1 /* hash - hashing table processing.
3 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007,
4 2009 Free 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 3 of the License, or
11 (at your option) any later version.
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, see <http://www.gnu.org/licenses/>. */
21 /* A generic hash table package. */
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! */
37 # ifndef obstack_chunk_alloc
38 # define obstack_chunk_alloc malloc
40 # ifndef obstack_chunk_free
41 # define obstack_chunk_free free
46 # define SIZE_MAX ((size_t) -1)
52 struct hash_entry *next;
57 /* The array of buckets starts at BUCKET and extends to BUCKET_LIMIT-1,
58 for a possibility of N_BUCKETS. Among those, N_BUCKETS_USED buckets
59 are not empty, there are N_ENTRIES active entries in the table. */
60 struct hash_entry *bucket;
61 struct hash_entry const *bucket_limit;
63 size_t n_buckets_used;
66 /* Tuning arguments, kept in a physically separate structure. */
67 const Hash_tuning *tuning;
69 /* Three functions are given to `hash_initialize', see the documentation
70 block for this function. In a word, HASHER randomizes a user entry
71 into a number up from 0 up to some maximum minus 1; COMPARATOR returns
72 true if two user entries compare equally; and DATA_FREER is the cleanup
73 function for a user entry. */
75 Hash_comparator comparator;
76 Hash_data_freer data_freer;
78 /* A linked list of freed struct hash_entry structs. */
79 struct hash_entry *free_entry_list;
82 /* Whenever obstacks are used, it is possible to allocate all overflowed
83 entries into a single stack, so they all can be freed in a single
84 operation. It is not clear if the speedup is worth the trouble. */
85 struct obstack entry_stack;
89 /* A hash table contains many internal entries, each holding a pointer to
90 some user-provided data (also called a user entry). An entry indistinctly
91 refers to both the internal entry and its associated user entry. A user
92 entry contents may be hashed by a randomization function (the hashing
93 function, or just `hasher' for short) into a number (or `slot') between 0
94 and the current table size. At each slot position in the hash table,
95 starts a linked chain of entries for which the user data all hash to this
96 slot. A bucket is the collection of all entries hashing to the same slot.
98 A good `hasher' function will distribute entries rather evenly in buckets.
99 In the ideal case, the length of each bucket is roughly the number of
100 entries divided by the table size. Finding the slot for a data is usually
101 done in constant time by the `hasher', and the later finding of a precise
102 entry is linear in time with the size of the bucket. Consequently, a
103 larger hash table size (that is, a larger number of buckets) is prone to
104 yielding shorter chains, *given* the `hasher' function behaves properly.
106 Long buckets slow down the lookup algorithm. One might use big hash table
107 sizes in hope to reduce the average length of buckets, but this might
108 become inordinate, as unused slots in the hash table take some space. The
109 best bet is to make sure you are using a good `hasher' function (beware
110 that those are not that easy to write! :-), and to use a table size
111 larger than the actual number of entries. */
113 /* If an insertion makes the ratio of nonempty buckets to table size larger
114 than the growth threshold (a number between 0.0 and 1.0), then increase
115 the table size by multiplying by the growth factor (a number greater than
116 1.0). The growth threshold defaults to 0.8, and the growth factor
117 defaults to 1.414, meaning that the table will have doubled its size
118 every second time 80% of the buckets get used. */
119 #define DEFAULT_GROWTH_THRESHOLD 0.8
120 #define DEFAULT_GROWTH_FACTOR 1.414
122 /* If a deletion empties a bucket and causes the ratio of used buckets to
123 table size to become smaller than the shrink threshold (a number between
124 0.0 and 1.0), then shrink the table by multiplying by the shrink factor (a
125 number greater than the shrink threshold but smaller than 1.0). The shrink
