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1 | /* -*-c-*- |
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2 | * |
3 | * General hashtable infrastructure |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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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. |
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16 | * |
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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. |
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21 | * |
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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 | |
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28 | #ifndef MLIB_HASH_H |
29 | #define MLIB_HASH_H |
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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 | |
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46 | #ifndef MLIB_ARENA_H |
47 | # include "arena.h" |
48 | #endif |
49 | |
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50 | #ifndef MLIB_BITS_H |
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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 | |
63 | typedef struct hash_table { |
64 | uint32 mask; /* Bit mask of hash bits */ |
65 | struct hash_base **v; /* Vector of hash bins */ |
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66 | arena *a; /* Allocation arena */ |
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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 | |
76 | typedef 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 | |
83 | typedef 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 | |
103 | extern 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 | |
115 | extern 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 | |
130 | extern 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 | |
142 | extern 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 | |
156 | extern 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 | |
170 | extern 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 | |
201 | extern hash_base *hash_next(hash_iter */*i*/); |
202 | |
203 | /*----- That's all, folks -------------------------------------------------*/ |
204 | |
205 | #ifdef __cplusplus |
206 | } |
207 | #endif |
208 | |
209 | #endif |