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Change header file guard names.
[mLib] / hash.h
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03d53b73 1/* -*-c-*-
2 *
c6e0eaf0 3 * $Id: hash.h,v 1.2 1999/12/10 23:42:04 mdw Exp $
03d53b73 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.h,v $
c6e0eaf0 33 * Revision 1.2 1999/12/10 23:42:04 mdw
34 * Change header file guard names.
35 *
03d53b73 36 * Revision 1.1 1999/08/02 14:45:48 mdw
37 * Break low-level hashtable code out from sym.
38 *
39 */
40
c6e0eaf0 41#ifndef MLIB_HASH_H
42#define MLIB_HASH_H
03d53b73 43
44#ifdef __cplusplus
45 extern "C" {
46#endif
47
48/*----- Notes -------------------------------------------------------------*
49 *
50 * This isn't a complete implementation of anything. It's a collection of
51 * useful types and functions which will help when building hashtables of
52 * things. The general-purpose hashtable is provided by the @sym@ functions.
53 */
54
55/*----- Header files ------------------------------------------------------*/
56
57#include <stddef.h>
58
c6e0eaf0 59#ifndef MLIB_BITS_H
03d53b73 60# include "bits.h"
61#endif
62
63/*----- Data structures ---------------------------------------------------*/
64
65/* --- Hashtable basics --- *
66 *
67 * This contains the bare minimum to actually get anything useful done. In
68 * particular it doesn't maintain any weighting information: when to extend
69 * the table is left up to the particular implementation.
70 */
71
72typedef struct hash_table {
73 uint32 mask; /* Bit mask of hash bits */
74 struct hash_base **v; /* Vector of hash bins */
75} hash_table;
76
77/* --- A hashtable entry --- *
78 *
79 * This is the bare minimum of what needs to be remembered in each hashtable
80 * entry. Comparison of elements is left to the implementation, so I don't
81 * need to know anything about how to represent hash keys here.
82 */
83
84typedef struct hash_base {
85 struct hash_base *next; /* Next entry in hash bin */
86 uint32 hash; /* Hash value for this entry */
87} hash_base;
88
89/* --- A hashtable iterator --- */
90
91typedef struct hash_iter {
92 hash_table *t; /* Hashtable being iterated */
93 hash_base *p; /* Address of next item to return */
94 size_t i; /* Index of next hash bin to use */
95} hash_iter;
96
97/*----- Functions provided ------------------------------------------------*/
98
99/* --- @hash_create@ --- *
100 *
101 * Arguments: @hash_table *t@ = pointer to hashtable to initialize
102 * @size_t n@ = number of bins to allocate (zero initially)
103 *
104 * Returns: ---
105 *
106 * Use: Initializes a hashtable with a given number of bins. The
107 * bins are initially empty. The number of bins must be a power
108 * of two. This is not checked.
109 */
110
111extern void hash_create(hash_table */*t*/, size_t /*n*/);
112
113/* --- @hash_destroy@ --- *
114 *
115 * Arguments: @hash_table *t@ = pointer to hashtable to destroy
116 *
117 * Returns: ---
118 *
119 * Use: Frees a hashtable. The items are not freed: they are the
120 * responsibility of the implementation.
121 */
122
123extern void hash_destroy(hash_table */*t*/);
124
125/* --- @hash_bin@ --- *
126 *
127 * Arguments: @hash_table *t@ = pointer to hashtable
128 * @uint32 hash@ = hash value to look up
129 *
130 * Returns: Pointer to the bin's list head.
131 *
132 * Use: Given a hash value return the address of the appropriate list
133 * head. It is safe to remove the current entry from the table.
134 */
135
136#define HASH_BIN(t, hash) ((t)->v + ((hash) & (t)->mask))
137
138extern hash_base **hash_bin(hash_table */*t*/, uint32 /*hash*/);
139
140/* --- @hash_extend@ --- *
141 *
142 * Arguments: @hash_table *t@ = pointer to hashtable to extend
143 *
144 * Returns: Nonzero if extension was successful.
145 *
146 * Use: Extends a hashtable. The number of bins is doubled and the
147 * entries are redistributed.
148 */
149
150extern int hash_extend(hash_table */*t*/);
151
152/* --- @hash_remove@ --- *
153 *
154 * Arguments: @hash_table *t@ = pointer to hashtable
155 * @hash_base *p@ = pointer to item to remove
156 *
157 * Returns: ---
158 *
159 * Use: Removes an item from a hashtable. The item itself is not
160 * freed, although it is removed from the data structure and is
161 * safe to free.
162 */
163
164extern void hash_remove(hash_table */*t*/, hash_base */*p*/);
165
166/* --- @hash_mkiter@ --- *
167 *
168 * Arguments: @hash_iter *i@ = pointer to iterator to create
169 * @hash_table *t@ = pointer to hashtable to iterate
170 *
171 * Returns: ---
172 *
173 * Use: Initializes a hashtable iterator.
174 */
175
176#define HASH_MKITER(i_, t_) ((i_)->t = (t_), (i_)->p = 0, (i_)->i = 0)
177
178extern void hash_mkiter(hash_iter */*i*/, hash_table */*t*/);
179
180/* --- @hash_next@ --- *
181 *
182 * Arguments: @hash_iter *i@ = pointer to iterator
183 *
184 * Returns: Pointer to the next hashtable entry found, or null.
185 *
186 * Use: Returns the next entry from the hashtable.
187 */
188
189#define HASH_NEXT(i_, b_) do { \
190 hash_iter *_i = (i_); \
191 hash_base *_p; \
192 hash_table *_t = _i->t; \
193 uint32 _m = _t->mask; \
194 \
195 for (;;) { \
196 if (_i->p) { \
197 _p = _i->p; \
198 _i->p = _p->next; \
199 break; \
200 } else if (_i->i > _m) { \
201 _p = 0; \
202 break; \
203 } else \
204 _i->p = _t->v[_i->i++]; \
205 } \
206 (b_) = _p; \
207} while (0)
208
209extern hash_base *hash_next(hash_iter */*i*/);
210
211/*----- That's all, folks -------------------------------------------------*/
212
213#ifdef __cplusplus
214 }
215#endif
216
217#endif