126 threshold and factor default to 0.0 and 1.0, meaning that the table never
128 #define DEFAULT_SHRINK_THRESHOLD 0.0
129 #define DEFAULT_SHRINK_FACTOR 1.0
131 /* Use this to initialize or reset a TUNING structure to
132 some sensible values. */
133 static const Hash_tuning default_tuning =
135 DEFAULT_SHRINK_THRESHOLD,
136 DEFAULT_SHRINK_FACTOR,
137 DEFAULT_GROWTH_THRESHOLD,
138 DEFAULT_GROWTH_FACTOR,
142 /* Information and lookup. */
144 /* The following few functions provide information about the overall hash
145 table organization: the number of entries, number of buckets and maximum
146 length of buckets. */
148 /* Return the number of buckets in the hash table. The table size, the total
149 number of buckets (used plus unused), or the maximum number of slots, are
150 the same quantity. */
153 hash_get_n_buckets (const Hash_table *table)
155 return table->n_buckets;
158 /* Return the number of slots in use (non-empty buckets). */
161 hash_get_n_buckets_used (const Hash_table *table)
163 return table->n_buckets_used;
166 /* Return the number of active entries. */
169 hash_get_n_entries (const Hash_table *table)
171 return table->n_entries;
174 /* Return the length of the longest chain (bucket). */
177 hash_get_max_bucket_length (const Hash_table *table)
179 struct hash_entry const *bucket;
180 size_t max_bucket_length = 0;
182 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
186 struct hash_entry const *cursor = bucket;
187 size_t bucket_length = 1;
189 while (cursor = cursor->next, cursor)
192 if (bucket_length > max_bucket_length)
193 max_bucket_length = bucket_length;
197 return max_bucket_length;
200 /* Do a mild validation of a hash table, by traversing it and checking two
204 hash_table_ok (const Hash_table *table)
206 struct hash_entry const *bucket;
207 size_t n_buckets_used = 0;
208 size_t n_entries = 0;
210 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
214 struct hash_entry const *cursor = bucket;
216 /* Count bucket head. */
220 /* Count bucket overflow. */
221 while (cursor = cursor->next, cursor)
226 if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries)
233 hash_print_statistics (const Hash_table *table, FILE *stream)
235 size_t n_entries = hash_get_n_entries (table);
236 size_t n_buckets = hash_get_n_buckets (table);
237 size_t n_buckets_used = hash_get_n_buckets_used (table);
238 size_t max_bucket_length = hash_get_max_bucket_length (table);
240 fprintf (stream, "# entries: %lu\n", (unsigned long int) n_entries);
241 fprintf (stream, "# buckets: %lu\n", (unsigned long int) n_buckets);
242 fprintf (stream, "# buckets used: %lu (%.2f%%)\n",
243 (unsigned long int) n_buckets_used,
244 (100.0 * n_buckets_used) / n_buckets);
245 fprintf (stream, "max bucket length: %lu\n",
246 (unsigned long int) max_bucket_length);
249 /* If ENTRY matches an entry already in the hash table, return the
250 entry from the table. Otherwise, return NULL. */
253 hash_lookup (const Hash_table *table, const void *entry)
255 struct hash_entry const *bucket
256 = table->bucket + table->hasher (entry, table->n_buckets);
257 struct hash_entry const *cursor;
259 if (! (bucket < table->bucket_limit))
262 if (bucket->data == NULL)
265 for (cursor = bucket; cursor; cursor = cursor->next)
266 if (entry == cursor->data || table->comparator (entry, cursor->data))
274 /* The functions in this page traverse the hash table and process the
275 contained entries. For the traversal to work properly, the hash table
276 should not be resized nor modified while any particular entry is being
277 processed. In particular, entries should not be added, and an entry
278 may be removed only if there is no shrink threshold and the entry being
279 removed has already been passed to hash_get_next. */
281 /* Return the first data in the table, or NULL if the table is empty. */
284 hash_get_first (const Hash_table *table)
286 struct hash_entry const *bucket;
288 if (table->n_entries == 0)
291 for (bucket = table->bucket; ; bucket++)
292 if (! (bucket < table->bucket_limit))
294 else if (bucket->data)
298 /* Return the user data for the entry following ENTRY, where ENTRY has been
299 returned by a previous call to either `hash_get_first' or `hash_get_next'.
