3 * $Id: hash.c,v 1.1 1999/08/02 14:45:48 mdw Exp $
5 * General hashtable infrastructure
7 * (c) 1999 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of the mLib utilities library.
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.
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.
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,
30 /*----- Revision history --------------------------------------------------*
33 * Revision 1.1 1999/08/02 14:45:48 mdw
34 * Break low-level hashtable code out from sym.
38 /*----- Header files ------------------------------------------------------*/
50 /*----- Main code ---------------------------------------------------------*/
52 /* --- @hash_create@ --- *
54 * Arguments: @hash_table *t@ = pointer to hashtable to initialize
55 * @size_t n@ = number of bins to allocate (zero initially)
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.
64 void hash_create(hash_table *t, size_t n)
67 TRACK_CTX("hashtable creation");
69 t->v = xmalloc(n * sizeof(hash_base *));
71 for (v = t->v; n; v++, n--)
76 /* --- @hash_destroy@ --- *
78 * Arguments: @hash_table *t@ = pointer to hashtable to destroy
82 * Use: Frees a hashtable. The items are not freed: they are the
83 * responsibility of the implementation.
86 void hash_destroy(hash_table *t)
88 TRACK_CTX("hashtable destruction");
94 /* --- @hash_bin@ --- *
96 * Arguments: @hash_table *t@ = pointer to hashtable
97 * @uint32 hash@ = hash value to look up
99 * Returns: Pointer to the bin's list head.
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.
105 hash_base **hash_bin(hash_table *t, uint32 hash)
107 return (HASH_BIN(t, hash));
110 /* --- @hash_extend@ --- *
112 * Arguments: @hash_table *t@ = pointer to hashtable to extend
114 * Returns: Nonzero if extension was successful.
116 * Use: Extends a hashtable. The number of bins is doubled and the
117 * entries are redistributed.
120 int hash_extend(hash_table *t)
123 uint32 m = t->mask + 1;
126 /* --- Push in a tracking context --- */
128 TRACK_CTX("hashtable extension");
131 /* --- Allocate a new hash bin vector --- */
133 if ((v = realloc(t->v, m * 2 * sizeof(hash_base *))) == 0) {
138 t->mask = (m * 2) - 1;
140 /* --- Wander through the table rehashing things --- */
142 for (i = 0; i < m; i++) {
143 hash_base **p = v + i;
144 hash_base **q = p + m;
147 if (!((*p)->hash & m))
163 /* --- @hash_remove@ --- *
165 * Arguments: @hash_table *t@ = pointer to hashtable
166 * @hash_base *p@ = pointer to item to remove
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
175 void hash_remove(hash_table *t, hash_base *p)
177 hash_base **b = HASH_BIN(t, p->hash);
188 /* --- @hash_mkiter@ --- *
190 * Arguments: @hash_iter *i@ = pointer to iterator to create
191 * @hash_table *t@ = pointer to hashtable to iterate
195 * Use: Initializes a hashtable iterator.
198 void hash_mkiter(hash_iter *i, hash_table *t) { HASH_MKITER(i, t); }
200 /* --- @hash_next@ --- *
202 * Arguments: @hash_iter *i@ = pointer to iterator
204 * Returns: Pointer to the next hashtable entry found, or null.
206 * Use: Returns the next entry from the hashtable.
209 hash_base *hash_next(hash_iter *i)
216 /*----- That's all, folks -------------------------------------------------*/