Commit | Line | Data |
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e2eaf477 | 1 | /* An expandable hash tables datatype. |
b1c933fc | 2 | Copyright (C) 1999, 2000, 2001, 2002 Free Software Foundation, Inc. |
e2eaf477 ILT |
3 | Contributed by Vladimir Makarov (vmakarov@cygnus.com). |
4 | ||
5 | This file is part of the libiberty library. | |
6 | Libiberty is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Library General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2 of the License, or (at your option) any later version. | |
10 | ||
11 | Libiberty is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Library General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Library General Public | |
17 | License along with libiberty; see the file COPYING.LIB. If | |
18 | not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
19 | Boston, MA 02111-1307, USA. */ | |
20 | ||
21 | /* This package implements basic hash table functionality. It is possible | |
22 | to search for an entry, create an entry and destroy an entry. | |
23 | ||
24 | Elements in the table are generic pointers. | |
25 | ||
26 | The size of the table is not fixed; if the occupancy of the table | |
27 | grows too high the hash table will be expanded. | |
28 | ||
29 | The abstract data implementation is based on generalized Algorithm D | |
30 | from Knuth's book "The art of computer programming". Hash table is | |
31 | expanded by creation of new hash table and transferring elements from | |
32 | the old table to the new table. */ | |
33 | ||
34 | #ifdef HAVE_CONFIG_H | |
35 | #include "config.h" | |
36 | #endif | |
37 | ||
38 | #include <sys/types.h> | |
39 | ||
40 | #ifdef HAVE_STDLIB_H | |
41 | #include <stdlib.h> | |
42 | #endif | |
43 | ||
5c82d20a ZW |
44 | #ifdef HAVE_STRING_H |
45 | #include <string.h> | |
46 | #endif | |
47 | ||
e2eaf477 ILT |
48 | #include <stdio.h> |
49 | ||
50 | #include "libiberty.h" | |
51 | #include "hashtab.h" | |
52 | ||
e2eaf477 ILT |
53 | /* This macro defines reserved value for empty table entry. */ |
54 | ||
e0f3df8f | 55 | #define EMPTY_ENTRY ((PTR) 0) |
e2eaf477 ILT |
56 | |
57 | /* This macro defines reserved value for table entry which contained | |
58 | a deleted element. */ | |
59 | ||
e0f3df8f | 60 | #define DELETED_ENTRY ((PTR) 1) |
e2eaf477 | 61 | |
eb383413 L |
62 | static unsigned long higher_prime_number PARAMS ((unsigned long)); |
63 | static hashval_t hash_pointer PARAMS ((const void *)); | |
64 | static int eq_pointer PARAMS ((const void *, const void *)); | |
99a4c1bd | 65 | static int htab_expand PARAMS ((htab_t)); |
e0f3df8f | 66 | static PTR *find_empty_slot_for_expand PARAMS ((htab_t, hashval_t)); |
eb383413 L |
67 | |
68 | /* At some point, we could make these be NULL, and modify the | |
69 | hash-table routines to handle NULL specially; that would avoid | |
70 | function-call overhead for the common case of hashing pointers. */ | |
71 | htab_hash htab_hash_pointer = hash_pointer; | |
72 | htab_eq htab_eq_pointer = eq_pointer; | |
73 | ||
5ca0f83d DD |
74 | /* The following function returns a nearest prime number which is |
75 | greater than N, and near a power of two. */ | |
