re PR c/70688 (bogus OpenACC data clause errors involving reductions)
[official-gcc.git] / libiberty / hashtab.c
blob04607ea6a0167bb2c48a7ac847bc5ac968b3a783
1 /* An expandable hash tables datatype.
2 Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2009, 2010
3 Free Software Foundation, Inc.
4 Contributed by Vladimir Makarov (vmakarov@cygnus.com).
6 This file is part of the libiberty library.
7 Libiberty is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Library General Public
9 License as published by the Free Software Foundation; either
10 version 2 of the License, or (at your option) any later version.
12 Libiberty is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Library General Public License for more details.
17 You should have received a copy of the GNU Library General Public
18 License along with libiberty; see the file COPYING.LIB. If
19 not, write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
20 Boston, MA 02110-1301, USA. */
22 /* This package implements basic hash table functionality. It is possible
23 to search for an entry, create an entry and destroy an entry.
25 Elements in the table are generic pointers.
27 The size of the table is not fixed; if the occupancy of the table
28 grows too high the hash table will be expanded.
30 The abstract data implementation is based on generalized Algorithm D
31 from Knuth's book "The art of computer programming". Hash table is
32 expanded by creation of new hash table and transferring elements from
33 the old table to the new table. */
35 #ifdef HAVE_CONFIG_H
36 #include "config.h"
37 #endif
39 #include <sys/types.h>
41 #ifdef HAVE_STDLIB_H
42 #include <stdlib.h>
43 #endif
44 #ifdef HAVE_STRING_H
45 #include <string.h>
46 #endif
47 #ifdef HAVE_MALLOC_H
48 #include <malloc.h>
49 #endif
50 #ifdef HAVE_LIMITS_H
51 #include <limits.h>
52 #endif
53 #ifdef HAVE_INTTYPES_H
54 #include <inttypes.h>
55 #endif
56 #ifdef HAVE_STDINT_H
57 #include <stdint.h>
58 #endif
60 #include <stdio.h>
62 #include "libiberty.h"
63 #include "ansidecl.h"
64 #include "hashtab.h"
66 #ifndef CHAR_BIT
67 #define CHAR_BIT 8
68 #endif
70 static unsigned int higher_prime_index (unsigned long);
71 static hashval_t htab_mod_1 (hashval_t, hashval_t, hashval_t, int);
72 static hashval_t htab_mod (hashval_t, htab_t);
73 static hashval_t htab_mod_m2 (hashval_t, htab_t);
74 static hashval_t hash_pointer (const void *);
75 static int eq_pointer (const void *, const void *);
76 static int htab_expand (htab_t);
77 static PTR *find_empty_slot_for_expand (htab_t, hashval_t);
79 /* At some point, we could make these be NULL, and modify the
80 hash-table routines to handle NULL specially; that would avoid
81 function-call overhead for the common case of hashing pointers. */
82 htab_hash htab_hash_pointer = hash_pointer;
83 htab_eq htab_eq_pointer = eq_pointer;
85 /* Table of primes and multiplicative inverses.
87 Note that these are not minimally reduced inverses. Unlike when generating
88 code to divide by a constant, we want to be able to use the same algorithm
89 all the time. All of these inverses (are implied to) have bit 32 set.
