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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: hash.c,v 1.2 2000/06/17 10:37:39 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 1.2 2000/06/17 10:37:39 mdw |
34 | * Add support for arena management. |
35 | * |
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36 | * Revision 1.1 1999/08/02 14:45:48 mdw |
37 | * Break low-level hashtable code out from sym. |
38 | * |
39 | */ |
40 | |
41 | /*----- Header files ------------------------------------------------------*/ |
42 | |
43 | #include <stdio.h> |
44 | #include <stdlib.h> |
45 | #include <string.h> |
46 | |
47 | #include "alloc.h" |
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48 | #include "arena.h" |
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49 | #include "bits.h" |
50 | #include "exc.h" |
51 | #include "hash.h" |
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52 | |
53 | /*----- Main code ---------------------------------------------------------*/ |
54 | |
55 | /* --- @hash_create@ --- * |
56 | * |
57 | * Arguments: @hash_table *t@ = pointer to hashtable to initialize |
58 | * @size_t n@ = number of bins to allocate (zero initially) |
59 | * |
60 | * Returns: --- |
61 | * |
62 | * Use: Initializes a hashtable with a given number of bins. The |
63 | * bins are initially empty. The number of bins must be a power |
64 | * of two. This is not checked. |
65 | */ |
66 | |
67 | void hash_create(hash_table *t, size_t n) |
68 | { |
69 | hash_base **v; |
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70 | |
71 | t->a = arena_global; |
72 | t->v = x_alloc(t->a, n * sizeof(hash_base *)); |
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73 | t->mask = n - 1; |
74 | for (v = t->v; n; v++, n--) |
75 | *v = 0; |
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76 | } |
77 | |
78 | /* --- @hash_destroy@ --- * |
79 | * |
80 | * Arguments: @hash_table *t@ = pointer to hashtable to destroy |
81 | * |
82 | * Returns: --- |
83 | * |
84 | * Use: Frees a hashtable. The items are not freed: they are the |
85 | * responsibility of the implementation. |
86 | */ |
87 | |
88 | void hash_destroy(hash_table *t) |
89 | { |
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90 | x_free(t->a, t->v); |
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91 | } |
92 | |
93 | /* --- @hash_bin@ --- * |
94 | * |
95 | * Arguments: @hash_table *t@ = pointer to hashtable |
96 | * @uint32 hash@ = hash value to look up |
97 | * |
98 | * Returns: Pointer to the bin's list head. |
99 | * |
100 | * Use: Given a hash value return the address of the appropriate list |
101 | * head. It is safe to remove the current entry from the table. |
102 | */ |
103 | |
104 | hash_base **hash_bin(hash_table *t, uint32 hash) |
105 | { |
106 | return (HASH_BIN(t, hash)); |
107 | } |
108 | |
109 | /* --- @hash_extend@ --- * |
110 | * |
111 | * Arguments: @hash_table *t@ = pointer to hashtable to extend |
112 | * |
113 | * Returns: Nonzero if extension was successful. |
114 | * |
115 | * Use: Extends a hashtable. The number of bins is doubled and the |
116 | * entries are redistributed. |
117 | */ |
118 | |
119 | int hash_extend(hash_table *t) |
120 | { |
121 | hash_base **v; |
122 | uint32 m = t->mask + 1; |
123 | size_t i; |
124 | |
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125 | /* --- Allocate a new hash bin vector --- */ |
126 | |
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127 | if ((v = A_REALLOC(t->a, t->v, m * 2 * sizeof(hash_base *))) == 0) { |
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128 | return (0); |
129 | } |
130 | t->v = v; |
131 | t->mask = (m * 2) - 1; |
132 | |
133 | /* --- Wander through the table rehashing things --- */ |
134 | |
135 | for (i = 0; i < m; i++) { |
136 | hash_base **p = v + i; |
137 | hash_base **q = p + m; |
138 | |
139 | while (*p) { |
140 | if (!((*p)->hash & m)) |
141 | p = &(*p)->next; |
142 | else { |
143 | *q = *p; |
144 | q = &(*q)->next; |
145 | *p = (*p)->next; |
146 | } |
147 | } |
148 | *p = 0; |
149 | *q = 0; |
150 | } |
151 | |
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152 | return (1); |
153 | } |
154 | |
155 | /* --- @hash_remove@ --- * |
156 | * |
157 | * Arguments: @hash_table *t@ = pointer to hashtable |
158 | * @hash_base *p@ = pointer to item to remove |
159 | * |
160 | * Returns: --- |
161 | * |
162 | * Use: Removes an item from a hashtable. The item itself is not |
163 | * freed, although it is removed from the data structure and is |
164 | * safe to free. |
165 | */ |
166 | |
167 | void hash_remove(hash_table *t, hash_base *p) |
168 | { |
169 | hash_base **b = HASH_BIN(t, p->hash); |
170 | while (*b) { |
171 | if (*b == p) { |
172 | *b = p->next; |
173 | return; |
174 | } |
175 | b = &(*b)->next; |
176 | } |
177 | return; |
178 | } |
179 | |
180 | /* --- @hash_mkiter@ --- * |
181 | * |
182 | * Arguments: @hash_iter *i@ = pointer to iterator to create |
183 | * @hash_table *t@ = pointer to hashtable to iterate |
184 | * |
185 | * Returns: --- |
186 | * |
187 | * Use: Initializes a hashtable iterator. |
188 | */ |
189 | |
190 | void hash_mkiter(hash_iter *i, hash_table *t) { HASH_MKITER(i, t); } |
191 | |
192 | /* --- @hash_next@ --- * |
193 | * |
194 | * Arguments: @hash_iter *i@ = pointer to iterator |
195 | * |
196 | * Returns: Pointer to the next hashtable entry found, or null. |
197 | * |
198 | * Use: Returns the next entry from the hashtable. |
199 | */ |
200 | |
201 | hash_base *hash_next(hash_iter *i) |
202 | { |
203 | hash_base *b; |
204 | HASH_NEXT(i, b); |
205 | return (b); |
206 | } |
207 | |
208 | /*----- That's all, folks -------------------------------------------------*/ |