1 /* hash - hashing table processing.
3 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Free Software
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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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! */
40 # ifndef obstack_chunk_alloc
41 # define obstack_chunk_alloc malloc
43 # ifndef obstack_chunk_free
44 # define obstack_chunk_free free
49 # define SIZE_MAX ((size_t) -1)
54 /* The array of buckets starts at BUCKET and extends to BUCKET_LIMIT-1,
55 for a possibility of N_BUCKETS. Among those, N_BUCKETS_USED buckets
56 are not empty, there are N_ENTRIES active entries in the table. */
57 struct hash_entry *bucket;
58 struct hash_entry const *bucket_limit;
60 size_t n_buckets_used;
63 /* Tuning arguments, kept in a physicaly separate structure. */
64 const Hash_tuning *tuning;
66 /* Three functions are given to `hash_initialize', see the documentation
67 block for this function. In a word, HASHER randomizes a user entry
68 into a number up from 0 up to some maximum minus 1; COMPARATOR returns
69 true if two user entries compare equally; and DATA_FREER is the cleanup
70 function for a user entry. */
72 Hash_comparator comparator;
73 Hash_data_freer data_freer;
75 /* A linked list of freed struct hash_entry structs. */
76 struct hash_entry *free_entry_list;
79 /* Whenever obstacks are used, it is possible to allocate all overflowed
80 entries into a single stack, so they all can be freed in a single
81 operation. It is not clear if the speedup is worth the trouble. */
82 struct obstack entry_stack;
86 /* A hash table contains many internal entries, each holding a pointer to
87 some user provided data (also called a user entry). An entry indistinctly
88 refers to both the internal entry and its associated user entry. A user
89 entry contents may be hashed by a randomization function (the hashing
90 function, or just `hasher' for short) into a number (or `slot') between 0
91 and the current table size. At each slot position in the hash table,
92 starts a linked chain of entries for which the user data all hash to this
93 slot. A bucket is the collection of all entries hashing to the same slot.
95 A good `hasher' function will distribute entries rather evenly in buckets.
96 In the ideal case, the length of each bucket is roughly the number of
97 entries divided by the table size. Finding the slot for a data is usually
98 done in constant time by the `hasher', and the later finding of a precise
99 entry is linear in time with the size of the bucket. Consequently, a
100 larger hash table size (that is, a larger number of buckets) is prone to
101 yielding shorter chains, *given* the `hasher' function behaves properly.
103 Long buckets slow down the lookup algorithm. One might use big hash table
104 sizes in hope to reduce the average length of buckets, but this might
105 become inordinate, as unused slots in the hash table take some space. The
106 best bet is to make sure you are using a good `hasher' function (beware
107 that those are not that easy to write! :-), and to use a table size
108 larger than the actual number of entries. */
110 /* If an insertion makes the ratio of nonempty buckets to table size larger
111 than the growth threshold (a number between 0.0 and 1.0), then increase
112 the table size by multiplying by the growth factor (a number greater than
113 1.0). The growth threshold defaults to 0.8, and the growth factor
114 defaults to 1.414, meaning that the table will have doubled its size
115 every second time 80% of the buckets get used. */
116 #define DEFAULT_GROWTH_THRESHOLD 0.8
117 #define DEFAULT_GROWTH_FACTOR 1.414
119 /* If a deletion empties a bucket and causes the ratio of used buckets to
120 table size to become smaller than the shrink threshold (a number between
121 0.0 and 1.0), then shrink the table by multiplying by the shrink factor (a
122 number greater than the shrink threshold but smaller than 1.0). The shrink
123 threshold and factor default to 0.0 and 1.0, meaning that the table never
