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- Committer: Bazaar Package Importer
- Author(s): Christoph Berg
- Date: 2009-12-02 10:25:26 UTC
- mfrom: (5.1.1 sid)
- Revision ID: james.westby@ubuntu.com-20091202102526-5luk0zsqhghu58l2
Tags: 2.6-2
* Update watch file.
* Section: vcs.
* Suggests: diffutils-doc instead of diff-doc, thanks Christoph Anton
Mitterer for spotting. Closes: #558974.
* Section: vcs.
* Suggests: diffutils-doc instead of diff-doc, thanks Christoph Anton
Mitterer for spotting. Closes: #558974.
added
removed
hash.c
1
/* hash - hashing table processing.
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3
Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Free Software
4
Foundation, Inc.
5
6
Written by Jim Meyering, 1992.
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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
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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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.
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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. */
21
22
/* A generic hash table package. */
23
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! */
26
27
#if HAVE_CONFIG_H
28
# include <config.h>
29
#endif
30
#if HAVE_STDLIB_H
31
# include <stdlib.h>
32
#endif
33
34
#include <limits.h>
35
#include <stdbool.h>
36
#include <stdio.h>
37
38
#ifndef HAVE_DECL_FREE
39
"this configure-time declaration test was not run"
40
#endif
41
#if !HAVE_DECL_FREE
42
void free ();
43
#endif
44
45
#ifndef HAVE_DECL_MALLOC
46
"this configure-time declaration test was not run"
47
#endif
48
#if !HAVE_DECL_MALLOC
49
char *malloc ();
50
#endif
51
52
#if USE_OBSTACK
53
# include "obstack.h"
54
# ifndef obstack_chunk_alloc
55
# define obstack_chunk_alloc malloc
56
# endif
57
# ifndef obstack_chunk_free
58
# define obstack_chunk_free free
59
# endif
60
#endif
61
62
#include "hash.h"
63
64
struct hash_table
65
{
66
/* The array of buckets starts at BUCKET and extends to BUCKET_LIMIT-1,
67
for a possibility of N_BUCKETS. Among those, N_BUCKETS_USED buckets
68
are not empty, there are N_ENTRIES active entries in the table. */
69
struct hash_entry *bucket;
70
struct hash_entry *bucket_limit;
71
unsigned n_buckets;
72
unsigned n_buckets_used;
73
unsigned n_entries;
74
75
/* Tuning arguments, kept in a physicaly separate structure. */
76
const Hash_tuning *tuning;
77
78
/* Three functions are given to `hash_initialize', see the documentation
79
block for this function. In a word, HASHER randomizes a user entry
80
into a number up from 0 up to some maximum minus 1; COMPARATOR returns
81
true if two user entries compare equally; and DATA_FREER is the cleanup
82
function for a user entry. */
83
Hash_hasher hasher;
84
Hash_comparator comparator;
85
Hash_data_freer data_freer;
86
87
/* A linked list of freed struct hash_entry structs. */
88
struct hash_entry *free_entry_list;
89
90
#if USE_OBSTACK
91
/* Whenever obstacks are used, it is possible to allocate all overflowed
92
entries into a single stack, so they all can be freed in a single
93
operation. It is not clear if the speedup is worth the trouble. */
94
struct obstack entry_stack;
95
#endif
96
};
97
98
/* A hash table contains many internal entries, each holding a pointer to
99
some user provided data (also called a user entry). An entry indistinctly
100
refers to both the internal entry and its associated user entry. A user
101
entry contents may be hashed by a randomization function (the hashing
102
function, or just `hasher' for short) into a number (or `slot') between 0
103
and the current table size. At each slot position in the hash table,
104
starts a linked chain of entries for which the user data all hash to this
105
slot. A bucket is the collection of all entries hashing to the same slot.
106
107
A good `hasher' function will distribute entries rather evenly in buckets.
108
In the ideal case, the length of each bucket is roughly the number of
109
entries divided by the table size. Finding the slot for a data is usually
110
done in constant time by the `hasher', and the later finding of a precise
111
entry is linear in time with the size of the bucket. Consequently, a
112
larger hash table size (that is, a larger number of buckets) is prone to
113
yielding shorter chains, *given* the `hasher' function behaves properly.
