[14547] | 1 | /* Hash tables for Objective C internal structures |
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| 2 | Copyright (C) 1993, 1996, 1997 Free Software Foundation, Inc. |
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| 3 | |
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[21198] | 4 | This file is part of GCC. |
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[14547] | 5 | |
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[21198] | 6 | GCC is free software; you can redistribute it and/or modify |
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[14547] | 7 | it under the terms of the GNU General Public License as published by |
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| 8 | the Free Software Foundation; either version 2, or (at your option) |
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| 9 | any later version. |
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| 10 | |
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[21198] | 11 | GCC is distributed in the hope that it will be useful, |
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[14547] | 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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| 14 | GNU General Public License for more details. |
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| 15 | |
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| 16 | You should have received a copy of the GNU General Public License |
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[21198] | 17 | along with GCC; see the file COPYING. If not, write to |
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[14547] | 18 | the Free Software Foundation, 59 Temple Place - Suite 330, |
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| 19 | Boston, MA 02111-1307, USA. */ |
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| 20 | |
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| 21 | /* As a special exception, if you link this library with files |
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| 22 | compiled with GCC to produce an executable, this does not cause |
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| 23 | the resulting executable to be covered by the GNU General Public License. |
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| 24 | This exception does not however invalidate any other reasons why |
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| 25 | the executable file might be covered by the GNU General Public License. */ |
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| 26 | |
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| 27 | #include "assert.h" |
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| 28 | |
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| 29 | #include "hash.h" |
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| 30 | |
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| 31 | #include "runtime.h" /* for DEBUG_PRINTF */ |
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| 32 | |
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| 33 | /* These two macros determine when a hash table is full and |
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| 34 | by how much it should be expanded respectively. |
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| 35 | |
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| 36 | These equations are percentages. */ |
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| 37 | #define FULLNESS(cache) \ |
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| 38 | ((((cache)->size * 75) / 100) <= (cache)->used) |
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| 39 | #define EXPANSION(cache) \ |
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| 40 | ((cache)->size * 2) |
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| 41 | |
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| 42 | cache_ptr |
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| 43 | hash_new (unsigned int size, hash_func_type hash_func, |
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| 44 | compare_func_type compare_func) |
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| 45 | { |
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| 46 | cache_ptr cache; |
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| 47 | |
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| 48 | /* Pass me a value greater than 0 and a power of 2. */ |
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| 49 | assert (size); |
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[20088] | 50 | assert (! (size & (size - 1))); |
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[14547] | 51 | |
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| 52 | /* Allocate the cache structure. calloc insures |
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| 53 | its initialization for default values. */ |
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| 54 | cache = (cache_ptr) objc_calloc (1, sizeof (struct cache)); |
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| 55 | assert (cache); |
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| 56 | |
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| 57 | /* Allocate the array of buckets for the cache. |
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| 58 | calloc initializes all of the pointers to NULL. */ |
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| 59 | cache->node_table |
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| 60 | = (node_ptr *) objc_calloc (size, sizeof (node_ptr)); |
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| 61 | assert (cache->node_table); |
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| 62 | |
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| 63 | cache->size = size; |
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| 64 | |
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| 65 | /* This should work for all processor architectures? */ |
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| 66 | cache->mask = (size - 1); |
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| 67 | |
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| 68 | /* Store the hashing function so that codes can be computed. */ |
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| 69 | cache->hash_func = hash_func; |
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| 70 | |
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| 71 | /* Store the function that compares hash keys to |
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| 72 | determine if they are equal. */ |
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| 73 | cache->compare_func = compare_func; |
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| 74 | |
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| 75 | return cache; |
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| 76 | } |
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| 77 | |
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| 78 | |
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| 79 | void |
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| 80 | hash_delete (cache_ptr cache) |
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| 81 | { |
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| 82 | node_ptr node; |
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| 83 | node_ptr next_node; |
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| 84 | unsigned int i; |
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| 85 | |
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| 86 | /* Purge all key/value pairs from the table. */ |
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| 87 | /* Step through the nodes one by one and remove every node WITHOUT |
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| 88 | using hash_next. this makes hash_delete much more efficient. */ |
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| 89 | for (i = 0;i < cache->size;i++) { |
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| 90 | if ((node = cache->node_table[i])) { |