125 #define DEFAULT_SHRINK_THRESHOLD 0.0
126 #define DEFAULT_SHRINK_FACTOR 1.0
128 /* Use this to initialize or reset a TUNING structure to
129 some sensible values. */
130 static const Hash_tuning default_tuning =
132 DEFAULT_SHRINK_THRESHOLD,
133 DEFAULT_SHRINK_FACTOR,
134 DEFAULT_GROWTH_THRESHOLD,
135 DEFAULT_GROWTH_FACTOR,
139 /* Information and lookup. */
141 /* The following few functions provide information about the overall hash
142 table organization: the number of entries, number of buckets and maximum
143 length of buckets. */
145 /* Return the number of buckets in the hash table. The table size, the total
146 number of buckets (used plus unused), or the maximum number of slots, are
147 the same quantity. */
150 hash_get_n_buckets (const Hash_table *table)
152 return table->n_buckets;
155 /* Return the number of slots in use (non-empty buckets). */
158 hash_get_n_buckets_used (const Hash_table *table)
160 return table->n_buckets_used;
163 /* Return the number of active entries. */
166 hash_get_n_entries (const Hash_table *table)
168 return table->n_entries;
171 /* Return the length of the longest chain (bucket). */
174 hash_get_max_bucket_length (const Hash_table *table)
176 struct hash_entry const *bucket;
177 size_t max_bucket_length = 0;
179 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
183 struct hash_entry const *cursor = bucket;
184 size_t bucket_length = 1;
186 while (cursor = cursor->next, cursor)
189 if (bucket_length > max_bucket_length)
190 max_bucket_length = bucket_length;
194 return max_bucket_length;
197 /* Do a mild validation of a hash table, by traversing it and checking two
201 hash_table_ok (const Hash_table *table)
203 struct hash_entry const *bucket;
204 size_t n_buckets_used = 0;
205 size_t n_entries = 0;
207 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
211 struct hash_entry const *cursor = bucket;
213 /* Count bucket head. */
217 /* Count bucket overflow. */
218 while (cursor = cursor->next, cursor)
223 if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries)
230 hash_print_statistics (const Hash_table *table, FILE *stream)
232 size_t n_entries = hash_get_n_entries (table);
233 size_t n_buckets = hash_get_n_buckets (table);
234 size_t n_buckets_used = hash_get_n_buckets_used (table);
235 size_t max_bucket_length = hash_get_max_bucket_length (table);
237 fprintf (stream, "# entries: %lu\n", (unsigned long int) n_entries);
238 fprintf (stream, "# buckets: %lu\n", (unsigned long int) n_buckets);
239 fprintf (stream, "# buckets used: %lu (%.2f%%)\n",
240 (unsigned long int) n_buckets_used,
241 (100.0 * n_buckets_used) / n_buckets);
242 fprintf (stream, "max bucket length: %lu\n",
243 (unsigned long int) max_bucket_length);
246 /* If ENTRY matches an entry already in the hash table, return the
247 entry from the table. Otherwise, return NULL. */
250 hash_lookup (const Hash_table *table, const void *entry)
252 struct hash_entry const *bucket
253 = table->bucket + table->hasher (entry, table->n_buckets);
254 struct hash_entry const *cursor;
256 if (! (bucket < table->bucket_limit))
259 if (bucket->data == NULL)
262 for (cursor = bucket; cursor; cursor = cursor->next)
263 if (table->comparator (entry, cursor->data))
271 /* The functions in this page traverse the hash table and process the
272 contained entries. For the traversal to work properly, the hash table
273 should not be resized nor modified while any particular entry is being
274 processed. In particular, entries should not be added or removed. */
276 /* Return the first data in the table, or NULL if the table is empty. */
279 hash_get_first (const Hash_table *table)
281 struct hash_entry const *bucket;
283 if (table->n_entries == 0)
286 for (bucket = table->bucket; ; bucket++)
287 if (! (bucket < table->bucket_limit))
289 else if (bucket->data)
293 /* Return the user data for the entry following ENTRY, where ENTRY has been
294 returned by a previous call to either `hash_get_first' or `hash_get_next'.
