2 * Copyright © 2009,2012 Intel Corporation
3 * Copyright © 1988-2004 Keith Packard and Bart Massey.
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:
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
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
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
31 * Eric Anholt <eric@anholt.net>
32 * Keith Packard <keithp@keithp.com>
36 * Implements an open-addressing, linear-reprobing hash table.
38 * For more information, see:
40 * http://cgit.freedesktop.org/~anholt/hash_table/tree/README
47 #include "hash_table.h"
51 static const uint32_t deleted_key_value
;
54 * From Knuth -- a good choice for hash/rehash values is p, p-2 where
55 * p and p-2 are both prime. These tables are sized to have an extra 10%
56 * free to avoid exponential performance degradation as the hash table fills
59 uint32_t max_entries
, size
, rehash
;
74 { 16384, 18043, 18041 },
75 { 32768, 36109, 36107 },
76 { 65536, 72091, 72089 },
77 { 131072, 144409, 144407 },
78 { 262144, 288361, 288359 },
79 { 524288, 576883, 576881 },
80 { 1048576, 1153459, 1153457 },
81 { 2097152, 2307163, 2307161 },
82 { 4194304, 4613893, 4613891 },
83 { 8388608, 9227641, 9227639 },
84 { 16777216, 18455029, 18455027 },
85 { 33554432, 36911011, 36911009 },
86 { 67108864, 73819861, 73819859 },
87 { 134217728, 147639589, 147639587 },
88 { 268435456, 295279081, 295279079 },
89 { 536870912, 590559793, 590559791 },
90 { 1073741824, 1181116273, 1181116271},
91 { 2147483648ul, 2362232233ul, 2362232231ul}
95 entry_is_free(const struct hash_entry
*entry
)
97 return entry
->key
== NULL
;
101 entry_is_deleted(const struct hash_table
*ht
, struct hash_entry
*entry
)
103 return entry
->key
== ht
->deleted_key
;
107 entry_is_present(const struct hash_table
*ht
, struct hash_entry
*entry
)
109 return entry
->key
!= NULL
&& entry
->key
!= ht
->deleted_key
;
113 _mesa_hash_table_create(void *mem_ctx
,
114 uint32_t (*key_hash_function
)(const void *key
),
115 bool (*key_equals_function
)(const void *a
,
118 struct hash_table
*ht
;
120 ht
= ralloc(mem_ctx
, struct hash_table
);
125 ht
->size
= hash_sizes
[ht
->size_index
].size
;
126 ht
->rehash
= hash_sizes
[ht
->size_index
].rehash
;
127 ht
->max_entries
= hash_sizes
[ht
->size_index
].max_entries
;
128 ht
->key_hash_function
= key_hash_function
;
129 ht
->key_equals_function
= key_equals_function
;
130 ht
->table
= rzalloc_array(ht
, struct hash_entry
, ht
->size
);
132 ht
->deleted_entries
= 0;
133 ht
->deleted_key
= &deleted_key_value
;
135 if (ht
->table
== NULL
) {
144 * Frees the given hash table.
146 * If delete_function is passed, it gets called on each entry present before
150 _mesa_hash_table_destroy(struct hash_table
*ht
,
151 void (*delete_function
)(struct hash_entry
*entry
))
156 if (delete_function
) {
157 struct hash_entry
*entry
;
159 hash_table_foreach(ht
, entry
) {
160 delete_function(entry
);
166 /** Sets the value of the key pointer used for deleted entries in the table.
168 * The assumption is that usually keys are actual pointers, so we use a
169 * default value of a pointer to an arbitrary piece of storage in the library.
170 * But in some cases a consumer wants to store some other sort of value in the
171 * table, like a uint32_t, in which case that pointer may conflict with one of
172 * their valid keys. This lets that user select a safe value.
174 * This must be called before any keys are actually deleted from the table.