e2eaf477 ILT |
76 | |
77 | static unsigned long | |
b4fe2683 JM |
78 | higher_prime_number (n) |
79 | unsigned long n; | |
e2eaf477 | 80 | { |
5ca0f83d DD |
81 | /* These are primes that are near, but slightly smaller than, a |
82 | power of two. */ | |
e6450fe5 | 83 | static const unsigned long primes[] = { |
b1e51b3c DD |
84 | (unsigned long) 7, |
85 | (unsigned long) 13, | |
86 | (unsigned long) 31, | |
87 | (unsigned long) 61, | |
88 | (unsigned long) 127, | |
89 | (unsigned long) 251, | |
90 | (unsigned long) 509, | |
91 | (unsigned long) 1021, | |
92 | (unsigned long) 2039, | |
93 | (unsigned long) 4093, | |
94 | (unsigned long) 8191, | |
95 | (unsigned long) 16381, | |
96 | (unsigned long) 32749, | |
97 | (unsigned long) 65521, | |
98 | (unsigned long) 131071, | |
99 | (unsigned long) 262139, | |
100 | (unsigned long) 524287, | |
101 | (unsigned long) 1048573, | |
102 | (unsigned long) 2097143, | |
103 | (unsigned long) 4194301, | |
104 | (unsigned long) 8388593, | |
105 | (unsigned long) 16777213, | |
106 | (unsigned long) 33554393, | |
107 | (unsigned long) 67108859, | |
108 | (unsigned long) 134217689, | |
109 | (unsigned long) 268435399, | |
110 | (unsigned long) 536870909, | |
111 | (unsigned long) 1073741789, | |
112 | (unsigned long) 2147483647, | |
113 | /* 4294967291L */ | |
06b0287c | 114 | ((unsigned long) 2147483647) + ((unsigned long) 2147483644), |
5ca0f83d DD |
115 | }; |
116 | ||
e6450fe5 DD |
117 | const unsigned long *low = &primes[0]; |
118 | const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])]; | |
5ca0f83d DD |
119 | |
120 | while (low != high) | |
121 | { | |
e6450fe5 | 122 | const unsigned long *mid = low + (high - low) / 2; |
5ca0f83d DD |
123 | if (n > *mid) |
124 | low = mid + 1; | |
125 | else | |
126 | high = mid; | |
127 | } | |
128 | ||
129 | /* If we've run out of primes, abort. */ | |
130 | if (n > *low) | |
131 | { | |
132 | fprintf (stderr, "Cannot find prime bigger than %lu\n", n); | |
133 | abort (); | |
134 | } | |
135 | ||
136 | return *low; | |
e2eaf477 ILT |
137 | } |
138 | ||
eb383413 L |
139 | /* Returns a hash code for P. */ |
140 | ||
141 | static hashval_t | |
142 | hash_pointer (p) | |
e0f3df8f | 143 | const PTR p; |
eb383413 L |
144 | { |
145 | return (hashval_t) ((long)p >> 3); | |
146 | } | |
147 | ||
148 | /* Returns non-zero if P1 and P2 are equal. */ | |
149 | ||
150 | static int | |
151 | eq_pointer (p1, p2) | |
e0f3df8f HPN |
152 | const PTR p1; |
153 | const PTR p2; | |
eb383413 L |
154 | { |
155 | return p1 == p2; | |
156 | } | |
157 | ||
e2eaf477 ILT |
158 | /* This function creates table with length slightly longer than given |
159 | source length. Created hash table is initiated as empty (all the | |
160 | hash table entries are EMPTY_ENTRY). The function returns the | |
18893690 | 161 | created hash table, or NULL if memory allocation fails. */ |
e2eaf477 | 162 | |
b4fe2683 | 163 | htab_t |
18893690 | 164 | htab_create_alloc (size, hash_f, eq_f, del_f, alloc_f, free_f) |
e2eaf477 | 165 | size_t size; |
b4fe2683 JM |
166 | htab_hash hash_f; |
167 | htab_eq eq_f; | |
168 | htab_del del_f; | |
18893690 DD |
169 | htab_alloc alloc_f; |
170 | htab_free free_f; | |