114
115
Long buckets slow down the lookup algorithm. One might use big hash table
116
sizes in hope to reduce the average length of buckets, but this might
117
become inordinate, as unused slots in the hash table take some space. The
118
best bet is to make sure you are using a good `hasher' function (beware
119
that those are not that easy to write! :-), and to use a table size
120
larger than the actual number of entries. */
121
122
/* If an insertion makes the ratio of nonempty buckets to table size larger
123
than the growth threshold (a number between 0.0 and 1.0), then increase
124
the table size by multiplying by the growth factor (a number greater than
125
1.0). The growth threshold defaults to 0.8, and the growth factor
126
defaults to 1.414, meaning that the table will have doubled its size
127
every second time 80% of the buckets get used. */
128
#define DEFAULT_GROWTH_THRESHOLD 0.8
129
#define DEFAULT_GROWTH_FACTOR 1.414
130
131
/* If a deletion empties a bucket and causes the ratio of used buckets to
132
table size to become smaller than the shrink threshold (a number between
133
0.0 and 1.0), then shrink the table by multiplying by the shrink factor (a
134
number greater than the shrink threshold but smaller than 1.0). The shrink
135
threshold and factor default to 0.0 and 1.0, meaning that the table never
136
shrinks. */
137
#define DEFAULT_SHRINK_THRESHOLD 0.0
138
#define DEFAULT_SHRINK_FACTOR 1.0
139
140
/* Use this to initialize or reset a TUNING structure to
141
some sensible values. */
142
static const Hash_tuning default_tuning =
143
{
144
DEFAULT_SHRINK_THRESHOLD,
145
DEFAULT_SHRINK_FACTOR,
146
DEFAULT_GROWTH_THRESHOLD,
147
DEFAULT_GROWTH_FACTOR,
148
false
149
};
150
151
/* Information and lookup. */
152
153
/* The following few functions provide information about the overall hash
154
table organization: the number of entries, number of buckets and maximum
155
length of buckets. */
156
157
/* Return the number of buckets in the hash table. The table size, the total
158
number of buckets (used plus unused), or the maximum number of slots, are
159
the same quantity. */
160
161
unsigned
162
hash_get_n_buckets (const Hash_table *table)
163
{
164
return table->n_buckets;
165
}
166
167
/* Return the number of slots in use (non-empty buckets). */
168
169
unsigned
170
hash_get_n_buckets_used (const Hash_table *table)
171
{
172
return table->n_buckets_used;
173
}
174
175
/* Return the number of active entries. */
176
177
unsigned
178
hash_get_n_entries (const Hash_table *table)
179
{
180
return table->n_entries;
181
}
182
183
/* Return the length of the longest chain (bucket). */
184
185
unsigned
186
hash_get_max_bucket_length (const Hash_table *table)
187
{
188
struct hash_entry *bucket;
189
unsigned max_bucket_length = 0;
190
191
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
192
{
193
if (bucket->data)
194
{
195
struct hash_entry *cursor = bucket;
196
unsigned bucket_length = 1;
197
198
while (cursor = cursor->next, cursor)
199
bucket_length++;
200
201
if (bucket_length > max_bucket_length)
202
max_bucket_length = bucket_length;
203
}
204
}
205
206
return max_bucket_length;
207
}
208
209
/* Do a mild validation of a hash table, by traversing it and checking two
210
statistics. */
211
212
bool
213
hash_table_ok (const Hash_table *table)
214
{
215
struct hash_entry *bucket;
216
unsigned n_buckets_used = 0;
217
unsigned n_entries = 0;
218
219
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
220
{
221
if (bucket->data)
222
{
223
struct hash_entry *cursor = bucket;
224
225
/* Count bucket head. */
226
n_buckets_used++;
227
n_entries++;
228
229
/* Count bucket overflow. */
230
while (cursor = cursor->next, cursor)
231
n_entries++;
232
}
233
}
234
235
if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries)
236
return true;
237
238
return false;
239
}
240
241
void
242
hash_print_statistics (const Hash_table *table, FILE *stream)
243
{
244
unsigned n_entries = hash_get_n_entries (table);
245
unsigned n_buckets = hash_get_n_buckets (table);
246
unsigned n_buckets_used = hash_get_n_buckets_used (table);
247
unsigned max_bucket_length = hash_get_max_bucket_length (table);
248
249
fprintf (stream, "# entries: %u\n", n_entries);
250
