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 | |
65 | typedef 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 | |
78 | typedef 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 | |
85 | typedef 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 | |
105 | extern 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 | |
117 | extern 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 | |
132 | extern 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 | |
144 | extern 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 | |
158 | extern 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 | |
172 | extern 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 | |
203 | extern hash_base *hash_next(hash_iter */*i*/); |
204 | |
205 | /*----- That's all, folks -------------------------------------------------*/ |
206 | |
207 | #ifdef __cplusplus |
208 | } |
209 | #endif |
210 | |
211 | #endif |