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Infrastructure: Split the files into subdirectories.
[mLib] / struct / hash.h
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03d53b73 1/* -*-c-*-
2 *
03d53b73 3 * General hashtable infrastructure
4 *
5 * (c) 1999 Straylight/Edgeware
6 */
7
d4efbcd9 8/*----- Licensing notice --------------------------------------------------*
03d53b73 9 *
10 * This file is part of the mLib utilities library.
11 *
12 * mLib is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
d4efbcd9 16 *
03d53b73 17 * mLib is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
d4efbcd9 21 *
03d53b73 22 * You should have received a copy of the GNU Library General Public
23 * License along with mLib; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
25 * MA 02111-1307, USA.
26 */
27
c6e0eaf0 28#ifndef MLIB_HASH_H
29#define MLIB_HASH_H
03d53b73 30
31#ifdef __cplusplus
32 extern "C" {
33#endif
34
35/*----- Notes -------------------------------------------------------------*
36 *
37 * This isn't a complete implementation of anything. It's a collection of
38 * useful types and functions which will help when building hashtables of
39 * things. The general-purpose hashtable is provided by the @sym@ functions.
40 */
41
42/*----- Header files ------------------------------------------------------*/
43
44#include <stddef.h>
45
20eb516f 46#ifndef MLIB_ARENA_H
47# include "arena.h"
48#endif
49
c6e0eaf0 50#ifndef MLIB_BITS_H
03d53b73 51# include "bits.h"
52#endif
53
54/*----- Data structures ---------------------------------------------------*/
55
56/* --- Hashtable basics --- *
57 *
58 * This contains the bare minimum to actually get anything useful done. In
59 * particular it doesn't maintain any weighting information: when to extend
60 * the table is left up to the particular implementation.
61 */
62
63typedef struct hash_table {
64 uint32 mask; /* Bit mask of hash bits */
65 struct hash_base **v; /* Vector of hash bins */
20eb516f 66 arena *a; /* Allocation arena */
03d53b73 67} hash_table;
68
69/* --- A hashtable entry --- *
70 *
71 * This is the bare minimum of what needs to be remembered in each hashtable
72 * entry. Comparison of elements is left to the implementation, so I don't
73 * need to know anything about how to represent hash keys here.
74 */
75
76typedef struct hash_base {
77 struct hash_base *next; /* Next entry in hash bin */
78 uint32 hash; /* Hash value for this entry */
79} hash_base;
80
81/* --- A hashtable iterator --- */
82
83typedef struct hash_iter {
84 hash_table *t; /* Hashtable being iterated */
85 hash_base *p; /* Address of next item to return */
86 size_t i; /* Index of next hash bin to use */
87} hash_iter;
88
89/*----- Functions provided ------------------------------------------------*/
90
91/* --- @hash_create@ --- *
92 *
93 * Arguments: @hash_table *t@ = pointer to hashtable to initialize
94 * @size_t n@ = number of bins to allocate (zero initially)
95 *
96 * Returns: ---
97 *
98 * Use: Initializes a hashtable with a given number of bins. The
99 * bins are initially empty. The number of bins must be a power
100 * of two. This is not checked.
101 */
102
103extern void hash_create(hash_table */*t*/, size_t /*n*/);
104
105/* --- @hash_destroy@ --- *
106 *
107 * Arguments: @hash_table *t@ = pointer to hashtable to destroy
108 *
109 * Returns: ---
110 *
111 * Use: Frees a hashtable. The items are not freed: they are the
112 * responsibility of the implementation.
113 */
114
115extern void hash_destroy(hash_table */*t*/);
116
117/* --- @hash_bin@ --- *
118 *
119 * Arguments: @hash_table *t@ = pointer to hashtable
120 * @uint32 hash@ = hash value to look up
121 *
122 * Returns: Pointer to the bin's list head.
123 *
124 * Use: Given a hash value return the address of the appropriate list
125 * head. It is safe to remove the current entry from the table.
126 */
127
128#define HASH_BIN(t, hash) ((t)->v + ((hash) & (t)->mask))
129
130extern hash_base **hash_bin(hash_table */*t*/, uint32 /*hash*/);
131
132/* --- @hash_extend@ --- *
133 *
134 * Arguments: @hash_table *t@ = pointer to hashtable to extend
135 *
136 * Returns: Nonzero if extension was successful.
137 *
138 * Use: Extends a hashtable. The number of bins is doubled and the
139 * entries are redistributed.
140 */
141
142extern int hash_extend(hash_table */*t*/);
143
144/* --- @hash_remove@ --- *
145 *
146 * Arguments: @hash_table *t@ = pointer to hashtable
147 * @hash_base *p@ = pointer to item to remove
148 *
149 * Returns: ---
150 *
151 * Use: Removes an item from a hashtable. The item itself is not
152 * freed, although it is removed from the data structure and is
153 * safe to free.
154 */
155
156extern void hash_remove(hash_table */*t*/, hash_base */*p*/);
157
158/* --- @hash_mkiter@ --- *
159 *
160 * Arguments: @hash_iter *i@ = pointer to iterator to create
161 * @hash_table *t@ = pointer to hashtable to iterate
162 *
163 * Returns: ---
164 *
165 * Use: Initializes a hashtable iterator.
166 */
167
168#define HASH_MKITER(i_, t_) ((i_)->t = (t_), (i_)->p = 0, (i_)->i = 0)
169
170extern void hash_mkiter(hash_iter */*i*/, hash_table */*t*/);
171
172/* --- @hash_next@ --- *
173 *
174 * Arguments: @hash_iter *i@ = pointer to iterator
175 *
176 * Returns: Pointer to the next hashtable entry found, or null.
177 *
178 * Use: Returns the next entry from the hashtable.
179 */
180
181#define HASH_NEXT(i_, b_) do { \
182 hash_iter *_i = (i_); \
183 hash_base *_p; \
184 hash_table *_t = _i->t; \
185 uint32 _m = _t->mask; \
186 \
187 for (;;) { \
188 if (_i->p) { \
189 _p = _i->p; \
190 _i->p = _p->next; \
191 break; \
192 } else if (_i->i > _m) { \
193 _p = 0; \
194 break; \
195 } else \
196 _i->p = _t->v[_i->i++]; \
197 } \
198 (b_) = _p; \
199} while (0)
200
201extern hash_base *hash_next(hash_iter */*i*/);
202
203/*----- That's all, folks -------------------------------------------------*/
204
205#ifdef __cplusplus
206 }
207#endif
208
209#endif