91 For the record, here's the function that computed the table; it's a
92 vastly simplified version of the function of the same name from gcc. */
94 #if 0
95 unsigned int
96 ceil_log2 (unsigned int x)
98 int i;
99 for (i = 31; i >= 0 ; --i)
100 if (x > (1u << i))
101 return i+1;
102 abort ();
105 unsigned int
106 choose_multiplier (unsigned int d, unsigned int *mlp, unsigned char *shiftp)
108 unsigned long long mhigh;
109 double nx;
110 int lgup, post_shift;
111 int pow, pow2;
112 int n = 32, precision = 32;
114 lgup = ceil_log2 (d);
115 pow = n + lgup;
116 pow2 = n + lgup - precision;
118 nx = ldexp (1.0, pow) + ldexp (1.0, pow2);
119 mhigh = nx / d;
121 *shiftp = lgup - 1;
122 *mlp = mhigh;
123 return mhigh >> 32;
125 #endif
127 struct prime_ent
129 hashval_t prime;
130 hashval_t inv;
131 hashval_t inv_m2; /* inverse of prime-2 */
132 hashval_t shift;
135 static struct prime_ent const prime_tab[] = {
136 { 7, 0x24924925, 0x9999999b, 2 },
137 { 13, 0x3b13b13c, 0x745d1747, 3 },
138 { 31, 0x08421085, 0x1a7b9612, 4 },
139 { 61, 0x0c9714fc, 0x15b1e5f8, 5 },
140 { 127, 0x02040811, 0x0624dd30, 6 },
141 { 251, 0x05197f7e, 0x073260a5, 7 },
142 { 509, 0x01824366, 0x02864fc8, 8 },
143 { 1021, 0x00c0906d, 0x014191f7, 9 },
144 { 2039, 0x0121456f, 0x0161e69e, 10 },
145 { 4093, 0x00300902, 0x00501908, 11 },
146 { 8191, 0x00080041, 0x00180241, 12 },
147 { 16381, 0x000c0091, 0x00140191, 13 },
148 { 32749, 0x002605a5, 0x002a06e6, 14 },
149 { 65521, 0x000f00e2, 0x00110122, 15 },
150 { 131071, 0x00008001, 0x00018003, 16 },
151 { 262139, 0x00014002, 0x0001c004, 17 },
152 { 524287, 0x00002001, 0x00006001, 18 },
153 { 1048573, 0x00003001, 0x00005001, 19 },
154 { 2097143, 0x00004801, 0x00005801, 20 },
155 { 4194301, 0x00000c01, 0x00001401, 21 },
156 { 8388593, 0x00001e01, 0x00002201, 22 },
157 { 16777213, 0x00000301, 0x00000501, 23 },
158 { 33554393, 0x00001381, 0x00001481, 24 },
159 { 67108859, 0x00000141, 0x000001c1, 25 },
160 { 134217689, 0x000004e1, 0x00000521, 26 },
161 { 268435399, 0x00000391, 0x000003b1, 27 },
162 { 536870909, 0x00000019, 0x00000029, 28 },
163 { 1073741789, 0x0000008d, 0x00000095, 29 },
164 { 2147483647, 0x00000003, 0x00000007, 30 },
165 /* Avoid "decimal constant so large it is unsigned" for 4294967291. */
166 { 0xfffffffb, 0x00000006, 0x00000008, 31 }
169 /* The following function returns an index into the above table of the
170 nearest prime number which is greater than N, and near a power of two. */
172 static unsigned int
173 higher_prime_index (unsigned long n)
175 unsigned int low = 0;
176 unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]);
178 while (low != high)
180 unsigned int mid = low + (high - low) / 2;
181 if (n > prime_tab[mid].prime)
182 low = mid + 1;
183 else
184 high = mid;
187 /* If we've run out of primes, abort. */
188 if (n > prime_tab[low].prime)
190 fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
191 abort ();
194 return low;
197 /* Returns non-zero if P1 and P2 are equal. */
199 static int
200 eq_pointer (const PTR p1, const PTR p2)
202 return p1 == p2;
206 /* The parens around the function names in the next two definitions
207 are essential in order to prevent macro expansions of the name.