300 Return NULL if there are no more entries. */
303 hash_get_next (const Hash_table *table, const void *entry)
305 struct hash_entry const *bucket
306 = table->bucket + table->hasher (entry, table->n_buckets);
307 struct hash_entry const *cursor;
309 if (! (bucket < table->bucket_limit))
312 /* Find next entry in the same bucket. */
313 for (cursor = bucket; cursor; cursor = cursor->next)
314 if (cursor->data == entry && cursor->next)
315 return cursor->next->data;
317 /* Find first entry in any subsequent bucket. */
318 while (++bucket < table->bucket_limit)
326 /* Fill BUFFER with pointers to active user entries in the hash table, then
327 return the number of pointers copied. Do not copy more than BUFFER_SIZE
331 hash_get_entries (const Hash_table *table, void **buffer,
335 struct hash_entry const *bucket;
336 struct hash_entry const *cursor;
338 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
342 for (cursor = bucket; cursor; cursor = cursor->next)
344 if (counter >= buffer_size)
346 buffer[counter++] = cursor->data;
354 /* Call a PROCESSOR function for each entry of a hash table, and return the
355 number of entries for which the processor function returned success. A
356 pointer to some PROCESSOR_DATA which will be made available to each call to
357 the processor function. The PROCESSOR accepts two arguments: the first is
358 the user entry being walked into, the second is the value of PROCESSOR_DATA
359 as received. The walking continue for as long as the PROCESSOR function
360 returns nonzero. When it returns zero, the walking is interrupted. */
363 hash_do_for_each (const Hash_table *table, Hash_processor processor,
364 void *processor_data)
367 struct hash_entry const *bucket;
368 struct hash_entry const *cursor;
370 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
374 for (cursor = bucket; cursor; cursor = cursor->next)
376 if (! processor (cursor->data, processor_data))
386 /* Allocation and clean-up. */
388 /* Return a hash index for a NUL-terminated STRING between 0 and N_BUCKETS-1.
389 This is a convenience routine for constructing other hashing functions. */
393 /* About hashings, Paul Eggert writes to me (FP), on 1994-01-01: "Please see
394 B. J. McKenzie, R. Harries & T. Bell, Selecting a hashing algorithm,
395 Software--practice & experience 20, 2 (Feb 1990), 209-224. Good hash
396 algorithms tend to be domain-specific, so what's good for [diffutils'] io.c
397 may not be good for your application." */
400 hash_string (const char *string, size_t n_buckets)
402 # define ROTATE_LEFT(Value, Shift) \
403 ((Value) << (Shift) | (Value) >> ((sizeof (size_t) * CHAR_BIT) - (Shift)))
404 # define HASH_ONE_CHAR(Value, Byte) \
405 ((Byte) + ROTATE_LEFT (Value, 7))
410 for (; (ch = *string); string++)
411 value = HASH_ONE_CHAR (value, ch);
412 return value % n_buckets;
415 # undef HASH_ONE_CHAR
418 #else /* not USE_DIFF_HASH */
420 /* This one comes from `recode', and performs a bit better than the above as
421 per a few experiments. It is inspired from a hashing routine found in the
422 very old Cyber `snoop', itself written in typical Greg Mansfield style.
