1 /* hash - hashing table processing.
3 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007 Free
4 Software Foundation, Inc.
6 Written by Jim Meyering, 1992.
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 2, or (at your option)
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.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software Foundation,
20 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
22 /* A generic hash table package. */
24 /* Define USE_OBSTACK to 1 if you want the allocator to use obstacks instead
25 of malloc. If you change USE_OBSTACK, you have to recompile! */
38 # ifndef obstack_chunk_alloc
39 # define obstack_chunk_alloc malloc
41 # ifndef obstack_chunk_free
42 # define obstack_chunk_free free
47 # define SIZE_MAX ((size_t) -1)
52 /* The array of buckets starts at BUCKET and extends to BUCKET_LIMIT-1,
53 for a possibility of N_BUCKETS. Among those, N_BUCKETS_USED buckets
54 are not empty, there are N_ENTRIES active entries in the table. */
55 struct hash_entry *bucket;
56 struct hash_entry const *bucket_limit;
58 size_t n_buckets_used;
61 /* Tuning arguments, kept in a physicaly separate structure. */
62 const Hash_tuning *tuning;
64 /* Three functions are given to `hash_initialize', see the documentation
65 block for this function. In a word, HASHER randomizes a user entry
66 into a number up from 0 up to some maximum minus 1; COMPARATOR returns
67 true if two user entries compare equally; and DATA_FREER is the cleanup
68 function for a user entry. */
70 Hash_comparator comparator;
71 Hash_data_freer data_freer;
73 /* A linked list of freed struct hash_entry structs. */
74 struct hash_entry *free_entry_list;
77 /* Whenever obstacks are used, it is possible to allocate all overflowed
78 entries into a single stack, so they all can be freed in a single
79 operation. It is not clear if the speedup is worth the trouble. */
80 struct obstack entry_stack;
84 /* A hash table contains many internal entries, each holding a pointer to
85 some user provided data (also called a user entry). An entry indistinctly
86 refers to both the internal entry and its associated user entry. A user
87 entry contents may be hashed by a randomization function (the hashing
88 function, or just `hasher' for short) into a number (or `slot') between 0
89 and the current table size. At each slot position in the hash table,
90 starts a linked chain of entries for which the user data all hash to this
91 slot. A bucket is the collection of all entries hashing to the same slot.
93 A good `hasher' function will distribute entries rather evenly in buckets.
94 In the ideal case, the length of each bucket is roughly the number of
95 entries divided by the table size. Finding the slot for a data is usually
96 done in constant time by the `hasher', and the later finding of a precise
97 entry is linear in time with the size of the bucket. Consequently, a
98 larger hash table size (that is, a larger number of buckets) is prone to
99 yielding shorter chains, *given* the `hasher' function behaves properly.
101 Long buckets slow down the lookup algorithm. One might use big hash table
102 sizes in hope to reduce the average length of buckets, but this might
103 become inordinate, as unused slots in the hash table take some space. The
104 best bet is to make sure you are using a good `hasher' function (beware
105 that those are not that easy to write! :-), and to use a table size
106 larger than the actual number of entries. */
108 /* If an insertion makes the ratio of nonempty buckets to table size larger
109 than the growth threshold (a number between 0.0 and 1.0), then increase
110 the table size by multiplying by the growth factor (a number greater than
111 1.0). The growth threshold defaults to 0.8, and the growth factor
112 defaults to 1.414, meaning that the table will have doubled its size
113 every second time 80% of the buckets get used. */
114 #define DEFAULT_GROWTH_THRESHOLD 0.8
115 #define DEFAULT_GROWTH_FACTOR 1.414
117 /* If a deletion empties a bucket and causes the ratio of used buckets to
118 table size to become smaller than the shrink threshold (a number between
