3 * $Id: hash.c,v 1.3 2000/07/16 12:29:16 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 1.3 2000/07/16 12:29:16 mdw
34 * Change to arena `realloc' interface, to fix a design bug.
36 * Revision 1.2 2000/06/17 10:37:39 mdw
37 * Add support for arena management.
39 * Revision 1.1 1999/08/02 14:45:48 mdw
40 * Break low-level hashtable code out from sym.
44 /*----- Header files ------------------------------------------------------*/
56 /*----- Main code ---------------------------------------------------------*/
58 /* --- @hash_create@ --- *
60 * Arguments: @hash_table *t@ = pointer to hashtable to initialize
61 * @size_t n@ = number of bins to allocate (zero initially)
65 * Use: Initializes a hashtable with a given number of bins. The
66 * bins are initially empty. The number of bins must be a power
67 * of two. This is not checked.
70 void hash_create(hash_table *t, size_t n)
75 t->v = x_alloc(t->a, n * sizeof(hash_base *));
77 for (v = t->v; n; v++, n--)
81 /* --- @hash_destroy@ --- *
83 * Arguments: @hash_table *t@ = pointer to hashtable to destroy
87 * Use: Frees a hashtable. The items are not freed: they are the
88 * responsibility of the implementation.
91 void hash_destroy(hash_table *t)
96 /* --- @hash_bin@ --- *
98 * Arguments: @hash_table *t@ = pointer to hashtable
99 * @uint32 hash@ = hash value to look up
101 * Returns: Pointer to the bin's list head.
103 * Use: Given a hash value return the address of the appropriate list
104 * head. It is safe to remove the current entry from the table.
107 hash_base **hash_bin(hash_table *t, uint32 hash)
109 return (HASH_BIN(t, hash));
112 /* --- @hash_extend@ --- *
114 * Arguments: @hash_table *t@ = pointer to hashtable to extend
116 * Returns: Nonzero if extension was successful.
118 * Use: Extends a hashtable. The number of bins is doubled and the
119 * entries are redistributed.
122 int hash_extend(hash_table *t)
125 uint32 m = t->mask + 1;
128 /* --- Allocate a new hash bin vector --- */
130 if ((v = A_REALLOC(t->a, t->v,
131 2 * m * sizeof(hash_base *),
132 m * sizeof(hash_base *))) == 0) {
136 t->mask = (m * 2) - 1;
138 /* --- Wander through the table rehashing things --- */
140 for (i = 0; i < m; i++) {
141 hash_base **p = v + i;
142 hash_base **q = p + m;
145 if (!((*p)->hash & m))
160 /* --- @hash_remove@ --- *
162 * Arguments: @hash_table *t@ = pointer to hashtable
163 * @hash_base *p@ = pointer to item to remove
167 * Use: Removes an item from a hashtable. The item itself is not
168 * freed, although it is removed from the data structure and is
172 void hash_remove(hash_table *t, hash_base *p)
174 hash_base **b = HASH_BIN(t, p->hash);
185 /* --- @hash_mkiter@ --- *
187 * Arguments: @hash_iter *i@ = pointer to iterator to create
188 * @hash_table *t@ = pointer to hashtable to iterate
192 * Use: Initializes a hashtable iterator.
195 void hash_mkiter(hash_iter *i, hash_table *t) { HASH_MKITER(i, t); }
197 /* --- @hash_next@ --- *
199 * Arguments: @hash_iter *i@ = pointer to iterator
201 * Returns: Pointer to the next hashtable entry found, or null.
203 * Use: Returns the next entry from the hashtable.
206 hash_base *hash_next(hash_iter *i)
213 /*----- That's all, folks -------------------------------------------------*/