t@ = pointer to hashtable to initialize |
47 | * @size_t n@ = number of bins to allocate (zero initially) |
48 | * |
49 | * Returns: --- |
50 | * |
51 | * Use: Initializes a hashtable with a given number of bins. The |
52 | * bins are initially empty. The number of bins must be a power |
53 | * of two. This is not checked. |
54 | */ |
55 | |
56 | void hash_create(hash_table *t, size_t n) |
57 | { |
58 | hash_base **v; |
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59 | |
60 | t->a = arena_global; |
61 | t->v = x_alloc(t->a, n * sizeof(hash_base *)); |
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62 | t->mask = n - 1; |
63 | for (v = t->v; n; v++, n--) |
64 | *v = 0; |
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65 | } |
66 | |
67 | /* --- @hash_destroy@ --- * |
68 | * |
69 | * Arguments: @hash_table *t@ = pointer to hashtable to destroy |
70 | * |
71 | * Returns: --- |
72 | * |
73 | * Use: Frees a hashtable. The items are not freed: they are the |
74 | * responsibility of the implementation. |
75 | */ |
76 | |
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77 | void hash_destroy(hash_table *t) { x_free(t->a, t->v); } |
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78 | |
79 | /* --- @hash_bin@ --- * |
80 | * |
81 | * Arguments: @hash_table *t@ = pointer to hashtable |
82 | * @uint32 hash@ = hash value to look up |
83 | * |
84 | * Returns: Pointer to the bin's list head. |
85 | * |
86 | * Use: Given a hash value return the address of the appropriate list |
87 | * head. It is safe to remove the current entry from the table. |
88 | */ |
89 | |
90 | hash_base **hash_bin(hash_table *t, uint32 hash) |
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91 | { return (HASH_BIN(t, hash)); } |
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92 | |
93 | /* --- @hash_extend@ --- * |
94 | * |
95 | * Arguments: @hash_table *t@ = pointer to hashtable to extend |
96 | * |
97 | * Returns: Nonzero if extension was successful. |
98 | * |
99 | * Use: Extends a hashtable. The number of bins is doubled and the |
100 | * entries are redistributed. |
101 | */ |
102 | |
103 | int hash_extend(hash_table *t) |
104 | { |
105 | hash_base **v; |
106 | uint32 m = t->mask + 1; |
107 | size_t i; |
108 | |
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109 | /* --- Allocate a new hash bin vector --- */ |
110 | |
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111 | if ((v = A_REALLOC(t->a, t->v, |
112 | 2 * m * sizeof(hash_base *), |
113 | m * sizeof(hash_base *))) == 0) { |
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114 | return (0); |
115 | } |
116 | t->v = v; |
117 | t->mask = (m * 2) - 1; |
118 | |
119 | /* --- Wander through the table rehashing things --- */ |
120 | |
121 | for (i = 0; i < m; i++) { |
122 | hash_base **p = v + i; |
123 | hash_base **q = p + m; |
124 | |
125 | while (*p) { |
126 | if (!((*p)->hash & m)) |
127 | p = &(*p)->next; |
128 | else { |
129 | *q = *p; |
130 | q = &(*q)->next; |
131 | *p = (*p)->next; |
132 | } |
133 | } |
134 | *p = 0; |
135 | *q = 0; |
136 | } |
137 | |
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138 | return (1); |
139 | } |
140 | |
141 | /* --- @hash_remove@ --- * |
142 | * |
143 | * Arguments: @hash_table *t@ = pointer to hashtable |
144 | * @hash_base *p@ = pointer to item to remove |
145 | * |
146 | * Returns: --- |
147 | * |
148 | * Use: Removes an item from a hashtable. The item itself is not |
149 | * freed, although it is removed from the data structure and is |
150 | * safe to free. |
151 | */ |
152 | |
153 | void hash_remove(hash_table *t, hash_base *p) |
154 | { |
155 | hash_base **b = HASH_BIN(t, p->hash); |
156 | while (*b) { |
157 | if (*b == p) { |
158 | *b = p->next; |
159 | return; |
160 | } |
161 | b = &(*b)->next; |
162 | } |
163 | return; |
164 | } |
165 | |
166 | /* --- @hash_mkiter@ --- * |
167 | * |
168 | * Arguments: @hash_iter *i@ = pointer to iterator to create |
169 | * @hash_table *t@ = pointer to hashtable to iterate |
170 | * |
171 | * Returns: --- |
172 | * |
173 | * Use: Initializes a hashtable iterator. |
174 | */ |
175 | |
176 | void hash_mkiter(hash_iter *i, hash_table *t) { HASH_MKITER(i, t); } |
177 | |
178 | /* --- @hash_next@ --- * |
179 | * |
180 | * Arguments: @hash_iter *i@ = pointer to iterator |
181 | * |
182 | * Returns: Pointer to the next hashtable entry found, or null. |
183 | * |
184 | * Use: Returns the next entry from the hashtable. |
185 | */ |
186 | |
187 | hash_base *hash_next(hash_iter *i) |
188 | { |
189 | hash_base *b; |
190 | HASH_NEXT(i, b); |
191 | return (b); |
192 | } |
193 | |
194 | /*----- That's all, folks -------------------------------------------------*/ |