119 0.0 and 1.0), then shrink the table by multiplying by the shrink factor (a
120 number greater than the shrink threshold but smaller than 1.0). The shrink
121 threshold and factor default to 0.0 and 1.0, meaning that the table never
123 #define DEFAULT_SHRINK_THRESHOLD 0.0
124 #define DEFAULT_SHRINK_FACTOR 1.0
126 /* Use this to initialize or reset a TUNING structure to
127 some sensible values. */
128 static const Hash_tuning default_tuning =
130 DEFAULT_SHRINK_THRESHOLD,
131 DEFAULT_SHRINK_FACTOR,
132 DEFAULT_GROWTH_THRESHOLD,
133 DEFAULT_GROWTH_FACTOR,
137 /* Information and lookup. */
139 /* The following few functions provide information about the overall hash
140 table organization: the number of entries, number of buckets and maximum
141 length of buckets. */
143 /* Return the number of buckets in the hash table. The table size, the total
144 number of buckets (used plus unused), or the maximum number of slots, are
145 the same quantity. */
148 hash_get_n_buckets (const Hash_table *table)
150 return table->n_buckets;
153 /* Return the number of slots in use (non-empty buckets). */
156 hash_get_n_buckets_used (const Hash_table *table)
158 return table->n_buckets_used;
161 /* Return the number of active entries. */
164 hash_get_n_entries (const Hash_table *table)
166 return table->n_entries;
169 /* Return the length of the longest chain (bucket). */
172 hash_get_max_bucket_length (const Hash_table *table)
174 struct hash_entry const *bucket;
175 size_t max_bucket_length = 0;
177 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
181 struct hash_entry const *cursor = bucket;
182 size_t bucket_length = 1;
184 while (cursor = cursor->next, cursor)
187 if (bucket_length > max_bucket_length)
188 max_bucket_length = bucket_length;
192 return max_bucket_length;
195 /* Do a mild validation of a hash table, by traversing it and checking two
199 hash_table_ok (const Hash_table *table)
201 struct hash_entry const *bucket;
202 size_t n_buckets_used = 0;
203 size_t n_entries = 0;
205 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
209 struct hash_entry const *cursor = bucket;
211 /* Count bucket head. */
215 /* Count bucket overflow. */
216 while (cursor = cursor->next, cursor)
221 if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries)
228 hash_print_statistics (const Hash_table *table, FILE *stream)
230 size_t n_entries = hash_get_n_entries (table);
231 size_t n_buckets = hash_get_n_buckets (table);
232 size_t n_buckets_used = hash_get_n_buckets_used (table);
233 size_t max_bucket_length = hash_get_max_bucket_length (table);
235 fprintf (stream, "# entries: %lu\n", (unsigned long int) n_entries);
236 fprintf (stream, "# buckets: %lu\n", (unsigned long int) n_buckets);
237 fprintf (stream, "# buckets used: %lu (%.2f%%)\n",
238 (unsigned long int) n_buckets_used,
239 (100.0 * n_buckets_used) / n_buckets);
240 fprintf (stream, "max bucket length: %lu\n",
241 (unsigned long int) max_bucket_length);
244 /* If ENTRY matches an entry already in the hash table, return the
245 entry from the table. Otherwise, return NULL. */
248 hash_lookup (const Hash_table *table, const void *entry)
250 struct hash_entry const *bucket
251 = table->bucket + table->hasher (entry, table->n_buckets);
252 struct hash_entry const *cursor;
254 if (! (bucket < table->bucket_limit))
257 if (bucket->data == NULL)
260 for (cursor = bucket; cursor; cursor = cursor->next)
261 if (table->comparator (entry, cursor->data))
269 /* The functions in this page traverse the hash table and process the
270 contained entries. For the traversal to work properly, the hash table
271 should not be resized nor modified while any particular entry is being
272 processed. In particular, entries should not be added or removed. */
274 /* Return the first data in the table, or NULL if the table is empty. */
277 hash_get_first (const Hash_table *table)
279 struct hash_entry const *bucket;
281 if (table->n_entries == 0)
284 for (bucket = table->bucket; ; bucket++)
285 if (! (bucket < table->bucket_limit))
287 else if (bucket->data)
291 /* Return the user data for the entry following ENTRY, where ENTRY has been
292 returned by a previous call to either `hash_get_first' or `hash_get_next'.