fprintf (stream, "# buckets: %u\n", n_buckets);
251
fprintf (stream, "# buckets used: %u (%.2f%%)\n", n_buckets_used,
252
(100.0 * n_buckets_used) / n_buckets);
253
fprintf (stream, "max bucket length: %u\n", max_bucket_length);
254
}
255
256
/* If ENTRY matches an entry already in the hash table, return the
257
entry from the table. Otherwise, return NULL. */
258
259
void *
260
hash_lookup (const Hash_table *table, const void *entry)
261
{
262
struct hash_entry *bucket
263
= table->bucket + table->hasher (entry, table->n_buckets);
264
struct hash_entry *cursor;
265
266
if (! (bucket < table->bucket_limit))
267
abort ();
268
269
if (bucket->data == NULL)
270
return NULL;
271
272
for (cursor = bucket; cursor; cursor = cursor->next)
273
if (table->comparator (entry, cursor->data))
274
return cursor->data;
275
276
return NULL;
277
}
278
279
/* Walking. */
280
281
/* The functions in this page traverse the hash table and process the
282
contained entries. For the traversal to work properly, the hash table
283
should not be resized nor modified while any particular entry is being
284
processed. In particular, entries should not be added or removed. */
285
286
/* Return the first data in the table, or NULL if the table is empty. */
287
288
void *
289
hash_get_first (const Hash_table *table)
290
{
291
struct hash_entry *bucket;
292
293
if (table->n_entries == 0)
294
return NULL;
295
296
for (bucket = table->bucket; ; bucket++)
297
if (! (bucket < table->bucket_limit))
298
abort ();
299
else if (bucket->data)
300
return bucket->data;
301
}
302
303
/* Return the user data for the entry following ENTRY, where ENTRY has been
304
returned by a previous call to either `hash_get_first' or `hash_get_next'.
305
Return NULL if there are no more entries. */
306
307
void *
308
hash_get_next (const Hash_table *table, const void *entry)
309
{
310
struct hash_entry *bucket
311
= table->bucket + table->hasher (entry, table->n_buckets);
312
struct hash_entry *cursor;
313
314
if (! (bucket < table->bucket_limit))
315
abort ();
316
317
/* Find next entry in the same bucket. */
318
for (cursor = bucket; cursor; cursor = cursor->next)
319
if (cursor->data == entry && cursor->next)
320
return cursor->next->data;
321
322
/* Find first entry in any subsequent bucket. */
323
while (++bucket < table->bucket_limit)
324
if (bucket->data)
325
return bucket->data;
326
327
/* None found. */
328
return NULL;
329
}
330
331
/* Fill BUFFER with pointers to active user entries in the hash table, then
332
return the number of pointers copied. Do not copy more than BUFFER_SIZE
333
pointers. */
334
335
unsigned
336
hash_get_entries (const Hash_table *table, void **buffer,
337
unsigned buffer_size)
338
{
339
unsigned counter = 0;
340
struct hash_entry *bucket;
341
struct hash_entry *cursor;
342
343
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
344
{
345
if (bucket->data)
346
{
347
for (cursor = bucket; cursor; cursor = cursor->next)
348
{
349
if (counter >= buffer_size)
350
return counter;
351
buffer[counter++] = cursor->data;
352
}
353
}
354
}
355
356
return counter;
357
}
358
359
/* Call a PROCESSOR function for each entry of a hash table, and return the
360
number of entries for which the processor function returned success. A
361
pointer to some PROCESSOR_DATA which will be made available to each call to
362
the processor function. The PROCESSOR accepts two arguments: the first is
363
the user entry being walked into, the second is the value of PROCESSOR_DATA
364
as received. The walking continue for as long as the PROCESSOR function
365
returns nonzero. When it returns zero, the walking is interrupted. */
366
367
unsigned
368
hash_do_for_each (const Hash_table *table, Hash_processor processor,
369
void *processor_data)
370
{
371
unsigned counter = 0;
372
struct hash_entry *bucket;
373
struct hash_entry *cursor;
374
375
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
376
{
377
if (bucket->data)
378
{
379
for (cursor = bucket; cursor; cursor = cursor->next)
380
{
381
if (!(*processor) (cursor->data, processor_data))
382
return counter;
383
counter++;
384
}
385
}
386
}
387
388
return counter;
389
}
390
391
/* Allocation and clean-up. */
392
393
/* Return a hash index for a NUL-terminated STRING between 0 and N_BUCKETS-1.