e2eaf477 | 171 | { |
b4fe2683 | 172 | htab_t result; |
e2eaf477 ILT |
173 | |
174 | size = higher_prime_number (size); | |
18893690 DD |
175 | result = (htab_t) (*alloc_f) (1, sizeof (struct htab)); |
176 | if (result == NULL) | |
177 | return NULL; | |
178 | result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR)); | |
179 | if (result->entries == NULL) | |
180 | { | |
181 | if (free_f != NULL) | |
182 | (*free_f) (result); | |
183 | return NULL; | |
184 | } | |
e2eaf477 | 185 | result->size = size; |
b4fe2683 JM |
186 | result->hash_f = hash_f; |
187 | result->eq_f = eq_f; | |
188 | result->del_f = del_f; | |
18893690 DD |
189 | result->alloc_f = alloc_f; |
190 | result->free_f = free_f; | |
99a4c1bd HPN |
191 | return result; |
192 | } | |
193 | ||
18893690 | 194 | /* These functions exist solely for backward compatibility. */ |
99a4c1bd | 195 | |
18893690 | 196 | #undef htab_create |
99a4c1bd | 197 | htab_t |
18893690 | 198 | htab_create (size, hash_f, eq_f, del_f) |
99a4c1bd HPN |
199 | size_t size; |
200 | htab_hash hash_f; | |
201 | htab_eq eq_f; | |
202 | htab_del del_f; | |
203 | { | |
18893690 DD |
204 | return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free); |
205 | } | |
99a4c1bd | 206 | |
18893690 DD |
207 | htab_t |
208 | htab_try_create (size, hash_f, eq_f, del_f) | |
209 | size_t size; | |
210 | htab_hash hash_f; | |
211 | htab_eq eq_f; | |
212 | htab_del del_f; | |
213 | { | |
214 | return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free); | |
e2eaf477 ILT |
215 | } |
216 | ||
217 | /* This function frees all memory allocated for given hash table. | |
218 | Naturally the hash table must already exist. */ | |
219 | ||
220 | void | |
b4fe2683 JM |
221 | htab_delete (htab) |
222 | htab_t htab; | |
e2eaf477 | 223 | { |
b4fe2683 | 224 | int i; |
eb383413 | 225 | |
b4fe2683 JM |
226 | if (htab->del_f) |
227 | for (i = htab->size - 1; i >= 0; i--) | |
eb383413 L |
228 | if (htab->entries[i] != EMPTY_ENTRY |
229 | && htab->entries[i] != DELETED_ENTRY) | |
230 | (*htab->del_f) (htab->entries[i]); | |
b4fe2683 | 231 | |
18893690 DD |
232 | if (htab->free_f != NULL) |
233 | { | |
234 | (*htab->free_f) (htab->entries); | |
235 | (*htab->free_f) (htab); | |
236 | } | |
e2eaf477 ILT |
237 | } |
238 | ||
239 | /* This function clears all entries in the given hash table. */ | |
240 | ||
241 | void | |
b4fe2683 JM |
242 | htab_empty (htab) |
243 | htab_t htab; | |
244 | { | |
245 | int i; | |
eb383413 | 246 | |
b4fe2683 JM |
247 | if (htab->del_f) |
248 | for (i = htab->size - 1; i >= 0; i--) | |
eb383413 L |
249 | if (htab->entries[i] != EMPTY_ENTRY |
250 | && htab->entries[i] != DELETED_ENTRY) | |
251 | (*htab->del_f) (htab->entries[i]); | |
b4fe2683 | 252 | |
e0f3df8f | 253 | memset (htab->entries, 0, htab->size * sizeof (PTR)); |
b4fe2683 JM |
254 | } |
255 | ||
256 | /* Similar to htab_find_slot, but without several unwanted side effects: | |
257 | - Does not call htab->eq_f when it finds an existing entry. | |
258 | - Does not change the count of elements/searches/collisions in the | |
259 | hash table. | |
260 | This function also assumes there are no deleted entries in the table. | |
