OLD | NEW |
(Empty) | |
| 1 /* hash - hashing table processing. |
| 2 |
| 3 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007 Free |
| 4 Software Foundation, Inc. |
| 5 |
| 6 Written by Jim Meyering, 1992. |
| 7 |
| 8 This program is free software: you can redistribute it and/or modify |
| 9 it under the terms of the GNU General Public License as published by |
| 10 the Free Software Foundation; either version 3 of the License, or |
| 11 (at your option) any later version. |
| 12 |
| 13 This program is distributed in the hope that it will be useful, |
| 14 but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 GNU General Public License for more details. |
| 17 |
| 18 You should have received a copy of the GNU General Public License |
| 19 along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 20 |
| 21 /* A generic hash table package. */ |
| 22 |
| 23 /* Define USE_OBSTACK to 1 if you want the allocator to use obstacks instead |
| 24 of malloc. If you change USE_OBSTACK, you have to recompile! */ |
| 25 |
| 26 #include <config.h> |
| 27 |
| 28 #include "hash.h" |
| 29 #include "xalloc.h" |
| 30 |
| 31 #include <limits.h> |
| 32 #include <stdio.h> |
| 33 #include <stdlib.h> |
| 34 |
| 35 #if USE_OBSTACK |
| 36 # include "obstack.h" |
| 37 # ifndef obstack_chunk_alloc |
| 38 # define obstack_chunk_alloc malloc |
| 39 # endif |
| 40 # ifndef obstack_chunk_free |
| 41 # define obstack_chunk_free free |
| 42 # endif |
| 43 #endif |
| 44 |
| 45 #ifndef SIZE_MAX |
| 46 # define SIZE_MAX ((size_t) -1) |
| 47 #endif |
| 48 |
| 49 struct hash_table |
| 50 { |
| 51 /* The array of buckets starts at BUCKET and extends to BUCKET_LIMIT-1, |
| 52 for a possibility of N_BUCKETS. Among those, N_BUCKETS_USED buckets |
| 53 are not empty, there are N_ENTRIES active entries in the table. */ |
| 54 struct hash_entry *bucket; |
| 55 struct hash_entry const *bucket_limit; |
| 56 size_t n_buckets; |
| 57 size_t n_buckets_used; |
| 58 size_t n_entries; |
| 59 |
| 60 /* Tuning arguments, kept in a physicaly separate structure. */ |
| 61 const Hash_tuning *tuning; |
| 62 |
| 63 /* Three functions are given to `hash_initialize', see the documentation |
| 64 block for this function. In a word, HASHER randomizes a user entry |
| 65 into a number up from 0 up to some maximum minus 1; COMPARATOR returns |
| 66 true if two user entries compare equally; and DATA_FREER is the cleanup |
| 67 function for a user entry. */ |
| 68 Hash_hasher hasher; |
| 69 Hash_comparator comparator; |
| 70 Hash_data_freer data_freer; |
| 71 |
| 72 /* A linked list of freed struct hash_entry structs. */ |
| 73 struct hash_entry *free_entry_list; |
| 74 |
| 75 #if USE_OBSTACK |
| 76 /* Whenever obstacks are used, it is possible to allocate all overflowed |
| 77 entries into a single stack, so they all can be freed in a single |
| 78 operation. It is not clear if the speedup is worth the trouble. */ |
| 79 struct obstack entry_stack; |
| 80 #endif |
| 81 }; |
| 82 |
| 83 /* A hash table contains many internal entries, each holding a pointer to |
| 84 some user provided data (also called a user entry). An entry indistinctly |
| 85 refers to both the internal entry and its associated user entry. A user |
| 86 entry contents may be hashed by a randomization function (the hashing |
| 87 function, or just `hasher' for short) into a number (or `slot') between 0 |
| 88 and the current table size. At each slot position in the hash table, |
| 89 starts a linked chain of entries for which the user data all hash to this |
| 90 slot. A bucket is the collection of all entries hashing to the same slot. |
| 91 |
| 92 A good `hasher' function will distribute entries rather evenly in buckets. |
| 93 In the ideal case, the length of each bucket is roughly the number of |
| 94 entries divided by the table size. Finding the slot for a data is usually |
| 95 done in constant time by the `hasher', and the later finding of a precise |
| 96 entry is linear in time with the size of the bucket. Consequently, a |
| 97 larger hash table size (that is, a larger number of buckets) is prone to |
| 98 yielding shorter chains, *given* the `hasher' function behaves properly. |
| 99 |
| 100 Long buckets slow down the lookup algorithm. One might use big hash table |
| 101 sizes in hope to reduce the average length of buckets, but this might |
| 102 become inordinate, as unused slots in the hash table take some space. The |
| 103 best bet is to make sure you are using a good `hasher' function (beware |
