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1 | /* An expandable hash tables datatype. |
2 | Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc. | |
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 | #include <sys/types.h> | |
35 | #include <stdlib.h> | |
36 | #include <string.h> | |
37 | #include <stdio.h> | |
38 | #include "hashtab.h" | |
39 | ||
40 | /* This macro defines reserved value for empty table entry. */ | |
41 | ||
42 | #define EMPTY_ENTRY ((void *) 0) | |
43 | ||
44 | /* This macro defines reserved value for table entry which contained | |
45 | a deleted element. */ | |
46 | ||
47 | #define DELETED_ENTRY ((void *) 1) | |
48 | ||
49 | static unsigned long higher_prime_number (unsigned long); | |
50 | static hashval_t hash_pointer (const void *); | |
51 | static int eq_pointer (const void *, const void *); | |
52 | static int htab_expand (htab_t); | |
53 | static void **find_empty_slot_for_expand (htab_t, hashval_t); | |
54 | ||
55 | /* At some point, we could make these be NULL, and modify the | |
56 | hash-table routines to handle NULL specially; that would avoid | |
57 | function-call overhead for the common case of hashing pointers. */ | |
58 | htab_hash htab_hash_pointer = hash_pointer; | |
59 | htab_eq htab_eq_pointer = eq_pointer; | |
60 | ||
61 | /* The following function returns a nearest prime number which is | |
62 | greater than N, and near a power of two. */ | |
63 | ||
64 | static unsigned long | |
65 | higher_prime_number (n) | |
66 | unsigned long n; | |
67 | { | |
68 | /* These are primes that are near, but slightly smaller than, a | |
69 | power of two. */ | |
70 | static unsigned long primes[] = { | |
71 | (unsigned long) 2, | |
72 | (unsigned long) 7, | |
73 | (unsigned long) 13, | |
74 | (unsigned long) 31, | |
75 | (unsigned long) 61, | |
76 | (unsigned long) 127, | |
77 | (unsigned long) 251, | |
78 | (unsigned long) 509, | |
79 | (unsigned long) 1021, | |
80 | (unsigned long) 2039, | |
81 | (unsigned long) 4093, | |
82 | (unsigned long) 8191, | |
83 | (unsigned long) 16381, | |
84 | (unsigned long) 32749, | |
85 | (unsigned long) 65521, | |
86 | (unsigned long) 131071, | |
87 | (unsigned long) 262139, | |
88 | (unsigned long) 524287, | |
89 | (unsigned long) 1048573, | |
90 | (unsigned long) 2097143, | |
91 | (unsigned long) 4194301, | |
92 | (unsigned long) 8388593, | |
93 | (unsigned long) 16777213, | |
94 | (unsigned long) 33554393, | |
95 | (unsigned long) 67108859, | |
96 | (unsigned long) 134217689, | |
97 | (unsigned long) 268435399, | |
98 | (unsigned long) 536870909, | |
99 | (unsigned long) 1073741789, | |
100 | (unsigned long) 2147483647, | |
101 | /* 4294967291L */ | |
102 | ((unsigned long) 2147483647) + ((unsigned long) 2147483644), | |
103 | }; | |
104 | ||
105 | unsigned long* low = &primes[0]; | |
106 | unsigned long* high = &primes[sizeof(primes) / sizeof(primes[0])]; | |
107 | ||
108 | while (low != high) | |
109 | { | |
110 | unsigned long* mid = low + (high - low) / 2; | |
111 | if (n > *mid) | |
112 | low = mid + 1; | |
113 | else | |
114 | high = mid; | |
115 | } | |
116 | ||
117 | /* If we've run out of primes, abort. */ | |
118 | if (n > *low) | |
119 | { | |
120 | fprintf (stderr, "Cannot find prime bigger than %lu\n", n); | |
121 | abort (); | |
122 | } | |
123 | ||
124 | return *low; | |
125 | } | |
126 | ||
127 | /* Returns a hash code for P. */ | |
128 | ||
129 | static hashval_t | |
130 | hash_pointer (p) | |
131 | const void * p; | |
132 | { | |
133 | return (hashval_t) ((long)p >> 3); | |
134 | } | |
135 | ||
136 | /* Returns non-zero if P1 and P2 are equal. */ | |
137 | ||
138 | static int | |
139 | eq_pointer (p1, p2) | |
140 | const void * p1; | |
141 | const void * p2; | |
142 | { | |
143 | return p1 == p2; | |
144 | } | |