293 Return NULL if there are no more entries. */
296 hash_get_next (const Hash_table *table, const void *entry)
298 struct hash_entry const *bucket
299 = table->bucket + table->hasher (entry, table->n_buckets);
300 struct hash_entry const *cursor;
302 if (! (bucket < table->bucket_limit))
305 /* Find next entry in the same bucket. */
306 for (cursor = bucket; cursor; cursor = cursor->next)
307 if (cursor->data == entry && cursor->next)
308 return cursor->next->data;
310 /* Find first entry in any subsequent bucket. */
311 while (++bucket < table->bucket_limit)
319 /* Fill BUFFER with pointers to active user entries in the hash table, then
320 return the number of pointers copied. Do not copy more than BUFFER_SIZE
324 hash_get_entries (const Hash_table *table, void **buffer,
328 struct hash_entry const *bucket;
329 struct hash_entry const *cursor;
331 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
335 for (cursor = bucket; cursor; cursor = cursor->next)
337 if (counter >= buffer_size)
339 buffer[counter++] = cursor->data;
347 /* Call a PROCESSOR function for each entry of a hash table, and return the
348 number of entries for which the processor function returned success. A
349 pointer to some PROCESSOR_DATA which will be made available to each call to
350 the processor function. The PROCESSOR accepts two arguments: the first is
351 the user entry being walked into, the second is the value of PROCESSOR_DATA
352 as received. The walking continue for as long as the PROCESSOR function
353 returns nonzero. When it returns zero, the walking is interrupted. */
356 hash_do_for_each (const Hash_table *table, Hash_processor processor,
357 void *processor_data)
360 struct hash_entry const *bucket;
361 struct hash_entry const *cursor;
363 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
367 for (cursor = bucket; cursor; cursor = cursor->next)
369 if (!(*processor) (cursor->data, processor_data))
379 /* Allocation and clean-up. */
381 /* Return a hash index for a NUL-terminated STRING between 0 and N_BUCKETS-1.
382 This is a convenience routine for constructing other hashing functions. */
386 /* About hashings, Paul Eggert writes to me (FP), on 1994-01-01: "Please see
387 B. J. McKenzie, R. Harries & T. Bell, Selecting a hashing algorithm,
388 Software--practice & experience 20, 2 (Feb 1990), 209-224. Good hash
389 algorithms tend to be domain-specific, so what's good for [diffutils'] io.c
390 may not be good for your application." */
393 hash_string (const char *string, size_t n_buckets)
395 # define ROTATE_LEFT(Value, Shift) \
396 ((Value) << (Shift) | (Value) >> ((sizeof (size_t) * CHAR_BIT) - (Shift)))
397 # define HASH_ONE_CHAR(Value, Byte) \
398 ((Byte) + ROTATE_LEFT (Value, 7))
403 for (; (ch = *string); string++)
404 value = HASH_ONE_CHAR (value, ch);
405 return value % n_buckets;
408 # undef HASH_ONE_CHAR
411 #else /* not USE_DIFF_HASH */
413 /* This one comes from `recode', and performs a bit better than the above as
414 per a few experiments. It is inspired from a hashing routine found in the
415 very old Cyber `snoop', itself written in typical Greg Mansfield style.
416 (By the way, what happened to this excellent man? Is he still alive?) */
419 hash_string (const char *string, size_t n_buckets)
424 for (; (ch = *string); string++)
425 value = (value * 31 + ch) % n_buckets;
429 #endif /* not USE_DIFF_HASH */
431 /* Return true if CANDIDATE is a prime number. CANDIDATE should be an odd
432 number at least equal to 11. */
435 is_prime (size_t candidate)
438 size_t square = divisor * divisor;
440 while (square < candidate && (candidate % divisor))
443 square += 4 * divisor;
447 return (candidate % divisor ? true : false);
450 /* Round a given CANDIDATE number up to the nearest prime, and return that
451 prime. Primes lower than 10 are merely skipped. */
454 next_prime (size_t candidate)
456 /* Skip small primes. */
460 /* Make it definitely odd. */
463 while (!is_prime (candidate))
470 hash_reset_tuning (Hash_tuning *tuning)
472 *tuning = default_tuning;
475 /* For the given hash TABLE, check the user supplied tuning structure for
476 reasonable values, and return true if there is no gross error with it.
477 Otherwise, definitively reset the TUNING field to some acceptable default
478 in the hash table (that is, the user loses the right of further modifying
479 tuning arguments), and return false. */
482 check_tuning (Hash_table *table)
484 const Hash_tuning *tuning = table->tuning;
486 /* Be a bit stricter than mathematics would require, so that
487 rounding errors in size calculations do not cause allocations to
488 fail to grow or shrink as they should. The smallest allocation
489 is 11 (due to next_prime's algorithm), so an epsilon of 0.1
490 should be good enough. */
491 float epsilon = 0.1f;
493 if (epsilon < tuning->growth_threshold
494 && tuning->growth_threshold < 1 - epsilon
495 && 1 + epsilon < tuning->growth_factor
496 && 0 <= tuning->shrink_threshold
497 && tuning->shrink_threshold + epsilon < tuning->shrink_factor
498 && tuning->shrink_factor <= 1
499 && tuning->shrink_threshold + epsilon < tuning->growth_threshold)
502 table->tuning = &default_tuning;
506 /* Allocate and return a new hash table, or NULL upon failure. The initial
507 number of buckets is automatically selected so as to _guarantee_ that you
508 may insert at least CANDIDATE different user entries before any growth of
509 the hash table size occurs. So, if have a reasonably tight a-priori upper
510 bound on the number of entries you intend to insert in the hash table, you
511 may save some table memory and insertion time, by specifying it here. If
512 the IS_N_BUCKETS field of the TUNING structure is true, the CANDIDATE
513 argument has its meaning changed to the wanted number of buckets.