| 104 that those are not that easy to write! :-), and to use a table size |
| 105 larger than the actual number of entries. */ |
| 106 |
| 107 /* If an insertion makes the ratio of nonempty buckets to table size larger |
| 108 than the growth threshold (a number between 0.0 and 1.0), then increase |
| 109 the table size by multiplying by the growth factor (a number greater than |
| 110 1.0). The growth threshold defaults to 0.8, and the growth factor |
| 111 defaults to 1.414, meaning that the table will have doubled its size |
| 112 every second time 80% of the buckets get used. */ |
| 113 #define DEFAULT_GROWTH_THRESHOLD 0.8 |
| 114 #define DEFAULT_GROWTH_FACTOR 1.414 |
| 115 |
| 116 /* If a deletion empties a bucket and causes the ratio of used buckets to |
| 117 table size to become smaller than the shrink threshold (a number between |
| 118 0.0 and 1.0), then shrink the table by multiplying by the shrink factor (a |
| 119 number greater than the shrink threshold but smaller than 1.0). The shrink |
| 120 threshold and factor default to 0.0 and 1.0, meaning that the table never |
| 121 shrinks. */ |
| 122 #define DEFAULT_SHRINK_THRESHOLD 0.0 |
| 123 #define DEFAULT_SHRINK_FACTOR 1.0 |
| 124 |
| 125 /* Use this to initialize or reset a TUNING structure to |
| 126 some sensible values. */ |
| 127 static const Hash_tuning default_tuning = |
| 128 { |
| 129 DEFAULT_SHRINK_THRESHOLD, |
| 130 DEFAULT_SHRINK_FACTOR, |
| 131 DEFAULT_GROWTH_THRESHOLD, |
| 132 DEFAULT_GROWTH_FACTOR, |
| 133 false |
| 134 }; |
| 135 |
| 136 /* Information and lookup. */ |
| 137 |
| 138 /* The following few functions provide information about the overall hash |
| 139 table organization: the number of entries, number of buckets and maximum |
| 140 length of buckets. */ |
| 141 |
| 142 /* Return the number of buckets in the hash table. The table size, the total |
| 143 number of buckets (used plus unused), or the maximum number of slots, are |
| 144 the same quantity. */ |
| 145 |
| 146 size_t |
| 147 hash_get_n_buckets (const Hash_table *table) |
| 148 { |
| 149 return table->n_buckets; |
| 150 } |
| 151 |
| 152 /* Return the number of slots in use (non-empty buckets). */ |
| 153 |
| 154 size_t |
| 155 hash_get_n_buckets_used (const Hash_table *table) |
| 156 { |
| 157 return table->n_buckets_used; |
| 158 } |
| 159 |
| 160 /* Return the number of active entries. */ |
| 161 |
| 162 size_t |
| 163 hash_get_n_entries (const Hash_table *table) |
| 164 { |
| 165 return table->n_entries; |
| 166 } |
| 167 |
| 168 /* Return the length of the longest chain (bucket). */ |
| 169 |
| 170 size_t |
| 171 hash_get_max_bucket_length (const Hash_table *table) |
| 172 { |
| 173 struct hash_entry const *bucket; |
| 174 size_t max_bucket_length = 0; |
| 175 |
| 176 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 177 { |
| 178 if (bucket->data) |
| 179 { |
| 180 struct hash_entry const *cursor = bucket; |
| 181 size_t bucket_length = 1; |
| 182 |
| 183 while (cursor = cursor->next, cursor) |
| 184 bucket_length++; |
| 185 |
| 186 if (bucket_length > max_bucket_length) |
| 187 max_bucket_length = bucket_length; |
| 188 } |
| 189 } |
| 190 |
| 191 return max_bucket_length; |
| 192 } |
| 193 |
| 194 /* Do a mild validation of a hash table, by traversing it and checking two |
| 195 statistics. */ |
| 196 |
| 197 bool |
| 198 hash_table_ok (const Hash_table *table) |
| 199 { |
| 200 struct hash_entry const *bucket; |
| 201 size_t n_buckets_used = 0; |
| 202 size_t n_entries = 0; |
| 203 |
| 204 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 205 { |
| 206 if (bucket->data) |
| 207 { |
| 208 struct hash_entry const *cursor = bucket; |
| 209 |
| 210 /* Count bucket head. */ |
| 211 n_buckets_used++; |
| 212 n_entries++; |
| 213 |
| 214 /* Count bucket overflow. */ |
| 215 while (cursor = cursor->next, cursor) |
| 216 n_entries++; |
| 217 } |
| 218 } |
| 219 |
| 220 if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries) |
| 221 return true; |
| 222 |
| 223 return false; |
| 224 } |
| 225 |
| 226 void |
| 227 hash_print_statistics (const Hash_table *table, FILE *stream) |
| 228 { |
| 229 size_t n_entries = hash_get_n_entries (table); |
| 230 size_t n_buckets = hash_get_n_buckets (table); |
| 231 size_t n_buckets_used = hash_get_n_buckets_used (table); |
| 232 size_t max_bucket_length = hash_get_max_bucket_length (table); |
| 233 |
| 234 fprintf (stream, "# entries: %lu\n", (unsigned long int) n_entries); |
| 235 fprintf (stream, "# buckets: %lu\n", (unsigned long int) n_buckets); |