208 The bodies, however, are expanded as expected, so they are not
209 recursive definitions. */
211 /* Return the current size of given hash table. */
213 #define htab_size(htab) ((htab)->size)
215 size_t
216 (htab_size) (htab_t htab)
218 return htab_size (htab);
221 /* Return the current number of elements in given hash table. */
223 #define htab_elements(htab) ((htab)->n_elements - (htab)->n_deleted)
225 size_t
226 (htab_elements) (htab_t htab)
228 return htab_elements (htab);
231 /* Return X % Y. */
233 static inline hashval_t
234 htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift)
236 /* The multiplicative inverses computed above are for 32-bit types, and
237 requires that we be able to compute a highpart multiply. */
238 #ifdef UNSIGNED_64BIT_TYPE
239 __extension__ typedef UNSIGNED_64BIT_TYPE ull;
240 if (sizeof (hashval_t) * CHAR_BIT <= 32)
242 hashval_t t1, t2, t3, t4, q, r;
244 t1 = ((ull)x * inv) >> 32;
245 t2 = x - t1;
246 t3 = t2 >> 1;
247 t4 = t1 + t3;
248 q = t4 >> shift;
249 r = x - (q * y);
251 return r;
253 #endif
255 /* Otherwise just use the native division routines. */
256 return x % y;
259 /* Compute the primary hash for HASH given HTAB's current size. */
261 static inline hashval_t
262 htab_mod (hashval_t hash, htab_t htab)
264 const struct prime_ent *p = &prime_tab[htab->size_prime_index];
265 return htab_mod_1 (hash, p->prime, p->inv, p->shift);
268 /* Compute the secondary hash for HASH given HTAB's current size. */
270 static inline hashval_t
271 htab_mod_m2 (hashval_t hash, htab_t htab)
273 const struct prime_ent *p = &prime_tab[htab->size_prime_index];
274 return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift);
277 /* This function creates table with length slightly longer than given
278 source length. Created hash table is initiated as empty (all the
279 hash table entries are HTAB_EMPTY_ENTRY). The function returns the
280 created hash table, or NULL if memory allocation fails. */
282 htab_t
283 htab_create_alloc (size_t size, htab_hash hash_f, htab_eq eq_f,
284 htab_del del_f, htab_alloc alloc_f, htab_free free_f)
286 return htab_create_typed_alloc (size, hash_f, eq_f, del_f, alloc_f, alloc_f,
287 free_f);
290 /* As above, but uses the variants of ALLOC_F and FREE_F which accept
291 an extra argument. */
293 htab_t
294 htab_create_alloc_ex (size_t size, htab_hash hash_f, htab_eq eq_f,
295 htab_del del_f, void *alloc_arg,
296 htab_alloc_with_arg alloc_f,
297 htab_free_with_arg free_f)
299 htab_t result;
300 unsigned int size_prime_index;
302 size_prime_index = higher_prime_index (size);
303 size = prime_tab[size_prime_index].prime;
305 result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab));
306 if (result == NULL)
307 return NULL;
308 result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR));
309 if (result->entries == NULL)
311 if (free_f != NULL)
312 (*free_f) (alloc_arg, result);
313 return NULL;
315 result->size = size;
316 result->size_prime_index = size_prime_index;
317 result->hash_f = hash_f;
318 result->eq_f = eq_f;
319 result->del_f = del_f;
320 result->alloc_arg = alloc_arg;
321 result->alloc_with_arg_f = alloc_f;
322 result->free_with_arg_f = free_f;
323 return result;
328 @deftypefn Supplemental htab_t htab_create_typed_alloc (size_t @var{size}, @
329 htab_hash @var{hash_f}, htab_eq @var{eq_f}, htab_del @var{del_f}, @
330 htab_alloc @var{alloc_tab_f}, htab_alloc @var{alloc_f}, @
331 htab_free @var{free_f})
333 This function creates a hash table that uses two different allocators
334 @var{alloc_tab_f} and @var{alloc_f} to use for allocating the table itself
335 and its entries respectively. This is useful when variables of different
336 types need to be allocated with different allocators.
338 The created hash table is slightly larger than @var{size} and it is
339 initially empty (all the hash table entries are @code{HTAB_EMPTY_ENTRY}).
340 The function returns the created hash table, or @code{NULL} if memory
341 allocation fails.
