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