145 | ||
146 | /* This function creates table with length slightly longer than given | |
147 | source length. The created hash table is initiated as empty (all the | |
148 | hash table entries are EMPTY_ENTRY). The function returns the created | |
149 | hash table. Memory allocation may fail; it may return NULL. */ | |
150 | ||
151 | htab_t | |
152 | htab_try_create (size, hash_f, eq_f, del_f) | |
153 | size_t size; | |
154 | htab_hash hash_f; | |
155 | htab_eq eq_f; | |
156 | htab_del del_f; | |
157 | { | |
158 | htab_t result; | |
159 | ||
160 | size = higher_prime_number (size); | |
161 | result = (htab_t) calloc (1, sizeof (struct htab)); | |
162 | if (result == NULL) | |
163 | return NULL; | |
164 | ||
165 | result->entries = (void **) calloc (size, sizeof (void *)); | |
166 | if (result->entries == NULL) | |
167 | { | |
168 | free (result); | |
169 | return NULL; | |
170 | } | |
171 | ||
172 | result->size = size; | |
173 | result->hash_f = hash_f; | |
174 | result->eq_f = eq_f; | |
175 | result->del_f = del_f; | |
176 | result->return_allocation_failure = 1; | |
177 | return result; | |
178 | } | |
179 | ||
180 | /* This function frees all memory allocated for given hash table. | |
181 | Naturally the hash table must already exist. */ | |
182 | ||
183 | void | |
184 | htab_delete (htab) | |
185 | htab_t htab; | |
186 | { | |
187 | int i; | |
188 | ||
189 | if (htab->del_f) | |
190 | for (i = htab->size - 1; i >= 0; i--) | |
191 | if (htab->entries[i] != EMPTY_ENTRY | |
192 | && htab->entries[i] != DELETED_ENTRY) | |
193 | (*htab->del_f) (htab->entries[i]); | |
194 | ||
195 | free (htab->entries); | |
196 | free (htab); | |
197 | } | |
198 | ||
199 | /* This function clears all entries in the given hash table. */ | |
200 | ||
201 | void | |
202 | htab_empty (htab) | |
203 | htab_t htab; | |
204 | { | |
205 | int i; | |
206 | ||
207 | if (htab->del_f) | |
208 | for (i = htab->size - 1; i >= 0; i--) | |
209 | if (htab->entries[i] != EMPTY_ENTRY | |
210 | && htab->entries[i] != DELETED_ENTRY) | |
211 | (*htab->del_f) (htab->entries[i]); | |
212 | ||
213 | memset (htab->entries, 0, htab->size * sizeof (void *)); | |
214 | } | |
215 | ||
216 | /* Similar to htab_find_slot, but without several unwanted side effects: | |
217 | - Does not call htab->eq_f when it finds an existing entry. | |
218 | - Does not change the count of elements/searches/collisions in the | |
219 | hash table. | |
220 | This function also assumes there are no deleted entries in the table. | |
221 | HASH is the hash value for the element to be inserted. */ | |
222 | ||
223 | static void ** | |
224 | find_empty_slot_for_expand (htab, hash) | |
225 | htab_t htab; | |
226 | hashval_t hash; | |
227 | { | |
228 | size_t size = htab->size; | |
229 | hashval_t hash2 = 1 + hash % (size - 2); | |
230 | unsigned int index = hash % size; | |
231 | ||
232 | for (;;) | |
233 | { | |
234 | void **slot = htab->entries + index; | |
235 | ||
236 | if (*slot == EMPTY_ENTRY) | |
237 | return slot; | |
238 | else if (*slot == DELETED_ENTRY) | |
239 | abort (); | |
240 | ||
241 | index += hash2; | |
242 | if (index >= size) | |
243 | index -= size; | |
244 | } | |
245 | } | |
246 | ||
247 | /* The following function changes size of memory allocated for the | |
248 | entries and repeatedly inserts the table elements. The occupancy | |
249 | of the table after the call will be about 50%. Naturally the hash | |
250 | table must already exist. Remember also that the place of the | |
251 | table entries is changed. If memory allocation failures are allowed, | |
252 | this function will return zero, indicating that the table could not be | |
253 | expanded. If all goes well, it will return a non-zero value. */ | |
254 | ||
255 | static int | |
256 | htab_expand (htab) | |
