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1 | /* Hash tables for Objective C internal structures | |
2 | Copyright (C) 1993-2013 Free Software Foundation, Inc. | |
3 | ||
4 | This file is part of GCC. | |
5 | ||
6 | GCC is free software; you can redistribute it and/or modify | |
7 | it under the terms of the GNU General Public License as published by | |
8 | the Free Software Foundation; either version 3, or (at your option) | |
9 | any later version. | |
10 | ||
11 | GCC 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 | |
14 | GNU General Public License for more details. | |
15 | ||
16 | Under Section 7 of GPL version 3, you are granted additional | |
17 | permissions described in the GCC Runtime Library Exception, version | |
18 | 3.1, as published by the Free Software Foundation. | |
19 | ||
20 | You should have received a copy of the GNU General Public License and | |
21 | a copy of the GCC Runtime Library Exception along with this program; | |
22 | see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |
23 | <http://www.gnu.org/licenses/>. */ | |
24 | ||
25 | #include "objc-private/common.h" | |
26 | #include <assert.h> /* For assert. */ | |
27 | ||
28 | #include "objc/runtime.h" /* For objc_calloc. */ | |
29 | #include "objc-private/hash.h" | |
30 | ||
31 | /* These two macros determine when a hash table is full and | |
32 | by how much it should be expanded respectively. | |
33 | ||
34 | These equations are percentages. */ | |
35 | #define FULLNESS(cache) \ | |
36 | ((((cache)->size * 75) / 100) <= (cache)->used) | |
37 | #define EXPANSION(cache) \ | |
38 | ((cache)->size * 2) | |
39 | ||
40 | cache_ptr | |
41 | objc_hash_new (unsigned int size, hash_func_type hash_func, | |
42 | compare_func_type compare_func) | |
43 | { | |
44 | cache_ptr cache; | |
45 | ||
46 | /* Pass me a value greater than 0 and a power of 2. */ | |
47 | assert (size); | |
48 | assert (! (size & (size - 1))); | |
49 | ||
50 | /* Allocate the cache structure. calloc insures its initialization | |
51 | for default values. */ | |
52 | cache = (cache_ptr) objc_calloc (1, sizeof (struct cache)); | |
53 | assert (cache); | |
54 | ||
55 | /* Allocate the array of buckets for the cache. calloc initializes | |
56 | all of the pointers to NULL. */ | |
57 | cache->node_table | |
58 | = (node_ptr *) objc_calloc (size, sizeof (node_ptr)); | |
59 | assert (cache->node_table); | |
60 | ||
61 | cache->size = size; | |
62 | ||
63 | /* This should work for all processor architectures (?). */ | |
64 | cache->mask = (size - 1); | |
65 | ||
66 | /* Store the hashing function so that codes can be computed. */ | |
67 | cache->hash_func = hash_func; | |
68 | ||
69 | /* Store the function that compares hash keys to determine if they | |
70 | are equal. */ | |
71 | cache->compare_func = compare_func; | |
72 | ||
73 | return cache; | |
74 | } | |
75 | ||
76 | ||
77 | void | |
78 | objc_hash_delete (cache_ptr cache) | |
79 | { | |
80 | node_ptr node; | |
81 | node_ptr next_node; | |
82 | unsigned int i; | |
83 | ||
84 | /* Purge all key/value pairs from the table. */ | |
85 | /* Step through the nodes one by one and remove every node WITHOUT | |
86 | using objc_hash_next. this makes objc_hash_delete much more | |
87 | efficient. */ | |
88 | for (i = 0; i < cache->size; i++) | |
89 | { | |
90 | if ((node = cache->node_table[i])) | |
91 | { | |
92 | /* An entry in the hash table has been found. Now step | |
93 | through the nodes next in the list and free them. */ | |
94 | while ((next_node = node->next)) | |
95 | { | |
96 | objc_hash_remove (cache,node->key); | |
97 | node = next_node; | |
98 | } | |
99 | objc_hash_remove (cache,node->key); | |
100 | } | |
101 | } | |
102 | ||
103 | /* Release the array of nodes and the cache itself. */ | |
104 | objc_free(cache->node_table); | |
105 | objc_free(cache); | |
106 | } | |
107 | ||
108 | ||
109 | void | |
110 | objc_hash_add (cache_ptr *cachep, const void *key, void *value) | |
111 | { | |
112 | size_t indx = (*(*cachep)->hash_func) (*cachep, key); | |
113 | node_ptr node = (node_ptr) objc_calloc (1, sizeof (struct cache_node)); | |
114 | ||
115 | assert (node); | |
116 | ||
117 | /* Initialize the new node. */ | |
118 | node->key = key; | |
119 | node->value = value; | |
120 | node->next = (*cachep)->node_table[indx]; | |
121 | ||
122 | /* Debugging. Check the list for another key. */ | |
123 | #ifdef DEBUG | |
124 | { | |
125 | node_ptr node1 = (*cachep)->node_table[indx]; | |
126 | while (node1) | |
127 | { | |
128 | assert (node1->key != key); | |
129 | node1 = node1->next; | |
130 | } | |
131 | } | |
132 | #endif | |
133 | ||
134 | /* Install the node as the first element on the list. */ | |
135 | (*cachep)->node_table[indx] = node; | |
136 | ||
137 | /* Bump the number of entries in the cache. */ | |
138 | ++(*cachep)->used; | |