394
This is a convenience routine for constructing other hashing functions. */
395
396
#if USE_DIFF_HASH
397
398
/* About hashings, Paul Eggert writes to me (FP), on 1994-01-01: "Please see
399
B. J. McKenzie, R. Harries & T. Bell, Selecting a hashing algorithm,
400
Software--practice & experience 20, 2 (Feb 1990), 209-224. Good hash
401
algorithms tend to be domain-specific, so what's good for [diffutils'] io.c
402
may not be good for your application." */
403
404
unsigned
405
hash_string (const char *string, unsigned n_buckets)
406
{
407
# define ROTATE_LEFT(Value, Shift) \
408
((Value) << (Shift) | (Value) >> ((sizeof (unsigned) * CHAR_BIT) - (Shift)))
409
# define HASH_ONE_CHAR(Value, Byte) \
410
((Byte) + ROTATE_LEFT (Value, 7))
411
412
unsigned value = 0;
413
414
for (; *string; string++)
415
value = HASH_ONE_CHAR (value, *(const unsigned char *) string);
416
return value % n_buckets;
417
418
# undef ROTATE_LEFT
419
# undef HASH_ONE_CHAR
420
}
421
422
#else /* not USE_DIFF_HASH */
423
424
/* This one comes from `recode', and performs a bit better than the above as
425
per a few experiments. It is inspired from a hashing routine found in the
426
very old Cyber `snoop', itself written in typical Greg Mansfield style.
427
(By the way, what happened to this excellent man? Is he still alive?) */
428
429
unsigned
430
hash_string (const char *string, unsigned n_buckets)
431
{
432
unsigned value = 0;
433
434
while (*string)
435
value = ((value * 31 + (int) *(const unsigned char *) string++)
436
% n_buckets);
437
return value;
438
}
439
440
#endif /* not USE_DIFF_HASH */
441
442
/* Return true if CANDIDATE is a prime number. CANDIDATE should be an odd
443
number at least equal to 11. */
444
445
static bool
446
is_prime (unsigned long candidate)
447
{
448
unsigned long divisor = 3;
449
unsigned long square = divisor * divisor;
450
451
while (square < candidate && (candidate % divisor))
452
{
453
divisor++;
454
square += 4 * divisor;
455
divisor++;
456
}
457
458
return (candidate % divisor ? true : false);
459
}
460
461
/* Round a given CANDIDATE number up to the nearest prime, and return that
462
prime. Primes lower than 10 are merely skipped. */
463
464
static unsigned long
465
next_prime (unsigned long candidate)
466
{
467
/* Skip small primes. */
468
if (candidate < 10)
469
candidate = 10;
470
471
/* Make it definitely odd. */
472
candidate |= 1;
473
474
while (!is_prime (candidate))
475
candidate += 2;
476
477
return candidate;
478
}
479
480
void
481
hash_reset_tuning (Hash_tuning *tuning)
482
{
483
*tuning = default_tuning;
484
}
485
486
/* For the given hash TABLE, check the user supplied tuning structure for
487
reasonable values, and return true if there is no gross error with it.