343 @end deftypefn
347 htab_t
348 htab_create_typed_alloc (size_t size, htab_hash hash_f, htab_eq eq_f,
349 htab_del del_f, htab_alloc alloc_tab_f,
350 htab_alloc alloc_f, htab_free free_f)
352 htab_t result;
353 unsigned int size_prime_index;
355 size_prime_index = higher_prime_index (size);
356 size = prime_tab[size_prime_index].prime;
358 result = (htab_t) (*alloc_tab_f) (1, sizeof (struct htab));
359 if (result == NULL)
360 return NULL;
361 result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR));
362 if (result->entries == NULL)
364 if (free_f != NULL)
365 (*free_f) (result);
366 return NULL;
368 result->size = size;
369 result->size_prime_index = size_prime_index;
370 result->hash_f = hash_f;
371 result->eq_f = eq_f;
372 result->del_f = del_f;
373 result->alloc_f = alloc_f;
374 result->free_f = free_f;
375 return result;
379 /* Update the function pointers and allocation parameter in the htab_t. */
381 void
382 htab_set_functions_ex (htab_t htab, htab_hash hash_f, htab_eq eq_f,
383 htab_del del_f, PTR alloc_arg,
384 htab_alloc_with_arg alloc_f, htab_free_with_arg free_f)
386 htab->hash_f = hash_f;
387 htab->eq_f = eq_f;
388 htab->del_f = del_f;
389 htab->alloc_arg = alloc_arg;
390 htab->alloc_with_arg_f = alloc_f;
391 htab->free_with_arg_f = free_f;
394 /* These functions exist solely for backward compatibility. */
396 #undef htab_create
397 htab_t
398 htab_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f)
400 return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free);
403 htab_t
404 htab_try_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f)
406 return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free);
409 /* This function frees all memory allocated for given hash table.
410 Naturally the hash table must already exist. */
412 void
413 htab_delete (htab_t htab)
415 size_t size = htab_size (htab);
416 PTR *entries = htab->entries;
417 int i;
419 if (htab->del_f)
420 for (i = size - 1; i >= 0; i--)
421 if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY)
422 (*htab->del_f) (entries[i]);
424 if (htab->free_f != NULL)
426 (*htab->free_f) (entries);
427 (*htab->free_f) (htab);
429 else if (htab->free_with_arg_f != NULL)
431 (*htab->free_with_arg_f) (htab->alloc_arg, entries);
432 (*htab->free_with_arg_f) (htab->alloc_arg, htab);
436 /* This function clears all entries in the given hash table. */
438 void
439 htab_empty (htab_t htab)
441 size_t size = htab_size (htab);
442 PTR *entries = htab->entries;
443 int i;
445 if (htab->del_f)
446 for (i = size - 1; i >= 0; i--)
447 if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY)
448 (*htab->del_f) (entries[i]);
450 /* Instead of clearing megabyte, downsize the table. */
451 if (size > 1024*1024 / sizeof (PTR))
453 int nindex = higher_prime_index (1024 / sizeof (PTR));
454 int nsize = prime_tab[nindex].prime;
456 if (htab->free_f != NULL)
457 (*htab->free_f) (htab->entries);
458 else if (htab->free_with_arg_f != NULL)
459 (*htab->free_with_arg_f) (htab->alloc_arg, htab->entries);
460 if (htab->alloc_with_arg_f != NULL)
461 htab->entries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize,
462 sizeof (PTR *));
463 else
464 htab->entries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *));
465 htab->size = nsize;
466 htab->size_prime_index = nindex;
468 else
469 memset (entries, 0, size * sizeof (PTR));
470 htab->n_deleted = 0;
471 htab->n_elements = 0;
474 /* Similar to htab_find_slot, but without several unwanted side effects:
475 - Does not call htab->eq_f when it finds an existing entry.
476 - Does not change the count of elements/searches/collisions in the
477 hash table.
