src/util/hash_table.c

   1 /*
   2  * Copyright © 2009,2012 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 /**
  36  * Implements an open-addressing, linear-reprobing hash table.
  37  *
  38  * For more information, see:
  39  *
  40  * http://cgit.freedesktop.org/~anholt/hash_table/tree/README
  41  */
  42
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <assert.h>
  46
  47 #include "hash_table.h"
  48 #include "ralloc.h"
  49 #include "macros.h"
  50
  51 static const uint32_t deleted_key_value;
  52
  53 /**
  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
  57  */
  58 static const struct {
  59    uint32_t max_entries, size, rehash;
  60 } hash_sizes[] = {
  61    { 2,                 5,              3         },
  62    { 4,                 7,              5         },
  63    { 8,                 13,             11        },
  64    { 16,                19,             17        },
  65    { 32,                43,             41        },
  66    { 64,                73,             71        },
  67    { 128,               151,            149       },
  68    { 256,               283,            281       },
  69    { 512,               571,            569       },
  70    { 1024,              1153,           1151      },
  71    { 2048,              2269,           2267      },
  72    { 4096,              4519,           4517      },
  73    { 8192,              9013,           9011      },
  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}
  92 };
  93
  94 static int
  95 entry_is_free(const struct hash_entry *entry)
  96 {
  97    return entry->key == NULL;
  98 }
  99
 100 static int
 101 entry_is_deleted(const struct hash_table *ht, struct hash_entry *entry)
 102 {
 103    return entry->key == ht->deleted_key;
 104 }
 105
 106 static int
 107 entry_is_present(const struct hash_table *ht, struct hash_entry *entry)
 108 {
 109    return entry->key != NULL && entry->key != ht->deleted_key;
 110 }
 111
 112 struct hash_table *
 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,
 116                                                     const void *b))
 117 {
 118    struct hash_table *ht;
 119
 120    ht = ralloc(mem_ctx, struct hash_table);
 121    if (ht == NULL)
 122       return NULL;
 123
 124    ht->size_index = 0;
 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);
 131    ht->entries = 0;
 132    ht->deleted_entries = 0;
 133    ht->deleted_key = &deleted_key_value;
 134
 135    if (ht->table == NULL) {
 136       ralloc_free(ht);
 137       return NULL;
 138    }
 139
 140    return ht;
 141 }
 142
 143 /**
 144  * Frees the given hash table.
 145  *
 146  * If delete_function is passed, it gets called on each entry present before
 147  * freeing.
 148  */
 149 void
 150 _mesa_hash_table_destroy(struct hash_table *ht,
 151                          void (*delete_function)(struct hash_entry *entry))
 152 {
 153    if (!ht)
 154       return;
 155
 156    if (delete_function) {
 157       struct hash_entry *entry;
 158
 159       hash_table_foreach(ht, entry) {
 160          delete_function(entry);
 161       }
 162    }
 163    ralloc_free(ht);
 164 }
 165
 166 /** Sets the value of the key pointer used for deleted entries in the table.
 167  *
 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.
 173  *
 174  * This must be called before any keys are actually deleted from the table.
 175  */
 176 void
 177 _mesa_hash_table_set_deleted_key(struct hash_table *ht, const void *deleted_key)
 178 {
 179    ht->deleted_key = deleted_key;
 180 }
 181
 182 static struct hash_entry *
 183 hash_table_search(struct hash_table *ht, uint32_t hash, const void *key)
 184 {
 185    uint32_t start_hash_address = hash % ht->size;
 186    uint32_t hash_address = start_hash_address;
 187
 188    do {
 189       uint32_t double_hash;
 190
 191       struct hash_entry *entry = ht->table + hash_address;
 192
 193       if (entry_is_free(entry)) {
 194          return NULL;
 195       } else if (entry_is_present(ht, entry) && entry->hash == hash) {
 196          if (ht->key_equals_function(key, entry->key)) {
 197             return entry;
 198          }
 199       }
 200
 201       double_hash = 1 + hash % ht->rehash;
 202
 203       hash_address = (hash_address + double_hash) % ht->size;
 204    } while (hash_address != start_hash_address);
 205
 206    return NULL;
 207 }
 208
 209 /**
 210  * Finds a hash table entry with the given key and hash of that key.