| 236 fprintf (stream, "# buckets used: %lu (%.2f%%)\n", |
| 237 (unsigned long int) n_buckets_used, |
| 238 (100.0 * n_buckets_used) / n_buckets); |
| 239 fprintf (stream, "max bucket length: %lu\n", |
| 240 (unsigned long int) max_bucket_length); |
| 241 } |
| 242 |
| 243 /* If ENTRY matches an entry already in the hash table, return the |
| 244 entry from the table. Otherwise, return NULL. */ |
| 245 |
| 246 void * |
| 247 hash_lookup (const Hash_table *table, const void *entry) |
| 248 { |
| 249 struct hash_entry const *bucket |
| 250 = table->bucket + table->hasher (entry, table->n_buckets); |
| 251 struct hash_entry const *cursor; |
| 252 |
| 253 if (! (bucket < table->bucket_limit)) |
| 254 abort (); |
| 255 |
| 256 if (bucket->data == NULL) |
| 257 return NULL; |
| 258 |
| 259 for (cursor = bucket; cursor; cursor = cursor->next) |
| 260 if (table->comparator (entry, cursor->data)) |
| 261 return cursor->data; |
| 262 |
| 263 return NULL; |
| 264 } |
| 265 |
| 266 /* Walking. */ |
| 267 |
| 268 /* The functions in this page traverse the hash table and process the |
| 269 contained entries. For the traversal to work properly, the hash table |
| 270 should not be resized nor modified while any particular entry is being |
| 271 processed. In particular, entries should not be added or removed. */ |
| 272 |
| 273 /* Return the first data in the table, or NULL if the table is empty. */ |
| 274 |
| 275 void * |
| 276 hash_get_first (const Hash_table *table) |
| 277 { |
| 278 struct hash_entry const *bucket; |
| 279 |
| 280 if (table->n_entries == 0) |
| 281 return NULL; |
| 282 |
| 283 for (bucket = table->bucket; ; bucket++) |
| 284 if (! (bucket < table->bucket_limit)) |
| 285 abort (); |
| 286 else if (bucket->data) |
| 287 return bucket->data; |
| 288 } |
| 289 |
| 290 /* Return the user data for the entry following ENTRY, where ENTRY has been |
| 291 returned by a previous call to either `hash_get_first' or `hash_get_next'. |
| 292 Return NULL if there are no more entries. */ |
| 293 |
| 294 void * |
| 295 hash_get_next (const Hash_table *table, const void *entry) |
| 296 { |
| 297 struct hash_entry const *bucket |
| 298 = table->bucket + table->hasher (entry, table->n_buckets); |
| 299 struct hash_entry const *cursor; |
| 300 |
| 301 if (! (bucket < table->bucket_limit)) |
| 302 abort (); |
| 303 |
| 304 /* Find next entry in the same bucket. */ |
| 305 for (cursor = bucket; cursor; cursor = cursor->next) |
| 306 if (cursor->data == entry && cursor->next) |
| 307 return cursor->next->data; |
| 308 |
| 309 /* Find first entry in any subsequent bucket. */ |
| 310 while (++bucket < table->bucket_limit) |
| 311 if (bucket->data) |
| 312 return bucket->data; |
| 313 |
| 314 /* None found. */ |
| 315 return NULL; |
| 316 } |
| 317 |
| 318 /* Fill BUFFER with pointers to active user entries in the hash table, then |
| 319 return the number of pointers copied. Do not copy more than BUFFER_SIZE |
| 320 pointers. */ |
| 321 |
| 322 size_t |
| 323 hash_get_entries (const Hash_table *table, void **buffer, |
| 324 size_t buffer_size) |
| 325 { |
| 326 size_t counter = 0; |
| 327 struct hash_entry const *bucket; |
| 328 struct hash_entry const *cursor; |
| 329 |
| 330 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 331 { |
| 332 if (bucket->data) |
| 333 { |
| 334 for (cursor = bucket; cursor; cursor = cursor->next) |
| 335 { |
| 336 if (counter >= buffer_size) |
| 337 return counter; |
| 338 buffer[counter++] = cursor->data; |
| 339 } |
| 340 } |
| 341 } |
| 342 |
| 343 return counter; |
| 344 } |
| 345 |
| 346 /* Call a PROCESSOR function for each entry of a hash table, and return the |
| 347 number of entries for which the processor function returned success. A |
| 348 pointer to some PROCESSOR_DATA which will be made available to each call to |
| 349 the processor function. The PROCESSOR accepts two arguments: the first is |
| 350 the user entry being walked into, the second is the value of PROCESSOR_DATA |
| 351 as received. The walking continue for as long as the PROCESSOR function |
| 352 returns nonzero. When it returns zero, the walking is interrupted. */ |
| 353 |
| 354 size_t |
| 355 hash_do_for_each (const Hash_table *table, Hash_processor processor, |
| 356 void *processor_data) |
| 357 { |
| 358 size_t counter = 0; |
| 359 struct hash_entry const *bucket; |
| 360 struct hash_entry const *cursor; |
| 361 |
| 362 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 363 { |
| 364 if (bucket->data) |
| 365 { |
