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 | |
99a4c1bd | 161 | created hash table. Memory allocation must not fail. */ |
e2eaf477 | 162 | |
b4fe2683 JM |
163 | htab_t |
164 | htab_create (size, hash_f, eq_f, del_f) | |
e2eaf477 | 165 | size_t size; |
b4fe2683 JM |
166 | htab_hash hash_f; |
167 | htab_eq eq_f; | |
168 | htab_del del_f; | |
e2eaf477 | 169 | { |
b4fe2683 | 170 | htab_t result; |
e2eaf477 ILT |
171 | |
172 | size = higher_prime_number (size); | |
b4fe2683 | 173 | result = (htab_t) xcalloc (1, sizeof (struct htab)); |
e0f3df8f | 174 | result->entries = (PTR *) xcalloc (size, sizeof (PTR)); |
e2eaf477 | 175 | result->size = size; |
b4fe2683 JM |
176 | result->hash_f = hash_f; |
177 | result->eq_f = eq_f; | |
178 | result->del_f = del_f; | |
99a4c1bd HPN |
179 | result->return_allocation_failure = 0; |
180 | return result; | |
181 | } | |
182 | ||
183 | /* This function creates table with length slightly longer than given | |
184 | source length. The created hash table is initiated as empty (all the | |
185 | hash table entries are EMPTY_ENTRY). The function returns the created | |
186 | hash table. Memory allocation may fail; it may return NULL. */ | |
187 | ||
188 | htab_t | |
189 | htab_try_create (size, hash_f, eq_f, del_f) | |
190 | size_t size; | |
191 | htab_hash hash_f; | |
192 | htab_eq eq_f; | |
193 | htab_del del_f; | |
194 | { | |
195 | htab_t result; | |
196 | ||
197 | size = higher_prime_number (size); | |
198 | result = (htab_t) calloc (1, sizeof (struct htab)); | |
199 | if (result == NULL) | |
200 | return NULL; | |
201 | ||
202 | result->entries = (PTR *) calloc (size, sizeof (PTR)); | |
203 | if (result->entries == NULL) | |
204 | { | |
205 | free (result); | |
206 | return NULL; | |
207 | } | |
208 | ||
209 | result->size = size; | |
210 | result->hash_f = hash_f; | |
211 | result->eq_f = eq_f; | |
212 | result->del_f = del_f; | |
213 | result->return_allocation_failure = 1; | |
e2eaf477 ILT |
214 | return result; |
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 | |
e2eaf477 ILT |
232 | free (htab->entries); |
233 | free (htab); | |
234 | } | |
235 | ||
236 | /* This function clears all entries in the given hash table. */ | |
237 | ||
238 | void | |
b4fe2683 JM |
239 | htab_empty (htab) |
240 | htab_t htab; | |
241 | { | |
242 | int i; | |
eb383413 | 243 | |
b4fe2683 JM |
244 | if (htab->del_f) |
245 | for (i = htab->size - 1; i >= 0; i--) | |
eb383413 L |
246 | if (htab->entries[i] != EMPTY_ENTRY |
247 | && htab->entries[i] != DELETED_ENTRY) | |
248 | (*htab->del_f) (htab->entries[i]); | |
b4fe2683 | 249 | |
e0f3df8f | 250 | memset (htab->entries, 0, htab->size * sizeof (PTR)); |
b4fe2683 JM |
251 | } |
252 | ||
253 | /* Similar to htab_find_slot, but without several unwanted side effects: | |
254 | - Does not call htab->eq_f when it finds an existing entry. | |
255 | - Does not change the count of elements/searches/collisions in the | |
256 | hash table. | |
257 | This function also assumes there are no deleted entries in the table. | |
258 | HASH is the hash value for the element to be inserted. */ | |
eb383413 | 259 | |
