Commit | Line | Data |
---|---|---|
e2eaf477 ILT |
1 | /* An expandable hash tables datatype. |
2 | Copyright (C) 1999 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 | #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 | ||
44 | #include <stdio.h> | |
45 | ||
46 | #include "libiberty.h" | |
47 | #include "hashtab.h" | |
48 | ||
49 | /* The following variable is used for debugging. Its value is number | |
50 | of all calls of `find_hash_table_entry' for all hash tables. */ | |
51 | ||
52 | static int all_searches = 0; | |
53 | ||
54 | /* The following variable is used for debugging. Its value is number | |
55 | of collisions fixed for time of work with all hash tables. */ | |
56 | ||
57 | static int all_collisions = 0; | |
58 | ||
59 | /* The following variable is used for debugging. Its value is number | |
60 | of all table expansions fixed for time of work with all hash | |
61 | tables. */ | |
62 | ||
63 | static int all_expansions = 0; | |
64 | ||
65 | /* This macro defines reserved value for empty table entry. */ | |
66 | ||
67 | #define EMPTY_ENTRY NULL | |
68 | ||
69 | /* This macro defines reserved value for table entry which contained | |
70 | a deleted element. */ | |
71 | ||
72 | #define DELETED_ENTRY ((void *) 1) | |
73 | ||
74 | /* The following function returns the nearest prime number which is | |
75 | greater than given source number. */ | |
76 | ||
77 | static unsigned long | |
78 | higher_prime_number (number) | |
79 | unsigned long number; | |
80 | { | |
81 | unsigned long i; | |
82 | ||
83 | for (number = (number / 2) * 2 + 3;; number += 2) | |
84 | { | |
85 | for (i = 3; i * i <= number; i += 2) | |
86 | if (number % i == 0) | |
87 | break; | |
88 | if (i * i > number) | |
89 | return number; | |
90 | } | |
91 | } | |
92 | ||
93 | /* This function creates table with length slightly longer than given | |
94 | source length. Created hash table is initiated as empty (all the | |
95 | hash table entries are EMPTY_ENTRY). The function returns the | |
96 | created hash table. */ | |
97 | ||
98 | hash_table_t | |
99 | create_hash_table (size, hash_function, eq_function) | |
100 | size_t size; | |
101 | unsigned (*hash_function) PARAMS ((hash_table_entry_t)); | |
102 | int (*eq_function) PARAMS ((hash_table_entry_t, hash_table_entry_t)); | |
103 | { | |
104 | hash_table_t result; | |
105 | ||
106 | size = higher_prime_number (size); | |
107 | result = (hash_table_t) xmalloc (sizeof (*result)); | |
108 | result->entries | |
109 | = (hash_table_entry_t *) xmalloc (size * sizeof (hash_table_entry_t)); | |
110 | result->size = size; | |
111 | result->hash_function = hash_function; | |
112 | result->eq_function = eq_function; | |
113 | result->number_of_elements = 0; | |
114 | result->number_of_deleted_elements = 0; | |
115 | result->searches = 0; | |
116 | result->collisions = 0; | |
117 | memset (result->entries, 0, size * sizeof (hash_table_entry_t)); | |
118 | return result; | |
119 | } | |
120 | ||
121 | /* This function frees all memory allocated for given hash table. | |
122 | Naturally the hash table must already exist. */ | |
123 | ||
124 | void | |
125 | delete_hash_table (htab) | |
126 | hash_table_t htab; | |
127 | { | |
128 | free (htab->entries); | |
129 | free (htab); | |
130 | } | |
131 | ||
132 | /* This function clears all entries in the given hash table. */ | |
133 | ||
134 | void | |
135 | empty_hash_table (htab) | |
136 | hash_table_t htab; | |
137 | { | |
138 | memset (htab->entries, 0, htab->size * sizeof (hash_table_entry_t)); | |
139 | } | |
140 | ||
141 | /* The following function changes size of memory allocated for the | |
142 | entries and repeatedly inserts the table elements. The occupancy | |
143 | of the table after the call will be about 50%. Naturally the hash | |
144 | table must already exist. Remember also that the place of the | |
145 | table entries is changed. */ | |
146 | ||
147 | static void | |
148 | expand_hash_table (htab) | |
149 | hash_table_t htab; | |
150 | { | |
151 | hash_table_t new_htab; | |
152 | hash_table_entry_t *entry_ptr; | |
153 | hash_table_entry_t *new_entry_ptr; | |
154 | ||
155 | new_htab = create_hash_table (htab->number_of_elements * 2, | |
156 | htab->hash_function, htab->eq_function); | |
157 | for (entry_ptr = htab->entries; entry_ptr < htab->entries + htab->size; | |
158 | entry_ptr++) | |
159 | if (*entry_ptr != EMPTY_ENTRY && *entry_ptr != DELETED_ENTRY) | |
160 | { | |
161 | new_entry_ptr = find_hash_table_entry (new_htab, *entry_ptr, 1); | |
162 | *new_entry_ptr = (*entry_ptr); | |
163 | } | |
164 | free (htab->entries); | |
165 | *htab = (*new_htab); | |
166 | free (new_htab); | |
167 | } | |
168 | ||
169 | /* This function searches for hash table entry which contains element | |
170 | equal to given value or empty entry in which given value can be | |
171 | placed (if the element with given value does not exist in the | |
172 | table). The function works in two regimes. The first regime is | |
173 | used only for search. The second is used for search and | |
174 | reservation empty entry for given value. The table is expanded if | |
175 | occupancy (taking into accout also deleted elements) is more than | |