| 366 for (cursor = bucket; cursor; cursor = cursor->next) |
| 367 { |
| 368 if (!(*processor) (cursor->data, processor_data)) |
| 369 return counter; |
| 370 counter++; |
| 371 } |
| 372 } |
| 373 } |
| 374 |
| 375 return counter; |
| 376 } |
| 377 |
| 378 /* Allocation and clean-up. */ |
| 379 |
| 380 /* Return a hash index for a NUL-terminated STRING between 0 and N_BUCKETS-1. |
| 381 This is a convenience routine for constructing other hashing functions. */ |
| 382 |
| 383 #if USE_DIFF_HASH |
| 384 |
| 385 /* About hashings, Paul Eggert writes to me (FP), on 1994-01-01: "Please see |
| 386 B. J. McKenzie, R. Harries & T. Bell, Selecting a hashing algorithm, |
| 387 Software--practice & experience 20, 2 (Feb 1990), 209-224. Good hash |
| 388 algorithms tend to be domain-specific, so what's good for [diffutils'] io.c |
| 389 may not be good for your application." */ |
| 390 |
| 391 size_t |
| 392 hash_string (const char *string, size_t n_buckets) |
| 393 { |
| 394 # define ROTATE_LEFT(Value, Shift) \ |
| 395 ((Value) << (Shift) | (Value) >> ((sizeof (size_t) * CHAR_BIT) - (Shift))) |
| 396 # define HASH_ONE_CHAR(Value, Byte) \ |
| 397 ((Byte) + ROTATE_LEFT (Value, 7)) |
| 398 |
| 399 size_t value = 0; |
| 400 unsigned char ch; |
| 401 |
| 402 for (; (ch = *string); string++) |
| 403 value = HASH_ONE_CHAR (value, ch); |
| 404 return value % n_buckets; |
| 405 |
| 406 # undef ROTATE_LEFT |
| 407 # undef HASH_ONE_CHAR |
| 408 } |
| 409 |
| 410 #else /* not USE_DIFF_HASH */ |
| 411 |
| 412 /* This one comes from `recode', and performs a bit better than the above as |
| 413 per a few experiments. It is inspired from a hashing routine found in the |
| 414 very old Cyber `snoop', itself written in typical Greg Mansfield style. |
| 415 (By the way, what happened to this excellent man? Is he still alive?) */ |
| 416 |
| 417 size_t |
| 418 hash_string (const char *string, size_t n_buckets) |
| 419 { |
| 420 size_t value = 0; |
| 421 unsigned char ch; |
| 422 |
| 423 for (; (ch = *string); string++) |
| 424 value = (value * 31 + ch) % n_buckets; |
| 425 return value; |
| 426 } |
| 427 |
| 428 #endif /* not USE_DIFF_HASH */ |
| 429 |
| 430 /* Return true if CANDIDATE is a prime number. CANDIDATE should be an odd |
| 431 number at least equal to 11. */ |
| 432 |
| 433 static bool |
| 434 is_prime (size_t candidate) |
| 435 { |
| 436 size_t divisor = 3; |
| 437 size_t square = divisor * divisor; |
| 438 |
| 439 while (square < candidate && (candidate % divisor)) |
| 440 { |
| 441 divisor++; |
| 442 square += 4 * divisor; |
| 443 divisor++; |
| 444 } |
| 445 |
| 446 return (candidate % divisor ? true : false); |
| 447 } |
| 448 |
| 449 /* Round a given CANDIDATE number up to the nearest prime, and return that |
| 450 prime. Primes lower than 10 are merely skipped. */ |
| 451 |
| 452 static size_t |
| 453 next_prime (size_t candidate) |
| 454 { |
| 455 /* Skip small primes. */ |
| 456 if (candidate < 10) |
| 457 candidate = 10; |
| 458 |
| 459 /* Make it definitely odd. */ |
| 460 candidate |= 1; |
| 461 |
| 462 while (!is_prime (candidate)) |
| 463 candidate += 2; |
| 464 |
| 465 return candidate; |
| 466 } |
| 467 |
| 468 void |
| 469 hash_reset_tuning (Hash_tuning *tuning) |
| 470 { |
| 471 *tuning = default_tuning; |
| 472 } |
| 473 |
| 474 /* For the given hash TABLE, check the user supplied tuning structure for |
| 475 reasonable values, and return true if there is no gross error with it. |
| 476 Otherwise, definitively reset the TUNING field to some acceptable default |
| 477 in the hash table (that is, the user loses the right of further modifying |
| 478 tuning arguments), and return false. */ |
| 479 |
| 480 static bool |
| 481 check_tuning (Hash_table *table) |
| 482 { |
| 483 const Hash_tuning *tuning = table->tuning; |
| 484 |
| 485 /* Be a bit stricter than mathematics would require, so that |
| 486 rounding errors in size calculations do not cause allocations to |
| 487 fail to grow or shrink as they should. The smallest allocation |
| 488 is 11 (due to next_prime's algorithm), so an epsilon of 0.1 |
| 489 should be good enough. */ |
| 490 float epsilon = 0.1f; |
| 491 |
| 492 if (epsilon < tuning->growth_threshold |
| 493 && tuning->growth_threshold < 1 - epsilon |
| 494 && 1 + epsilon < tuning->growth_factor |
| 495 && 0 <= tuning->shrink_threshold |
| 496 && tuning->shrink_threshold + epsilon < tuning->shrink_factor |
| 497 && tuning->shrink_factor <= 1 |
| 498 && tuning->shrink_threshold + epsilon < tuning->growth_threshold) |