515 TUNING points to a structure of user-supplied values, in case some fine
516 tuning is wanted over the default behavior of the hasher. If TUNING is
517 NULL, the default tuning parameters are used instead.
519 The user-supplied HASHER function should be provided. It accepts two
520 arguments ENTRY and TABLE_SIZE. It computes, by hashing ENTRY contents, a
521 slot number for that entry which should be in the range 0..TABLE_SIZE-1.
522 This slot number is then returned.
524 The user-supplied COMPARATOR function should be provided. It accepts two
525 arguments pointing to user data, it then returns true for a pair of entries
526 that compare equal, or false otherwise. This function is internally called
527 on entries which are already known to hash to the same bucket index.
529 The user-supplied DATA_FREER function, when not NULL, may be later called
530 with the user data as an argument, just before the entry containing the
531 data gets freed. This happens from within `hash_free' or `hash_clear'.
532 You should specify this function only if you want these functions to free
533 all of your `data' data. This is typically the case when your data is
534 simply an auxiliary struct that you have malloc'd to aggregate several
538 hash_initialize (size_t candidate, const Hash_tuning *tuning,
539 Hash_hasher hasher, Hash_comparator comparator,
540 Hash_data_freer data_freer)
544 if (hasher == NULL || comparator == NULL)
547 table = malloc (sizeof *table);
552 tuning = &default_tuning;
553 table->tuning = tuning;
554 if (!check_tuning (table))
556 /* Fail if the tuning options are invalid. This is the only occasion
557 when the user gets some feedback about it. Once the table is created,
558 if the user provides invalid tuning options, we silently revert to
559 using the defaults, and ignore further request to change the tuning
564 if (!tuning->is_n_buckets)
566 float new_candidate = candidate / tuning->growth_threshold;
567 if (SIZE_MAX <= new_candidate)
569 candidate = new_candidate;
572 if (xalloc_oversized (candidate, sizeof *table->bucket))
574 table->n_buckets = next_prime (candidate);
575 if (xalloc_oversized (table->n_buckets, sizeof *table->bucket))
578 table->bucket = calloc (table->n_buckets, sizeof *table->bucket);
579 if (table->bucket == NULL)
581 table->bucket_limit = table->bucket + table->n_buckets;
582 table->n_buckets_used = 0;
583 table->n_entries = 0;
585 table->hasher = hasher;
586 table->comparator = comparator;
587 table->data_freer = data_freer;
589 table->free_entry_list = NULL;
591 obstack_init (&table->entry_stack);
600 /* Make all buckets empty, placing any chained entries on the free list.