488
Otherwise, definitively reset the TUNING field to some acceptable default
489
in the hash table (that is, the user loses the right of further modifying
490
tuning arguments), and return false. */
491
492
static bool
493
check_tuning (Hash_table *table)
494
{
495
const Hash_tuning *tuning = table->tuning;
496
497
if (tuning->growth_threshold > 0.0
498
&& tuning->growth_threshold < 1.0
499
&& tuning->growth_factor > 1.0
500
&& tuning->shrink_threshold >= 0.0
501
&& tuning->shrink_threshold < 1.0
502
&& tuning->shrink_factor > tuning->shrink_threshold
503
&& tuning->shrink_factor <= 1.0
504
&& tuning->shrink_threshold < tuning->growth_threshold)
505
return true;
506
507
table->tuning = &default_tuning;
508
return false;
509
}
510
511
/* Allocate and return a new hash table, or NULL upon failure. The initial
512
number of buckets is automatically selected so as to _guarantee_ that you
513
may insert at least CANDIDATE different user entries before any growth of
514
the hash table size occurs. So, if have a reasonably tight a-priori upper
515
bound on the number of entries you intend to insert in the hash table, you
516
may save some table memory and insertion time, by specifying it here. If
517
the IS_N_BUCKETS field of the TUNING structure is true, the CANDIDATE
518
argument has its meaning changed to the wanted number of buckets.
519
520
TUNING points to a structure of user-supplied values, in case some fine
521
tuning is wanted over the default behavior of the hasher. If TUNING is
522
NULL, the default tuning parameters are used instead.
523
524
The user-supplied HASHER function should be provided. It accepts two
525
arguments ENTRY and TABLE_SIZE. It computes, by hashing ENTRY contents, a
526
slot number for that entry which should be in the range 0..TABLE_SIZE-1.
527
This slot number is then returned.
528
529
The user-supplied COMPARATOR function should be provided. It accepts two
530
arguments pointing to user data, it then returns true for a pair of entries
531
that compare equal, or false otherwise. This function is internally called
532
on entries which are already known to hash to the same bucket index.
533
534
The user-supplied DATA_FREER function, when not NULL, may be later called
535
with the user data as an argument, just before the entry containing the
536
data gets freed. This happens from within `hash_free' or `hash_clear'.
537
You should specify this function only if you want these functions to free
538
all of your `data' data. This is typically the case when your data is
539
simply an auxiliary struct that you have malloc'd to aggregate several
540
values. */
541
542
Hash_table *
543
hash_initialize (unsigned candidate, const Hash_tuning *tuning,
544
Hash_hasher hasher, Hash_comparator comparator,
545
Hash_data_freer data_freer)
546
{
547
Hash_table *table;
548
struct hash_entry *bucket;
549
550
if (hasher == NULL || comparator == NULL)
551
return NULL;
552
553
table = (Hash_table *) malloc (sizeof (Hash_table));
554
if (table == NULL)
555
return NULL;
556
557
if (!tuning)
558
tuning = &default_tuning;
559
table->tuning = tuning;
560
if (!check_tuning (table))
561
{
562
/* Fail if the tuning options are invalid. This is the only occasion
563
when the user gets some feedback about it. Once the table is created,
564
if the user provides invalid tuning options, we silently revert to
565
using the defaults, and ignore further request to change the tuning
566
options. */
567
free (table);
568
return NULL;
569
}
570
571
table->n_buckets
572
= next_prime (tuning->is_n_buckets ? candidate
573
: (unsigned) (candidate / tuning->growth_threshold));
574
575
table->bucket = (struct hash_entry *)
576
malloc (table->n_buckets * sizeof (struct hash_entry));
577
if (table->bucket == NULL)
578
{
579
free (table);
580
return NULL;
581
}
582
table->bucket_limit = table->bucket + table->n_buckets;
583
584
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
585
{
586
bucket->data = NULL;
587
bucket->next = NULL;
588
}
589
table->n_buckets_used = 0;
590
table->n_entries = 0;
591
592
table->hasher = hasher;
593
table->comparator = comparator;
594
table->data_freer = data_freer;
595
596
table->free_entry_list = NULL;
597
#if USE_OBSTACK
598
obstack_init (&table->entry_stack);
599
#endif
600
return table;
601
}
602
603
/* Make all buckets empty, placing any chained entries on the free list.