478 This function also assumes there are no deleted entries in the table.
479 HASH is the hash value for the element to be inserted. */
481 static PTR *
482 find_empty_slot_for_expand (htab_t htab, hashval_t hash)
484 hashval_t index = htab_mod (hash, htab);
485 size_t size = htab_size (htab);
486 PTR *slot = htab->entries + index;
487 hashval_t hash2;
489 if (*slot == HTAB_EMPTY_ENTRY)
490 return slot;
491 else if (*slot == HTAB_DELETED_ENTRY)
492 abort ();
494 hash2 = htab_mod_m2 (hash, htab);
495 for (;;)
497 index += hash2;
498 if (index >= size)
499 index -= size;
501 slot = htab->entries + index;
502 if (*slot == HTAB_EMPTY_ENTRY)
503 return slot;
504 else if (*slot == HTAB_DELETED_ENTRY)
505 abort ();
509 /* The following function changes size of memory allocated for the
510 entries and repeatedly inserts the table elements. The occupancy
511 of the table after the call will be about 50%. Naturally the hash
512 table must already exist. Remember also that the place of the
513 table entries is changed. If memory allocation failures are allowed,
514 this function will return zero, indicating that the table could not be
515 expanded. If all goes well, it will return a non-zero value. */
517 static int
518 htab_expand (htab_t htab)
520 PTR *oentries;
521 PTR *olimit;
522 PTR *p;
523 PTR *nentries;
524 size_t nsize, osize, elts;
525 unsigned int oindex, nindex;
527 oentries = htab->entries;
528 oindex = htab->size_prime_index;
529 osize = htab->size;
530 olimit = oentries + osize;
531 elts = htab_elements (htab);
533 /* Resize only when table after removal of unused elements is either
534 too full or too empty. */
535 if (elts * 2 > osize || (elts * 8 < osize && osize > 32))
537 nindex = higher_prime_index (elts * 2);
538 nsize = prime_tab[nindex].prime;
540 else
542 nindex = oindex;
543 nsize = osize;
546 if (htab->alloc_with_arg_f != NULL)
547 nentries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize,
548 sizeof (PTR *));
549 else
550 nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *));
551 if (nentries == NULL)
552 return 0;
553 htab->entries = nentries;
554 htab->size = nsize;
555 htab->size_prime_index = nindex;
556 htab->n_elements -= htab->n_deleted;
557 htab->n_deleted = 0;
559 p = oentries;
562 PTR x = *p;
564 if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
566 PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x));
568 *q = x;
571 p++;
573 while (p < olimit);
575 if (htab->free_f != NULL)
576 (*htab->free_f) (oentries);
577 else if (htab->free_with_arg_f != NULL)
578 (*htab->free_with_arg_f) (htab->alloc_arg, oentries);
579 return 1;
582 /* This function searches for a hash table entry equal to the given
583 element. It cannot be used to insert or delete an element. */
586 htab_find_with_hash (htab_t htab, const PTR element, hashval_t hash)
588 hashval_t index, hash2;
589 size_t size;
590 PTR entry;
592 htab->searches++;
593 size = htab_size (htab);
594 index = htab_mod (hash, htab);
596 entry = htab->entries[index];
597 if (entry == HTAB_EMPTY_ENTRY
598 || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element)))
599 return entry;
601 hash2 = htab_mod_m2 (hash, htab);
602 for (;;)
604 htab->collisions++;
605 index += hash2;
606 if (index >= size)
607 index -= size;
609 entry = htab->entries[index];
610 if (entry == HTAB_EMPTY_ENTRY
611 || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element)))
612 return entry;
616 /* Like htab_find_slot_with_hash, but compute the hash value from the
617 element. */
620 htab_find (htab_t htab, const PTR element)
622 return htab_find_with_hash (htab, element, (*htab->hash_f) (element));
625 /* This function searches for a hash table slot containing an entry
626 equal to the given element. To delete an entry, call this with
627 insert=NO_INSERT, then call htab_clear_slot on the slot returned
628 (possibly after doing some checks). To insert an entry, call this
629 with insert=INSERT, then write the value you want into the returned
630 slot. When inserting an entry, NULL may be returned if memory
631 allocation fails. */
633 PTR *