295 Return NULL if there are no more entries. */
298 hash_get_next (const Hash_table *table, const void *entry)
300 struct hash_entry const *bucket
301 = table->bucket + table->hasher (entry, table->n_buckets);
302 struct hash_entry const *cursor;
304 if (! (bucket < table->bucket_limit))
307 /* Find next entry in the same bucket. */
308 for (cursor = bucket; cursor; cursor = cursor->next)
309 if (cursor->data == entry && cursor->next)
310 return cursor->next->data;
312 /* Find first entry in any subsequent bucket. */
313 while (++bucket < table->bucket_limit)
321 /* Fill BUFFER with pointers to active user entries in the hash table, then
322 return the number of pointers copied. Do not copy more than BUFFER_SIZE
326 hash_get_entries (const Hash_table *table, void **buffer,
330 struct hash_entry const *bucket;
331 struct hash_entry const *cursor;
333 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
337 for (cursor = bucket; cursor; cursor = cursor->next)
339 if (counter >= buffer_size)
341 buffer[counter++] = cursor->data;
349 /* Call a PROCESSOR function for each entry of a hash table, and return the
350 number of entries for which the processor function returned success. A
351 pointer to some PROCESSOR_DATA which will be made available to each call to
352 the processor function. The PROCESSOR accepts two arguments: the first is
353 the user entry being walked into, the second is the value of PROCESSOR_DATA
354 as received. The walking continue for as long as the PROCESSOR function
355 returns nonzero. When it returns zero, the walking is interrupted. */
358 hash_do_for_each (const Hash_table *table, Hash_processor processor,
359 void *processor_data)
362 struct hash_entry const *bucket;
363 struct hash_entry const *cursor;
365 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
369 for (cursor = bucket; cursor; cursor = cursor->next)
371 if (!(*processor) (cursor->data, processor_data))
381 /* Allocation and clean-up. */
383 /* Return a hash index for a NUL-terminated STRING between 0 and N_BUCKETS-1.
384 This is a convenience routine for constructing other hashing functions. */
388 /* About hashings, Paul Eggert writes to me (FP), on 1994-01-01: "Please see
389 B. J. McKenzie, R. Harries & T. Bell, Selecting a hashing algorithm,
390 Software--practice & experience 20, 2 (Feb 1990), 209-224. Good hash
391 algorithms tend to be domain-specific, so what's good for [diffutils'] io.c
392 may not be good for your application." */
395 hash_string (const char *string, size_t n_buckets)
397 # define ROTATE_LEFT(Value, Shift) \
398 ((Value) << (Shift) | (Value) >> ((sizeof (size_t) * CHAR_BIT) - (Shift)))
399 # define HASH_ONE_CHAR(Value, Byte) \
400 ((Byte) + ROTATE_LEFT (Value, 7))
404 for (; *string; string++)
405 value = HASH_ONE_CHAR (value, (unsigned char) *string);
406 return value % n_buckets;
409 # undef HASH_ONE_CHAR
412 #else /* not USE_DIFF_HASH */
414 /* This one comes from `recode', and performs a bit better than the above as
415 per a few experiments. It is inspired from a hashing routine found in the
416 very old Cyber `snoop', itself written in typical Greg Mansfield style.
417 (By the way, what happened to this excellent man? Is he still alive?) */
420 hash_string (const char *string, size_t n_buckets)
425 value = (value * 31 + (unsigned char) *string++) % 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 table->bucket_limit = table->bucket + table->n_buckets;
580 table->n_buckets_used = 0;
581 table->n_entries = 0;
583 table->hasher = hasher;
584 table->comparator = comparator;
585 table->data_freer = data_freer;
587 table->free_entry_list = NULL;
589 obstack_init (&table->entry_stack);
598 /* Make all buckets empty, placing any chained entries on the free list.
599 Apply the user-specified function data_freer (if any) to the datas of any
603 hash_clear (Hash_table *table)
605 struct hash_entry *bucket;
607 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
611 struct hash_entry *cursor;
612 struct hash_entry *next;
614 /* Free the bucket overflow. */
615 for (cursor = bucket->next; cursor; cursor = next)
617 if (table->data_freer)
618 (*table->data_freer) (cursor->data);
622 /* Relinking is done one entry at a time, as it is to be expected
623 that overflows are either rare or short. */
624 cursor->next = table->free_entry_list;
625 table->free_entry_list = cursor;
628 /* Free the bucket head. */
629 if (table->data_freer)
630 (*table->data_freer) (bucket->data);
636 table->n_buckets_used = 0;
637 table->n_entries = 0;
640 /* Reclaim all storage associated with a hash table. If a data_freer
641 function has been supplied by the user when the hash table was created,
642 this function applies it to the data of each entry before freeing that
646 hash_free (Hash_table *table)
648 struct hash_entry *bucket;
649 struct hash_entry *cursor;
650 struct hash_entry *next;
652 /* Call the user data_freer function. */
653 if (table->data_freer && table->n_entries)
655 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
659 for (cursor = bucket; cursor; cursor = cursor->next)
661 (*table->data_freer) (cursor->data);
669 obstack_free (&table->entry_stack, NULL);
673 /* Free all bucket overflowed entries. */
674 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
676 for (cursor = bucket->next; cursor; cursor = next)
683 /* Also reclaim the internal list of previously freed entries. */
684 for (cursor = table->free_entry_list; cursor; cursor = next)
692 /* Free the remainder of the hash table structure. */
693 free (table->bucket);
697 /* Insertion and deletion. */
699 /* Get a new hash entry for a bucket overflow, possibly by reclying a
700 previously freed one. If this is not possible, allocate a new one. */
702 static struct hash_entry *
703 allocate_entry (Hash_table *table)
705 struct hash_entry *new;
707 if (table->free_entry_list)
709 new = table->free_entry_list;
710 table->free_entry_list = new->next;
715 new = obstack_alloc (&table->entry_stack, sizeof *new);
717 new = malloc (sizeof *new);
724 /* Free a hash entry which was part of some bucket overflow,
725 saving it for later recycling. */
728 free_entry (Hash_table *table, struct hash_entry *entry)
731 entry->next = table->free_entry_list;
732 table->free_entry_list = entry;
735 /* This private function is used to help with insertion and deletion. When
736 ENTRY matches an entry in the table, return a pointer to the corresponding
737 user data and set *BUCKET_HEAD to the head of the selected bucket.