604
Apply the user-specified function data_freer (if any) to the datas of any
605
affected entries. */
606
607
void
608
hash_clear (Hash_table *table)
609
{
610
struct hash_entry *bucket;
611
612
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
613
{
614
if (bucket->data)
615
{
616
struct hash_entry *cursor;
617
struct hash_entry *next;
618
619
/* Free the bucket overflow. */
620
for (cursor = bucket->next; cursor; cursor = next)
621
{
622
if (table->data_freer)
623
(*table->data_freer) (cursor->data);
624
cursor->data = NULL;
625
626
next = cursor->next;
627
/* Relinking is done one entry at a time, as it is to be expected
628
that overflows are either rare or short. */
629
cursor->next = table->free_entry_list;
630
table->free_entry_list = cursor;
631
}
632
633
/* Free the bucket head. */
634
if (table->data_freer)
635
(*table->data_freer) (bucket->data);
636
bucket->data = NULL;
637
bucket->next = NULL;
638
}
639
}
640
641
table->n_buckets_used = 0;
642
table->n_entries = 0;
643
}
644
645
/* Reclaim all storage associated with a hash table. If a data_freer
646
function has been supplied by the user when the hash table was created,
647
this function applies it to the data of each entry before freeing that
648
entry. */
649
650
void
651
hash_free (Hash_table *table)
652
{
653
struct hash_entry *bucket;
654
struct hash_entry *cursor;
655
struct hash_entry *next;
656
657
/* Call the user data_freer function. */
658
if (table->data_freer && table->n_entries)
659
{
660
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
661
{
662
if (bucket->data)
663
{
664
for (cursor = bucket; cursor; cursor = cursor->next)
665
{
666
(*table->data_freer) (cursor->data);
667
}
668
}
669
}
670
}
671
672
#if USE_OBSTACK
673
674
obstack_free (&table->entry_stack, NULL);
675
676
#else
677
678
/* Free all bucket overflowed entries. */
679
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
680
{
681
for (cursor = bucket->next; cursor; cursor = next)
682
{
683
next = cursor->next;
684
free (cursor);
685
}
686
}
687
688
/* Also reclaim the internal list of previously freed entries. */
689
for (cursor = table->free_entry_list; cursor; cursor = next)
690
{
691
next = cursor->next;
692
free (cursor);
693
}
694
695
#endif
696
697
/* Free the remainder of the hash table structure. */
698
free (table->bucket);
699
free (table);
700
}
701
702
/* Insertion and deletion. */
703
704
/* Get a new hash entry for a bucket overflow, possibly by reclying a
705
previously freed one. If this is not possible, allocate a new one. */
706
707
static struct hash_entry *
708
allocate_entry (Hash_table *table)
709
{
710
struct hash_entry *new;
711
712
if (table->free_entry_list)
713
{
714
new = table->free_entry_list;
715
table->free_entry_list = new->next;
716
}
717
else
718
{
719
#if USE_OBSTACK
720
new = (struct hash_entry *)
721
obstack_alloc (&table->entry_stack, sizeof (struct hash_entry));
722
#else
723
new = (struct hash_entry *) malloc (sizeof (struct hash_entry));
724
#endif
725
}
726
727
return new;
728
}
729
730
/* Free a hash entry which was part of some bucket overflow,
731
saving it for later recycling. */
732
733
static void
734
free_entry (Hash_table *table, struct hash_entry *entry)
735
{
736
entry->data = NULL;
737
entry->next = table->free_entry_list;
738
table->free_entry_list = entry;
739
}
740
741
/* This private function is used to help with insertion and deletion. When
742
ENTRY matches an entry in the table, return a pointer to the corresponding
743
user data and set *BUCKET_HEAD to the head of the selected bucket.