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| 91 | /* an entry in the hash table has been found, now step through the |
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| 92 | nodes next in the list and free them. */ |
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| 93 | while ((next_node = node->next)) { |
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| 94 | hash_remove (cache,node->key); |
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| 95 | node = next_node; |
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| 96 | } |
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| 97 | |
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| 98 | hash_remove (cache,node->key); |
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| 99 | } |
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| 100 | } |
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| 101 | |
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| 102 | /* Release the array of nodes and the cache itself. */ |
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| 103 | objc_free(cache->node_table); |
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| 104 | objc_free(cache); |
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| 105 | } |
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| 106 | |
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| 107 | |
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| 108 | void |
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| 109 | hash_add (cache_ptr *cachep, const void *key, void *value) |
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| 110 | { |
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| 111 | size_t indx = (*(*cachep)->hash_func)(*cachep, key); |
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| 112 | node_ptr node = (node_ptr) objc_calloc (1, sizeof (struct cache_node)); |
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| 113 | |
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| 114 | |
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| 115 | assert (node); |
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| 116 | |
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| 117 | /* Initialize the new node. */ |
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| 118 | node->key = key; |
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| 119 | node->value = value; |
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| 120 | node->next = (*cachep)->node_table[indx]; |
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| 121 | |
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| 122 | /* Debugging. |
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| 123 | Check the list for another key. */ |
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| 124 | #ifdef DEBUG |
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| 125 | { node_ptr node1 = (*cachep)->node_table[indx]; |
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| 126 | |
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| 127 | while (node1) { |
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| 128 | |
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| 129 | assert (node1->key != key); |
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| 130 | node1 = node1->next; |
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| 131 | } |
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| 132 | } |
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| 133 | #endif |
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| 134 | |
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| 135 | /* Install the node as the first element on the list. */ |
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| 136 | (*cachep)->node_table[indx] = node; |
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| 137 | |
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| 138 | /* Bump the number of entries in the cache. */ |
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| 139 | ++(*cachep)->used; |
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| 140 | |
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| 141 | /* Check the hash table's fullness. We're going |
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| 142 | to expand if it is above the fullness level. */ |
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| 143 | if (FULLNESS (*cachep)) { |
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| 144 | |
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| 145 | /* The hash table has reached its fullness level. Time to |
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| 146 | expand it. |
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| 147 | |
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| 148 | I'm using a slow method here but is built on other |
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| 149 | primitive functions thereby increasing its |
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| 150 | correctness. */ |
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| 151 | node_ptr node1 = NULL; |
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| 152 | cache_ptr new = hash_new (EXPANSION (*cachep), |
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| 153 | (*cachep)->hash_func, |
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| 154 | (*cachep)->compare_func); |
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| 155 | |
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| 156 | DEBUG_PRINTF ("Expanding cache %#x from %d to %d\n", |
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| 157 | *cachep, (*cachep)->size, new->size); |
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| 158 | |
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| 159 | /* Copy the nodes from the first hash table to the new one. */ |
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| 160 | while ((node1 = hash_next (*cachep, node1))) |
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| 161 | hash_add (&new, node1->key, node1->value); |
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| 162 | |
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| 163 | /* Trash the old cache. */ |
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| 164 | hash_delete (*cachep); |
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| 165 | |
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| 166 | /* Return a pointer to the new hash table. */ |
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| 167 | *cachep = new; |
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| 168 | } |
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| 169 | } |
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| 170 | |
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| 171 | |
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| 172 | void |
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| 173 | hash_remove (cache_ptr cache, const void *key) |
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| 174 | { |
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| 175 | size_t indx = (*cache->hash_func)(cache, key); |
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| 176 | node_ptr node = cache->node_table[indx]; |
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| 177 | |
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| 178 | |
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| 179 | /* We assume there is an entry in the table. Error if it is not. */ |
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| 180 | assert (node); |
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| 181 | |
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| 182 | /* Special case. First element is the key/value pair to be removed. */ |
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| 183 | if ((*cache->compare_func)(node->key, key)) { |
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| 184 | cache->node_table[indx] = node->next; |
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| 185 | objc_free(node); |
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| 186 | } else { |
