chiark / gitweb /
buf: Fix two embarassing bugs found while writing Lisp bindings.
[mLib] / hash.h
CommitLineData
03d53b73 1/* -*-c-*-
2 *
8656dc50 3 * $Id: hash.h,v 1.4 2004/04/08 01:36:11 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
c6e0eaf0 30#ifndef MLIB_HASH_H
31#define MLIB_HASH_H
03d53b73 32
33#ifdef __cplusplus
34 extern "C" {
35#endif
36
37/*----- Notes -------------------------------------------------------------*
38 *
39 * This isn't a complete implementation of anything. It's a collection of
40 * useful types and functions which will help when building hashtables of
41 * things. The general-purpose hashtable is provided by the @sym@ functions.
42 */
43
44/*----- Header files ------------------------------------------------------*/
45
46#include <stddef.h>
47
20eb516f 48#ifndef MLIB_ARENA_H
49# include "arena.h"
50#endif
51
c6e0eaf0 52#ifndef MLIB_BITS_H
03d53b73 53# include "bits.h"
54#endif
55
56/*----- Data structures ---------------------------------------------------*/
57
58/* --- Hashtable basics --- *
59 *
60 * This contains the bare minimum to actually get anything useful done. In
61 * particular it doesn't maintain any weighting information: when to extend
62 * the table is left up to the particular implementation.
63 */
64
65typedef struct hash_table {
66 uint32 mask; /* Bit mask of hash bits */
67 struct hash_base **v; /* Vector of hash bins */
20eb516f 68 arena *a; /* Allocation arena */
03d53b73 69} hash_table;
70
71/* --- A hashtable entry --- *
72 *
73 * This is the bare minimum of what needs to be remembered in each hashtable
74 * entry. Comparison of elements is left to the implementation, so I don't
75 * need to know anything about how to represent hash keys here.
76 */
77
78typedef struct hash_base {
79 struct hash_base *next; /* Next entry in hash bin */
80 uint32 hash; /* Hash value for this entry */
81} hash_base;
82
83/* --- A hashtable iterator --- */
84
85typedef struct hash_iter {
86 hash_table *t; /* Hashtable being iterated */
87 hash_base *p; /* Address of next item to return */
88 size_t i; /* Index of next hash bin to use */
89} hash_iter;
90
91/*----- Functions provided ------------------------------------------------*/
92
93/* --- @hash_create@ --- *
94 *
95 * Arguments: @hash_table *t@ = pointer to hashtable to initialize
96 * @size_t n@ = number of bins to allocate (zero initially)
97 *
98 * Returns: ---
99 *
100 * Use: Initializes a hashtable with a given number of bins. The
101 * bins are initially empty. The number of bins must be a power
102 * of two. This is not checked.
103 */
104
105extern void hash_create(hash_table */*t*/, size_t /*n*/);
106
107/* --- @hash_destroy@ --- *
108 *
109 * Arguments: @hash_table *t@ = pointer to hashtable to destroy
110 *
111 * Returns: ---
112 *
113 * Use: Frees a hashtable. The items are not freed: they are the
114 * responsibility of the implementation.
115 */
116
117extern void hash_destroy(hash_table */*t*/);
118
119/* --- @hash_bin@ --- *
120 *
121 * Arguments: @hash_table *t@ = pointer to hashtable
122 * @uint32 hash@ = hash value to look up
123 *
124 * Returns: Pointer to the bin's list head.
125 *
126 * Use: Given a hash value return the address of the appropriate list
127 * head. It is safe to remove the current entry from the table.
128 */
129
130#define HASH_BIN(t, hash) ((t)->v + ((hash) & (t)->mask))
131
132extern hash_base **hash_bin(hash_table */*t*/, uint32 /*hash*/);
133
134/* --- @hash_extend@ --- *
135 *
136 * Arguments: @hash_table *t@ = pointer to hashtable to extend
137 *
138 * Returns: Nonzero if extension was successful.
139 *
140 * Use: Extends a hashtable. The number of bins is doubled and the
141 * entries are redistributed.
142 */
143
144extern int hash_extend(hash_table */*t*/);
145
146/* --- @hash_remove@ --- *
147 *
148 * Arguments: @hash_table *t@ = pointer to hashtable
149 * @hash_base *p@ = pointer to item to remove
150 *
151 * Returns: ---
152 *
153 * Use: Removes an item from a hashtable. The item itself is not
154 * freed, although it is removed from the data structure and is
155 * safe to free.
156 */
157
158extern void hash_remove(hash_table */*t*/, hash_base */*p*/);
159
160/* --- @hash_mkiter@ --- *
161 *
162 * Arguments: @hash_iter *i@ = pointer to iterator to create
163 * @hash_table *t@ = pointer to hashtable to iterate
164 *
165 * Returns: ---
166 *
167 * Use: Initializes a hashtable iterator.
168 */
169
170#define HASH_MKITER(i_, t_) ((i_)->t = (t_), (i_)->p = 0, (i_)->i = 0)
171
172extern void hash_mkiter(hash_iter */*i*/, hash_table */*t*/);
173
174/* --- @hash_next@ --- *
175 *
176 * Arguments: @hash_iter *i@ = pointer to iterator
177 *
178 * Returns: Pointer to the next hashtable entry found, or null.
179 *
180 * Use: Returns the next entry from the hashtable.
181 */
182
183#define HASH_NEXT(i_, b_) do { \
184 hash_iter *_i = (i_); \
185 hash_base *_p; \
186 hash_table *_t = _i->t; \
187 uint32 _m = _t->mask; \
188 \
189 for (;;) { \
190 if (_i->p) { \
191 _p = _i->p; \
192 _i->p = _p->next; \
193 break; \
194 } else if (_i->i > _m) { \
195 _p = 0; \
196 break; \
197 } else \
198 _i->p = _t->v[_i->i++]; \
199 } \
200 (b_) = _p; \
201} while (0)
202
203extern hash_base *hash_next(hash_iter */*i*/);
204
205/*----- That's all, folks -------------------------------------------------*/
206
207#ifdef __cplusplus
208 }
209#endif
210
211#endif