744
Otherwise, return NULL. When DELETE is true and ENTRY matches an entry in
745
the table, unlink the matching entry. */
746
747
static void *
748
hash_find_entry (Hash_table *table, const void *entry,
749
struct hash_entry **bucket_head, bool delete)
750
{
751
struct hash_entry *bucket
752
= table->bucket + table->hasher (entry, table->n_buckets);
753
struct hash_entry *cursor;
754
755
if (! (bucket < table->bucket_limit))
756
abort ();
757
758
*bucket_head = bucket;
759
760
/* Test for empty bucket. */
761
if (bucket->data == NULL)
762
return NULL;
763
764
/* See if the entry is the first in the bucket. */
765
if ((*table->comparator) (entry, bucket->data))
766
{
767
void *data = bucket->data;
768
769
if (delete)
770
{
771
if (bucket->next)
772
{
773
struct hash_entry *next = bucket->next;
774
775
/* Bump the first overflow entry into the bucket head, then save
776
the previous first overflow entry for later recycling. */
777
*bucket = *next;
778
free_entry (table, next);
779
}
780
else
781
{
782
bucket->data = NULL;
783
}
784
}
785
786
return data;
787
}
788
789
/* Scan the bucket overflow. */
790
for (cursor = bucket; cursor->next; cursor = cursor->next)
791
{
792
if ((*table->comparator) (entry, cursor->next->data))
793
{
794
void *data = cursor->next->data;
795
796
if (delete)
797
{
798
struct hash_entry *next = cursor->next;
799
800
/* Unlink the entry to delete, then save the freed entry for later
801
recycling. */
802
cursor->next = next->next;
803
free_entry (table, next);
804
}
805
806
return data;
807
}
808
}
809
810
/* No entry found. */
811
return NULL;
812
}
813
814
/* For an already existing hash table, change the number of buckets through
815
specifying CANDIDATE. The contents of the hash table are preserved. The
816
new number of buckets is automatically selected so as to _guarantee_ that
817
the table may receive at least CANDIDATE different user entries, including
818
those already in the table, before any other growth of the hash table size
819
occurs. If TUNING->IS_N_BUCKETS is true, then CANDIDATE specifies the
820
exact number of buckets desired. */
821
822
bool
823
hash_rehash (Hash_table *table, unsigned candidate)
824
{
825
Hash_table *new_table;
826
struct hash_entry *bucket;
827
struct hash_entry *cursor;
828
struct hash_entry *next;
829
830
new_table = hash_initialize (candidate, table->tuning, table->hasher,
831
table->comparator, table->data_freer);
832
if (new_table == NULL)
833
return false;
834
835
/* Merely reuse the extra old space into the new table. */
836
#if USE_OBSTACK
837
obstack_free (&new_table->entry_stack, NULL);
838
new_table->entry_stack = table->entry_stack;
839
#endif
840
new_table->free_entry_list = table->free_entry_list;
841
842
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
843
if (bucket->data)
844
for (cursor = bucket; cursor; cursor = next)
845
{
846
void *data = cursor->data;
847
struct hash_entry *new_bucket
848
= (new_table->bucket
849
+ new_table->hasher (data, new_table->n_buckets));
850
851
if (! (new_bucket < new_table->bucket_limit))
852
abort ();
853
854
next = cursor->next;
855
856
if (new_bucket->data)
857
{
858
if (cursor == bucket)
859
{
860
/* Allocate or recycle an entry, when moving from a bucket
861
header into a bucket overflow. */
862
struct hash_entry *new_entry = allocate_entry (new_table);
863
864
if (new_entry == NULL)
865
return false;
866
867
new_entry->data = data;
868
new_entry->next = new_bucket->next;
869
new_bucket->next = new_entry;
870
}
871
else
872
{
873
/* Merely relink an existing entry, when moving from a
874
bucket overflow into a bucket overflow. */
875
cursor->next = new_bucket->next;
876
new_bucket->next = cursor;
877
}
878
}
879
else
880
{
881
/* Free an existing entry, when moving from a bucket
882
overflow into a bucket header. Also take care of the
883
simple case of moving from a bucket header into a bucket
884
header. */
885
new_bucket->data = data;
886
new_table->n_buckets_used++;
887
if (cursor != bucket)
888
free_entry (new_table, cursor);
889
}
890
}
891
892
free (table->bucket);
893
table->bucket = new_table->bucket;
894
table->bucket_limit = new_table->bucket_limit;
895
table->n_buckets = new_table->n_buckets;
896
table->n_buckets_used = new_table->n_buckets_used;
897
table->free_entry_list = new_table->free_entry_list;
898
/* table->n_entries already holds its value. */
899
#if USE_OBSTACK
900
table->entry_stack = new_table->entry_stack;
901
#endif
902
free (new_table);
903
904
return true;
905
}
906
907
/* If ENTRY matches an entry already in the hash table, return the pointer
908
to the entry from the table. Otherwise, insert ENTRY and return ENTRY.
