1 /*
2 * Copyright © 2009 Intel Corporation
3 * Copyright © 1988-2004 Keith Packard and Bart Massey.
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
22 * IN THE SOFTWARE.
23 *
24 * Except as contained in this notice, the names of the authors
25 * or their institutions shall not be used in advertising or
26 * otherwise to promote the sale, use or other dealings in this
27 * Software without prior written authorization from the
28 * authors.
29 *
30 * Authors:
31 * Eric Anholt <eric@anholt.net>
32 * Keith Packard <keithp@keithp.com>
33 */
34
35 #include "config.h"
36
37 #include <stdlib.h>
38 #include <stdint.h>
39
40 #include "hash.h"
41
42 struct hash_entry {
43 uint32_t hash;
44 void *data;
45 };
46
47 struct hash_table {
48 struct hash_entry *table;
49 uint32_t size;
50 uint32_t rehash;
51 uint32_t max_entries;
52 uint32_t size_index;
53 uint32_t entries;
54 uint32_t deleted_entries;
55 };
56
57 #define ARRAY_SIZE(array) (sizeof(array) / sizeof(array[0]))
58
59 /*
60 * From Knuth -- a good choice for hash/rehash values is p, p-2 where
61 * p and p-2 are both prime. These tables are sized to have an extra 10%
62 * free to avoid exponential performance degradation as the hash table fills
63 */
64
65 static const uint32_t deleted_data;
66
67 static const struct {
68 uint32_t max_entries, size, rehash;
69 } hash_sizes[] = {
70 { 2, 5, 3 },
71 { 4, 7, 5 },
72 { 8, 13, 11 },
73 { 16, 19, 17 },
74 { 32, 43, 41 },
75 { 64, 73, 71 },
76 { 128, 151, 149 },
77 { 256, 283, 281 },
78 { 512, 571, 569 },
79 { 1024, 1153, 1151 },
80 { 2048, 2269, 2267 },
81 { 4096, 4519, 4517 },
82 { 8192, 9013, 9011 },
83 { 16384, 18043, 18041 },
84 { 32768, 36109, 36107 },
85 { 65536, 72091, 72089 },
86 { 131072, 144409, 144407 },
87 { 262144, 288361, 288359 },
88 { 524288, 576883, 576881 },
89 { 1048576, 1153459, 1153457 },
90 { 2097152, 2307163, 2307161 },
91 { 4194304, 4613893, 4613891 },
92 { 8388608, 9227641, 9227639 },
93 { 16777216, 18455029, 18455027 },
94 { 33554432, 36911011, 36911009 },
95 { 67108864, 73819861, 73819859 },
96 { 134217728, 147639589, 147639587 },
97 { 268435456, 295279081, 295279079 },
98 { 536870912, 590559793, 590559791 },
99 { 1073741824, 1181116273, 1181116271},
100 { 2147483648ul, 2362232233ul, 2362232231ul}
101 };
102
103 static int
entry_is_free(struct hash_entry * entry)104 entry_is_free(struct hash_entry *entry)
105 {
106 return entry->data == NULL;
107 }
108
109 static int
entry_is_deleted(struct hash_entry * entry)110 entry_is_deleted(struct hash_entry *entry)
111 {
112 return entry->data == &deleted_data;
113 }
114
115 static int
entry_is_present(struct hash_entry * entry)116 entry_is_present(struct hash_entry *entry)
117 {
118 return entry->data != NULL && entry->data != &deleted_data;
119 }
120
121 struct hash_table *
hash_table_create(void)122 hash_table_create(void)
123 {
124 struct hash_table *ht;
125
126 ht = malloc(sizeof(*ht));
127 if (ht == NULL)
128 return NULL;
129
130 ht->size_index = 0;
131 ht->size = hash_sizes[ht->size_index].size;
132 ht->rehash = hash_sizes[ht->size_index].rehash;
133 ht->max_entries = hash_sizes[ht->size_index].max_entries;
134 ht->table = calloc(ht->size, sizeof(*ht->table));
135 ht->entries = 0;
136 ht->deleted_entries = 0;
137
138 if (ht->table == NULL) {
139 free(ht);
140 return NULL;
141 }
142
143 return ht;
144 }
145
146 /**
147 * Frees the given hash table.
148 */
149 void
hash_table_destroy(struct hash_table * ht)150 hash_table_destroy(struct hash_table *ht)
151 {
152 if (!ht)
153 return;
154
155 free(ht->table);
156 free(ht);
157 }
158
159 /**
160 * Finds a hash table entry with the given key and hash of that key.
161 *
162 * Returns NULL if no entry is found. Note that the data pointer may be
163 * modified by the user.
