chiark / gitweb /
Add global unihash table; use universal hashing instead of CRC.
[mLib] / assoc.c
CommitLineData
dcda5944 1/* -*-c-*-
2 *
efa99d05 3 * $Id: assoc.c,v 1.3 2001/01/25 21:12:38 mdw Exp $
dcda5944 4 *
5 * Assocation tables
6 *
7 * (c) 2000 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: assoc.c,v $
efa99d05 33 * Revision 1.3 2001/01/25 21:12:38 mdw
34 * Use @ATOM_HASH@ rather than digging in the @atom@ structure.
35 *
6f5e97ac 36 * Revision 1.2 2001/01/21 19:04:59 mdw
37 * Fix bugs.
38 *
dcda5944 39 * Revision 1.1 2001/01/20 11:50:58 mdw
40 * Hash tables indexed by atoms, to avoid expense of hashing keys on each
41 * lookup, and to reduce storage used by key texts.
42 *
43 */
44
45/*----- Header files ------------------------------------------------------*/
46
47#include "alloc.h"
48#include "assoc.h"
49#include "atom.h"
50#include "hash.h"
51
52/*----- Main code ---------------------------------------------------------*/
53
54/* --- @assoc_create@ --- *
55 *
56 * Arguments: @assoc_table *t@ = pointer to an association table
57 *
58 * Returns: ---
59 *
60 * Use: Creates a new association table.
61 */
62
63void assoc_create(assoc_table *t)
64{
65 hash_create(&t->t, SYM_INITSZ);
66 t->load = SYM_LIMIT(SYM_INITSZ);
67}
68
69/* --- @assoc_destroy@ --- *
70 *
71 * Arguments: @assoc_table *t@ = pointer to an association table
72 *
73 * Returns: ---
74 *
75 * Use: Destroys an association table.
76 */
77
78void assoc_destroy(assoc_table *t)
79{
80 hash_iter i;
81
82 HASH_MKITER(&i, &t->t);
83 for (;;) {
84 hash_base *p;
85 HASH_NEXT(&i, p);
6f5e97ac 86 if (!p)
87 break;
dcda5944 88 x_free(t->t.a, p);
89 }
90 hash_destroy(&t->t);
91}
92
93/* --- @assoc_find@ --- *
94 *
95 * Arguments: @assoc_table *t@ = pointer to an association table
96 * @atom *a@ = an atom to label the item
97 * @size_t sz@ = size of block to allocate
98 * @unsigned *f@ = pointer to `found' flag
99 *
100 * Returns: A pointer to the item located or null.
101 *
102 * Use: Looks up an atom in an association table. If the atom is
103 * found, the association is returned. If not, and @sz@ is
104 * zero, a null pointer is returned. Otherwise, a block of size
105 * @sz@ is allocated, its @assoc_base@ header is filled in, and
106 * the pointer returned. The flag @*f@ is cleared if the item
107 * couldn't be found, or set if it was.
108 *
109 * All the atoms used in a particular table should
110 */
111
112void *assoc_find(assoc_table *t, atom *a, size_t sz, unsigned *f)
113{
efa99d05 114 hash_base **bin = HASH_BIN(&t->t, ATOM_HASH(a)), **p;
dcda5944 115 assoc_base *q;
116
117 /* --- Try to find the association --- */
118
119 for (p = bin; *p; p = &(*p)->next) {
120 q = (assoc_base *)*p;
121 if (q->a == a) {
122 *p = q->b.next;
123 q->b.next = *bin;
124 *bin = &q->b;
125 if (f) *f = 1;
126 return (q);
127 }
128 }
129
130 /* --- Failed to find a match --- */
131
132 if (f) *f = 0;
133 if (!sz) return (0);
134
135 /* --- Make a new assoication --- */
136
137 q = x_alloc(t->t.a, sz);
6f5e97ac 138 q->a = a;
dcda5944 139 q->b.next = *bin;
140 q->b.hash = ATOM_HASH(a);
141 *bin = &q->b;
142
143 /* --- Maybe extend the table --- */
144
145 if (t->load)
146 t->load--;
147 if (!t->load && hash_extend(&t->t))
148 t->load = SYM_LIMIT(t->t.mask + 1);
149 return (q);
150}
151
152/* --- @assoc_remove@ --- *
153 *
154 * Arguments: @assoc_table *t@ = pointer to an association table
155 * @void *p@ = pointer to a block to remove
156 *
157 * Returns: ---
158 *
159 * Use: Removes an association from a table.
160 */
161
162void assoc_remove(assoc_table *t, void *p)
163{
164 assoc_base *q = p;
165 hash_remove(&t->t, &q->b);
166 x_free(t->t.a, q);
167 t->load++;
168}
169
170/* --- @assoc_mkiter@, @assoc_next@ --- *
171 *
172 * Arguments: @assoc_iter *i@ = pointer to an iterator
173 * @assoc_table *t@ = pointer to an association table
174 *
175 * Returns: Next association, or null, for @assoc_next@; nothing for
176 * @assoc_mkiter@.
177 *
178 * Use: Iterates over the associations in a table.
179 */
180
181void assoc_mkiter(assoc_iter *i, assoc_table *t) { ASSOC_MKITER(i, t); }
182void *assoc_next(assoc_iter *i) { void *p; ASSOC_NEXT(i, p); return (p); }
183
184/*----- That's all, folks -------------------------------------------------*/