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| 187 | |
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| 188 | /* Otherwise, find the hash entry. */ |
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| 189 | node_ptr prev = node; |
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| 190 | BOOL removed = NO; |
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| 191 | |
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| 192 | do { |
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| 193 | |
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| 194 | if ((*cache->compare_func)(node->key, key)) { |
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| 195 | prev->next = node->next, removed = YES; |
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| 196 | objc_free(node); |
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| 197 | } else |
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| 198 | prev = node, node = node->next; |
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[20088] | 199 | } while (! removed && node); |
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[14547] | 200 | assert (removed); |
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| 201 | } |
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| 202 | |
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| 203 | /* Decrement the number of entries in the hash table. */ |
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| 204 | --cache->used; |
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| 205 | } |
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| 206 | |
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| 207 | |
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| 208 | node_ptr |
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| 209 | hash_next (cache_ptr cache, node_ptr node) |
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| 210 | { |
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| 211 | /* If the scan is being started then reset the last node |
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| 212 | visitied pointer and bucket index. */ |
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[20088] | 213 | if (! node) |
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[14547] | 214 | cache->last_bucket = 0; |
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| 215 | |
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| 216 | /* If there is a node visited last then check for another |
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| 217 | entry in the same bucket; Otherwise step to the next bucket. */ |
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| 218 | if (node) { |
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| 219 | if (node->next) |
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| 220 | /* There is a node which follows the last node |
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| 221 | returned. Step to that node and retun it. */ |
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| 222 | return node->next; |
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| 223 | else |
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| 224 | ++cache->last_bucket; |
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| 225 | } |
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| 226 | |
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| 227 | /* If the list isn't exhausted then search the buckets for |
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| 228 | other nodes. */ |
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| 229 | if (cache->last_bucket < cache->size) { |
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| 230 | /* Scan the remainder of the buckets looking for an entry |
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| 231 | at the head of the list. Return the first item found. */ |
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| 232 | while (cache->last_bucket < cache->size) |
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| 233 | if (cache->node_table[cache->last_bucket]) |
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| 234 | return cache->node_table[cache->last_bucket]; |
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| 235 | else |
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| 236 | ++cache->last_bucket; |
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| 237 | |
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| 238 | /* No further nodes were found in the hash table. */ |
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| 239 | return NULL; |
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| 240 | } else |
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| 241 | return NULL; |
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| 242 | } |
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| 243 | |
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| 244 | |
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| 245 | /* Given KEY, return corresponding value for it in CACHE. |
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| 246 | Return NULL if the KEY is not recorded. */ |
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| 247 | |
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| 248 | void * |
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| 249 | hash_value_for_key (cache_ptr cache, const void *key) |
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| 250 | { |
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| 251 | node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)]; |
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| 252 | void *retval = NULL; |
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| 253 | |
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| 254 | if (node) |
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| 255 | do { |
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| 256 | if ((*cache->compare_func)(node->key, key)) { |
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| 257 | retval = node->value; |
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| 258 | break; |
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| 259 | } else |
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| 260 | node = node->next; |
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[20088] | 261 | } while (! retval && node); |
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[14547] | 262 | |
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| 263 | return retval; |
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| 264 | } |
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| 265 | |
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| 266 | /* Given KEY, return YES if it exists in the CACHE. |
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| 267 | Return NO if it does not */ |
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| 268 | |
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| 269 | BOOL |
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| 270 | hash_is_key_in_hash (cache_ptr cache, const void *key) |
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| 271 | { |
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| 272 | node_ptr node = cache->node_table[(*cache->hash_func)(cache, key)]; |
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| 273 | |
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| 274 | if (node) |
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| 275 | do { |
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| 276 | if ((*cache->compare_func)(node->key, key)) |
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| 277 | return YES; |
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| 278 | else |
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| 279 | node = node->next; |
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| 280 | } while (node); |
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| 281 | |
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| 282 | return NO; |
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| 283 | } |
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