423 (By the way, what happened to this excellent man? Is he still alive?) */
426 hash_string (const char *string, size_t n_buckets)
431 for (; (ch = *string); string++)
432 value = (value * 31 + ch) % n_buckets;
436 #endif /* not USE_DIFF_HASH */
438 /* Return true if CANDIDATE is a prime number. CANDIDATE should be an odd
439 number at least equal to 11. */
442 is_prime (size_t candidate)
445 size_t square = divisor * divisor;
447 while (square < candidate && (candidate % divisor))
450 square += 4 * divisor;
454 return (candidate % divisor ? true : false);
457 /* Round a given CANDIDATE number up to the nearest prime, and return that
458 prime. Primes lower than 10 are merely skipped. */
461 next_prime (size_t candidate)
463 /* Skip small primes. */
467 /* Make it definitely odd. */
470 while (!is_prime (candidate))
477 hash_reset_tuning (Hash_tuning *tuning)
479 *tuning = default_tuning;
482 /* If the user passes a NULL hasher, we hash the raw pointer. */
484 raw_hasher (const void *data, size_t n)
486 /* When hashing unique pointers, it is often the case that they were
487 generated by malloc and thus have the property that the low-order
488 bits are 0. As this tends to give poorer performance with small
489 tables, we rotate the pointer value before performing division,
490 in an attempt to improve hash quality. */
491 size_t val = (size_t) data;
492 val = ((val >> 3) | (val << (CHAR_BIT * sizeof val - 3))) & SIZE_MAX;
496 /* If the user passes a NULL comparator, we use pointer comparison. */
498 raw_comparator (const void *a, const void *b)
504 /* For the given hash TABLE, check the user supplied tuning structure for
505 reasonable values, and return true if there is no gross error with it.
506 Otherwise, definitively reset the TUNING field to some acceptable default
507 in the hash table (that is, the user loses the right of further modifying
508 tuning arguments), and return false. */
511 check_tuning (Hash_table *table)
513 const Hash_tuning *tuning = table->tuning;
514 if (tuning == &default_tuning)
517 /* Be a bit stricter than mathematics would require, so that
518 rounding errors in size calculations do not cause allocations to
519 fail to grow or shrink as they should. The smallest allocation
520 is 11 (due to next_prime's algorithm), so an epsilon of 0.1
521 should be good enough. */
522 float epsilon = 0.1f;
524 if (epsilon < tuning->growth_threshold
525 && tuning->growth_threshold < 1 - epsilon
526 && 1 + epsilon < tuning->growth_factor
527 && 0 <= tuning->shrink_threshold
528 && tuning->shrink_threshold + epsilon < tuning->shrink_factor
529 && tuning->shrink_factor <= 1
530 && tuning->shrink_threshold + epsilon < tuning->growth_threshold)
533 table->tuning = &default_tuning;
537 /* Allocate and return a new hash table, or NULL upon failure. The initial
538 number of buckets is automatically selected so as to _guarantee_ that you
539 may insert at least CANDIDATE different user entries before any growth of
540 the hash table size occurs. So, if have a reasonably tight a-priori upper
541 bound on the number of entries you intend to insert in the hash table, you
542 may save some table memory and insertion time, by specifying it here. If
543 the IS_N_BUCKETS field of the TUNING structure is true, the CANDIDATE
544 argument has its meaning changed to the wanted number of buckets.
546 TUNING points to a structure of user-supplied values, in case some fine
547 tuning is wanted over the default behavior of the hasher. If TUNING is
548 NULL, the default tuning parameters are used instead. If TUNING is
549 provided but the values requested are out of bounds or might cause
550 rounding errors, return NULL.
552 The user-supplied HASHER function, when not NULL, accepts two
553 arguments ENTRY and TABLE_SIZE. It computes, by hashing ENTRY contents, a
554 slot number for that entry which should be in the range 0..TABLE_SIZE-1.
555 This slot number is then returned.
557 The user-supplied COMPARATOR function, when not NULL, accepts two
558 arguments pointing to user data, it then returns true for a pair of entries
559 that compare equal, or false otherwise. This function is internally called
560 on entries which are already known to hash to the same bucket index,
561 but which are distinct pointers.
563 The user-supplied DATA_FREER function, when not NULL, may be later called
564 with the user data as an argument, just before the entry containing the
565 data gets freed. This happens from within `hash_free' or `hash_clear'.
