src/mesa/main/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
  46 #include "main/hash_table.h"
  47 #include "main/macros.h"
  48 #include "ralloc.h"
  49
  50 static const uint32_t deleted_key_value;
  51
  52 /**
  53  * From Knuth -- a good choice for hash/rehash values is p, p-2 where
  54  * p and p-2 are both prime.  These tables are sized to have an extra 10%
  55  * free to avoid exponential performance degradation as the hash table fills
  56  */
  57 static const struct {
  58    uint32_t max_entries, size, rehash;
  59 } hash_sizes[] = {
  60    { 2,                 5,              3         },
  61    { 4,                 7,              5         },
  62    { 8,                 13,             11        },
  63    { 16,                19,             17        },
  64    { 32,                43,             41        },
  65    { 64,                73,             71        },
  66    { 128,               151,            149       },
  67    { 256,               283,            281       },
  68    { 512,               571,            569       },
  69    { 1024,              1153,           1151      },
  70    { 2048,              2269,           2267      },
  71    { 4096,              4519,           4517      },
  72    { 8192,              9013,           9011      },
  73    { 16384,             18043,          18041     },
  74    { 32768,             36109,          36107     },
  75    { 65536,             72091,          72089     },
  76    { 131072,            144409,         144407    },
  77    { 262144,            288361,         288359    },
  78    { 524288,            576883,         576881    },
  79    { 1048576,           1153459,        1153457   },
  80    { 2097152,           2307163,        2307161   },
  81    { 4194304,           4613893,        4613891   },
  82    { 8388608,           9227641,        9227639   },
  83    { 16777216,          18455029,       18455027  },
  84    { 33554432,          36911011,       36911009  },
  85    { 67108864,          73819861,       73819859  },
  86    { 134217728,         147639589,      147639587 },
  87    { 268435456,         295279081,      295279079 },
  88    { 536870912,         590559793,      590559791 },
  89    { 1073741824,        1181116273,     1181116271},
  90    { 2147483648ul,      2362232233ul,   2362232231ul}
  91 };
  92
  93 static int
  94 entry_is_free(const struct hash_entry *entry)
  95 {
  96    return entry->key == NULL;
  97 }
  98
  99 static int
 100 entry_is_deleted(const struct hash_table *ht, struct hash_entry *entry)
 101 {
 102    return entry->key == ht->deleted_key;
 103 }
 104
 105 static int
 106 entry_is_present(const struct hash_table *ht, struct hash_entry *entry)
 107 {
 108    return entry->key != NULL && entry->key != ht->deleted_key;
 109 }
 110
 111 struct hash_table *
 112 _mesa_hash_table_create(void *mem_ctx,
 113                         bool (*key_equals_function)(const void *a,
 114                                                     const void *b))
 115 {
 116    struct hash_table *ht;
 117
 118    ht = ralloc(mem_ctx, struct hash_table);
 119    if (ht == NULL)
 120       return NULL;
 121
 122    ht->mem_ctx = mem_ctx;
 123    ht->size_index = 0;
 124    ht->size = hash_sizes[ht->size_index].size;
 125    ht->rehash = hash_sizes[ht->size_index].rehash;
 126    ht->max_entries = hash_sizes[ht->size_index].max_entries;
 127    ht->key_equals_function = key_equals_function;
 128    ht->table = rzalloc_array(ht, struct hash_entry, ht->size);
 129    ht->entries = 0;
 130    ht->deleted_entries = 0;
 131    ht->deleted_key = &deleted_key_value;
 132
 133    if (ht->table == NULL) {
 134       ralloc_free(ht);
 135       return NULL;
 136    }
 137
 138    return ht;
 139 }
 140
 141 /**
 142  * Frees the given hash table.
 143  *
 144  * If delete_function is passed, it gets called on each entry present before
 145  * freeing.
 146  */
 147 void
 148 _mesa_hash_table_destroy(struct hash_table *ht,
 149                          void (*delete_function)(struct hash_entry *entry))
 150 {
 151    if (!ht)
 152       return;
 153
 154    if (delete_function) {
 155       struct hash_entry *entry;
 156
 157       hash_table_foreach(ht, entry) {
 158          delete_function(entry);
 159       }
 160    }
 161    ralloc_free(ht);
 162 }
 163
 164 /** Sets the value of the key pointer used for deleted entries in the table.
 165  *
 166  * The assumption is that usually keys are actual pointers, so we use a
 167  * default value of a pointer to an arbitrary piece of storage in the library.