| 499 return true; |
| 500 |
| 501 table->tuning = &default_tuning; |
| 502 return false; |
| 503 } |
| 504 |
| 505 /* Allocate and return a new hash table, or NULL upon failure. The initial |
| 506 number of buckets is automatically selected so as to _guarantee_ that you |
| 507 may insert at least CANDIDATE different user entries before any growth of |
| 508 the hash table size occurs. So, if have a reasonably tight a-priori upper |
| 509 bound on the number of entries you intend to insert in the hash table, you |
| 510 may save some table memory and insertion time, by specifying it here. If |
| 511 the IS_N_BUCKETS field of the TUNING structure is true, the CANDIDATE |
| 512 argument has its meaning changed to the wanted number of buckets. |
| 513 |
| 514 TUNING points to a structure of user-supplied values, in case some fine |
| 515 tuning is wanted over the default behavior of the hasher. If TUNING is |
| 516 NULL, the default tuning parameters are used instead. |
| 517 |
| 518 The user-supplied HASHER function should be provided. It accepts two |
| 519 arguments ENTRY and TABLE_SIZE. It computes, by hashing ENTRY contents, a |
| 520 slot number for that entry which should be in the range 0..TABLE_SIZE-1. |
| 521 This slot number is then returned. |
| 522 |
| 523 The user-supplied COMPARATOR function should be provided. It accepts two |
| 524 arguments pointing to user data, it then returns true for a pair of entries |
| 525 that compare equal, or false otherwise. This function is internally called |
| 526 on entries which are already known to hash to the same bucket index. |
| 527 |
| 528 The user-supplied DATA_FREER function, when not NULL, may be later called |
| 529 with the user data as an argument, just before the entry containing the |
| 530 data gets freed. This happens from within `hash_free' or `hash_clear'. |
| 531 You should specify this function only if you want these functions to free |
| 532 all of your `data' data. This is typically the case when your data is |
| 533 simply an auxiliary struct that you have malloc'd to aggregate several |
| 534 values. */ |
| 535 |
| 536 Hash_table * |
| 537 hash_initialize (size_t candidate, const Hash_tuning *tuning, |
| 538 Hash_hasher hasher, Hash_comparator comparator, |
| 539 Hash_data_freer data_freer) |
| 540 { |
| 541 Hash_table *table; |
| 542 |
| 543 if (hasher == NULL || comparator == NULL) |
| 544 return NULL; |
| 545 |
| 546 table = malloc (sizeof *table); |
| 547 if (table == NULL) |
| 548 return NULL; |
| 549 |
| 550 if (!tuning) |
| 551 tuning = &default_tuning; |
| 552 table->tuning = tuning; |
| 553 if (!check_tuning (table)) |
| 554 { |
| 555 /* Fail if the tuning options are invalid. This is the only occasion |
| 556 when the user gets some feedback about it. Once the table is created, |
| 557 if the user provides invalid tuning options, we silently revert to |
| 558 using the defaults, and ignore further request to change the tuning |
| 559 options. */ |
| 560 goto fail; |
| 561 } |
| 562 |
| 563 if (!tuning->is_n_buckets) |
| 564 { |
| 565 float new_candidate = candidate / tuning->growth_threshold; |
| 566 if (SIZE_MAX <= new_candidate) |
| 567 goto fail; |
| 568 candidate = new_candidate; |
| 569 } |
| 570 |
| 571 if (xalloc_oversized (candidate, sizeof *table->bucket)) |
| 572 goto fail; |
| 573 table->n_buckets = next_prime (candidate); |
| 574 if (xalloc_oversized (table->n_buckets, sizeof *table->bucket)) |
| 575 goto fail; |
| 576 |
| 577 table->bucket = calloc (table->n_buckets, sizeof *table->bucket); |
| 578 if (table->bucket == NULL) |
| 579 goto fail; |
| 580 table->bucket_limit = table->bucket + table->n_buckets; |
| 581 table->n_buckets_used = 0; |
| 582 table->n_entries = 0; |
| 583 |
| 584 table->hasher = hasher; |
| 585 table->comparator = comparator; |
| 586 table->data_freer = data_freer; |
| 587 |
| 588 table->free_entry_list = NULL; |
| 589 #if USE_OBSTACK |
| 590 obstack_init (&table->entry_stack); |
| 591 #endif |
| 592 return table; |
| 593 |
| 594 fail: |
| 595 free (table); |
| 596 return NULL; |
| 597 } |
| 598 |
| 599 /* Make all buckets empty, placing any chained entries on the free list. |
| 600 Apply the user-specified function data_freer (if any) to the datas of any |
| 601 affected entries. */ |
| 602 |
| 603 void |
| 604 hash_clear (Hash_table *table) |
| 605 { |
| 606 struct hash_entry *bucket; |
| 607 |
| 608 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 609 { |
| 610 if (bucket->data) |
| 611 { |
| 612 struct hash_entry *cursor; |