e0f3df8f | 260 | static PTR * |
b4fe2683 JM |
261 | find_empty_slot_for_expand (htab, hash) |
262 | htab_t htab; | |
eb383413 | 263 | hashval_t hash; |
e2eaf477 | 264 | { |
b4fe2683 | 265 | size_t size = htab->size; |
b4fe2683 | 266 | unsigned int index = hash % size; |
b1c933fc RH |
267 | PTR *slot = htab->entries + index; |
268 | hashval_t hash2; | |
269 | ||
270 | if (*slot == EMPTY_ENTRY) | |
271 | return slot; | |
272 | else if (*slot == DELETED_ENTRY) | |
273 | abort (); | |
b4fe2683 | 274 | |
b1c933fc | 275 | hash2 = 1 + hash % (size - 2); |
b4fe2683 JM |
276 | for (;;) |
277 | { | |
b1c933fc RH |
278 | index += hash2; |
279 | if (index >= size) | |
280 | index -= size; | |
eb383413 | 281 | |
b1c933fc | 282 | slot = htab->entries + index; |
b4fe2683 JM |
283 | if (*slot == EMPTY_ENTRY) |
284 | return slot; | |
eb383413 | 285 | else if (*slot == DELETED_ENTRY) |
b4fe2683 | 286 | abort (); |
b4fe2683 | 287 | } |
e2eaf477 ILT |
288 | } |
289 | ||
290 | /* The following function changes size of memory allocated for the | |
291 | entries and repeatedly inserts the table elements. The occupancy | |
292 | of the table after the call will be about 50%. Naturally the hash | |
293 | table must already exist. Remember also that the place of the | |
99a4c1bd HPN |
294 | table entries is changed. If memory allocation failures are allowed, |
295 | this function will return zero, indicating that the table could not be | |
296 | expanded. If all goes well, it will return a non-zero value. */ | |
e2eaf477 | 297 | |
99a4c1bd | 298 | static int |
b4fe2683 JM |
299 | htab_expand (htab) |
300 | htab_t htab; | |
e2eaf477 | 301 | { |
e0f3df8f HPN |
302 | PTR *oentries; |
303 | PTR *olimit; | |
304 | PTR *p; | |
b4fe2683 JM |
305 | |
306 | oentries = htab->entries; | |
307 | olimit = oentries + htab->size; | |
308 | ||
309 | htab->size = higher_prime_number (htab->size * 2); | |
99a4c1bd HPN |
310 | |
311 | if (htab->return_allocation_failure) | |
312 | { | |
313 | PTR *nentries = (PTR *) calloc (htab->size, sizeof (PTR *)); | |
314 | if (nentries == NULL) | |
315 | return 0; | |
316 | htab->entries = nentries; | |
317 | } | |
318 | else | |
319 | htab->entries = (PTR *) xcalloc (htab->size, sizeof (PTR *)); | |
b4fe2683 JM |
320 | |
321 | htab->n_elements -= htab->n_deleted; | |
322 | htab->n_deleted = 0; | |
323 | ||
324 | p = oentries; | |
325 | do | |
326 | { | |
e0f3df8f | 327 | PTR x = *p; |
eb383413 | 328 | |
b4fe2683 JM |
329 | if (x != EMPTY_ENTRY && x != DELETED_ENTRY) |
330 | { | |
e0f3df8f | 331 | PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x)); |
eb383413 | 332 | |
b4fe2683 JM |
333 | *q = x; |
334 | } | |
eb383413 | 335 | |
b4fe2683 JM |
336 | p++; |
337 | } | |
338 | while (p < olimit); | |
eb383413 | 339 | |
b4fe2683 | 340 | free (oentries); |
99a4c1bd | 341 | return 1; |
e2eaf477 ILT |
342 | } |
343 | ||
b4fe2683 JM |
344 | /* This function searches for a hash table entry equal to the given |
345 | element. It cannot be used to insert or delete an element. */ | |
346 | ||
e0f3df8f | 347 | PTR |
b4fe2683 JM |
348 | htab_find_with_hash (htab, element, hash) |
349 | htab_t htab; | |
