| 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 |