 168  * But in some cases a consumer wants to store some other sort of value in the
 169  * table, like a uint32_t, in which case that pointer may conflict with one of
 170  * their valid keys.  This lets that user select a safe value.
 171  *
 172  * This must be called before any keys are actually deleted from the table.
 173  */
 174 void
 175 _mesa_hash_table_set_deleted_key(struct hash_table *ht, const void *deleted_key)
 176 {
 177    ht->deleted_key = deleted_key;
 178 }
 179
 180 /**
 181  * Finds a hash table entry with the given key and hash of that key.
 182  *
 183  * Returns NULL if no entry is found.  Note that the data pointer may be
 184  * modified by the user.
 185  */
 186 struct hash_entry *
 187 _mesa_hash_table_search(struct hash_table *ht, uint32_t hash,
 188                         const void *key)
 189 {
 190    uint32_t start_hash_address = hash % ht->size;
 191    uint32_t hash_address = start_hash_address;
 192
 193    do {
 194       uint32_t double_hash;
 195
 196       struct hash_entry *entry = ht->table + hash_address;
 197
 198       if (entry_is_free(entry)) {
 199          return NULL;
 200       } else if (entry_is_present(ht, entry) && entry->hash == hash) {
 201          if (ht->key_equals_function(key, entry->key)) {
 202             return entry;
 203          }
 204       }
 205
 206       double_hash = 1 + hash % ht->rehash;
 207
 208       hash_address = (hash_address + double_hash) % ht->size;
 209    } while (hash_address != start_hash_address);
 210
 211    return NULL;
 212 }
 213
 214 static void
 215 _mesa_hash_table_rehash(struct hash_table *ht, int new_size_index)
 216 {
 217    struct hash_table old_ht;
 218    struct hash_entry *table, *entry;
 219
 220    if (new_size_index >= ARRAY_SIZE(hash_sizes))
 221       return;
 222
 223    table = rzalloc_array(ht, struct hash_entry,
 224                          hash_sizes[new_size_index].size);
 225    if (table == NULL)
 226       return;
 227
 228    old_ht = *ht;
 229
 230    ht->table = table;
 231    ht->size_index = new_size_index;
 232    ht->size = hash_sizes[ht->size_index].size;
 233    ht->rehash = hash_sizes[ht->size_index].rehash;
 234    ht->max_entries = hash_sizes[ht->size_index].max_entries;
 235    ht->entries = 0;
 236    ht->deleted_entries = 0;
 237
 238    hash_table_foreach(&old_ht, entry) {
 239       _mesa_hash_table_insert(ht, entry->hash,
 240                               entry->key, entry->data);
 241    }
 242
 243    ralloc_free(old_ht.table);
 244 }
 245
 246 /**
 247  * Inserts the key with the given hash into the table.
 248  *
 249  * Note that insertion may rearrange the table on a resize or rehash,
 250  * so previously found hash_entries are no longer valid after this function.
 251  */
 252 struct hash_entry *
 253 _mesa_hash_table_insert(struct hash_table *ht, uint32_t hash,
 254                         const void *key, void *data)
 255 {
 256    uint32_t start_hash_address, hash_address;
 257
 258    if (ht->entries >= ht->max_entries) {
 259       _mesa_hash_table_rehash(ht, ht->size_index + 1);
 260    } else if (ht->deleted_entries + ht->entries >= ht->max_entries) {
 261       _mesa_hash_table_rehash(ht, ht->size_index);
 262    }
 263
 264    start_hash_address = hash % ht->size;
 265    hash_address = start_hash_address;
 266    do {
 267       struct hash_entry *entry = ht->table + hash_address;
 268       uint32_t double_hash;
 269
 270       if (!entry_is_present(ht, entry)) {
 271          if (entry_is_deleted(ht, entry))
 272             ht->deleted_entries--;
 273          entry->hash = hash;
 274          entry->key = key;
 275          entry->data = data;
 276          ht->entries++;
 277          return entry;
 278       }
 279
 280       /* Implement replacement when another insert happens
 281        * with a matching key.  This is a relatively common
 282        * feature of hash tables, with the alternative
 283        * generally being "insert the new value as well, and
 284        * return it first when the key is searched for".
 285        *
 286        * Note that the hash table doesn't have a delete
 287        * callback.  If freeing of old data pointers is
 288        * required to avoid memory leaks, perform a search
 289        * before inserting.