738 Otherwise, return NULL. When DELETE is true and ENTRY matches an entry in
739 the table, unlink the matching entry. */
742 hash_find_entry (Hash_table *table, const void *entry,
743 struct hash_entry **bucket_head, bool delete)
745 struct hash_entry *bucket
746 = table->bucket + table->hasher (entry, table->n_buckets);
747 struct hash_entry *cursor;
749 if (! (bucket < table->bucket_limit))
752 *bucket_head = bucket;
754 /* Test for empty bucket. */
755 if (bucket->data == NULL)
758 /* See if the entry is the first in the bucket. */
759 if ((*table->comparator) (entry, bucket->data))
761 void *data = bucket->data;
767 struct hash_entry *next = bucket->next;
769 /* Bump the first overflow entry into the bucket head, then save
770 the previous first overflow entry for later recycling. */
772 free_entry (table, next);
783 /* Scan the bucket overflow. */
784 for (cursor = bucket; cursor->next; cursor = cursor->next)
786 if ((*table->comparator) (entry, cursor->next->data))
788 void *data = cursor->next->data;
792 struct hash_entry *next = cursor->next;
794 /* Unlink the entry to delete, then save the freed entry for later
796 cursor->next = next->next;
797 free_entry (table, next);
804 /* No entry found. */
808 /* For an already existing hash table, change the number of buckets through
809 specifying CANDIDATE. The contents of the hash table are preserved. The
810 new number of buckets is automatically selected so as to _guarantee_ that
811 the table may receive at least CANDIDATE different user entries, including
812 those already in the table, before any other growth of the hash table size
813 occurs. If TUNING->IS_N_BUCKETS is true, then CANDIDATE specifies the
814 exact number of buckets desired. */
817 hash_rehash (Hash_table *table, size_t candidate)
819 Hash_table *new_table;
820 struct hash_entry *bucket;
821 struct hash_entry *cursor;
822 struct hash_entry *next;
824 new_table = hash_initialize (candidate, table->tuning, table->hasher,
825 table->comparator, table->data_freer);
826 if (new_table == NULL)
829 /* Merely reuse the extra old space into the new table. */
831 obstack_free (&new_table->entry_stack, NULL);
832 new_table->entry_stack = table->entry_stack;
834 new_table->free_entry_list = table->free_entry_list;
836 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
838 for (cursor = bucket; cursor; cursor = next)
840 void *data = cursor->data;
841 struct hash_entry *new_bucket
843 + new_table->hasher (data, new_table->n_buckets));
845 if (! (new_bucket < new_table->bucket_limit))
850 if (new_bucket->data)
852 if (cursor == bucket)
854 /* Allocate or recycle an entry, when moving from a bucket
855 header into a bucket overflow. */
856 struct hash_entry *new_entry = allocate_entry (new_table);
858 if (new_entry == NULL)
861 new_entry->data = data;
862 new_entry->next = new_bucket->next;
863 new_bucket->next = new_entry;
867 /* Merely relink an existing entry, when moving from a
868 bucket overflow into a bucket overflow. */
869 cursor->next = new_bucket->next;
870 new_bucket->next = cursor;
875 /* Free an existing entry, when moving from a bucket
876 overflow into a bucket header. Also take care of the
877 simple case of moving from a bucket header into a bucket
879 new_bucket->data = data;
880 new_table->n_buckets_used++;
881 if (cursor != bucket)
882 free_entry (new_table, cursor);
886 free (table->bucket);
887 table->bucket = new_table->bucket;
888 table->bucket_limit = new_table->bucket_limit;
889 table->n_buckets = new_table->n_buckets;
890 table->n_buckets_used = new_table->n_buckets_used;
891 table->free_entry_list = new_table->free_entry_list;
892 /* table->n_entries already holds its value. */
894 table->entry_stack = new_table->entry_stack;
901 /* If ENTRY matches an entry already in the hash table, return the pointer
902 to the entry from the table. Otherwise, insert ENTRY and return ENTRY.
