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/>. */
25 #include "objc-private/common.h"
26 #include <assert.h> /* For assert. */
28 #include "objc/runtime.h" /* For objc_calloc. */
29 #include "objc/thr.h" /* Required by objc-private/runtime.h. */
30 #include "objc-private/hash.h"
31 #include "objc-private/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) \
43 objc_hash_new (unsigned int size, hash_func_type hash_func,
44 compare_func_type compare_func)
48 /* Pass me a value greater than 0 and a power of 2. */
50 assert (! (size & (size - 1)));
52 /* Allocate the cache structure. calloc insures its initialization
53 for default values. */
54 cache = (cache_ptr) objc_calloc (1, sizeof (struct cache));
57 /* Allocate the array of buckets for the cache. calloc initializes
58 all of the pointers to NULL. */
60 = (node_ptr *) objc_calloc (size, sizeof (node_ptr));
61 assert (cache->node_table);
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 determine if they
73 cache->compare_func = compare_func;
80 objc_hash_delete (cache_ptr cache)
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
90 for (i = 0; i < cache->size; i++)
92 if ((node = cache->node_table[i]))
94 /* An entry in the hash table has been found. Now step
95 through the nodes next in the list and free them. */
96 while ((next_node = node->next))
98 objc_hash_remove (cache,node->key);
101 objc_hash_remove (cache,node->key);
105 /* Release the array of nodes and the cache itself. */
106 objc_free(cache->node_table);
112 objc_hash_add (cache_ptr *cachep, const void *key, void *value)
114 size_t indx = (*(*cachep)->hash_func) (*cachep, key);
115 node_ptr node = (node_ptr) objc_calloc (1, sizeof (struct cache_node));
119 /* Initialize the new node. */
122 node->next = (*cachep)->node_table[indx];
124 /* Debugging. Check the list for another key. */
127 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 to expand if it is
143 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 primitive
150 functions thereby increasing its 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. */
172 objc_hash_remove (cache_ptr cache, const void *key)
174 size_t indx = (*cache->hash_func) (cache, key);
175 node_ptr node = cache->node_table[indx];
177 /* We assume there is an entry in the table. Error if it is
181 /* Special case. First element is the key/value pair to be
183 if ((*cache->compare_func) (node->key, key))
185 cache->node_table[indx] = node->next;
190 /* Otherwise, find the hash entry. */
191 node_ptr prev = node;
195 if ((*cache->compare_func) (node->key, key))
197 prev->next = node->next, removed = YES;
201 prev = node, node = node->next;
203 while (!removed && node);
207 /* Decrement the number of entries in the hash table. */
213 objc_hash_next (cache_ptr cache, node_ptr node)
215 /* If the scan is being started then reset the last node visitied
216 pointer and bucket index. */
218 cache->last_bucket = 0;
220 /* If there is a node visited last then check for another entry in
221 the same bucket. Otherwise step to the next bucket. */
226 /* There is a node which follows the last node returned.
227 Step to that node and retun it. */
231 ++cache->last_bucket;
234 /* If the list isn't exhausted then search the buckets for other
236 if (cache->last_bucket < cache->size)
238 /* Scan the remainder of the buckets looking for an entry at
239 the head of the list. Return the first item found. */
240 while (cache->last_bucket < cache->size)
241 if (cache->node_table[cache->last_bucket])
242 return cache->node_table[cache->last_bucket];
244 ++cache->last_bucket;
246 /* No further nodes were found in the hash table. */
254 /* Given KEY, return corresponding value for it in CACHE. Return NULL
255 if the KEY is not recorded. */
257 objc_hash_value_for_key (cache_ptr cache, const void *key)
259 node_ptr node = cache->node_table[(*cache->hash_func) (cache, key)];
265 if ((*cache->compare_func) (node->key, key))
267 retval = node->value;
273 while (! retval && node);
278 /* Given KEY, return YES if it exists in the CACHE. Return NO if it
281 objc_hash_is_key_in_hash (cache_ptr cache, const void *key)
283 node_ptr node = cache->node_table[(*cache->hash_func) (cache, key)];
288 if ((*cache->compare_func)(node->key, key))