177 _mesa_hash_table_set_deleted_key(struct hash_table
*ht
, const void *deleted_key
)
179 ht
->deleted_key
= deleted_key
;
182 static struct hash_entry
*
183 hash_table_search(struct hash_table
*ht
, uint32_t hash
, const void *key
)
185 uint32_t start_hash_address
= hash
% ht
->size
;
186 uint32_t hash_address
= start_hash_address
;
189 uint32_t double_hash
;
191 struct hash_entry
*entry
= ht
->table
+ hash_address
;
193 if (entry_is_free(entry
)) {
195 } else if (entry_is_present(ht
, entry
) && entry
->hash
== hash
) {
196 if (ht
->key_equals_function(key
, entry
->key
)) {
201 double_hash
= 1 + hash
% ht
->rehash
;
203 hash_address
= (hash_address
+ double_hash
) % ht
->size
;
204 } while (hash_address
!= start_hash_address
);
210 * Finds a hash table entry with the given key and hash of that key.
212 * Returns NULL if no entry is found. Note that the data pointer may be
213 * modified by the user.
216 _mesa_hash_table_search(struct hash_table
*ht
, const void *key
)
218 assert(ht
->key_hash_function
);
219 return hash_table_search(ht
, ht
->key_hash_function(key
), key
);
223 _mesa_hash_table_search_pre_hashed(struct hash_table
*ht
, uint32_t hash
,
226 assert(ht
->key_hash_function
== NULL
|| hash
== ht
->key_hash_function(key
));
227 return hash_table_search(ht
, hash
, key
);
230 static struct hash_entry
*
231 hash_table_insert(struct hash_table
*ht
, uint32_t hash
,
232 const void *key
, void *data
);
235 _mesa_hash_table_rehash(struct hash_table
*ht
, unsigned new_size_index
)
237 struct hash_table old_ht
;
238 struct hash_entry
*table
, *entry
;
240 if (new_size_index
>= ARRAY_SIZE(hash_sizes
))
243 table
= rzalloc_array(ht
, struct hash_entry
,
244 hash_sizes
[new_size_index
].size
);
251 ht
->size_index
= new_size_index
;
252 ht
->size
= hash_sizes
[ht
->size_index
].size
;
253 ht
->rehash
= hash_sizes
[ht
->size_index
].rehash
;
254 ht
->max_entries
= hash_sizes
[ht
->size_index
].max_entries
;
256 ht
->deleted_entries
= 0;
258 hash_table_foreach(&old_ht
, entry
) {
259 hash_table_insert(ht
, entry
->hash
, entry
->key
, entry
->data
);
262 ralloc_free(old_ht
.table
);
265 static struct hash_entry
*
266 hash_table_insert(struct hash_table
*ht
, uint32_t hash
,
267 const void *key
, void *data
)
269 uint32_t start_hash_address
, hash_address
;
270 struct hash_entry
*available_entry
= NULL
;
272 if (ht
->entries
>= ht
->max_entries
) {
273 _mesa_hash_table_rehash(ht
, ht
->size_index
+ 1);
274 } else if (ht
->deleted_entries
+ ht
->entries
>= ht
->max_entries
) {
275 _mesa_hash_table_rehash(ht
, ht
->size_index
);
278 start_hash_address
= hash
% ht
->size
;
279 hash_address
= start_hash_address
;
281 struct hash_entry
*entry
= ht
->table
+ hash_address
;
282 uint32_t double_hash
;
284 if (!entry_is_present(ht
, entry
)) {
285 /* Stash the first available entry we find */
286 if (available_entry
== NULL
)
287 available_entry
= entry
;
288 if (entry_is_free(entry
))
292 /* Implement replacement when another insert happens
293 * with a matching key. This is a relatively common
294 * feature of hash tables, with the alternative
295 * generally being "insert the new value as well, and
296 * return it first when the key is searched for".