261 | HASH is the hash value for the element to be inserted. */ | |
eb383413 | 262 | |
e0f3df8f | 263 | static PTR * |
b4fe2683 JM |
264 | find_empty_slot_for_expand (htab, hash) |
265 | htab_t htab; | |
eb383413 | 266 | hashval_t hash; |
e2eaf477 | 267 | { |
b4fe2683 | 268 | size_t size = htab->size; |
b4fe2683 | 269 | unsigned int index = hash % size; |
b1c933fc RH |
270 | PTR *slot = htab->entries + index; |
271 | hashval_t hash2; | |
272 | ||
273 | if (*slot == EMPTY_ENTRY) | |
274 | return slot; | |
275 | else if (*slot == DELETED_ENTRY) | |
276 | abort (); | |
b4fe2683 | 277 | |
b1c933fc | 278 | hash2 = 1 + hash % (size - 2); |
b4fe2683 JM |
279 | for (;;) |
280 | { | |
b1c933fc RH |
281 | index += hash2; |
282 | if (index >= size) | |
283 | index -= size; | |
eb383413 | 284 | |
b1c933fc | 285 | slot = htab->entries + index; |
b4fe2683 JM |
286 | if (*slot == EMPTY_ENTRY) |
287 | return slot; | |
eb383413 | 288 | else if (*slot == DELETED_ENTRY) |
b4fe2683 | 289 | abort (); |
b4fe2683 | 290 | } |
e2eaf477 ILT |
291 | } |
292 | ||
293 | /* The following function changes size of memory allocated for the | |
294 | entries and repeatedly inserts the table elements. The occupancy | |
295 | of the table after the call will be about 50%. Naturally the hash | |
296 | table must already exist. Remember also that the place of the | |
99a4c1bd HPN |
297 | table entries is changed. If memory allocation failures are allowed, |
298 | this function will return zero, indicating that the table could not be | |
299 | expanded. If all goes well, it will return a non-zero value. */ | |
e2eaf477 | 300 | |
99a4c1bd | 301 | static int |
b4fe2683 JM |
302 | htab_expand (htab) |
303 | htab_t htab; | |
e2eaf477 | 304 | { |
e0f3df8f HPN |
305 | PTR *oentries; |
306 | PTR *olimit; | |
307 | PTR *p; | |
18893690 | 308 | PTR *nentries; |
eed2b28c | 309 | size_t nsize; |
b4fe2683 JM |
310 | |
311 | oentries = htab->entries; | |
312 | olimit = oentries + htab->size; | |
313 | ||
eed2b28c | 314 | nsize = higher_prime_number (htab->size * 2); |
99a4c1bd | 315 | |
eed2b28c | 316 | nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR)); |
18893690 DD |
317 | if (nentries == NULL) |
318 | return 0; | |
319 | htab->entries = nentries; | |
eed2b28c | 320 | htab->size = nsize; |
b4fe2683 JM |
321 | |
322 | htab->n_elements -= htab->n_deleted; | |
323 | htab->n_deleted = 0; | |
324 | ||
325 | p = oentries; | |
326 | do | |
327 | { | |
e0f3df8f | 328 | PTR x = *p; |
eb383413 | 329 | |
b4fe2683 JM |
330 | if (x != EMPTY_ENTRY && x != DELETED_ENTRY) |
331 | { | |
e0f3df8f | 332 | PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x)); |
eb383413 | 333 | |
b4fe2683 JM |
334 | *q = x; |
335 | } | |
eb383413 | 336 | |
b4fe2683 JM |
337 | p++; |
338 | } | |
339 | while (p < olimit); | |
eb383413 | 340 | |
18893690 DD |
341 | if (htab->free_f != NULL) |
342 | (*htab->free_f) (oentries); | |
99a4c1bd | 343 | return 1; |
e2eaf477 ILT |
344 | } |
345 | ||
b4fe2683 JM |
346 | /* This function searches for a hash table entry equal to the given |
347 | element. It cannot be used to insert or delete an element. */ | |
348 | ||
e0f3df8f | 349 | PTR |