903 Return NULL if the storage required for insertion cannot be allocated. */
906 hash_insert (Hash_table *table, const void *entry)
909 struct hash_entry *bucket;
911 /* The caller cannot insert a NULL entry. */
915 /* If there's a matching entry already in the table, return that. */
916 if ((data = hash_find_entry (table, entry, &bucket, false)) != NULL)
919 /* ENTRY is not matched, it should be inserted. */
923 struct hash_entry *new_entry = allocate_entry (table);
925 if (new_entry == NULL)
928 /* Add ENTRY in the overflow of the bucket. */
930 new_entry->data = (void *) entry;
931 new_entry->next = bucket->next;
932 bucket->next = new_entry;
934 return (void *) entry;
937 /* Add ENTRY right in the bucket head. */
939 bucket->data = (void *) entry;
941 table->n_buckets_used++;
943 /* If the growth threshold of the buckets in use has been reached, increase
944 the table size and rehash. There's no point in checking the number of
945 entries: if the hashing function is ill-conditioned, rehashing is not
946 likely to improve it. */
948 if (table->n_buckets_used
949 > table->tuning->growth_threshold * table->n_buckets)
951 /* Check more fully, before starting real work. If tuning arguments
952 became invalid, the second check will rely on proper defaults. */
953 check_tuning (table);
954 if (table->n_buckets_used
955 > table->tuning->growth_threshold * table->n_buckets)
957 const Hash_tuning *tuning = table->tuning;
959 (tuning->is_n_buckets
960 ? (table->n_buckets * tuning->growth_factor)
961 : (table->n_buckets * tuning->growth_factor
962 * tuning->growth_threshold));
964 if (SIZE_MAX <= candidate)
967 /* If the rehash fails, arrange to return NULL. */
968 if (!hash_rehash (table, candidate))
973 return (void *) entry;
976 /* If ENTRY is already in the table, remove it and return the just-deleted
977 data (the user may want to deallocate its storage). If ENTRY is not in the
978 table, don't modify the table and return NULL. */
981 hash_delete (Hash_table *table, const void *entry)
984 struct hash_entry *bucket;
986 data = hash_find_entry (table, entry, &bucket, true);
993 table->n_buckets_used--;
995 /* If the shrink threshold of the buckets in use has been reached,
996 rehash into a smaller table. */
998 if (table->n_buckets_used
999 < table->tuning->shrink_threshold * table->n_buckets)
1001 /* Check more fully, before starting real work. If tuning arguments
1002 became invalid, the second check will rely on proper defaults. */
1003 check_tuning (table);
1004 if (table->n_buckets_used
1005 < table->tuning->shrink_threshold * table->n_buckets)
1007 const Hash_tuning *tuning = table->tuning;
1009 (tuning->is_n_buckets
1010 ? table->n_buckets * tuning->shrink_factor
1011 : (table->n_buckets * tuning->shrink_factor
1012 * tuning->growth_threshold));
1014 hash_rehash (table, candidate);
1027 hash_print (const Hash_table *table)
1029 struct hash_entry const *bucket;
1031 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
1033 struct hash_entry *cursor;
1036 printf ("%lu:\n", (unsigned long int) (bucket - table->bucket));
1038 for (cursor = bucket; cursor; cursor = cursor->next)
1040 char const *s = cursor->data;
1043 printf (" %s\n", s);
1048 #endif /* TESTING */