257 | htab_t htab; | |
258 | { | |
259 | void **oentries; | |
260 | void **olimit; | |
261 | void **p; | |
262 | ||
263 | oentries = htab->entries; | |
264 | olimit = oentries + htab->size; | |
265 | ||
266 | htab->size = higher_prime_number (htab->size * 2); | |
267 | ||
268 | if (htab->return_allocation_failure) | |
269 | { | |
270 | void **nentries = (void **) calloc (htab->size, sizeof (void **)); | |
271 | if (nentries == NULL) | |
272 | return 0; | |
273 | htab->entries = nentries; | |
274 | } | |
275 | ||
276 | htab->n_elements -= htab->n_deleted; | |
277 | htab->n_deleted = 0; | |
278 | ||
279 | p = oentries; | |
280 | do | |
281 | { | |
282 | void * x = *p; | |
283 | ||
284 | if (x != EMPTY_ENTRY && x != DELETED_ENTRY) | |
285 | { | |
286 | void **q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x)); | |
287 | ||
288 | *q = x; | |
289 | } | |
290 | ||
291 | p++; | |
292 | } | |
293 | while (p < olimit); | |
294 | ||
295 | free (oentries); | |
296 | return 1; | |
297 | } | |
298 | ||
299 | /* This function searches for a hash table entry equal to the given | |
300 | element. It cannot be used to insert or delete an element. */ | |
301 | ||
302 | void * | |
303 | htab_find_with_hash (htab, element, hash) | |
304 | htab_t htab; | |
305 | const void * element; | |
306 | hashval_t hash; | |
307 | { | |
308 | unsigned int index; | |
309 | hashval_t hash2; | |
310 | size_t size; | |
311 | void * entry; | |
312 | ||
313 | htab->searches++; | |
314 | size = htab->size; | |
315 | index = hash % size; | |
316 | ||
317 | entry = htab->entries[index]; | |
318 | if (entry == EMPTY_ENTRY | |
319 | || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
320 | return entry; | |
321 | ||
322 | hash2 = 1 + hash % (size - 2); | |
323 | ||
324 | for (;;) | |
325 | { | |
326 | htab->collisions++; | |
327 | index += hash2; | |
328 | if (index >= size) | |
329 | index -= size; | |
330 | ||
331 | entry = htab->entries[index]; | |
332 | if (entry == EMPTY_ENTRY | |
333 | || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
334 | return entry; | |
335 | } | |
336 | } | |
337 | ||
338 | /* Like htab_find_slot_with_hash, but compute the hash value from the | |
339 | element. */ | |
340 | ||
341 | void * | |
342 | htab_find (htab, element) | |
343 | htab_t htab; | |
344 | const void * element; | |
345 | { | |
346 | return htab_find_with_hash (htab, element, (*htab->hash_f) (element)); | |
347 | } | |
348 | ||
349 | /* This function searches for a hash table slot containing an entry | |
350 | equal to the given element. To delete an entry, call this with | |
351 | INSERT = 0, then call htab_clear_slot on the slot returned (possibly | |
352 | after doing some checks). To insert an entry, call this with | |
353 | INSERT = 1, then write the value you want into the returned slot. | |
354 | When inserting an entry, NULL may be returned if memory allocation | |
355 | fails. */ | |
356 | ||
357 | void ** | |
358 | htab_find_slot_with_hash (htab, element, hash, insert) | |
359 | htab_t htab; | |
360 | const void * element; | |
361 | hashval_t hash; | |
362 | enum insert_option insert; | |
363 | { | |
364 | void **first_deleted_slot; | |
365 | unsigned int index; | |
366 | hashval_t hash2; | |
367 | size_t size; | |
368 | ||
369 | if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4 | |
370 | && htab_expand (htab) == 0) | |
371 | return NULL; | |
372 | ||
373 | size = htab->size; | |
374 | hash2 = 1 + hash % (size - 2); | |
375 | index = hash % size; | |
376 | ||
377 | htab->searches++; | |
378 | first_deleted_slot = NULL; | |
379 | ||
380 | for (;;) | |
381 | { | |
382 | void * entry = htab->entries[index]; | |
383 | if (entry == EMPTY_ENTRY) | |
384 | { | |
385 | if (insert == NO_INSERT) | |
386 | return NULL; | |
387 | ||