b4fe2683 JM |
350 | htab_find_with_hash (htab, element, hash) |
351 | htab_t htab; | |
e0f3df8f | 352 | const PTR element; |
eb383413 | 353 | hashval_t hash; |
e2eaf477 | 354 | { |
eb383413 L |
355 | unsigned int index; |
356 | hashval_t hash2; | |
b4fe2683 | 357 | size_t size; |
e0f3df8f | 358 | PTR entry; |
e2eaf477 | 359 | |
b4fe2683 JM |
360 | htab->searches++; |
361 | size = htab->size; | |
b4fe2683 JM |
362 | index = hash % size; |
363 | ||
eb383413 L |
364 | entry = htab->entries[index]; |
365 | if (entry == EMPTY_ENTRY | |
366 | || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
367 | return entry; | |
368 | ||
369 | hash2 = 1 + hash % (size - 2); | |
370 | ||
b4fe2683 | 371 | for (;;) |
e2eaf477 | 372 | { |
b4fe2683 JM |
373 | htab->collisions++; |
374 | index += hash2; | |
375 | if (index >= size) | |
376 | index -= size; | |
eb383413 L |
377 | |
378 | entry = htab->entries[index]; | |
379 | if (entry == EMPTY_ENTRY | |
380 | || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
381 | return entry; | |
e2eaf477 | 382 | } |
b4fe2683 JM |
383 | } |
384 | ||
385 | /* Like htab_find_slot_with_hash, but compute the hash value from the | |
386 | element. */ | |
eb383413 | 387 | |
e0f3df8f | 388 | PTR |
b4fe2683 JM |
389 | htab_find (htab, element) |
390 | htab_t htab; | |
e0f3df8f | 391 | const PTR element; |
b4fe2683 JM |
392 | { |
393 | return htab_find_with_hash (htab, element, (*htab->hash_f) (element)); | |
394 | } | |
395 | ||
396 | /* This function searches for a hash table slot containing an entry | |
397 | equal to the given element. To delete an entry, call this with | |
398 | INSERT = 0, then call htab_clear_slot on the slot returned (possibly | |
399 | after doing some checks). To insert an entry, call this with | |
99a4c1bd HPN |
400 | INSERT = 1, then write the value you want into the returned slot. |
401 | When inserting an entry, NULL may be returned if memory allocation | |
402 | fails. */ | |
b4fe2683 | 403 | |
e0f3df8f | 404 | PTR * |
b4fe2683 JM |
405 | htab_find_slot_with_hash (htab, element, hash, insert) |
406 | htab_t htab; | |
e0f3df8f | 407 | const PTR element; |
eb383413 L |
408 | hashval_t hash; |
409 | enum insert_option insert; | |
b4fe2683 | 410 | { |
e0f3df8f | 411 | PTR *first_deleted_slot; |
eb383413 L |
412 | unsigned int index; |
413 | hashval_t hash2; | |
b4fe2683 | 414 | size_t size; |
b1c933fc | 415 | PTR entry; |
b4fe2683 | 416 | |
99a4c1bd HPN |
417 | if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4 |
418 | && htab_expand (htab) == 0) | |
419 | return NULL; | |
b4fe2683 JM |
420 | |
421 | size = htab->size; | |
b4fe2683 JM |
422 | index = hash % size; |
423 | ||
e2eaf477 | 424 | htab->searches++; |
b4fe2683 JM |
425 | first_deleted_slot = NULL; |
426 | ||
b1c933fc RH |
427 | entry = htab->entries[index]; |
428 | if (entry == EMPTY_ENTRY) | |
429 | goto empty_entry; | |
430 | else if (entry == DELETED_ENTRY) | |
431 | first_deleted_slot = &htab->entries[index]; | |
432 | else if ((*htab->eq_f) (entry, element)) | |
433 | return &htab->entries[index]; | |
434 | ||
435 | hash2 = 1 + hash % (size - 2); | |
b4fe2683 | 436 | for (;;) |
e2eaf477 | 437 | { |
b1c933fc RH |
