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