388 | htab->n_elements++; | |
389 | ||
390 | if (first_deleted_slot) | |
391 | { | |
392 | *first_deleted_slot = EMPTY_ENTRY; | |
393 | return first_deleted_slot; | |
394 | } | |
395 | ||
396 | return &htab->entries[index]; | |
397 | } | |
398 | ||
399 | if (entry == DELETED_ENTRY) | |
400 | { | |
401 | if (!first_deleted_slot) | |
402 | first_deleted_slot = &htab->entries[index]; | |
403 | } | |
404 | else if ((*htab->eq_f) (entry, element)) | |
405 | return &htab->entries[index]; | |
406 | ||
407 | htab->collisions++; | |
408 | index += hash2; | |
409 | if (index >= size) | |
410 | index -= size; | |
411 | } | |
412 | } | |
413 | ||
414 | /* Like htab_find_slot_with_hash, but compute the hash value from the | |
415 | element. */ | |
416 | ||
417 | void ** | |
418 | htab_find_slot (htab, element, insert) | |
419 | htab_t htab; | |
420 | const void * element; | |
421 | enum insert_option insert; | |
422 | { | |
423 | return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element), | |
424 | insert); | |
425 | } | |
426 | ||
427 | /* This function deletes an element with the given value from hash | |
428 | table. If there is no matching element in the hash table, this | |
429 | function does nothing. */ | |
430 | ||
431 | void | |
432 | htab_remove_elt (htab, element) | |
433 | htab_t htab; | |
434 | void * element; | |
435 | { | |
436 | void **slot; | |
437 | ||
438 | slot = htab_find_slot (htab, element, NO_INSERT); | |
439 | if (*slot == EMPTY_ENTRY) | |
440 | return; | |
441 | ||
442 | if (htab->del_f) | |
443 | (*htab->del_f) (*slot); | |
444 | ||
445 | *slot = DELETED_ENTRY; | |
446 | htab->n_deleted++; | |
447 | } | |
448 | ||
449 | /* This function clears a specified slot in a hash table. It is | |
450 | useful when you've already done the lookup and don't want to do it | |
451 | again. */ | |
452 | ||
453 | void | |
454 | htab_clear_slot (htab, slot) | |
455 | htab_t htab; | |
456 | void **slot; | |
457 | { | |
458 | if (slot < htab->entries || slot >= htab->entries + htab->size | |
459 | || *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY) | |
460 | abort (); | |
461 | ||
462 | if (htab->del_f) | |
463 | (*htab->del_f) (*slot); | |
464 | ||
465 | *slot = DELETED_ENTRY; | |
466 | htab->n_deleted++; | |
467 | } | |
468 | ||
469 | /* This function scans over the entire hash table calling | |
470 | CALLBACK for each live entry. If CALLBACK returns false, | |
471 | the iteration stops. INFO is passed as CALLBACK's second | |
472 | argument. */ | |
473 | ||
474 | void | |
475 | htab_traverse (htab, callback, info) | |
476 | htab_t htab; | |
477 | htab_trav callback; | |
478 | void * info; | |
479 | { | |
480 | void **slot = htab->entries; | |
481 | void **limit = slot + htab->size; | |
482 | ||
483 | do | |
484 | { | |
485 | void * x = *slot; | |
486 | ||
487 | if (x != EMPTY_ENTRY && x != DELETED_ENTRY) | |
488 | if (!(*callback) (slot, info)) | |
489 | break; | |
490 | } | |
491 | while (++slot < limit); | |
492 | } | |
493 | ||
494 | /* Return the current size of given hash table. */ | |
495 | ||
496 | size_t | |
497 | htab_size (htab) | |
498 | htab_t htab; | |
499 | { | |
500 | return htab->size; | |
501 | } | |
502 | ||
503 | /* Return the current number of elements in given hash table. */ | |
504 | ||
505 | size_t | |
506 | htab_elements (htab) | |
507 | htab_t htab; | |
508 | { | |
509 | return htab->n_elements - htab->n_deleted; | |
510 | } | |
511 | ||
512 | /* Return the fraction of fixed collisions during all work with given | |
513 | hash table. */ | |
514 | ||
515 | double | |
516 | htab_collisions (htab) | |
517 | htab_t htab; | |
518 | { | |
519 | if (htab->searches == 0) | |
520 | return 0.0; | |
521 | ||
522 | return (double) htab->collisions / (double) htab->searches; | |
523 | } |