438 | htab->collisions++; |
439 | index += hash2; | |
440 | if (index >= size) | |
441 | index -= size; | |
442 | ||
443 | entry = htab->entries[index]; | |
b4fe2683 | 444 | if (entry == EMPTY_ENTRY) |
b1c933fc RH |
445 | goto empty_entry; |
446 | else if (entry == DELETED_ENTRY) | |
b4fe2683 JM |
447 | { |
448 | if (!first_deleted_slot) | |
449 | first_deleted_slot = &htab->entries[index]; | |
450 | } | |
b1c933fc | 451 | else if ((*htab->eq_f) (entry, element)) |
eb383413 | 452 | return &htab->entries[index]; |
e2eaf477 | 453 | } |
b1c933fc RH |
454 | |
455 | empty_entry: | |
456 | if (insert == NO_INSERT) | |
457 | return NULL; | |
458 | ||
459 | htab->n_elements++; | |
460 | ||
461 | if (first_deleted_slot) | |
462 | { | |
463 | *first_deleted_slot = EMPTY_ENTRY; | |
464 | return first_deleted_slot; | |
465 | } | |
466 | ||
467 | return &htab->entries[index]; | |
e2eaf477 ILT |
468 | } |
469 | ||
b4fe2683 JM |
470 | /* Like htab_find_slot_with_hash, but compute the hash value from the |
471 | element. */ | |
eb383413 | 472 | |
e0f3df8f | 473 | PTR * |
b4fe2683 JM |
474 | htab_find_slot (htab, element, insert) |
475 | htab_t htab; | |
e0f3df8f | 476 | const PTR element; |
eb383413 | 477 | enum insert_option insert; |
b4fe2683 JM |
478 | { |
479 | return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element), | |
480 | insert); | |
481 | } | |
482 | ||
483 | /* This function deletes an element with the given value from hash | |
484 | table. If there is no matching element in the hash table, this | |
485 | function does nothing. */ | |
e2eaf477 ILT |
486 | |
487 | void | |
b4fe2683 JM |
488 | htab_remove_elt (htab, element) |
489 | htab_t htab; | |
e0f3df8f | 490 | PTR element; |
e2eaf477 | 491 | { |
e0f3df8f | 492 | PTR *slot; |
b4fe2683 | 493 | |
eb383413 | 494 | slot = htab_find_slot (htab, element, NO_INSERT); |
b4fe2683 JM |
495 | if (*slot == EMPTY_ENTRY) |
496 | return; | |
497 | ||
498 | if (htab->del_f) | |
499 | (*htab->del_f) (*slot); | |
e2eaf477 | 500 | |
b4fe2683 JM |
501 | *slot = DELETED_ENTRY; |
502 | htab->n_deleted++; | |
e2eaf477 ILT |
503 | } |
504 | ||
b4fe2683 JM |
505 | /* This function clears a specified slot in a hash table. It is |
506 | useful when you've already done the lookup and don't want to do it | |
507 | again. */ | |
e2eaf477 ILT |
508 | |
509 | void | |
b4fe2683 JM |
510 | htab_clear_slot (htab, slot) |
511 | htab_t htab; | |
e0f3df8f | 512 | PTR *slot; |
e2eaf477 ILT |
513 | { |
514 | if (slot < htab->entries || slot >= htab->entries + htab->size | |
515 | || *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY) | |
516 | abort (); | |
eb383413 | 517 | |
b4fe2683 JM |
518 | if (htab->del_f) |
519 | (*htab->del_f) (*slot); | |
eb383413 | 520 | |
e2eaf477 | 521 | *slot = DELETED_ENTRY; |
b4fe2683 | 522 | htab->n_deleted++; |
e2eaf477 ILT |
523 | } |
524 | ||
525 | /* This function scans over the entire hash table calling | |
526 | CALLBACK for each live entry. If CALLBACK returns false, | |
527 | the iteration stops. INFO is passed as CALLBACK's second | |
528 | argument. */ | |
529 | ||
530 | void | |
b4fe2683 JM |
531 | htab_traverse (htab, callback, info) |
532 | htab_t htab; | |
