1 /* Hash tables for Objective C internal structures 2 Copyright (C) 1993, 1996, 1997, 2004, 2009 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 "assert.h" 26 27 #include "objc/hash.h" 28 29 #include "objc/runtime.h" /* for DEBUG_PRINTF */ 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 51 its initialization 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. 56 calloc initializes 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 70 determine if they 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 efficient. */ 87 for (i = 0;i < cache->size;i++) { 88 if ((node = cache->node_table[i])) { 89 /* an entry in the hash table has been found, now step through the 90 nodes next in the list and free them. */ 91 while ((next_node = node->next)) { 92 objc_hash_remove (cache,node->key); 93 node = next_node; 94 } 95 96 objc_hash_remove (cache,node->key); 97 } 98 } 99 100 /* Release the array of nodes and the cache itself. */ 101 objc_free(cache->node_table); 102 objc_free(cache); 103 } 104 105 106 void 107 objc_hash_add (cache_ptr *cachep, const void *key, void *value) 108 { 109 size_t indx = (*(*cachep)->hash_func)(*cachep, key); 110 node_ptr node = (node_ptr) objc_calloc (1, sizeof (struct cache_node)); 111 112 113 assert (node); 114 115 /* Initialize the new node. */ 116 node->key = key; 117 node->value = value; 118 node->next = (*cachep)->node_table[indx]; 119 120 /* Debugging. 121 Check the list for another key. */ 122 #ifdef DEBUG 123 { node_ptr node1 = (*cachep)->node_table[indx]; 124 125 while (node1) { 126 127 assert (node1->key != key); 128 node1 = node1->next; 129 } 130 } 131 #endif 132 133 /* Install the node as the first element on the list. */ 134 (*cachep)->node_table[indx] = node; 135 136 /* Bump the number of entries in the cache. */ 137 ++(*cachep)->used; 138 139 /* Check the hash table's fullness. We're going 140 to expand if it is above the fullness level. */ 141 if (FULLNESS (*cachep)) { 142 143 /* The hash table has reached its fullness level. Time to 144 expand it. 145 146 I'm using a slow method here but is built on other 147 primitive functions thereby increasing its 148 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 %p from %d to %d\n", 155 *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 } 168 169 170 void 171 objc_hash_remove (cache_ptr cache, const void *key) 172 { 173 size_t indx = (*cache->hash_func)(cache, key); 174 node_ptr node = cache->node_table[indx]; 175 176 177 /* We assume there is an entry in the table. Error if it is not. */ 178 assert (node); 179 180 /* Special case. First element is the key/value pair to be removed. */ 181 if ((*cache->compare_func)(node->key, key)) { 182 cache->node_table[indx] = node->next; 183 objc_free(node); 184 } else { 185 186 /* Otherwise, find the hash entry. */ 187 node_ptr prev = node; 188 BOOL removed = NO; 189 190 do { 191 192 if ((*cache->compare_func)(node->key, key)) { 193 prev->next = node->next, removed = YES; 194 objc_free(node); 195 } else 196 prev = node, node = node->next; 197 } while (! removed && node); 198 assert (removed); 199 } 200 201 /* Decrement the number of entries in the hash table. */ 202 --cache->used; 203 } 204 205 206 node_ptr 207 objc_hash_next (cache_ptr cache, node_ptr node) 208 { 209 /* If the scan is being started then reset the last node 210 visitied pointer and bucket index. */ 211 if (! node) 212 cache->last_bucket = 0; 213 214 /* If there is a node visited last then check for another 215 entry in the same bucket; Otherwise step to the next bucket. */ 216 if (node) { 217 if (node->next) 218 /* There is a node which follows the last node 219 returned. Step to that node and retun it. */ 220 return node->next; 221 else 222 ++cache->last_bucket; 223 } 224 225 /* If the list isn't exhausted then search the buckets for 226 other nodes. */ 227 if (cache->last_bucket < cache->size) { 228 /* Scan the remainder of the buckets looking for an entry 229 at the head of the list. Return the first item found. */ 230 while (cache->last_bucket < cache->size) 231 if (cache->node_table[cache->last_bucket]) 232 return cache->node_table[cache->last_bucket]; 233 else 234 ++cache->last_bucket; 235 236 /* No further nodes were found in the hash table. */ 237 return NULL; 238 } else 239 return NULL; 240 } 241 242 243 /* Given KEY, return corresponding value for it in CACHE. 244 Return NULL if the KEY is not recorded. */ 245 246 void * 247 objc_hash_value_for_key (cache_ptr cache, const void *key) 248 { 249 node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)]; 250 void *retval = NULL; 251 252 if (node) 253 do { 254 if ((*cache->compare_func)(node->key, key)) { 255 retval = node->value; 256 break; 257 } else 258 node = node->next; 259 } while (! retval && node); 260 261 return retval; 262 } 263 264 /* Given KEY, return YES if it exists in the CACHE. 265 Return NO if it does not */ 266 267 BOOL 268 objc_hash_is_key_in_hash (cache_ptr cache, const void *key) 269 { 270 node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)]; 271 272 if (node) 273 do { 274 if ((*cache->compare_func)(node->key, key)) 275 return YES; 276 else 277 node = node->next; 278 } while (node); 279 280 return NO; 281 } 282