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1 | /* -*-c-*- |
2 | * |
3 | * $Id: hash.c,v 1.1 1999/08/02 14:45:48 mdw Exp $ |
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 $ |
33 | * Revision 1.1 1999/08/02 14:45:48 mdw |
34 | * Break low-level hashtable code out from sym. |
35 | * |
36 | */ |
37 | |
38 | /*----- Header files ------------------------------------------------------*/ |
39 | |
40 | #include <stdio.h> |
41 | #include <stdlib.h> |
42 | #include <string.h> |
43 | |
44 | #include "alloc.h" |
45 | #include "bits.h" |
46 | #include "exc.h" |
47 | #include "hash.h" |
48 | #include "track.h" |
49 | |
50 | /*----- Main code ---------------------------------------------------------*/ |
51 | |
52 | /* --- @hash_create@ --- * |
53 | * |
54 | * Arguments: @hash_table *t@ = pointer to hashtable to initialize |
55 | * @size_t n@ = number of bins to allocate (zero initially) |
56 | * |
57 | * Returns: --- |
58 | * |
59 | * Use: Initializes a hashtable with a given number of bins. The |
60 | * bins are initially empty. The number of bins must be a power |
61 | * of two. This is not checked. |
62 | */ |
63 | |
64 | void hash_create(hash_table *t, size_t n) |
65 | { |
66 | hash_base **v; |
67 | TRACK_CTX("hashtable creation"); |
68 | TRACK_PUSH; |
69 | t->v = xmalloc(n * sizeof(hash_base *)); |
70 | t->mask = n - 1; |
71 | for (v = t->v; n; v++, n--) |
72 | *v = 0; |
73 | TRACK_POP; |
74 | } |
75 | |
76 | /* --- @hash_destroy@ --- * |
77 | * |
78 | * Arguments: @hash_table *t@ = pointer to hashtable to destroy |
79 | * |
80 | * Returns: --- |
81 | * |
82 | * Use: Frees a hashtable. The items are not freed: they are the |
83 | * responsibility of the implementation. |
84 | */ |
85 | |
86 | void hash_destroy(hash_table *t) |
87 | { |
88 | TRACK_CTX("hashtable destruction"); |
89 | TRACK_PUSH; |
90 | free(t->v); |
91 | TRACK_POP; |
92 | } |
93 | |
94 | /* --- @hash_bin@ --- * |
95 | * |
96 | * Arguments: @hash_table *t@ = pointer to hashtable |
97 | * @uint32 hash@ = hash value to look up |
98 | * |
99 | * Returns: Pointer to the bin's list head. |
100 | * |
101 | * Use: Given a hash value return the address of the appropriate list |
102 | * head. It is safe to remove the current entry from the table. |
103 | */ |
104 | |
105 | hash_base **hash_bin(hash_table *t, uint32 hash) |
106 | { |
107 | return (HASH_BIN(t, hash)); |
108 | } |
109 | |
110 | /* --- @hash_extend@ --- * |
111 | * |
112 | * Arguments: @hash_table *t@ = pointer to hashtable to extend |
113 | * |
114 | * Returns: Nonzero if extension was successful. |
115 | * |
116 | * Use: Extends a hashtable. The number of bins is doubled and the |
117 | * entries are redistributed. |
118 | */ |
119 | |
120 | int hash_extend(hash_table *t) |
121 | { |
122 | hash_base **v; |
123 | uint32 m = t->mask + 1; |
124 | size_t i; |
125 | |
126 | /* --- Push in a tracking context --- */ |
127 | |
128 | TRACK_CTX("hashtable extension"); |
129 | TRACK_PUSH; |
130 | |
131 | /* --- Allocate a new hash bin vector --- */ |
132 | |
133 | if ((v = realloc(t->v, m * 2 * sizeof(hash_base *))) == 0) { |
134 | TRACK_POP; |
135 | return (0); |
136 | } |
137 | t->v = v; |
138 | t->mask = (m * 2) - 1; |
139 | |
140 | /* --- Wander through the table rehashing things --- */ |
141 | |
142 | for (i = 0; i < m; i++) { |
143 | hash_base **p = v + i; |
144 | hash_base **q = p + m; |
145 | |
146 | while (*p) { |
147 | if (!((*p)->hash & m)) |
148 | p = &(*p)->next; |
149 | else { |
150 | *q = *p; |
151 | q = &(*q)->next; |
152 | *p = (*p)->next; |
153 | } |
154 | } |
155 | *p = 0; |
156 | *q = 0; |
157 | } |
158 | |
159 | TRACK_POP; |
160 | return (1); |
161 | } |
162 | |
163 | /* --- @hash_remove@ --- * |
164 | * |
165 | * Arguments: @hash_table *t@ = pointer to hashtable |
166 | * @hash_base *p@ = pointer to item to remove |
167 | * |
168 | * Returns: --- |
169 | * |
170 | * Use: Removes an item from a hashtable. The item itself is not |
171 | * freed, although it is removed from the data structure and is |
172 | * safe to free. |
173 | */ |
174 | |
175 | void hash_remove(hash_table *t, hash_base *p) |
176 | { |
177 | hash_base **b = HASH_BIN(t, p->hash); |
178 | while (*b) { |
179 | if (*b == p) { |
180 | *b = p->next; |
181 | return; |
182 | } |
183 | b = &(*b)->next; |
184 | } |
185 | return; |
186 | } |
187 | |
188 | /* --- @hash_mkiter@ --- * |
189 | * |
190 | * Arguments: @hash_iter *i@ = pointer to iterator to create |
191 | * @hash_table *t@ = pointer to hashtable to iterate |
192 | * |
193 | * Returns: --- |
194 | * |
195 | * Use: Initializes a hashtable iterator. |
196 | */ |
197 | |
198 | void hash_mkiter(hash_iter *i, hash_table *t) { HASH_MKITER(i, t); } |
199 | |
200 | /* --- @hash_next@ --- * |
201 | * |
202 | * Arguments: @hash_iter *i@ = pointer to iterator |
203 | * |
204 | * Returns: Pointer to the next hashtable entry found, or null. |
205 | * |
206 | * Use: Returns the next entry from the hashtable. |
207 | */ |
208 | |
209 | hash_base *hash_next(hash_iter *i) |
210 | { |
211 | hash_base *b; |
212 | HASH_NEXT(i, b); |
213 | return (b); |
214 | } |
215 | |
216 | /*----- That's all, folks -------------------------------------------------*/ |