566 You should specify this function only if you want these functions to free
567 all of your `data' data. This is typically the case when your data is
568 simply an auxiliary struct that you have malloc'd to aggregate several
572 hash_initialize (size_t candidate, const Hash_tuning *tuning,
573 Hash_hasher hasher, Hash_comparator comparator,
574 Hash_data_freer data_freer)
580 if (comparator == NULL)
581 comparator = raw_comparator;
583 table = malloc (sizeof *table);
588 tuning = &default_tuning;
589 table->tuning = tuning;
590 if (!check_tuning (table))
592 /* Fail if the tuning options are invalid. This is the only occasion
593 when the user gets some feedback about it. Once the table is created,
594 if the user provides invalid tuning options, we silently revert to
595 using the defaults, and ignore further request to change the tuning
600 if (!tuning->is_n_buckets)
602 float new_candidate = candidate / tuning->growth_threshold;
603 if (SIZE_MAX <= new_candidate)
605 candidate = new_candidate;
608 if (xalloc_oversized (candidate, sizeof *table->bucket))
610 table->n_buckets = next_prime (candidate);
611 if (xalloc_oversized (table->n_buckets, sizeof *table->bucket))
614 table->bucket = calloc (table->n_buckets, sizeof *table->bucket);
615 if (table->bucket == NULL)
617 table->bucket_limit = table->bucket + table->n_buckets;
618 table->n_buckets_used = 0;
619 table->n_entries = 0;
621 table->hasher = hasher;
622 table->comparator = comparator;
623 table->data_freer = data_freer;
625 table->free_entry_list = NULL;
627 obstack_init (&table->entry_stack);
636 /* Make all buckets empty, placing any chained entries on the free list.
637 Apply the user-specified function data_freer (if any) to the datas of any
641 hash_clear (Hash_table *table)
643 struct hash_entry *bucket;
645 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
649 struct hash_entry *cursor;
650 struct hash_entry *next;
652 /* Free the bucket overflow. */
653 for (cursor = bucket->next; cursor; cursor = next)
655 if (table->data_freer)
656 table->data_freer (cursor->data);
660 /* Relinking is done one entry at a time, as it is to be expected
661 that overflows are either rare or short. */
662 cursor->next = table->free_entry_list;
663 table->free_entry_list = cursor;
666 /* Free the bucket head. */
667 if (table->data_freer)
668 table->data_freer (bucket->data);
674 table->n_buckets_used = 0;
675 table->n_entries = 0;
678 /* Reclaim all storage associated with a hash table. If a data_freer
679 function has been supplied by the user when the hash table was created,
680 this function applies it to the data of each entry before freeing that
684 hash_free (Hash_table *table)
686 struct hash_entry *bucket;
687 struct hash_entry *cursor;
688 struct hash_entry *next;
690 /* Call the user data_freer function. */
691 if (table->data_freer && table->n_entries)
693 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
697 for (cursor = bucket; cursor; cursor = cursor->next)
698 table->data_freer (cursor->data);
705 obstack_free (&table->entry_stack, NULL);
709 /* Free all bucket overflowed entries. */
710 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
712 for (cursor = bucket->next; cursor; cursor = next)
719 /* Also reclaim the internal list of previously freed entries. */
720 for (cursor = table->free_entry_list; cursor; cursor = next)
728 /* Free the remainder of the hash table structure. */
729 free (table->bucket);
733 /* Insertion and deletion. */
735 /* Get a new hash entry for a bucket overflow, possibly by recycling a
736 previously freed one. If this is not possible, allocate a new one. */
738 static struct hash_entry *
739 allocate_entry (Hash_table *table)
741 struct hash_entry *new;
743 if (table->free_entry_list)
745 new = table->free_entry_list;
746 table->free_entry_list = new->next;
751 new = obstack_alloc (&table->entry_stack, sizeof *new);
753 new = malloc (sizeof *new);
760 /* Free a hash entry which was part of some bucket overflow,
761 saving it for later recycling. */
764 free_entry (Hash_table *table, struct hash_entry *entry)
767 entry->next = table->free_entry_list;
768 table->free_entry_list = entry;
771 /* This private function is used to help with insertion and deletion. When
772 ENTRY matches an entry in the table, return a pointer to the corresponding
773 user data and set *BUCKET_HEAD to the head of the selected bucket.