601 Apply the user-specified function data_freer (if any) to the datas of any
605 hash_clear (Hash_table *table)
607 struct hash_entry *bucket;
609 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
613 struct hash_entry *cursor;
614 struct hash_entry *next;
616 /* Free the bucket overflow. */
617 for (cursor = bucket->next; cursor; cursor = next)
619 if (table->data_freer)
620 (*table->data_freer) (cursor->data);
624 /* Relinking is done one entry at a time, as it is to be expected
625 that overflows are either rare or short. */
626 cursor->next = table->free_entry_list;
627 table->free_entry_list = cursor;
630 /* Free the bucket head. */
631 if (table->data_freer)
632 (*table->data_freer) (bucket->data);
638 table->n_buckets_used = 0;
639 table->n_entries = 0;
642 /* Reclaim all storage associated with a hash table. If a data_freer
643 function has been supplied by the user when the hash table was created,
644 this function applies it to the data of each entry before freeing that
648 hash_free (Hash_table *table)
650 struct hash_entry *bucket;
651 struct hash_entry *cursor;
652 struct hash_entry *next;
654 /* Call the user data_freer function. */
655 if (table->data_freer && table->n_entries)
657 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
661 for (cursor = bucket; cursor; cursor = cursor->next)
663 (*table->data_freer) (cursor->data);
671 obstack_free (&table->entry_stack, NULL);
675 /* Free all bucket overflowed entries. */
676 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
678 for (cursor = bucket->next; cursor; cursor = next)
685 /* Also reclaim the internal list of previously freed entries. */
686 for (cursor = table->free_entry_list; cursor; cursor = next)
694 /* Free the remainder of the hash table structure. */
695 free (table->bucket);
699 /* Insertion and deletion. */
701 /* Get a new hash entry for a bucket overflow, possibly by reclying a
702 previously freed one. If this is not possible, allocate a new one. */
704 static struct hash_entry *
705 allocate_entry (Hash_table *table)
707 struct hash_entry *new;
709 if (table->free_entry_list)
711 new = table->free_entry_list;
712 table->free_entry_list = new->next;
717 new = obstack_alloc (&table->entry_stack, sizeof *new);
719 new = malloc (sizeof *new);
726 /* Free a hash entry which was part of some bucket overflow,
727 saving it for later recycling. */
730 free_entry (Hash_table *table, struct hash_entry *entry)
733 entry->next = table->free_entry_list;
734 table->free_entry_list = entry;
737 /* This private function is used to help with insertion and deletion. When
738 ENTRY matches an entry in the table, return a pointer to the corresponding
739 user data and set *BUCKET_HEAD to the head of the selected bucket.
740 Otherwise, return NULL. When DELETE is true and ENTRY matches an entry in
741 the table, unlink the matching entry. */
744 hash_find_entry (Hash_table *table, const void *entry,
745 struct hash_entry **bucket_head, bool delete)
747 struct hash_entry *bucket
748 = table->bucket + table->hasher (entry, table->n_buckets);
749 struct hash_entry *cursor;
751 if (! (bucket < table->bucket_limit))
754 *bucket_head = bucket;
756 /* Test for empty bucket. */
757 if (bucket->data == NULL)
760 /* See if the entry is the first in the bucket. */
761 if ((*table->comparator) (entry, bucket->data))
763 void *data = bucket->data;
769 struct hash_entry *next = bucket->next;
771 /* Bump the first overflow entry into the bucket head, then save
772 the previous first overflow entry for later recycling. */
774 free_entry (table, next);
785 /* Scan the bucket overflow. */
786 for (cursor = bucket; cursor->next; cursor = cursor->next)
788 if ((*table->comparator) (entry, cursor->next->data))
790 void *data = cursor->next->data;
794 struct hash_entry *next = cursor->next;
796 /* Unlink the entry to delete, then save the freed entry for later
798 cursor->next = next->next;
799 free_entry (table, next);
806 /* No entry found. */
810 /* For an already existing hash table, change the number of buckets through
811 specifying CANDIDATE. The contents of the hash table are preserved. The
812 new number of buckets is automatically selected so as to _guarantee_ that
813 the table may receive at least CANDIDATE different user entries, including
814 those already in the table, before any other growth of the hash table size
815 occurs. If TUNING->IS_N_BUCKETS is true, then CANDIDATE specifies the
816 exact number of buckets desired. */
819 hash_rehash (Hash_table *table, size_t candidate)
821 Hash_table *new_table;
822 struct hash_entry *bucket;
823 struct hash_entry *cursor;
824 struct hash_entry *next;
826 new_table = hash_initialize (candidate, table->tuning, table->hasher,
827 table->comparator, table->data_freer);
828 if (new_table == NULL)
831 /* Merely reuse the extra old space into the new table. */
833 obstack_free (&new_table->entry_stack, NULL);
834 new_table->entry_stack = table->entry_stack;
836 new_table->free_entry_list = table->free_entry_list;
838 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
840 for (cursor = bucket; cursor; cursor = next)
842 void *data = cursor->data;
843 struct hash_entry *new_bucket
845 + new_table->hasher (data, new_table->n_buckets));
847 if (! (new_bucket < new_table->bucket_limit))
852 if (new_bucket->data)
854 if (cursor == bucket)
856 /* Allocate or recycle an entry, when moving from a bucket
857 header into a bucket overflow. */
858 struct hash_entry *new_entry = allocate_entry (new_table);
860 if (new_entry == NULL)
863 new_entry->data = data;
864 new_entry->next = new_bucket->next;
865 new_bucket->next = new_entry;
869 /* Merely relink an existing entry, when moving from a
870 bucket overflow into a bucket overflow. */
871 cursor->next = new_bucket->next;
872 new_bucket->next = cursor;
877 /* Free an existing entry, when moving from a bucket
878 overflow into a bucket header. Also take care of the
879 simple case of moving from a bucket header into a bucket
881 new_bucket->data = data;
882 new_table->n_buckets_used++;
883 if (cursor != bucket)
884 free_entry (new_table, cursor);
888 free (table->bucket);
889 table->bucket = new_table->bucket;
890 table->bucket_limit = new_table->bucket_limit;
891 table->n_buckets = new_table->n_buckets;
892 table->n_buckets_used = new_table->n_buckets_used;
893 table->free_entry_list = new_table->free_entry_list;
894 /* table->n_entries already holds its value. */
896 table->entry_stack = new_table->entry_stack;
903 /* If ENTRY matches an entry already in the hash table, return the pointer
904 to the entry from the table. Otherwise, insert ENTRY and return ENTRY.
