chiark / gitweb /
examples/disorder.init.in: Read settings from `/etc/default/disorder'.
[disorder] / lib / hash.c
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460b9539 1/*
2 * This file is part of DisOrder
5aff007d 3 * Copyright (C) 2005-2008 Richard Kettlewell
460b9539 4 *
e7eb3a27 5 * This program is free software: you can redistribute it and/or modify
460b9539 6 * it under the terms of the GNU General Public License as published by
e7eb3a27 7 * the Free Software Foundation, either version 3 of the License, or
460b9539 8 * (at your option) any later version.
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9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
460b9539 15 * You should have received a copy of the GNU General Public License
e7eb3a27 16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
460b9539 17 */
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18/** @file lib/hash.c
19 * @brief A simple hash table
20 */
05b75f8d 21#include "common.h"
460b9539 22
23#include "hash.h"
24#include "mem.h"
25#include "log.h"
9faa7a88 26#include "kvp.h"
460b9539 27
598b07b7 28/** @brief One entry in a hash table */
460b9539 29struct entry {
30 struct entry *next; /* next entry same key */
31 size_t h; /* hash of KEY */
32 const char *key; /* key of this entry */
33 void *value; /* value of this entry */
34};
35
598b07b7 36/** @brief A hash table */
460b9539 37struct hash {
38 size_t nslots; /* number of slots */
39 size_t nitems; /* total number of entries */
40 struct entry **slots; /* table of slots */
41 size_t valuesize; /* size of a value */
42};
43
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44/** @brief Hash function
45 * @param key Key to hash
46 * @return Hash code
47 */
460b9539 48static size_t hashfn(const char *key) {
49 size_t i = 0;
50
51 while(*key)
52 i = 33 * i + (unsigned char)*key++;
53 return i;
54}
55
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56/** @brief Expand a hash table
57 * @param h Hash table to expand
58 */
460b9539 59static void grow(hash *h) {
60 size_t n, newnslots;
61 struct entry **newslots, *e, *f;
62
63 /* Allocate a new, larger array */
64 newnslots = 2 * h->nslots;
65 newslots = xcalloc(newnslots, sizeof (struct entry *));
66 /* Copy everything to it */
67 for(n = 0; n < h->nslots; ++n) {
68 for(e = h->slots[n]; e; e = f) {
69 f = e->next;
70 e->next = newslots[e->h & (newnslots - 1)];
71 newslots[e->h & (newnslots - 1)] = e;
72 }
73 }
74 h->slots = newslots;
75 h->nslots = newnslots;
76}
77
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78/** @brief Create a new hash table
79 * @param valuesize Size of value type
80 * @return Hash table
81 */
460b9539 82hash *hash_new(size_t valuesize) {
83 hash *h = xmalloc(sizeof *h);
84
85 h->nslots = 256;
86 h->slots = xcalloc(h->nslots, sizeof (struct slot *));
87 h->valuesize = valuesize;
88 return h;
89}
90
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91/** @brief Add an element to a hash table
92 * @param h Hash table
93 * @param key Key
94 * @param value New value (will be shallow-copied)
95 * @param mode Add mode
96 * @return 0 on success, -1 if the value could not be added
97 *
98 * Possible add modes are:
99 * - @ref HASH_INSERT - key must not exist yet
100 * - @ref HASH_REPLACE - key must already exist
101 * - @ref HASH_INSERT_OR_REPLACE - key may or may not exist
102 */
460b9539 103int hash_add(hash *h, const char *key, const void *value, int mode) {
104 size_t n = hashfn(key);
105 struct entry *e;
106
107 for(e = h->slots[n & (h->nslots - 1)]; e; e = e->next)
108 if(e->h == n || !strcmp(e->key, key))
109 break;
110 if(e) {
111 /* This key is already present. */
112 if(mode == HASH_INSERT) return -1;
113 if(value) memcpy(e->value, value, h->valuesize);
114 return 0;
115 } else {
116 /* This key is absent. */
117 if(mode == HASH_REPLACE) return -1;
118 if(h->nitems >= h->nslots) /* bound mean chain length */
119 grow(h);
120 e = xmalloc(sizeof *e);
121 e->next = h->slots[n & (h->nslots - 1)];
122 e->h = n;
123 e->key = xstrdup(key);
124 e->value = xmalloc(h->valuesize);
125 if(value) memcpy(e->value, value, h->valuesize);
126 h->slots[n & (h->nslots - 1)] = e;
127 ++h->nitems;
128 return 0;
129 }
130}
131
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132/** @brief Remove an element from a hash table
133 * @param h Hash table
134 * @param key Key to remove
135 * @return 0 on success, -1 if the key wasn't found
136 */
460b9539 137int hash_remove(hash *h, const char *key) {
138 size_t n = hashfn(key);
139 struct entry *e, **ee;
140
141 for(ee = &h->slots[n & (h->nslots - 1)]; (e = *ee); ee = &e->next)
142 if(e->h == n || !strcmp(e->key, key))
143 break;
144 if(e) {
145 *ee = e->next;
146 --h->nitems;
147 return 0;
148 } else
149 return -1;
150}
151
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152/** @brief Find an item in a hash table
153 * @param h Hash table
154 * @param key Key to find
155 * @return Pointer to value or NULL if not found
156 *
157 * The return value points inside the hash table and should not be modified.
158 */
460b9539 159void *hash_find(hash *h, const char *key) {
160 size_t n = hashfn(key);
161 struct entry *e;
162
163 for(e = h->slots[n & (h->nslots - 1)]; e; e = e->next)
164 if(e->h == n || !strcmp(e->key, key))
165 return e->value;
166 return 0;
167}
168
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169/** @brief Visit every item in a hash table
170 * @param h Hash Table
171 * @param callback Function to call for each item
172 * @param u Passed to @p callback
173 * @return 0 on completion, else last return from @p callback
174 *
175 * @p callback should return 0 to continue or non-0 to stop. The @p key and @p
176 * value pointers passed to it point into the hash table and should not be
177 * modified.
178 *
179 * It's safe to remove items from inside the callback including the visited
180 * one. It is not safe to add items from inside the callback.
181 *
182 * No particular ordering is used.
183 */
460b9539 184int hash_foreach(hash *h,
185 int (*callback)(const char *key, void *value, void *u),
186 void *u) {
187 size_t n;
188 int ret;
189 struct entry *e, *f;
190
191 for(n = 0; n < h->nslots; ++n)
192 for(e = h->slots[n]; e; e = f) {
193 f = e->next;
194 if((ret = callback(e->key, e->value, u)))
195 return ret;
196 }
197 return 0;
198}
199
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200/** @brief Count the size of a hash table
201 * @param h Hash table
202 * @return Number of elements in hash table
203 */
460b9539 204size_t hash_count(hash *h) {
205 return h->nitems;
206}
207
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208/** @brief Get all the keys of a hash table
209 * @param h Hash table
210 * @return NULL-terminated list of keys
211 *
212 * The keys point into the hash table itself and should not be modified.
213 *
214 * No particular ordering is used.
215 */
460b9539 216char **hash_keys(hash *h) {
217 size_t n;
218 char **vec = xcalloc(h->nitems + 1, sizeof (char *)), **vp = vec;
219 struct entry *e;
220
221 for(n = 0; n < h->nslots; ++n)
222 for(e = h->slots[n]; e; e = e->next)
223 *vp++ = (char *)e->key;
224 *vp = 0;
225 return vec;
226}
227
228/*
229Local Variables:
230c-basic-offset:2
231comment-column:40
232fill-column:79
233indent-tabs-mode:nil
234End:
235*/