774 Otherwise, return NULL. When DELETE is true and ENTRY matches an entry in
775 the table, unlink the matching entry. */
778 hash_find_entry (Hash_table *table, const void *entry,
779 struct hash_entry **bucket_head, bool delete)
781 struct hash_entry *bucket
782 = table->bucket + table->hasher (entry, table->n_buckets);
783 struct hash_entry *cursor;
785 if (! (bucket < table->bucket_limit))
788 *bucket_head = bucket;
790 /* Test for empty bucket. */
791 if (bucket->data == NULL)
794 /* See if the entry is the first in the bucket. */
795 if (entry == bucket->data || table->comparator (entry, bucket->data))
797 void *data = bucket->data;
803 struct hash_entry *next = bucket->next;
805 /* Bump the first overflow entry into the bucket head, then save
806 the previous first overflow entry for later recycling. */
808 free_entry (table, next);
819 /* Scan the bucket overflow. */
820 for (cursor = bucket; cursor->next; cursor = cursor->next)
822 if (entry == cursor->next->data
823 || table->comparator (entry, cursor->next->data))
825 void *data = cursor->next->data;
829 struct hash_entry *next = cursor->next;
831 /* Unlink the entry to delete, then save the freed entry for later
833 cursor->next = next->next;
834 free_entry (table, next);
841 /* No entry found. */
845 /* For an already existing hash table, change the number of buckets through
846 specifying CANDIDATE. The contents of the hash table are preserved. The
847 new number of buckets is automatically selected so as to _guarantee_ that
848 the table may receive at least CANDIDATE different user entries, including
849 those already in the table, before any other growth of the hash table size
850 occurs. If TUNING->IS_N_BUCKETS is true, then CANDIDATE specifies the
851 exact number of buckets desired. Return true iff the rehash succeeded. */
854 hash_rehash (Hash_table *table, size_t candidate)
856 Hash_table *new_table;
857 struct hash_entry *bucket;
858 struct hash_entry *cursor;
859 struct hash_entry *next;
861 new_table = hash_initialize (candidate, table->tuning, table->hasher,
862 table->comparator, table->data_freer);
863 if (new_table == NULL)
866 /* Merely reuse the extra old space into the new table. */
868 obstack_free (&new_table->entry_stack, NULL);
869 new_table->entry_stack = table->entry_stack;
871 new_table->free_entry_list = table->free_entry_list;
873 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
875 for (cursor = bucket; cursor; cursor = next)
877 void *data = cursor->data;
878 struct hash_entry *new_bucket
880 + new_table->hasher (data, new_table->n_buckets));
882 if (! (new_bucket < new_table->bucket_limit))
887 if (new_bucket->data)
889 if (cursor == bucket)
891 /* Allocate or recycle an entry, when moving from a bucket
892 header into a bucket overflow. */
893 struct hash_entry *new_entry = allocate_entry (new_table);
895 if (new_entry == NULL)
898 new_entry->data = data;
899 new_entry->next = new_bucket->next;
900 new_bucket->next = new_entry;
904 /* Merely relink an existing entry, when moving from a
905 bucket overflow into a bucket overflow. */
906 cursor->next = new_bucket->next;
907 new_bucket->next = cursor;
912 /* Free an existing entry, when moving from a bucket
913 overflow into a bucket header. Also take care of the
914 simple case of moving from a bucket header into a bucket
916 new_bucket->data = data;
917 new_table->n_buckets_used++;
918 if (cursor != bucket)
919 free_entry (new_table, cursor);
923 free (table->bucket);
924 table->bucket = new_table->bucket;
925 table->bucket_limit = new_table->bucket_limit;
926 table->n_buckets = new_table->n_buckets;
927 table->n_buckets_used = new_table->n_buckets_used;
928 table->free_entry_list = new_table->free_entry_list;
929 /* table->n_entries already holds its value. */
931 table->entry_stack = new_table->entry_stack;
938 /* If ENTRY matches an entry already in the hash table, return the pointer
939 to the entry from the table. Otherwise, insert ENTRY and return ENTRY.