139 | ||
140 | /* Check the hash table's fullness. We're going to expand if it is | |
141 | above the fullness level. */ | |
142 | if (FULLNESS (*cachep)) | |
143 | { | |
144 | /* The hash table has reached its fullness level. Time to | |
145 | expand it. | |
146 | ||
147 | I'm using a slow method here but is built on other primitive | |
148 | functions thereby increasing its correctness. */ | |
149 | node_ptr node1 = NULL; | |
150 | cache_ptr new = objc_hash_new (EXPANSION (*cachep), | |
151 | (*cachep)->hash_func, | |
152 | (*cachep)->compare_func); | |
153 | ||
154 | DEBUG_PRINTF ("Expanding cache %#x from %d to %d\n", | |
155 | (int) *cachep, (*cachep)->size, new->size); | |
156 | ||
157 | /* Copy the nodes from the first hash table to the new one. */ | |
158 | while ((node1 = objc_hash_next (*cachep, node1))) | |
159 | objc_hash_add (&new, node1->key, node1->value); | |
160 | ||
161 | /* Trash the old cache. */ | |
162 | objc_hash_delete (*cachep); | |
163 | ||
164 | /* Return a pointer to the new hash table. */ | |
165 | *cachep = new; | |
166 | } | |
167 | } | |
168 | ||
169 | void | |
170 | objc_hash_remove (cache_ptr cache, const void *key) | |
171 | { | |
172 | size_t indx = (*cache->hash_func) (cache, key); | |
173 | node_ptr node = cache->node_table[indx]; | |
174 | ||
175 | /* We assume there is an entry in the table. Error if it is | |
176 | not. */ | |
177 | assert (node); | |
178 | ||
179 | /* Special case. First element is the key/value pair to be | |
180 | removed. */ | |
181 | if ((*cache->compare_func) (node->key, key)) | |
182 | { | |
183 | cache->node_table[indx] = node->next; | |
184 | objc_free(node); | |
185 | } | |
186 | else | |
187 | { | |
188 | /* Otherwise, find the hash entry. */ | |
189 | node_ptr prev = node; | |
190 | BOOL removed = NO; | |
191 | do | |
192 | { | |
193 | if ((*cache->compare_func) (node->key, key)) | |
194 | { | |
195 | prev->next = node->next, removed = YES; | |
196 | objc_free(node); | |
197 | } | |
198 | else | |
199 | prev = node, node = node->next; | |
200 | } | |
201 | while (!removed && node); | |
202 | assert (removed); | |
203 | } | |
204 | ||
205 | /* Decrement the number of entries in the hash table. */ | |
206 | --cache->used; | |
207 | } | |
208 | ||
209 | ||
210 | node_ptr | |
211 | objc_hash_next (cache_ptr cache, node_ptr node) | |
212 | { | |
213 | /* If the scan is being started then reset the last node visitied | |
214 | pointer and bucket index. */ | |
215 | if (!node) | |
216 | cache->last_bucket = 0; | |
217 | ||
218 | /* If there is a node visited last then check for another entry in | |
219 | the same bucket. Otherwise step to the next bucket. */ | |
220 | if (node) | |
221 | { | |
222 | if (node->next) | |
223 | { | |
224 | /* There is a node which follows the last node returned. | |
225 | Step to that node and retun it. */ | |
226 | return node->next; | |
227 | } | |
228 | else | |
229 | ++cache->last_bucket; | |
230 | } | |
231 | ||
232 | /* If the list isn't exhausted then search the buckets for other | |
233 | nodes. */ | |
234 | if (cache->last_bucket < cache->size) | |
235 | { | |
236 | /* Scan the remainder of the buckets looking for an entry at | |
237 | the head of the list. Return the first item found. */ | |
238 | while (cache->last_bucket < cache->size) | |
239 | if (cache->node_table[cache->last_bucket]) | |
240 | return cache->node_table[cache->last_bucket]; | |
241 | else | |
242 | ++cache->last_bucket; | |
243 | ||
244 | /* No further nodes were found in the hash table. */ | |
245 | return NULL; | |
246 | } | |
247 | else | |
248 | return NULL; | |
249 | } | |
250 | ||
251 | ||
252 | /* Given KEY, return corresponding value for it in CACHE. Return NULL | |
253 | if the KEY is not recorded. */ | |
254 | void * | |
255 | objc_hash_value_for_key (cache_ptr cache, const void *key) | |
256 | { | |
257 | node_ptr node = cache->node_table[(*cache->hash_func) (cache, key)]; | |
258 | void *retval = NULL; | |
259 | ||
260 | if (node) | |
261 | do | |
262 | { | |
263 | if ((*cache->compare_func) (node->key, key)) | |
264 | { | |
265 | retval = node->value; | |
266 | break; | |
267 | } | |
268 | else | |
269 | node = node->next; | |
270 | } | |
271 | while (! retval && node); | |
272 | ||
273 | return retval; | |
274 | } | |
275 | ||
276 | /* Given KEY, return YES if it exists in the CACHE. Return NO if it | |
277 | does not */ | |
278 | BOOL | |
279 | objc_hash_is_key_in_hash (cache_ptr cache, const void *key) | |
280 | { | |
281 | node_ptr node = cache->node_table[(*cache->hash_func) (cache, key)]; | |
282 | ||
283 | if (node) | |
284 | do | |
285 | { | |
286 | if ((*cache->compare_func)(node->key, key)) | |
287 | return YES; | |
288 | else | |
289 | node = node->next; | |
290 | } | |
291 | while (node); | |
292 | ||
293 | return NO; | |
294 | } |