533 | htab_trav callback; | |
e0f3df8f | 534 | PTR info; |
e2eaf477 | 535 | { |
e0f3df8f HPN |
536 | PTR *slot = htab->entries; |
537 | PTR *limit = slot + htab->size; | |
eb383413 | 538 | |
b4fe2683 JM |
539 | do |
540 | { | |
e0f3df8f | 541 | PTR x = *slot; |
eb383413 | 542 | |
b4fe2683 JM |
543 | if (x != EMPTY_ENTRY && x != DELETED_ENTRY) |
544 | if (!(*callback) (slot, info)) | |
545 | break; | |
546 | } | |
547 | while (++slot < limit); | |
e2eaf477 ILT |
548 | } |
549 | ||
eb383413 | 550 | /* Return the current size of given hash table. */ |
e2eaf477 ILT |
551 | |
552 | size_t | |
b4fe2683 JM |
553 | htab_size (htab) |
554 | htab_t htab; | |
e2eaf477 ILT |
555 | { |
556 | return htab->size; | |
557 | } | |
558 | ||
eb383413 | 559 | /* Return the current number of elements in given hash table. */ |
e2eaf477 ILT |
560 | |
561 | size_t | |
b4fe2683 JM |
562 | htab_elements (htab) |
563 | htab_t htab; | |
e2eaf477 | 564 | { |
b4fe2683 | 565 | return htab->n_elements - htab->n_deleted; |
e2eaf477 ILT |
566 | } |
567 | ||
eb383413 L |
568 | /* Return the fraction of fixed collisions during all work with given |
569 | hash table. */ | |
e2eaf477 | 570 | |
b4fe2683 JM |
571 | double |
572 | htab_collisions (htab) | |
573 | htab_t htab; | |
e2eaf477 | 574 | { |
eb383413 | 575 | if (htab->searches == 0) |
b4fe2683 | 576 | return 0.0; |
eb383413 L |
577 | |
578 | return (double) htab->collisions / (double) htab->searches; | |
e2eaf477 | 579 | } |
8fc34799 | 580 | |
68a41de7 DD |
581 | /* Hash P as a null-terminated string. |
582 | ||
583 | Copied from gcc/hashtable.c. Zack had the following to say with respect | |
584 | to applicability, though note that unlike hashtable.c, this hash table | |
585 | implementation re-hashes rather than chain buckets. | |
586 | ||
587 | http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html | |
588 | From: Zack Weinberg <zackw@panix.com> | |
589 | Date: Fri, 17 Aug 2001 02:15:56 -0400 | |
590 | ||
591 | I got it by extracting all the identifiers from all the source code | |
592 | I had lying around in mid-1999, and testing many recurrences of | |
593 | the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either | |
594 | prime numbers or the appropriate identity. This was the best one. | |
595 | I don't remember exactly what constituted "best", except I was | |
596 | looking at bucket-length distributions mostly. | |
597 | ||
598 | So it should be very good at hashing identifiers, but might not be | |
599 | as good at arbitrary strings. | |
600 | ||
601 | I'll add that it thoroughly trounces the hash functions recommended | |
602 | for this use at http://burtleburtle.net/bob/hash/index.html, both | |
603 | on speed and bucket distribution. I haven't tried it against the | |
604 | function they just started using for Perl's hashes. */ | |
8fc34799 DD |
605 | |
606 | hashval_t | |
607 | htab_hash_string (p) | |
608 | const PTR p; | |
609 | { | |
610 | const unsigned char *str = (const unsigned char *) p; | |
611 | hashval_t r = 0; | |
612 | unsigned char c; | |
613 | ||
614 | while ((c = *str++) != 0) | |
615 | r = r * 67 + c - 113; | |
616 | ||
617 | return r; | |
618 | } |