| 613 struct hash_entry *next; |
| 614 |
| 615 /* Free the bucket overflow. */ |
| 616 for (cursor = bucket->next; cursor; cursor = next) |
| 617 { |
| 618 if (table->data_freer) |
| 619 (*table->data_freer) (cursor->data); |
| 620 cursor->data = NULL; |
| 621 |
| 622 next = cursor->next; |
| 623 /* Relinking is done one entry at a time, as it is to be expected |
| 624 that overflows are either rare or short. */ |
| 625 cursor->next = table->free_entry_list; |
| 626 table->free_entry_list = cursor; |
| 627 } |
| 628 |
| 629 /* Free the bucket head. */ |
| 630 if (table->data_freer) |
| 631 (*table->data_freer) (bucket->data); |
| 632 bucket->data = NULL; |
| 633 bucket->next = NULL; |
| 634 } |
| 635 } |
| 636 |
| 637 table->n_buckets_used = 0; |
| 638 table->n_entries = 0; |
| 639 } |
| 640 |
| 641 /* Reclaim all storage associated with a hash table. If a data_freer |
| 642 function has been supplied by the user when the hash table was created, |
| 643 this function applies it to the data of each entry before freeing that |
| 644 entry. */ |
| 645 |
| 646 void |
| 647 hash_free (Hash_table *table) |
| 648 { |
| 649 struct hash_entry *bucket; |
| 650 struct hash_entry *cursor; |
| 651 struct hash_entry *next; |
| 652 |
| 653 /* Call the user data_freer function. */ |
| 654 if (table->data_freer && table->n_entries) |
| 655 { |
| 656 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 657 { |
| 658 if (bucket->data) |
| 659 { |
| 660 for (cursor = bucket; cursor; cursor = cursor->next) |
| 661 { |
| 662 (*table->data_freer) (cursor->data); |
| 663 } |
| 664 } |
| 665 } |
| 666 } |
| 667 |
| 668 #if USE_OBSTACK |
| 669 |
| 670 obstack_free (&table->entry_stack, NULL); |
| 671 |
| 672 #else |
| 673 |
| 674 /* Free all bucket overflowed entries. */ |
| 675 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 676 { |
| 677 for (cursor = bucket->next; cursor; cursor = next) |
| 678 { |
| 679 next = cursor->next; |
| 680 free (cursor); |
| 681 } |
| 682 } |
| 683 |
| 684 /* Also reclaim the internal list of previously freed entries. */ |
| 685 for (cursor = table->free_entry_list; cursor; cursor = next) |
| 686 { |
| 687 next = cursor->next; |
| 688 free (cursor); |
| 689 } |
| 690 |
| 691 #endif |
| 692 |
| 693 /* Free the remainder of the hash table structure. */ |
| 694 free (table->bucket); |
| 695 free (table); |
| 696 } |
| 697 |
| 698 /* Insertion and deletion. */ |
| 699 |
| 700 /* Get a new hash entry for a bucket overflow, possibly by reclying a |
| 701 previously freed one. If this is not possible, allocate a new one. */ |
| 702 |
| 703 static struct hash_entry * |
| 704 allocate_entry (Hash_table *table) |
| 705 { |
| 706 struct hash_entry *new; |
| 707 |
| 708 if (table->free_entry_list) |
| 709 { |
| 710 new = table->free_entry_list; |
| 711 table->free_entry_list = new->next; |
| 712 } |
| 713 else |
| 714 { |
| 715 #if USE_OBSTACK |
| 716 new = obstack_alloc (&table->entry_stack, sizeof *new); |
| 717 #else |
| 718 new = malloc (sizeof *new); |
| 719 #endif |
| 720 } |
| 721 |
| 722 return new; |
| 723 } |
| 724 |
| 725 /* Free a hash entry which was part of some bucket overflow, |
| 726 saving it for later recycling. */ |
| 727 |
| 728 static void |
| 729 free_entry (Hash_table *table, struct hash_entry *entry) |
| 730 { |
| 731 entry->data = NULL; |
| 732 entry->next = table->free_entry_list; |
| 733 table->free_entry_list = entry; |
| 734 } |
| 735 |
| 736 /* This private function is used to help with insertion and deletion. When |
| 737 ENTRY matches an entry in the table, return a pointer to the corresponding |
| 738 user data and set *BUCKET_HEAD to the head of the selected bucket. |
| 739 Otherwise, return NULL. When DELETE is true and ENTRY matches an entry in |
| 740 the table, unlink the matching entry. */ |
| 741 |
| 742 static void * |
| 743 hash_find_entry (Hash_table *table, const void *entry, |
| 744 struct hash_entry **bucket_head, bool delete) |
| 745 { |
| 746 struct hash_entry *bucket |
| 747 = table->bucket + table->hasher (entry, table->n_buckets); |
| 748 struct hash_entry *cursor; |
| 749 |
| 750 if (! (bucket < table->bucket_limit)) |
| 751 abort (); |
| 752 |
| 753 *bucket_head = bucket; |
| 754 |
| 755 /* Test for empty bucket. */ |
| 756 if (bucket->data == NULL) |
| 757 return NULL; |
| 758 |
| 759 /* See if the entry is the first in the bucket. */ |
| 760 if ((*table->comparator) (entry, bucket->data)) |
| 761 { |
| 762 void *data = bucket->data; |
| 763 |
| 764 if (delete) |