 211  *
 212  * Returns NULL if no entry is found.  Note that the data pointer may be
 213  * modified by the user.
 214  */
 215 struct hash_entry *
 216 _mesa_hash_table_search(struct hash_table *ht, const void *key)
 217 {
 218    assert(ht->key_hash_function);
 219    return hash_table_search(ht, ht->key_hash_function(key), key);
 220 }
 221
 222 struct hash_entry *
 223 _mesa_hash_table_search_pre_hashed(struct hash_table *ht, uint32_t hash,
 224                                   const void *key)
 225 {
 226    assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
 227    return hash_table_search(ht, hash, key);
 228 }
 229
 230 static struct hash_entry *
 231 hash_table_insert(struct hash_table *ht, uint32_t hash,
 232                   const void *key, void *data);
 233
 234 static void
 235 _mesa_hash_table_rehash(struct hash_table *ht, unsigned new_size_index)
 236 {
 237    struct hash_table old_ht;
 238    struct hash_entry *table, *entry;
 239
 240    if (new_size_index >= ARRAY_SIZE(hash_sizes))
 241       return;
 242
 243    table = rzalloc_array(ht, struct hash_entry,
 244                          hash_sizes[new_size_index].size);
 245    if (table == NULL)
 246       return;
 247
 248    old_ht = *ht;
 249
 250    ht->table = table;
 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;
 255    ht->entries = 0;
 256    ht->deleted_entries = 0;
 257
 258    hash_table_foreach(&old_ht, entry) {
 259       hash_table_insert(ht, entry->hash, entry->key, entry->data);
 260    }
 261
 262    ralloc_free(old_ht.table);
 263 }
 264
 265 static struct hash_entry *
 266 hash_table_insert(struct hash_table *ht, uint32_t hash,
 267                   const void *key, void *data)
 268 {
 269    uint32_t start_hash_address, hash_address;
 270    struct hash_entry *available_entry = NULL;
 271
 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);
 276    }
 277
 278    start_hash_address = hash % ht->size;
 279    hash_address = start_hash_address;
 280    do {
 281       struct hash_entry *entry = ht->table + hash_address;
 282       uint32_t double_hash;
 283
 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))
 289             break;
 290       }
 291
 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".
 297        *
 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
 301        * before inserting.
 302        */
 303       if (!entry_is_deleted(ht, entry) &&
 304           entry->hash == hash &&
 305           ht->key_equals_function(key, entry->key)) {
 306          entry->key = key;
 307          entry->data = data;
 308          return entry;
 309       }
 310
 311
 312       double_hash = 1 + hash % ht->rehash;
 313
 314       hash_address = (hash_address + double_hash) % ht->size;
 315    } while (hash_address != start_hash_address);
 316
 317    if (available_entry) {
 318       if (entry_is_deleted(ht, available_entry))
 319          ht->deleted_entries--;
 320       available_entry->hash = hash;
 321       available_entry->key = key;
 322       available_entry->data = data;
 323       ht->entries++;
 324       return available_entry;
 325    }
 326
 327    /* We could hit here if a required resize failed. An unchecked-malloc
 328     * application could ignore this result.
 329     */
 330    return NULL;
 331 }
 332
 333 /**
 334  * Inserts the key with the given hash into the table.
 335  *
 336  * Note that insertion may rearrange the table on a resize or rehash,
 337  * so previously found hash_entries are no longer valid after this function.
 338  */
 339 struct hash_entry *
 340 _mesa_hash_table_insert(struct hash_table *ht, const void *key, void *data)
 341 {
 342    assert(ht->key_hash_function);
 343    return hash_table_insert(ht, ht->key_hash_function(key), key, data);
 344 }
 345
 346 struct hash_entry *
 347 _mesa_hash_table_insert_pre_hashed(struct hash_table *ht, uint32_t hash,
 348                                    const void *key, void *data)
 349 {
 350    assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
 351    return hash_table_insert(ht, hash, key, data);
 352 }
 353
 354 /**
 355  * This function deletes the given hash table entry.