e0f3df8f | 350 | const PTR element; |
eb383413 | 351 | hashval_t hash; |
e2eaf477 | 352 | { |
eb383413 L |
353 | unsigned int index; |
354 | hashval_t hash2; | |
b4fe2683 | 355 | size_t size; |
e0f3df8f | 356 | PTR entry; |
e2eaf477 | 357 | |
b4fe2683 JM |
358 | htab->searches++; |
359 | size = htab->size; | |
b4fe2683 JM |
360 | index = hash % size; |
361 | ||
eb383413 L |
362 | entry = htab->entries[index]; |
363 | if (entry == EMPTY_ENTRY | |
364 | || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
365 | return entry; | |
366 | ||
367 | hash2 = 1 + hash % (size - 2); | |
368 | ||
b4fe2683 | 369 | for (;;) |
e2eaf477 | 370 | { |
b4fe2683 JM |
371 | htab->collisions++; |
372 | index += hash2; | |
373 | if (index >= size) | |
374 | index -= size; | |
eb383413 L |
375 | |
376 | entry = htab->entries[index]; | |
377 | if (entry == EMPTY_ENTRY | |
378 | || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
379 | return entry; | |
e2eaf477 | 380 | } |
b4fe2683 JM |
381 | } |
382 | ||
383 | /* Like htab_find_slot_with_hash, but compute the hash value from the | |
384 | element. */ | |
eb383413 | 385 | |
e0f3df8f | 386 | PTR |
b4fe2683 JM |
387 | htab_find (htab, element) |
388 | htab_t htab; | |
e0f3df8f | 389 | const PTR element; |
b4fe2683 JM |
390 | { |
391 | return htab_find_with_hash (htab, element, (*htab->hash_f) (element)); | |
392 | } | |
393 | ||
394 | /* This function searches for a hash table slot containing an entry | |
395 | equal to the given element. To delete an entry, call this with | |
396 | INSERT = 0, then call htab_clear_slot on the slot returned (possibly | |
397 | after doing some checks). To insert an entry, call this with | |
99a4c1bd HPN |
398 | INSERT = 1, then write the value you want into the returned slot. |
399 | When inserting an entry, NULL may be returned if memory allocation | |
400 | fails. */ | |
b4fe2683 | 401 | |
e0f3df8f | 402 | PTR * |
b4fe2683 JM |
403 | htab_find_slot_with_hash (htab, element, hash, insert) |
404 | htab_t htab; | |
e0f3df8f | 405 | const PTR element; |
eb383413 L |
406 | hashval_t hash; |
407 | enum insert_option insert; | |
b4fe2683 | 408 | { |
e0f3df8f | 409 | PTR *first_deleted_slot; |
eb383413 L |
410 | unsigned int index; |
411 | hashval_t hash2; | |
b4fe2683 | 412 | size_t size; |
b1c933fc | 413 | PTR entry; |
b4fe2683 | 414 | |
99a4c1bd HPN |
415 | if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4 |
416 | && htab_expand (htab) == 0) | |
417 | return NULL; | |
b4fe2683 JM |
418 | |
419 | size = htab->size; | |
b4fe2683 JM |
420 | index = hash % size; |
421 | ||
e2eaf477 | 422 | htab->searches++; |
b4fe2683 JM |
423 | first_deleted_slot = NULL; |
424 | ||
b1c933fc RH |
425 | entry = htab->entries[index]; |
426 | if (entry == EMPTY_ENTRY) | |
427 | goto empty_entry; | |
428 | else if (entry == DELETED_ENTRY) | |
429 | first_deleted_slot = &htab->entries[index]; | |
430 | else if ((*htab->eq_f) (entry, element)) | |
431 | return &htab->entries[index]; | |
432 | ||
433 | hash2 = 1 + hash % (size - 2); | |
b4fe2683 | 434 | for (;;) |
e2eaf477 | 435 | { |
b1c933fc RH |
436 | htab->collisions++; |
437 | index += hash2; | |