| 765 { |
| 766 if (bucket->next) |
| 767 { |
| 768 struct hash_entry *next = bucket->next; |
| 769 |
| 770 /* Bump the first overflow entry into the bucket head, then save |
| 771 the previous first overflow entry for later recycling. */ |
| 772 *bucket = *next; |
| 773 free_entry (table, next); |
| 774 } |
| 775 else |
| 776 { |
| 777 bucket->data = NULL; |
| 778 } |
| 779 } |
| 780 |
| 781 return data; |
| 782 } |
| 783 |
| 784 /* Scan the bucket overflow. */ |
| 785 for (cursor = bucket; cursor->next; cursor = cursor->next) |
| 786 { |
| 787 if ((*table->comparator) (entry, cursor->next->data)) |
| 788 { |
| 789 void *data = cursor->next->data; |
| 790 |
| 791 if (delete) |
| 792 { |
| 793 struct hash_entry *next = cursor->next; |
| 794 |
| 795 /* Unlink the entry to delete, then save the freed entry for later |
| 796 recycling. */ |
| 797 cursor->next = next->next; |
| 798 free_entry (table, next); |
| 799 } |
| 800 |
| 801 return data; |
| 802 } |
| 803 } |
| 804 |
| 805 /* No entry found. */ |
| 806 return NULL; |
| 807 } |
| 808 |
| 809 /* For an already existing hash table, change the number of buckets through |
| 810 specifying CANDIDATE. The contents of the hash table are preserved. The |
| 811 new number of buckets is automatically selected so as to _guarantee_ that |
| 812 the table may receive at least CANDIDATE different user entries, including |
| 813 those already in the table, before any other growth of the hash table size |
| 814 occurs. If TUNING->IS_N_BUCKETS is true, then CANDIDATE specifies the |
| 815 exact number of buckets desired. */ |
| 816 |
| 817 bool |
| 818 hash_rehash (Hash_table *table, size_t candidate) |
| 819 { |
| 820 Hash_table *new_table; |
| 821 struct hash_entry *bucket; |
| 822 struct hash_entry *cursor; |
| 823 struct hash_entry *next; |
| 824 |
| 825 new_table = hash_initialize (candidate, table->tuning, table->hasher, |
| 826 table->comparator, table->data_freer); |
| 827 if (new_table == NULL) |
| 828 return false; |
| 829 |
| 830 /* Merely reuse the extra old space into the new table. */ |
| 831 #if USE_OBSTACK |
| 832 obstack_free (&new_table->entry_stack, NULL); |
| 833 new_table->entry_stack = table->entry_stack; |
| 834 #endif |
| 835 new_table->free_entry_list = table->free_entry_list; |
| 836 |
| 837 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 838 if (bucket->data) |
| 839 for (cursor = bucket; cursor; cursor = next) |
| 840 { |
| 841 void *data = cursor->data; |
| 842 struct hash_entry *new_bucket |
| 843 = (new_table->bucket |
| 844 + new_table->hasher (data, new_table->n_buckets)); |
| 845 |
| 846 if (! (new_bucket < new_table->bucket_limit)) |
| 847 abort (); |
| 848 |
| 849 next = cursor->next; |
| 850 |
| 851 if (new_bucket->data) |
| 852 { |
| 853 if (cursor == bucket) |
| 854 { |
| 855 /* Allocate or recycle an entry, when moving from a bucket |
| 856 header into a bucket overflow. */ |
| 857 struct hash_entry *new_entry = allocate_entry (new_table); |
| 858 |
| 859 if (new_entry == NULL) |
| 860 return false; |
| 861 |
| 862 new_entry->data = data; |
| 863 new_entry->next = new_bucket->next; |
| 864 new_bucket->next = new_entry; |
| 865 } |
| 866 else |
| 867 { |
| 868 /* Merely relink an existing entry, when moving from a |
| 869 bucket overflow into a bucket overflow. */ |
| 870 cursor->next = new_bucket->next; |
| 871 new_bucket->next = cursor; |
| 872 } |
| 873 } |
| 874 else |
| 875 { |
| 876 /* Free an existing entry, when moving from a bucket |
| 877 overflow into a bucket header. Also take care of the |
| 878 simple case of moving from a bucket header into a bucket |
| 879 header. */ |
| 880 new_bucket->data = data; |
| 881 new_table->n_buckets_used++; |
| 882 if (cursor != bucket) |
| 883 free_entry (new_table, cursor); |
| 884 } |
| 885 } |
| 886 |
| 887 free (table->bucket); |
| 888 table->bucket = new_table->bucket; |
| 889 table->bucket_limit = new_table->bucket_limit; |
| 890 table->n_buckets = new_table->n_buckets; |
| 891 table->n_buckets_used = new_table->n_buckets_used; |
| 892 table->free_entry_list = new_table->free_entry_list; |
| 893 /* table->n_entries already holds its value. */ |
| 894 #if USE_OBSTACK |
| 895 table->entry_stack = new_table->entry_stack; |
| 896 #endif |
| 897 free (new_table); |
| 898 |
| 899 return true; |
| 900 } |
| 901 |
| 902 /* If ENTRY matches an entry already in the hash table, return the pointer |
| 903 to the entry from the table. Otherwise, insert ENTRY and return ENTRY. |