905 Return NULL if the storage required for insertion cannot be allocated. */
908 hash_insert (Hash_table *table, const void *entry)
911 struct hash_entry *bucket;
913 /* The caller cannot insert a NULL entry. */
917 /* If there's a matching entry already in the table, return that. */
918 if ((data = hash_find_entry (table, entry, &bucket, false)) != NULL)
921 /* ENTRY is not matched, it should be inserted. */
925 struct hash_entry *new_entry = allocate_entry (table);
927 if (new_entry == NULL)
930 /* Add ENTRY in the overflow of the bucket. */
932 new_entry->data = (void *) entry;
933 new_entry->next = bucket->next;
934 bucket->next = new_entry;
936 return (void *) entry;
939 /* Add ENTRY right in the bucket head. */
941 bucket->data = (void *) entry;
943 table->n_buckets_used++;
945 /* If the growth threshold of the buckets in use has been reached, increase
946 the table size and rehash. There's no point in checking the number of
947 entries: if the hashing function is ill-conditioned, rehashing is not
948 likely to improve it. */
950 if (table->n_buckets_used
951 > table->tuning->growth_threshold * table->n_buckets)
953 /* Check more fully, before starting real work. If tuning arguments
954 became invalid, the second check will rely on proper defaults. */
955 check_tuning (table);
956 if (table->n_buckets_used
957 > table->tuning->growth_threshold * table->n_buckets)
959 const Hash_tuning *tuning = table->tuning;
961 (tuning->is_n_buckets
962 ? (table->n_buckets * tuning->growth_factor)
963 : (table->n_buckets * tuning->growth_factor
964 * tuning->growth_threshold));
966 if (SIZE_MAX <= candidate)
969 /* If the rehash fails, arrange to return NULL. */
970 if (!hash_rehash (table, candidate))
975 return (void *) entry;
978 /* If ENTRY is already in the table, remove it and return the just-deleted
979 data (the user may want to deallocate its storage). If ENTRY is not in the
980 table, don't modify the table and return NULL. */
983 hash_delete (Hash_table *table, const void *entry)
986 struct hash_entry *bucket;
988 data = hash_find_entry (table, entry, &bucket, true);
995 table->n_buckets_used--;
997 /* If the shrink threshold of the buckets in use has been reached,
998 rehash into a smaller table. */
1000 if (table->n_buckets_used
1001 < table->tuning->shrink_threshold * table->n_buckets)
1003 /* Check more fully, before starting real work. If tuning arguments
1004 became invalid, the second check will rely on proper defaults. */
1005 check_tuning (table);
1006 if (table->n_buckets_used
1007 < table->tuning->shrink_threshold * table->n_buckets)
1009 const Hash_tuning *tuning = table->tuning;
1011 (tuning->is_n_buckets
1012 ? table->n_buckets * tuning->shrink_factor
1013 : (table->n_buckets * tuning->shrink_factor
1014 * tuning->growth_threshold));
1016 hash_rehash (table, candidate);
1029 hash_print (const Hash_table *table)
1031 struct hash_entry const *bucket;
1033 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
1035 struct hash_entry *cursor;
1038 printf ("%lu:\n", (unsigned long int) (bucket - table->bucket));
1040 for (cursor = bucket; cursor; cursor = cursor->next)
1042 char const *s = cursor->data;
1045 printf (" %s\n", s);
1050 #endif /* TESTING */