2005-06-07 Thomas Koenig <Thomas.Koenig@online.de>
[official-gcc.git] / libobjc / hash.c
blobe2072b605f78aad30ddf4eb71678f17ea40a0dc6
1 /* Hash tables for Objective C internal structures
2 Copyright (C) 1993, 1996, 1997, 2004 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 2, or (at your option)
9 any later version.
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 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 /* As a special exception, if you link this library with files
22 compiled with GCC to produce an executable, this does not cause
23 the resulting executable to be covered by the GNU General Public License.
24 This exception does not however invalidate any other reasons why
25 the executable file might be covered by the GNU General Public License. */
27 #include "assert.h"
29 #include "hash.h"
31 #include "runtime.h" /* for DEBUG_PRINTF */
33 /* These two macros determine when a hash table is full and
34 by how much it should be expanded respectively.
36 These equations are percentages. */
37 #define FULLNESS(cache) \
38 ((((cache)->size * 75) / 100) <= (cache)->used)
39 #define EXPANSION(cache) \
40 ((cache)->size * 2)
42 cache_ptr
43 objc_hash_new (unsigned int size, hash_func_type hash_func,
44 compare_func_type compare_func)
46 cache_ptr cache;
48 /* Pass me a value greater than 0 and a power of 2. */
49 assert (size);
50 assert (! (size & (size - 1)));
52 /* Allocate the cache structure. calloc insures
53 its initialization for default values. */
54 cache = (cache_ptr) objc_calloc (1, sizeof (struct cache));
55 assert (cache);
57 /* Allocate the array of buckets for the cache.
58 calloc initializes all of the pointers to NULL. */
59 cache->node_table
60 = (node_ptr *) objc_calloc (size, sizeof (node_ptr));
61 assert (cache->node_table);
63 cache->size = size;
65 /* This should work for all processor architectures? */
66 cache->mask = (size - 1);
68 /* Store the hashing function so that codes can be computed. */
69 cache->hash_func = hash_func;
71 /* Store the function that compares hash keys to
72 determine if they are equal. */
73 cache->compare_func = compare_func;
75 return cache;
79 void
80 objc_hash_delete (cache_ptr cache)
82 node_ptr node;
83 node_ptr next_node;
84 unsigned int i;
86 /* Purge all key/value pairs from the table. */
87 /* Step through the nodes one by one and remove every node WITHOUT
88 using objc_hash_next. this makes objc_hash_delete much more efficient. */
89 for (i = 0;i < cache->size;i++) {
90 if ((node = cache->node_table[i])) {
91 /* an entry in the hash table has been found, now step through the
92 nodes next in the list and free them. */
93 while ((next_node = node->next)) {
94 objc_hash_remove (cache,node->key);
95 node = next_node;
98 objc_hash_remove (cache,node->key);
102 /* Release the array of nodes and the cache itself. */
103 objc_free(cache->node_table);
104 objc_free(cache);
108 void
109 objc_hash_add (cache_ptr *cachep, const void *key, void *value)
111 size_t indx = (*(*cachep)->hash_func)(*cachep, key);
112 node_ptr node = (node_ptr) objc_calloc (1, sizeof (struct cache_node));
115 assert (node);
117 /* Initialize the new node. */
118 node->key = key;
119 node->value = value;
120 node->next = (*cachep)->node_table[indx];
122 /* Debugging.
123 Check the list for another key. */
124 #ifdef DEBUG
125 { node_ptr node1 = (*cachep)->node_table[indx];
127 while (node1) {
129 assert (node1->key != key);
130 node1 = node1->next;
133 #endif
135 /* Install the node as the first element on the list. */
136 (*cachep)->node_table[indx] = node;
138 /* Bump the number of entries in the cache. */
139 ++(*cachep)->used;
141 /* Check the hash table's fullness. We're going
142 to expand if it is above the fullness level. */
143 if (FULLNESS (*cachep)) {
145 /* The hash table has reached its fullness level. Time to
146 expand it.
148 I'm using a slow method here but is built on other
149 primitive functions thereby increasing its
150 correctness. */
151 node_ptr node1 = NULL;
152 cache_ptr new = objc_hash_new (EXPANSION (*cachep),
153 (*cachep)->hash_func,
154 (*cachep)->compare_func);
156 DEBUG_PRINTF ("Expanding cache %#x from %d to %d\n",
157 (int) *cachep, (*cachep)->size, new->size);
159 /* Copy the nodes from the first hash table to the new one. */
160 while ((node1 = objc_hash_next (*cachep, node1)))
161 objc_hash_add (&new, node1->key, node1->value);
163 /* Trash the old cache. */
164 objc_hash_delete (*cachep);
166 /* Return a pointer to the new hash table. */
167 *cachep = new;
172 void
173 objc_hash_remove (cache_ptr cache, const void *key)
175 size_t indx = (*cache->hash_func)(cache, key);
176 node_ptr node = cache->node_table[indx];
179 /* We assume there is an entry in the table. Error if it is not. */
180 assert (node);
182 /* Special case. First element is the key/value pair to be removed. */
183 if ((*cache->compare_func)(node->key, key)) {
184 cache->node_table[indx] = node->next;
185 objc_free(node);
186 } else {
188 /* Otherwise, find the hash entry. */
189 node_ptr prev = node;
190 BOOL removed = NO;
192 do {
194 if ((*cache->compare_func)(node->key, key)) {
195 prev->next = node->next, removed = YES;
196 objc_free(node);
197 } else
198 prev = node, node = node->next;
199 } while (! removed && node);
200 assert (removed);
203 /* Decrement the number of entries in the hash table. */
204 --cache->used;
208 node_ptr
209 objc_hash_next (cache_ptr cache, node_ptr node)
211 /* If the scan is being started then reset the last node
212 visitied pointer and bucket index. */
213 if (! node)
214 cache->last_bucket = 0;
216 /* If there is a node visited last then check for another
217 entry in the same bucket; Otherwise step to the next bucket. */
218 if (node) {
219 if (node->next)
220 /* There is a node which follows the last node
221 returned. Step to that node and retun it. */
222 return node->next;
223 else
224 ++cache->last_bucket;
227 /* If the list isn't exhausted then search the buckets for
228 other nodes. */
229 if (cache->last_bucket < cache->size) {
230 /* Scan the remainder of the buckets looking for an entry
231 at the head of the list. Return the first item found. */
232 while (cache->last_bucket < cache->size)
233 if (cache->node_table[cache->last_bucket])
234 return cache->node_table[cache->last_bucket];
235 else
236 ++cache->last_bucket;
238 /* No further nodes were found in the hash table. */
239 return NULL;
240 } else
241 return NULL;
245 /* Given KEY, return corresponding value for it in CACHE.
246 Return NULL if the KEY is not recorded. */
248 void *
249 objc_hash_value_for_key (cache_ptr cache, const void *key)
251 node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)];
252 void *retval = NULL;
254 if (node)
255 do {
256 if ((*cache->compare_func)(node->key, key)) {
257 retval = node->value;
258 break;
259 } else
260 node = node->next;
261 } while (! retval && node);
263 return retval;
266 /* Given KEY, return YES if it exists in the CACHE.
267 Return NO if it does not */
269 BOOL
270 objc_hash_is_key_in_hash (cache_ptr cache, const void *key)
272 node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)];
274 if (node)
275 do {
276 if ((*cache->compare_func)(node->key, key))
277 return YES;
278 else
279 node = node->next;
280 } while (node);
282 return NO;