634 htab_find_slot_with_hash (htab_t htab, const PTR element,
635 hashval_t hash, enum insert_option insert)
637 PTR *first_deleted_slot;
638 hashval_t index, hash2;
639 size_t size;
640 PTR entry;
642 size = htab_size (htab);
643 if (insert == INSERT && size * 3 <= htab->n_elements * 4)
645 if (htab_expand (htab) == 0)
646 return NULL;
647 size = htab_size (htab);
650 index = htab_mod (hash, htab);
652 htab->searches++;
653 first_deleted_slot = NULL;
655 entry = htab->entries[index];
656 if (entry == HTAB_EMPTY_ENTRY)
657 goto empty_entry;
658 else if (entry == HTAB_DELETED_ENTRY)
659 first_deleted_slot = &htab->entries[index];
660 else if ((*htab->eq_f) (entry, element))
661 return &htab->entries[index];
663 hash2 = htab_mod_m2 (hash, htab);
664 for (;;)
666 htab->collisions++;
667 index += hash2;
668 if (index >= size)
669 index -= size;
671 entry = htab->entries[index];
672 if (entry == HTAB_EMPTY_ENTRY)
673 goto empty_entry;
674 else if (entry == HTAB_DELETED_ENTRY)
676 if (!first_deleted_slot)
677 first_deleted_slot = &htab->entries[index];
679 else if ((*htab->eq_f) (entry, element))
680 return &htab->entries[index];
683 empty_entry:
684 if (insert == NO_INSERT)
685 return NULL;
687 if (first_deleted_slot)
689 htab->n_deleted--;
690 *first_deleted_slot = HTAB_EMPTY_ENTRY;
691 return first_deleted_slot;
694 htab->n_elements++;
695 return &htab->entries[index];
698 /* Like htab_find_slot_with_hash, but compute the hash value from the
699 element. */
701 PTR *
702 htab_find_slot (htab_t htab, const PTR element, enum insert_option insert)
704 return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element),
705 insert);
708 /* This function deletes an element with the given value from hash
709 table (the hash is computed from the element). If there is no matching
710 element in the hash table, this function does nothing. */
712 void
713 htab_remove_elt (htab_t htab, PTR element)
715 htab_remove_elt_with_hash (htab, element, (*htab->hash_f) (element));
719 /* This function deletes an element with the given value from hash
720 table. If there is no matching element in the hash table, this
721 function does nothing. */
723 void
724 htab_remove_elt_with_hash (htab_t htab, PTR element, hashval_t hash)
726 PTR *slot;
728 slot = htab_find_slot_with_hash (htab, element, hash, NO_INSERT);
729 if (*slot == HTAB_EMPTY_ENTRY)
730 return;
732 if (htab->del_f)
733 (*htab->del_f) (*slot);
735 *slot = HTAB_DELETED_ENTRY;
736 htab->n_deleted++;
739 /* This function clears a specified slot in a hash table. It is
740 useful when you've already done the lookup and don't want to do it
741 again. */
743 void
744 htab_clear_slot (htab_t htab, PTR *slot)
746 if (slot < htab->entries || slot >= htab->entries + htab_size (htab)
747 || *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY)
748 abort ();
750 if (htab->del_f)
751 (*htab->del_f) (*slot);
753 *slot = HTAB_DELETED_ENTRY;
754 htab->n_deleted++;
757 /* This function scans over the entire hash table calling
758 CALLBACK for each live entry. If CALLBACK returns false,
759 the iteration stops. INFO is passed as CALLBACK's second
760 argument. */
762 void
763 htab_traverse_noresize (htab_t htab, htab_trav callback, PTR info)
765 PTR *slot;
766 PTR *limit;
768 slot = htab->entries;
769 limit = slot + htab_size (htab);
773 PTR x = *slot;
775 if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
776 if (!(*callback) (slot, info))
777 break;
779 while (++slot < limit);
782 /* Like htab_traverse_noresize, but does resize the table when it is
783 too empty to improve effectivity of subsequent calls. */
785 void
786 htab_traverse (htab_t htab, htab_trav callback, PTR info)
788 size_t size = htab_size (htab);
789 if (htab_elements (htab) * 8 < size && size > 32)
790 htab_expand (htab);
792 htab_traverse_noresize (htab, callback, info);
795 /* Return the fraction of fixed collisions during all work with given
796 hash table. */
798 double
799 htab_collisions (htab_t htab)
801 if (htab->searches == 0)
802 return 0.0;
804 return (double) htab->collisions / (double) htab->searches;
807 /* Hash P as a null-terminated string.