438 | if (index >= size) | |
439 | index -= size; | |
440 | ||
441 | entry = htab->entries[index]; | |
b4fe2683 | 442 | if (entry == EMPTY_ENTRY) |
b1c933fc RH |
443 | goto empty_entry; |
444 | else if (entry == DELETED_ENTRY) | |
b4fe2683 JM |
445 | { |
446 | if (!first_deleted_slot) | |
447 | first_deleted_slot = &htab->entries[index]; | |
448 | } | |
b1c933fc | 449 | else if ((*htab->eq_f) (entry, element)) |
eb383413 | 450 | return &htab->entries[index]; |
e2eaf477 | 451 | } |
b1c933fc RH |
452 | |
453 | empty_entry: | |
454 | if (insert == NO_INSERT) | |
455 | return NULL; | |
456 | ||
457 | htab->n_elements++; | |
458 | ||
459 | if (first_deleted_slot) | |
460 | { | |
461 | *first_deleted_slot = EMPTY_ENTRY; | |
462 | return first_deleted_slot; | |
463 | } | |
464 | ||
465 | return &htab->entries[index]; | |
e2eaf477 ILT |
466 | } |
467 | ||
b4fe2683 JM |
468 | /* Like htab_find_slot_with_hash, but compute the hash value from the |
469 | element. */ | |
eb383413 | 470 | |
e0f3df8f | 471 | PTR * |
b4fe2683 JM |
472 | htab_find_slot (htab, element, insert) |
473 | htab_t htab; | |
e0f3df8f | 474 | const PTR element; |
eb383413 | 475 | enum insert_option insert; |
b4fe2683 JM |
476 | { |
477 | return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element), | |
478 | insert); | |
479 | } | |
480 | ||
481 | /* This function deletes an element with the given value from hash | |
482 | table. If there is no matching element in the hash table, this | |
483 | function does nothing. */ | |
e2eaf477 ILT |
484 | |
485 | void | |
b4fe2683 JM |
486 | htab_remove_elt (htab, element) |
487 | htab_t htab; | |
e0f3df8f | 488 | PTR element; |
e2eaf477 | 489 | { |
e0f3df8f | 490 | PTR *slot; |
b4fe2683 | 491 | |
eb383413 | 492 | slot = htab_find_slot (htab, element, NO_INSERT); |
b4fe2683 JM |
493 | if (*slot == EMPTY_ENTRY) |
494 | return; | |
495 | ||
496 | if (htab->del_f) | |
497 | (*htab->del_f) (*slot); | |
e2eaf477 | 498 | |
b4fe2683 JM |
499 | *slot = DELETED_ENTRY; |
500 | htab->n_deleted++; | |
e2eaf477 ILT |
501 | } |
502 | ||
b4fe2683 JM |
503 | /* This function clears a specified slot in a hash table. It is |
504 | useful when you've already done the lookup and don't want to do it | |
505 | again. */ | |
e2eaf477 ILT |
506 | |
507 | void | |
b4fe2683 JM |
508 | htab_clear_slot (htab, slot) |
509 | htab_t htab; | |
e0f3df8f | 510 | PTR *slot; |
e2eaf477 ILT |
511 | { |
512 | if (slot < htab->entries || slot >= htab->entries + htab->size | |
513 | || *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY) | |
514 | abort (); | |
eb383413 | 515 | |
b4fe2683 JM |
516 | if (htab->del_f) |
517 | (*htab->del_f) (*slot); | |
eb383413 | 518 | |
e2eaf477 | 519 | *slot = DELETED_ENTRY; |
b4fe2683 | 520 | htab->n_deleted++; |
e2eaf477 ILT |
521 | } |
522 | ||
523 | /* This function scans over the entire hash table calling | |
524 | CALLBACK for each live entry. If CALLBACK returns false, | |
525 | the iteration stops. INFO is passed as CALLBACK's second | |
526 | argument. */ | |
527 | ||
528 | void | |
b4fe2683 JM |
529 | htab_traverse (htab, callback, info) |
530 | htab_t htab; | |
531 | htab_trav callback; | |