 290        */
 291       if (entry->hash == hash &&
 292           ht->key_equals_function(key, entry->key)) {
 293          entry->key = key;
 294          entry->data = data;
 295          return entry;
 296       }
 297
 298
 299       double_hash = 1 + hash % ht->rehash;
 300
 301       hash_address = (hash_address + double_hash) % ht->size;
 302    } while (hash_address != start_hash_address);
 303
 304    /* We could hit here if a required resize failed. An unchecked-malloc
 305     * application could ignore this result.
 306     */
 307    return NULL;
 308 }
 309
 310 /**
 311  * This function deletes the given hash table entry.
 312  *
 313  * Note that deletion doesn't otherwise modify the table, so an iteration over
 314  * the table deleting entries is safe.
 315  */
 316 void
 317 _mesa_hash_table_remove(struct hash_table *ht,
 318                         struct hash_entry *entry)
 319 {
 320    if (!entry)
 321       return;
 322
 323    entry->key = ht->deleted_key;
 324    ht->entries--;
 325    ht->deleted_entries++;
 326 }
 327
 328 /**
 329  * This function is an iterator over the hash table.
 330  *
 331  * Pass in NULL for the first entry, as in the start of a for loop.  Note that
 332  * an iteration over the table is O(table_size) not O(entries).
 333  */
 334 struct hash_entry *
 335 _mesa_hash_table_next_entry(struct hash_table *ht,
 336                             struct hash_entry *entry)
 337 {
 338    if (entry == NULL)
 339       entry = ht->table;
 340    else
 341       entry = entry + 1;
 342
 343    for (; entry != ht->table + ht->size; entry++) {
 344       if (entry_is_present(ht, entry)) {
 345          return entry;
 346       }
 347    }
 348
 349    return NULL;
 350 }
 351
 352 /**
 353  * Returns a random entry from the hash table.
 354  *
 355  * This may be useful in implementing random replacement (as opposed
 356  * to just removing everything) in caches based on this hash table
 357  * implementation.  @predicate may be used to filter entries, or may
 358  * be set to NULL for no filtering.
 359  */
 360 struct hash_entry *
 361 _mesa_hash_table_random_entry(struct hash_table *ht,
 362                               bool (*predicate)(struct hash_entry *entry))
 363 {
 364    struct hash_entry *entry;
 365    uint32_t i = rand() % ht->size;
 366
 367    if (ht->entries == 0)
 368       return NULL;
 369
 370    for (entry = ht->table + i; entry != ht->table + ht->size; entry++) {
 371       if (entry_is_present(ht, entry) &&
 372           (!predicate || predicate(entry))) {
 373          return entry;
 374       }
 375    }
 376
 377    for (entry = ht->table; entry != ht->table + i; entry++) {
 378       if (entry_is_present(ht, entry) &&
 379           (!predicate || predicate(entry))) {
 380          return entry;
 381       }
 382    }
 383
 384    return NULL;
 385 }
 386
 387
 388 /**
 389  * Quick FNV-1 hash implementation based on:
 390  * http://www.isthe.com/chongo/tech/comp/fnv/
 391  *
 392  * FNV-1 is not be the best hash out there -- Jenkins's lookup3 is supposed to
 393  * be quite good, and it probably beats FNV.  But FNV has the advantage that
 394  * it involves almost no code.  For an improvement on both, see Paul
 395  * Hsieh's http://www.azillionmonkeys.com/qed/hash.html
 396  */
 397 uint32_t
 398 _mesa_hash_data(const void *data, size_t size)
 399 {
 400    uint32_t hash = 2166136261ul;
 401    const uint8_t *bytes = data;
 402
 403    while (size-- != 0) {
 404       hash ^= *bytes;
 405       hash = hash * 0x01000193;
 406       bytes++;
 407    }
 408
 409    return hash;
 410 }
 411
 412 /** FNV-1 string hash implementation */
 413 uint32_t
 414 _mesa_hash_string(const char *key)
 415 {
 416    uint32_t hash = 2166136261ul;
 417
 418    while (*key != 0) {
 419       hash ^= *key;
 420       hash = hash * 0x01000193;
 421       key++;
 422    }
 423
 424    return hash;
 425 }
 426
 427 /**
 428  * String compare function for use as the comparison callback in
 429  * _mesa_hash_table_create().
 430  */
 431 bool
 432 _mesa_key_string_equal(const void *a, const void *b)
 433 {
 434    return strcmp(a, b) == 0;
 435 }
 436
 437 bool
 438 _mesa_key_pointer_equal(const void *a, const void *b)
 439 {
 440    return a == b;
 441 }