809 Copied from gcc/hashtable.c. Zack had the following to say with respect
810 to applicability, though note that unlike hashtable.c, this hash table
811 implementation re-hashes rather than chain buckets.
813 http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html
814 From: Zack Weinberg <zackw@panix.com>
815 Date: Fri, 17 Aug 2001 02:15:56 -0400
817 I got it by extracting all the identifiers from all the source code
818 I had lying around in mid-1999, and testing many recurrences of
819 the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either
820 prime numbers or the appropriate identity. This was the best one.
821 I don't remember exactly what constituted "best", except I was
822 looking at bucket-length distributions mostly.
824 So it should be very good at hashing identifiers, but might not be
825 as good at arbitrary strings.
827 I'll add that it thoroughly trounces the hash functions recommended
828 for this use at http://burtleburtle.net/bob/hash/index.html, both
829 on speed and bucket distribution. I haven't tried it against the
830 function they just started using for Perl's hashes. */
832 hashval_t
833 htab_hash_string (const PTR p)
835 const unsigned char *str = (const unsigned char *) p;
836 hashval_t r = 0;
837 unsigned char c;
839 while ((c = *str++) != 0)
840 r = r * 67 + c - 113;
842 return r;
845 /* DERIVED FROM:
846 --------------------------------------------------------------------
847 lookup2.c, by Bob Jenkins, December 1996, Public Domain.
848 hash(), hash2(), hash3, and mix() are externally useful functions.
849 Routines to test the hash are included if SELF_TEST is defined.
850 You can use this free for any purpose. It has no warranty.
851 --------------------------------------------------------------------
855 --------------------------------------------------------------------
856 mix -- mix 3 32-bit values reversibly.
857 For every delta with one or two bit set, and the deltas of all three
858 high bits or all three low bits, whether the original value of a,b,c
859 is almost all zero or is uniformly distributed,
860 * If mix() is run forward or backward, at least 32 bits in a,b,c
861 have at least 1/4 probability of changing.
862 * If mix() is run forward, every bit of c will change between 1/3 and
863 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.)
864 mix() was built out of 36 single-cycle latency instructions in a
865 structure that could supported 2x parallelism, like so:
866 a -= b;
867 a -= c; x = (c>>13);
868 b -= c; a ^= x;
869 b -= a; x = (a<<8);
870 c -= a; b ^= x;
871 c -= b; x = (b>>13);
873 Unfortunately, superscalar Pentiums and Sparcs can't take advantage
874 of that parallelism. They've also turned some of those single-cycle
875 latency instructions into multi-cycle latency instructions. Still,
876 this is the fastest good hash I could find. There were about 2^^68
877 to choose from. I only looked at a billion or so.
878 --------------------------------------------------------------------
880 /* same, but slower, works on systems that might have 8 byte hashval_t's */
881 #define mix(a,b,c) \
883 a -= b; a -= c; a ^= (c>>13); \
884 b -= c; b -= a; b ^= (a<< 8); \
885 c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
886 a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
887 b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
888 c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
889 a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
890 b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
891 c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
895 --------------------------------------------------------------------
896 hash() -- hash a variable-length key into a 32-bit value
897 k : the key (the unaligned variable-length array of bytes)
898 len : the length of the key, counting by bytes
899 level : can be any 4-byte value
900 Returns a 32-bit value. Every bit of the key affects every bit of
901 the return value. Every 1-bit and 2-bit delta achieves avalanche.