 356  *
 357  * Note that deletion doesn't otherwise modify the table, so an iteration over
 358  * the table deleting entries is safe.
 359  */
 360 void
 361 _mesa_hash_table_remove(struct hash_table *ht,
 362                         struct hash_entry *entry)
 363 {
 364    if (!entry)
 365       return;
 366
 367    entry->key = ht->deleted_key;
 368    ht->entries--;
 369    ht->deleted_entries++;
 370 }
 371
 372 /**
 373  * This function is an iterator over the hash table.
 374  *
 375  * Pass in NULL for the first entry, as in the start of a for loop.  Note that
 376  * an iteration over the table is O(table_size) not O(entries).
 377  */
 378 struct hash_entry *
 379 _mesa_hash_table_next_entry(struct hash_table *ht,
 380                             struct hash_entry *entry)
 381 {
 382    if (entry == NULL)
 383       entry = ht->table;
 384    else
 385       entry = entry + 1;
 386
 387    for (; entry != ht->table + ht->size; entry++) {
 388       if (entry_is_present(ht, entry)) {
 389          return entry;
 390       }
 391    }
 392
 393    return NULL;
 394 }
 395
 396 /**
 397  * Returns a random entry from the hash table.
 398  *
 399  * This may be useful in implementing random replacement (as opposed
 400  * to just removing everything) in caches based on this hash table
 401  * implementation.  @predicate may be used to filter entries, or may
 402  * be set to NULL for no filtering.
 403  */
 404 struct hash_entry *
 405 _mesa_hash_table_random_entry(struct hash_table *ht,
 406                               bool (*predicate)(struct hash_entry *entry))
 407 {
 408    struct hash_entry *entry;
 409    uint32_t i = rand() % ht->size;
 410
 411    if (ht->entries == 0)
 412       return NULL;
 413
 414    for (entry = ht->table + i; entry != ht->table + ht->size; entry++) {
 415       if (entry_is_present(ht, entry) &&
 416           (!predicate || predicate(entry))) {
 417          return entry;
 418       }
 419    }
 420
 421    for (entry = ht->table; entry != ht->table + i; entry++) {
 422       if (entry_is_present(ht, entry) &&
 423           (!predicate || predicate(entry))) {
 424          return entry;
 425       }
 426    }
 427
 428    return NULL;
 429 }
 430
 431
 432 /**
 433  * Quick FNV-1a hash implementation based on:
 434  * http://www.isthe.com/chongo/tech/comp/fnv/
 435  *
 436  * FNV-1a is not be the best hash out there -- Jenkins's lookup3 is supposed
 437  * to be quite good, and it probably beats FNV.  But FNV has the advantage
 438  * that it involves almost no code.  For an improvement on both, see Paul
 439  * Hsieh's http://www.azillionmonkeys.com/qed/hash.html
 440  */
 441 uint32_t
 442 _mesa_hash_data(const void *data, size_t size)
 443 {
 444    return _mesa_fnv32_1a_accumulate_block(_mesa_fnv32_1a_offset_bias,
 445                                           data, size);
 446 }
 447
 448 /** FNV-1a string hash implementation */
 449 uint32_t
 450 _mesa_hash_string(const char *key)
 451 {
 452    uint32_t hash = _mesa_fnv32_1a_offset_bias;
 453
 454    while (*key != 0) {
 455       hash = _mesa_fnv32_1a_accumulate(hash, *key);
 456       key++;
 457    }
 458
 459    return hash;
 460 }
 461
 462 /**
 463  * String compare function for use as the comparison callback in
 464  * _mesa_hash_table_create().
 465  */
 466 bool
 467 _mesa_key_string_equal(const void *a, const void *b)
 468 {
 469    return strcmp(a, b) == 0;
 470 }
 471
 472 bool
 473 _mesa_key_pointer_equal(const void *a, const void *b)
 474 {
 475    return a == b;
 476 }