1 /* Hash tables for Objective C internal structures
2 Copyright (C) 1993, 1996, 1997, 2004, 2009 Free Software Foundation, Inc.
4 This file is part of GCC.
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)
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.
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.
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/>. */
27 #include "objc/objc.h"
28 #include "objc/objc-api.h"
30 #include "objc/hash.h"
31 #include "objc/objc-list.h"
32 #include "objc-private/runtime.h" /* for DEBUG_PRINTF */
34 /* These two macros determine when a hash table is full and
35 by how much it should be expanded respectively.
37 These equations are percentages. */
38 #define FULLNESS(cache) \
39 ((((cache)->size * 75) / 100) <= (cache)->used)
40 #define EXPANSION(cache) \
44 objc_hash_new (unsigned int size, hash_func_type hash_func,
45 compare_func_type compare_func)
49 /* Pass me a value greater than 0 and a power of 2. */
51 assert (! (size & (size - 1)));
53 /* Allocate the cache structure. calloc insures
54 its initialization for default values. */
55 cache = (cache_ptr) objc_calloc (1, sizeof (struct cache));
58 /* Allocate the array of buckets for the cache.
59 calloc initializes all of the pointers to NULL. */
61 = (node_ptr *) objc_calloc (size, sizeof (node_ptr));
62 assert (cache->node_table);
66 /* This should work for all processor architectures? */
67 cache->mask = (size - 1);
69 /* Store the hashing function so that codes can be computed. */
70 cache->hash_func = hash_func;
72 /* Store the function that compares hash keys to
73 determine if they are equal. */
74 cache->compare_func = compare_func;
81 objc_hash_delete (cache_ptr cache)
87 /* Purge all key/value pairs from the table. */
88 /* Step through the nodes one by one and remove every node WITHOUT
89 using objc_hash_next. this makes objc_hash_delete much more efficient. */
90 for (i = 0;i < cache->size;i++) {
91 if ((node = cache->node_table[i])) {
92 /* an entry in the hash table has been found, now step through the
93 nodes next in the list and free them. */
94 while ((next_node = node->next)) {
95 objc_hash_remove (cache,node->key);
99 objc_hash_remove (cache,node->key);
103 /* Release the array of nodes and the cache itself. */
104 objc_free(cache->node_table);
110 objc_hash_add (cache_ptr *cachep, const void *key, void *value)
112 size_t indx = (*(*cachep)->hash_func)(*cachep, key);
113 node_ptr node = (node_ptr) objc_calloc (1, sizeof (struct cache_node));
118 /* Initialize the new node. */
121 node->next = (*cachep)->node_table[indx];
124 Check the list for another key. */
126 { node_ptr node1 = (*cachep)->node_table[indx];
130 assert (node1->key != key);
136 /* Install the node as the first element on the list. */
137 (*cachep)->node_table[indx] = node;
139 /* Bump the number of entries in the cache. */
142 /* Check the hash table's fullness. We're going
143 to expand if it is above the fullness level. */
144 if (FULLNESS (*cachep)) {
146 /* The hash table has reached its fullness level. Time to
149 I'm using a slow method here but is built on other
150 primitive functions thereby increasing its
152 node_ptr node1 = NULL;
153 cache_ptr new = objc_hash_new (EXPANSION (*cachep),
154 (*cachep)->hash_func,
155 (*cachep)->compare_func);
157 DEBUG_PRINTF ("Expanding cache %#x from %d to %d\n",
158 (int) *cachep, (*cachep)->size, new->size);
160 /* Copy the nodes from the first hash table to the new one. */
161 while ((node1 = objc_hash_next (*cachep, node1)))
162 objc_hash_add (&new, node1->key, node1->value);
164 /* Trash the old cache. */
165 objc_hash_delete (*cachep);
167 /* Return a pointer to the new hash table. */
174 objc_hash_remove (cache_ptr cache, const void *key)
176 size_t indx = (*cache->hash_func)(cache, key);
177 node_ptr node = cache->node_table[indx];
180 /* We assume there is an entry in the table. Error if it is not. */
183 /* Special case. First element is the key/value pair to be removed. */
184 if ((*cache->compare_func)(node->key, key)) {
185 cache->node_table[indx] = node->next;
189 /* Otherwise, find the hash entry. */
190 node_ptr prev = node;
195 if ((*cache->compare_func)(node->key, key)) {
196 prev->next = node->next, removed = YES;
199 prev = node, node = node->next;
200 } while (! removed && node);
204 /* Decrement the number of entries in the hash table. */
210 objc_hash_next (cache_ptr cache, node_ptr node)
212 /* If the scan is being started then reset the last node
213 visitied pointer and bucket index. */
215 cache->last_bucket = 0;
217 /* If there is a node visited last then check for another
218 entry in the same bucket; Otherwise step to the next bucket. */
221 /* There is a node which follows the last node
222 returned. Step to that node and retun it. */
225 ++cache->last_bucket;
228 /* If the list isn't exhausted then search the buckets for
230 if (cache->last_bucket < cache->size) {
231 /* Scan the remainder of the buckets looking for an entry
232 at the head of the list. Return the first item found. */
233 while (cache->last_bucket < cache->size)
234 if (cache->node_table[cache->last_bucket])
235 return cache->node_table[cache->last_bucket];
237 ++cache->last_bucket;
239 /* No further nodes were found in the hash table. */
246 /* Given KEY, return corresponding value for it in CACHE.
247 Return NULL if the KEY is not recorded. */
250 objc_hash_value_for_key (cache_ptr cache, const void *key)
252 node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)];
257 if ((*cache->compare_func)(node->key, key)) {
258 retval = node->value;
262 } while (! retval && node);
267 /* Given KEY, return YES if it exists in the CACHE.
268 Return NO if it does not */
271 objc_hash_is_key_in_hash (cache_ptr cache, const void *key)
273 node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)];
277 if ((*cache->compare_func)(node->key, key))