e0f3df8f | 532 | PTR info; |
e2eaf477 | 533 | { |
e0f3df8f HPN |
534 | PTR *slot = htab->entries; |
535 | PTR *limit = slot + htab->size; | |
eb383413 | 536 | |
b4fe2683 JM |
537 | do |
538 | { | |
e0f3df8f | 539 | PTR x = *slot; |
eb383413 | 540 | |
b4fe2683 JM |
541 | if (x != EMPTY_ENTRY && x != DELETED_ENTRY) |
542 | if (!(*callback) (slot, info)) | |
543 | break; | |
544 | } | |
545 | while (++slot < limit); | |
e2eaf477 ILT |
546 | } |
547 | ||
eb383413 | 548 | /* Return the current size of given hash table. */ |
e2eaf477 ILT |
549 | |
550 | size_t | |
b4fe2683 JM |
551 | htab_size (htab) |
552 | htab_t htab; | |
e2eaf477 ILT |
553 | { |
554 | return htab->size; | |
555 | } | |
556 | ||
eb383413 | 557 | /* Return the current number of elements in given hash table. */ |
e2eaf477 ILT |
558 | |
559 | size_t | |
b4fe2683 JM |
560 | htab_elements (htab) |
561 | htab_t htab; | |
e2eaf477 | 562 | { |
b4fe2683 | 563 | return htab->n_elements - htab->n_deleted; |
e2eaf477 ILT |
564 | } |
565 | ||
eb383413 L |
566 | /* Return the fraction of fixed collisions during all work with given |
567 | hash table. */ | |
e2eaf477 | 568 | |
b4fe2683 JM |
569 | double |
570 | htab_collisions (htab) | |
571 | htab_t htab; | |
e2eaf477 | 572 | { |
eb383413 | 573 | if (htab->searches == 0) |
b4fe2683 | 574 | return 0.0; |
eb383413 L |
575 | |
576 | return (double) htab->collisions / (double) htab->searches; | |
e2eaf477 | 577 | } |
8fc34799 | 578 | |
68a41de7 DD |
579 | /* Hash P as a null-terminated string. |
580 | ||
581 | Copied from gcc/hashtable.c. Zack had the following to say with respect | |
582 | to applicability, though note that unlike hashtable.c, this hash table | |
583 | implementation re-hashes rather than chain buckets. | |
584 | ||
585 | http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html | |
586 | From: Zack Weinberg <zackw@panix.com> | |
587 | Date: Fri, 17 Aug 2001 02:15:56 -0400 | |
588 | ||
589 | I got it by extracting all the identifiers from all the source code | |
590 | I had lying around in mid-1999, and testing many recurrences of | |
591 | the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either | |
592 | prime numbers or the appropriate identity. This was the best one. | |
593 | I don't remember exactly what constituted "best", except I was | |
594 | looking at bucket-length distributions mostly. | |
595 | ||
596 | So it should be very good at hashing identifiers, but might not be | |
597 | as good at arbitrary strings. | |
598 | ||
599 | I'll add that it thoroughly trounces the hash functions recommended | |
600 | for this use at http://burtleburtle.net/bob/hash/index.html, both | |
601 | on speed and bucket distribution. I haven't tried it against the | |
602 | function they just started using for Perl's hashes. */ | |
8fc34799 DD |
603 | |
604 | hashval_t | |
605 | htab_hash_string (p) | |
606 | const PTR p; | |
607 | { | |
608 | const unsigned char *str = (const unsigned char *) p; | |
609 | hashval_t r = 0; | |
610 | unsigned char c; | |
611 | ||
612 | while ((c = *str++) != 0) | |
613 | r = r * 67 + c - 113; | |
614 | ||
615 | return r; | |
616 | } |