902 About 36+6len instructions.
904 The best hash table sizes are powers of 2. There is no need to do
905 mod a prime (mod is sooo slow!). If you need less than 32 bits,
906 use a bitmask. For example, if you need only 10 bits, do
907 h = (h & hashmask(10));
908 In which case, the hash table should have hashsize(10) elements.
910 If you are hashing n strings (ub1 **)k, do it like this:
911 for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);
913 By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this
914 code any way you wish, private, educational, or commercial. It's free.
916 See http://burtleburtle.net/bob/hash/evahash.html
917 Use for hash table lookup, or anything where one collision in 2^32 is
918 acceptable. Do NOT use for cryptographic purposes.
919 --------------------------------------------------------------------
922 hashval_t
923 iterative_hash (const PTR k_in /* the key */,
924 register size_t length /* the length of the key */,
925 register hashval_t initval /* the previous hash, or
926 an arbitrary value */)
928 register const unsigned char *k = (const unsigned char *)k_in;
929 register hashval_t a,b,c,len;
931 /* Set up the internal state */
932 len = length;
933 a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
934 c = initval; /* the previous hash value */
936 /*---------------------------------------- handle most of the key */
937 #ifndef WORDS_BIGENDIAN
938 /* On a little-endian machine, if the data is 4-byte aligned we can hash
939 by word for better speed. This gives nondeterministic results on
940 big-endian machines. */
941 if (sizeof (hashval_t) == 4 && (((size_t)k)&3) == 0)
942 while (len >= 12) /* aligned */
944 a += *(hashval_t *)(k+0);
945 b += *(hashval_t *)(k+4);
946 c += *(hashval_t *)(k+8);
947 mix(a,b,c);
948 k += 12; len -= 12;
950 else /* unaligned */
951 #endif
952 while (len >= 12)
954 a += (k[0] +((hashval_t)k[1]<<8) +((hashval_t)k[2]<<16) +((hashval_t)k[3]<<24));
955 b += (k[4] +((hashval_t)k[5]<<8) +((hashval_t)k[6]<<16) +((hashval_t)k[7]<<24));
956 c += (k[8] +((hashval_t)k[9]<<8) +((hashval_t)k[10]<<16)+((hashval_t)k[11]<<24));
957 mix(a,b,c);
958 k += 12; len -= 12;
961 /*------------------------------------- handle the last 11 bytes */
962 c += length;
963 switch(len) /* all the case statements fall through */
965 case 11: c+=((hashval_t)k[10]<<24);
966 case 10: c+=((hashval_t)k[9]<<16);
967 case 9 : c+=((hashval_t)k[8]<<8);
968 /* the first byte of c is reserved for the length */
969 case 8 : b+=((hashval_t)k[7]<<24);
970 case 7 : b+=((hashval_t)k[6]<<16);
971 case 6 : b+=((hashval_t)k[5]<<8);
972 case 5 : b+=k[4];
973 case 4 : a+=((hashval_t)k[3]<<24);
974 case 3 : a+=((hashval_t)k[2]<<16);
975 case 2 : a+=((hashval_t)k[1]<<8);
976 case 1 : a+=k[0];
977 /* case 0: nothing left to add */
979 mix(a,b,c);
980 /*-------------------------------------------- report the result */
981 return c;
984 /* Returns a hash code for pointer P. Simplified version of evahash */
986 static hashval_t
987 hash_pointer (const PTR p)
989 intptr_t v = (intptr_t) p;
990 unsigned a, b, c;
992 a = b = 0x9e3779b9;
993 a += v >> (sizeof (intptr_t) * CHAR_BIT / 2);
994 b += v & (((intptr_t) 1 << (sizeof (intptr_t) * CHAR_BIT / 2)) - 1);
995 c = 0x42135234;
996 mix (a, b, c);
997 return c;