164 */
165 static void *
hash_table_search(struct hash_table * ht,uint32_t hash)166 hash_table_search(struct hash_table *ht, uint32_t hash)
167 {
168 uint32_t hash_address;
169
170 hash_address = hash % ht->size;
171 do {
172 uint32_t double_hash;
173
174 struct hash_entry *entry = ht->table + hash_address;
175
176 if (entry_is_free(entry)) {
177 return NULL;
178 } else if (entry_is_present(entry) && entry->hash == hash) {
179 return entry;
180 }
181
182 double_hash = 1 + hash % ht->rehash;
183
184 hash_address = (hash_address + double_hash) % ht->size;
185 } while (hash_address != hash % ht->size);
186
187 return NULL;
188 }
189
190 void
hash_table_for_each(struct hash_table * ht,hash_table_iterator_func_t func,void * data)191 hash_table_for_each(struct hash_table *ht,
192 hash_table_iterator_func_t func, void *data)
193 {
194 struct hash_entry *entry;
195 uint32_t i;
196
197 for (i = 0; i < ht->size; i++) {
198 entry = ht->table + i;
199 if (entry_is_present(entry))
200 func(entry->data, data);
201 }
202 }
203
204 void *
hash_table_lookup(struct hash_table * ht,uint32_t hash)205 hash_table_lookup(struct hash_table *ht, uint32_t hash)
206 {
207 struct hash_entry *entry;
208
209 entry = hash_table_search(ht, hash);
210 if (entry != NULL)
211 return entry->data;
212
213 return NULL;
214 }
215
216 static void
hash_table_rehash(struct hash_table * ht,unsigned int new_size_index)217 hash_table_rehash(struct hash_table *ht, unsigned int new_size_index)
218 {
219 struct hash_table old_ht;
220 struct hash_entry *table, *entry;
221
222 if (new_size_index >= ARRAY_SIZE(hash_sizes))
223 return;
224
225 table = calloc(hash_sizes[new_size_index].size, sizeof(*ht->table));
226 if (table == NULL)
227 return;
228
229 old_ht = *ht;
230
231 ht->table = table;
232 ht->size_index = new_size_index;
233 ht->size = hash_sizes[ht->size_index].size;
234 ht->rehash = hash_sizes[ht->size_index].rehash;
235 ht->max_entries = hash_sizes[ht->size_index].max_entries;
236 ht->entries = 0;
237 ht->deleted_entries = 0;
238
239 for (entry = old_ht.table;
240 entry != old_ht.table + old_ht.size;
241 entry++) {
242 if (entry_is_present(entry)) {
243 hash_table_insert(ht, entry->hash, entry->data);
244 }
245 }
246
247 free(old_ht.table);
248 }
249
250 /**
251 * Inserts the data with the given hash into the table.
252 *
253 * Note that insertion may rearrange the table on a resize or rehash,
254 * so previously found hash_entries are no longer valid after this function.
255 */
256 int
hash_table_insert(struct hash_table * ht,uint32_t hash,void * data)257 hash_table_insert(struct hash_table *ht, uint32_t hash, void *data)
258 {
259 uint32_t hash_address;
260
261 if (ht->entries >= ht->max_entries) {
262 hash_table_rehash(ht, ht->size_index + 1);
263 } else if (ht->deleted_entries + ht->entries >= ht->max_entries) {
264 hash_table_rehash(ht, ht->size_index);
265 }
266
267 hash_address = hash % ht->size;
268 do {
269 struct hash_entry *entry = ht->table + hash_address;
270 uint32_t double_hash;
271
272 if (!entry_is_present(entry)) {
273 if (entry_is_deleted(entry))
274 ht->deleted_entries--;
275 entry->hash = hash;
276 entry->data = data;
277 ht->entries++;
278 return 0;
279 }
280
281 double_hash = 1 + hash % ht->rehash;
282
283 hash_address = (hash_address + double_hash) % ht->size;
284 } while (hash_address != hash % ht->size);
285
286 /* We could hit here if a required resize failed. An unchecked-malloc
287 * application could ignore this result.
288 */
289 return -1;
290 }
291
292 /**
293 * This function deletes the given hash table entry.
294 *
295 * Note that deletion doesn't otherwise modify the table, so an iteration over
296 * the table deleting entries is safe.
297 */
298 void
hash_table_remove(struct hash_table * ht,uint32_t hash)299 hash_table_remove(struct hash_table *ht, uint32_t hash)
300 {
301 struct hash_entry *entry;
302
303 entry = hash_table_search(ht, hash);
304 if (entry != NULL) {
305 entry->data = (void *) &deleted_data;
306 ht->entries--;
307 ht->deleted_entries++;
308 }
309 }
310