909
Return NULL if the storage required for insertion cannot be allocated. */
910
911
void *
912
hash_insert (Hash_table *table, const void *entry)
913
{
914
void *data;
915
struct hash_entry *bucket;
916
917
/* The caller cannot insert a NULL entry. */
918
if (! entry)
919
abort ();
920
921
/* If there's a matching entry already in the table, return that. */
922
if ((data = hash_find_entry (table, entry, &bucket, false)) != NULL)
923
return data;
924
925
/* ENTRY is not matched, it should be inserted. */
926
927
if (bucket->data)
928
{
929
struct hash_entry *new_entry = allocate_entry (table);
930
931
if (new_entry == NULL)
932
return NULL;
933
934
/* Add ENTRY in the overflow of the bucket. */
935
936
new_entry->data = (void *) entry;
937
new_entry->next = bucket->next;
938
bucket->next = new_entry;
939
table->n_entries++;
940
return (void *) entry;
941
}
942
943
/* Add ENTRY right in the bucket head. */
944
945
bucket->data = (void *) entry;
946
table->n_entries++;
947
table->n_buckets_used++;
948
949
/* If the growth threshold of the buckets in use has been reached, increase
950
the table size and rehash. There's no point in checking the number of
951
entries: if the hashing function is ill-conditioned, rehashing is not
952
likely to improve it. */
953
954
if (table->n_buckets_used
955
> table->tuning->growth_threshold * table->n_buckets)
956
{
957
/* Check more fully, before starting real work. If tuning arguments
958
became invalid, the second check will rely on proper defaults. */
959
check_tuning (table);
960
if (table->n_buckets_used
961
> table->tuning->growth_threshold * table->n_buckets)
962
{
963
const Hash_tuning *tuning = table->tuning;
964
unsigned candidate
965
= (unsigned) (tuning->is_n_buckets
966
? (table->n_buckets * tuning->growth_factor)
967
: (table->n_buckets * tuning->growth_factor
968
* tuning->growth_threshold));
969
970
/* If the rehash fails, arrange to return NULL. */
971
if (!hash_rehash (table, candidate))
972
entry = NULL;
973
}
974
}
975
976
return (void *) entry;
977
}
978
979
/* If ENTRY is already in the table, remove it and return the just-deleted
980
data (the user may want to deallocate its storage). If ENTRY is not in the
981
table, don't modify the table and return NULL. */
982
983
void *
984
hash_delete (Hash_table *table, const void *entry)
985
{
986
void *data;
987
struct hash_entry *bucket;
988
989
data = hash_find_entry (table, entry, &bucket, true);
990
if (!data)
991
return NULL;
992
993
table->n_entries--;
994
if (!bucket->data)
995
{
996
table->n_buckets_used--;
997
998
/* If the shrink threshold of the buckets in use has been reached,
999
rehash into a smaller table. */
1000
1001
if (table->n_buckets_used
1002
< table->tuning->shrink_threshold * table->n_buckets)
1003
{
1004
/* Check more fully, before starting real work. If tuning arguments
1005
became invalid, the second check will rely on proper defaults. */
1006
check_tuning (table);
1007
if (table->n_buckets_used
1008
< table->tuning->shrink_threshold * table->n_buckets)
1009
{
1010
const Hash_tuning *tuning = table->tuning;
1011
unsigned candidate
1012
= (unsigned) (tuning->is_n_buckets
1013
? table->n_buckets * tuning->shrink_factor
1014
: (table->n_buckets * tuning->shrink_factor
1015
* tuning->growth_threshold));
1016
1017
hash_rehash (table, candidate);
1018
}
1019
}
1020
}
1021
1022
return data;
1023
}
1024
1025
/* Testing. */
1026
1027
#if TESTING
1028
1029
void
1030
hash_print (const Hash_table *table)
1031
{
1032
struct hash_entry *bucket;
1033
1034
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
1035
{
1036
struct hash_entry *cursor;
1037
1038
if (bucket)
1039
printf ("%d:\n", bucket - table->bucket);
1040
1041
for (cursor = bucket; cursor; cursor = cursor->next)
1042
{
1043
char *s = (char *) cursor->data;
1044
/* FIXME */
1045
if (s)
1046
printf (" %s\n", s);
1047
}
1048
}
1049
}
1050
1051
#endif /* TESTING */
Loggerhead is a web-based interface for Breezy
Version: 2.0.1