940 Return NULL if the storage required for insertion cannot be allocated.
941 This implementation does not support duplicate entries or insertion of
945 hash_insert (Hash_table *table, const void *entry)
948 struct hash_entry *bucket;
950 /* The caller cannot insert a NULL entry. */
954 /* If there's a matching entry already in the table, return that. */
955 if ((data = hash_find_entry (table, entry, &bucket, false)) != NULL)
958 /* If the growth threshold of the buckets in use has been reached, increase
959 the table size and rehash. There's no point in checking the number of
960 entries: if the hashing function is ill-conditioned, rehashing is not
961 likely to improve it. */
963 if (table->n_buckets_used
964 > table->tuning->growth_threshold * table->n_buckets)
966 /* Check more fully, before starting real work. If tuning arguments
967 became invalid, the second check will rely on proper defaults. */
968 check_tuning (table);
969 if (table->n_buckets_used
970 > table->tuning->growth_threshold * table->n_buckets)
972 const Hash_tuning *tuning = table->tuning;
974 (tuning->is_n_buckets
975 ? (table->n_buckets * tuning->growth_factor)
976 : (table->n_buckets * tuning->growth_factor
977 * tuning->growth_threshold));
979 if (SIZE_MAX <= candidate)
982 /* If the rehash fails, arrange to return NULL. */
983 if (!hash_rehash (table, candidate))
986 /* Update the bucket we are interested in. */
987 if (hash_find_entry (table, entry, &bucket, false) != NULL)
992 /* ENTRY is not matched, it should be inserted. */
996 struct hash_entry *new_entry = allocate_entry (table);
998 if (new_entry == NULL)
1001 /* Add ENTRY in the overflow of the bucket. */
1003 new_entry->data = (void *) entry;
1004 new_entry->next = bucket->next;
1005 bucket->next = new_entry;
1007 return (void *) entry;
1010 /* Add ENTRY right in the bucket head. */
1012 bucket->data = (void *) entry;
1014 table->n_buckets_used++;
1016 return (void *) entry;
1019 /* If ENTRY is already in the table, remove it and return the just-deleted
1020 data (the user may want to deallocate its storage). If ENTRY is not in the
1021 table, don't modify the table and return NULL. */
1024 hash_delete (Hash_table *table, const void *entry)
1027 struct hash_entry *bucket;
1029 data = hash_find_entry (table, entry, &bucket, true);
1036 table->n_buckets_used--;
1038 /* If the shrink threshold of the buckets in use has been reached,
1039 rehash into a smaller table. */
1041 if (table->n_buckets_used
1042 < table->tuning->shrink_threshold * table->n_buckets)
1044 /* Check more fully, before starting real work. If tuning arguments
1045 became invalid, the second check will rely on proper defaults. */
1046 check_tuning (table);
1047 if (table->n_buckets_used
1048 < table->tuning->shrink_threshold * table->n_buckets)
1050 const Hash_tuning *tuning = table->tuning;
1052 (tuning->is_n_buckets
1053 ? table->n_buckets * tuning->shrink_factor
1054 : (table->n_buckets * tuning->shrink_factor
1055 * tuning->growth_threshold));
1057 hash_rehash (table, candidate);
1070 hash_print (const Hash_table *table)
1072 struct hash_entry const *bucket;
1074 for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
1076 struct hash_entry *cursor;
1079 printf ("%lu:\n", (unsigned long int) (bucket - table->bucket));
1081 for (cursor = bucket; cursor; cursor = cursor->next)
1083 char const *s = cursor->data;
1086 printf (" %s\n", s);
1091 #endif /* TESTING */