298 * Note that the hash table doesn't have a delete
299 * callback. If freeing of old data pointers is
300 * required to avoid memory leaks, perform a search
303 if (entry
->hash
== hash
&&
304 ht
->key_equals_function(key
, entry
->key
)) {
311 double_hash
= 1 + hash
% ht
->rehash
;
313 hash_address
= (hash_address
+ double_hash
) % ht
->size
;
314 } while (hash_address
!= start_hash_address
);
316 if (available_entry
) {
317 if (entry_is_deleted(ht
, available_entry
))
318 ht
->deleted_entries
--;
319 available_entry
->hash
= hash
;
320 available_entry
->key
= key
;
321 available_entry
->data
= data
;
323 return available_entry
;
326 /* We could hit here if a required resize failed. An unchecked-malloc
327 * application could ignore this result.
333 * Inserts the key with the given hash into the table.
335 * Note that insertion may rearrange the table on a resize or rehash,
336 * so previously found hash_entries are no longer valid after this function.
339 _mesa_hash_table_insert(struct hash_table
*ht
, const void *key
, void *data
)
341 assert(ht
->key_hash_function
);
342 return hash_table_insert(ht
, ht
->key_hash_function(key
), key
, data
);
346 _mesa_hash_table_insert_pre_hashed(struct hash_table
*ht
, uint32_t hash
,
347 const void *key
, void *data
)
349 assert(ht
->key_hash_function
== NULL
|| hash
== ht
->key_hash_function(key
));
350 return hash_table_insert(ht
, hash
, key
, data
);
354 * This function deletes the given hash table entry.
356 * Note that deletion doesn't otherwise modify the table, so an iteration over
357 * the table deleting entries is safe.
360 _mesa_hash_table_remove(struct hash_table
*ht
,
361 struct hash_entry
*entry
)
366 entry
->key
= ht
->deleted_key
;
368 ht
->deleted_entries
++;
372 * This function is an iterator over the hash table.
374 * Pass in NULL for the first entry, as in the start of a for loop. Note that
375 * an iteration over the table is O(table_size) not O(entries).
378 _mesa_hash_table_next_entry(struct hash_table
*ht
,
379 struct hash_entry
*entry
)
386 for (; entry
!= ht
->table
+ ht
->size
; entry
++) {
387 if (entry_is_present(ht
, entry
)) {
396 * Returns a random entry from the hash table.
398 * This may be useful in implementing random replacement (as opposed
399 * to just removing everything) in caches based on this hash table
400 * implementation. @predicate may be used to filter entries, or may
401 * be set to NULL for no filtering.
404 _mesa_hash_table_random_entry(struct hash_table
*ht
,
405 bool (*predicate
)(struct hash_entry
*entry
))
407 struct hash_entry
*entry
;
408 uint32_t i
= rand() % ht
->size
;
410 if (ht
->entries
== 0)
413 for (entry
= ht
->table
+ i
; entry
!= ht
->table
+ ht
->size
; entry
++) {
414 if (entry_is_present(ht
, entry
) &&
415 (!predicate
|| predicate(entry
))) {
420 for (entry
= ht
->table
; entry
!= ht
->table
+ i
; entry
++) {
421 if (entry_is_present(ht
, entry
) &&
422 (!predicate
|| predicate(entry
))) {
432 * Quick FNV-1a hash implementation based on:
433 * http://www.isthe.com/chongo/tech/comp/fnv/
435 * FNV-1a is not be the best hash out there -- Jenkins's lookup3 is supposed
436 * to be quite good, and it probably beats FNV. But FNV has the advantage
437 * that it involves almost no code. For an improvement on both, see Paul
438 * Hsieh's http://www.azillionmonkeys.com/qed/hash.html
441 _mesa_hash_data(const void *data
, size_t size
)
443 return _mesa_fnv32_1a_accumulate_block(_mesa_fnv32_1a_offset_bias
,
447 /** FNV-1a string hash implementation */
449 _mesa_hash_string(const char *key
)
451 uint32_t hash
= _mesa_fnv32_1a_offset_bias
;
454 hash
= _mesa_fnv32_1a_accumulate(hash
, *key
);
462 * String compare function for use as the comparison callback in
463 * _mesa_hash_table_create().
466 _mesa_key_string_equal(const void *a
, const void *b
)
468 return strcmp(a
, b
) == 0;
472 _mesa_key_pointer_equal(const void *a
, const void *b
)