| 904 Return NULL if the storage required for insertion cannot be allocated. */ |
| 905 |
| 906 void * |
| 907 hash_insert (Hash_table *table, const void *entry) |
| 908 { |
| 909 void *data; |
| 910 struct hash_entry *bucket; |
| 911 |
| 912 /* The caller cannot insert a NULL entry. */ |
| 913 if (! entry) |
| 914 abort (); |
| 915 |
| 916 /* If there's a matching entry already in the table, return that. */ |
| 917 if ((data = hash_find_entry (table, entry, &bucket, false)) != NULL) |
| 918 return data; |
| 919 |
| 920 /* ENTRY is not matched, it should be inserted. */ |
| 921 |
| 922 if (bucket->data) |
| 923 { |
| 924 struct hash_entry *new_entry = allocate_entry (table); |
| 925 |
| 926 if (new_entry == NULL) |
| 927 return NULL; |
| 928 |
| 929 /* Add ENTRY in the overflow of the bucket. */ |
| 930 |
| 931 new_entry->data = (void *) entry; |
| 932 new_entry->next = bucket->next; |
| 933 bucket->next = new_entry; |
| 934 table->n_entries++; |
| 935 return (void *) entry; |
| 936 } |
| 937 |
| 938 /* Add ENTRY right in the bucket head. */ |
| 939 |
| 940 bucket->data = (void *) entry; |
| 941 table->n_entries++; |
| 942 table->n_buckets_used++; |
| 943 |
| 944 /* If the growth threshold of the buckets in use has been reached, increase |
| 945 the table size and rehash. There's no point in checking the number of |
| 946 entries: if the hashing function is ill-conditioned, rehashing is not |
| 947 likely to improve it. */ |
| 948 |
| 949 if (table->n_buckets_used |
| 950 > table->tuning->growth_threshold * table->n_buckets) |
| 951 { |
| 952 /* Check more fully, before starting real work. If tuning arguments |
| 953 became invalid, the second check will rely on proper defaults. */ |
| 954 check_tuning (table); |
| 955 if (table->n_buckets_used |
| 956 > table->tuning->growth_threshold * table->n_buckets) |
| 957 { |
| 958 const Hash_tuning *tuning = table->tuning; |
| 959 float candidate = |
| 960 (tuning->is_n_buckets |
| 961 ? (table->n_buckets * tuning->growth_factor) |
| 962 : (table->n_buckets * tuning->growth_factor |
| 963 * tuning->growth_threshold)); |
| 964 |
| 965 if (SIZE_MAX <= candidate) |
| 966 return NULL; |
| 967 |
| 968 /* If the rehash fails, arrange to return NULL. */ |
| 969 if (!hash_rehash (table, candidate)) |
| 970 entry = NULL; |
| 971 } |
| 972 } |
| 973 |
| 974 return (void *) entry; |
| 975 } |
| 976 |
| 977 /* If ENTRY is already in the table, remove it and return the just-deleted |
| 978 data (the user may want to deallocate its storage). If ENTRY is not in the |
| 979 table, don't modify the table and return NULL. */ |
| 980 |
| 981 void * |
| 982 hash_delete (Hash_table *table, const void *entry) |
| 983 { |
| 984 void *data; |
| 985 struct hash_entry *bucket; |
| 986 |
| 987 data = hash_find_entry (table, entry, &bucket, true); |
| 988 if (!data) |
| 989 return NULL; |
| 990 |
| 991 table->n_entries--; |
| 992 if (!bucket->data) |
| 993 { |
| 994 table->n_buckets_used--; |
| 995 |
| 996 /* If the shrink threshold of the buckets in use has been reached, |
| 997 rehash into a smaller table. */ |
| 998 |
| 999 if (table->n_buckets_used |
| 1000 < table->tuning->shrink_threshold * table->n_buckets) |
| 1001 { |
| 1002 /* Check more fully, before starting real work. If tuning arguments |
| 1003 became invalid, the second check will rely on proper defaults. */ |
| 1004 check_tuning (table); |
| 1005 if (table->n_buckets_used |
| 1006 < table->tuning->shrink_threshold * table->n_buckets) |
| 1007 { |
| 1008 const Hash_tuning *tuning = table->tuning; |
| 1009 size_t candidate = |
| 1010 (tuning->is_n_buckets |
| 1011 ? table->n_buckets * tuning->shrink_factor |
| 1012 : (table->n_buckets * tuning->shrink_factor |
| 1013 * tuning->growth_threshold)); |
| 1014 |
| 1015 hash_rehash (table, candidate); |
| 1016 } |
| 1017 } |
| 1018 } |
| 1019 |
| 1020 return data; |
| 1021 } |
| 1022 |
| 1023 /* Testing. */ |
| 1024 |
| 1025 #if TESTING |
| 1026 |
| 1027 void |
| 1028 hash_print (const Hash_table *table) |
| 1029 { |
| 1030 struct hash_entry const *bucket; |
| 1031 |
| 1032 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++) |
| 1033 { |
| 1034 struct hash_entry *cursor; |
| 1035 |
| 1036 if (bucket) |
| 1037 printf ("%lu:\n", (unsigned long int) (bucket - table->bucket)); |
| 1038 |
| 1039 for (cursor = bucket; cursor; cursor = cursor->next) |
| 1040 { |
| 1041 char const *s = cursor->data; |
| 1042 /* FIXME */ |
| 1043 if (s) |
| 1044 printf (" %s\n", s); |
| 1045 } |
| 1046 } |
| 1047 } |
| 1048 |
| 1049 #endif /* TESTING */ |
OLD | NEW |