176 | 75%. Naturally the hash table must already exist. If reservation | |
177 | flag is TRUE then the element with given value should be inserted | |
178 | into the table entry before another call of | |
179 | `find_hash_table_entry'. */ | |
180 | ||
181 | hash_table_entry_t * | |
182 | find_hash_table_entry (htab, element, reserve) | |
183 | hash_table_t htab; | |
184 | hash_table_entry_t element; | |
185 | int reserve; | |
186 | { | |
187 | hash_table_entry_t *entry_ptr; | |
188 | hash_table_entry_t *first_deleted_entry_ptr; | |
189 | unsigned index, hash_value, secondary_hash_value; | |
190 | ||
191 | if (htab->size * 3 <= htab->number_of_elements * 4) | |
192 | { | |
193 | all_expansions++; | |
194 | expand_hash_table (htab); | |
195 | } | |
196 | hash_value = (*htab->hash_function) (element); | |
197 | secondary_hash_value = 1 + hash_value % (htab->size - 2); | |
198 | index = hash_value % htab->size; | |
199 | htab->searches++; | |
200 | all_searches++; | |
201 | first_deleted_entry_ptr = NULL; | |
202 | for (;;htab->collisions++, all_collisions++) | |
203 | { | |
204 | entry_ptr = htab->entries + index; | |
205 | if (*entry_ptr == EMPTY_ENTRY) | |
206 | { | |
207 | if (reserve) | |
208 | { | |
209 | htab->number_of_elements++; | |
210 | if (first_deleted_entry_ptr != NULL) | |
211 | { | |
212 | entry_ptr = first_deleted_entry_ptr; | |
213 | *entry_ptr = EMPTY_ENTRY; | |
214 | } | |
215 | } | |
216 | break; | |
217 | } | |
218 | else if (*entry_ptr != DELETED_ENTRY) | |
219 | { | |
220 | if ((*htab->eq_function) (*entry_ptr, element)) | |
221 | break; | |
222 | } | |
223 | else if (first_deleted_entry_ptr == NULL) | |
224 | first_deleted_entry_ptr = entry_ptr; | |
225 | index += secondary_hash_value; | |
226 | if (index >= htab->size) | |
227 | index -= htab->size; | |
228 | } | |
229 | return entry_ptr; | |
230 | } | |
231 | ||
232 | /* This function deletes element with given value from hash table. | |
233 | The hash table entry value will be `DELETED_ENTRY' after the | |
234 | function call. Naturally the hash table must already exist. Hash | |
235 | table entry for given value should be not empty (or deleted). */ | |
236 | ||
237 | void | |
238 | remove_element_from_hash_table_entry (htab, element) | |
239 | hash_table_t htab; | |
240 | hash_table_entry_t element; | |
241 | { | |
242 | hash_table_entry_t *entry_ptr; | |
243 | ||
244 | entry_ptr = find_hash_table_entry (htab, element, 0); | |
245 | *entry_ptr = DELETED_ENTRY; | |
246 | htab->number_of_deleted_elements++; | |
247 | } | |
248 | ||
249 | /* This function clears a specified slot in a hash table. | |
250 | It is useful when you've already done the lookup and don't want to | |
251 | do it again. */ | |
252 | ||
253 | void | |
254 | clear_hash_table_slot (htab, slot) | |
255 | hash_table_t htab; | |
256 | hash_table_entry_t *slot; | |
257 | { | |
258 | if (slot < htab->entries || slot >= htab->entries + htab->size | |
259 | || *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY) | |
260 | abort (); | |
261 | *slot = DELETED_ENTRY; | |
262 | htab->number_of_deleted_elements++; | |
263 | } | |
264 | ||
265 | /* This function scans over the entire hash table calling | |
266 | CALLBACK for each live entry. If CALLBACK returns false, | |
267 | the iteration stops. INFO is passed as CALLBACK's second | |
268 | argument. */ | |
269 | ||
270 | void | |
271 | traverse_hash_table (htab, callback, info) | |
272 | hash_table_t htab; | |
273 | int (*callback) PARAMS ((hash_table_entry_t, void *)); | |
274 | void *info; | |
275 | { | |
276 | hash_table_entry_t *entry_ptr; | |
277 | for (entry_ptr = htab->entries; entry_ptr < htab->entries + htab->size; | |
278 | entry_ptr++) | |
279 | if (*entry_ptr != EMPTY_ENTRY && *entry_ptr != DELETED_ENTRY) | |
280 | if (!callback (*entry_ptr, info)) | |
281 | break; | |
282 | } | |
283 | ||
284 | /* The following function returns current size of given hash table. */ | |
285 | ||
286 | size_t | |
287 | hash_table_size (htab) | |
288 | hash_table_t htab; | |
289 | { | |
290 | return htab->size; | |
291 | } | |
292 | ||
293 | /* The following function returns current number of elements in given | |
294 | hash table. */ | |
295 | ||
296 | size_t | |
297 | hash_table_elements_number (htab) | |
298 | hash_table_t htab; | |
299 | { | |
300 | return htab->number_of_elements - htab->number_of_deleted_elements; | |
301 | } | |
302 | ||
303 | /* The following function returns number of percents of fixed | |
304 | collisions during all work with given hash table. */ | |
305 | ||
306 | int | |
307 | hash_table_collisions (htab) | |
308 | hash_table_t htab; | |
309 | { | |
310 | int searches; | |
311 | ||
312 | searches = htab->searches; | |
313 | if (searches == 0) | |
314 | searches++; | |
315 | return htab->collisions * 100 / searches; | |
316 | } | |
317 | ||
318 | /* The following function returns number of percents of fixed | |
319 | collisions during all work with all hash tables. */ | |
320 | ||
321 | int | |
322 | all_hash_table_collisions () | |
323 | { | |
324 | int searches; | |
325 | ||
326 | searches = all_searches; | |
327 | if (searches == 0) | |
328 | searches++; | |
329 | return all_collisions * 100 / searches; | |
330 | } |