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424 lines
11 KiB
424 lines
11 KiB
/*
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* Copyright © 2009 Intel Corporation
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* Copyright © 1988-2004 Keith Packard and Bart Massey.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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* Except as contained in this notice, the names of the authors
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* or their institutions shall not be used in advertising or
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* otherwise to promote the sale, use or other dealings in this
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* Software without prior written authorization from the
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* authors.
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*
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* Authors:
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* Eric Anholt <eric@anholt.net>
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* Keith Packard <keithp@keithp.com>
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*/
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#include <assert.h>
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#include <stdlib.h>
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#include <hash_table.h>
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#include <allocate.h>
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#define ARRAY_SIZE(array) ((int)(sizeof(array) / sizeof(array[0])))
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/*
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* From Knuth -- a good choice for hash/rehash values is p, p-2 where
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* p and p-2 are both prime. These tables are sized to have an extra 10%
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* free to avoid exponential performance degradation as the hash table fills
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*/
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static const uint32_t deleted_key_value = 0;
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static const void *deleted_key = &deleted_key_value;
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static const struct {
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uint32_t max_entries, size, rehash;
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} hash_sizes[] = {
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{ 2, 5, 3 },
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{ 4, 7, 5 },
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{ 8, 13, 11 },
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{ 16, 19, 17 },
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{ 32, 43, 41 },
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{ 64, 73, 71 },
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{ 128, 151, 149 },
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{ 256, 283, 281 },
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{ 512, 571, 569 },
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{ 1024, 1153, 1151 },
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{ 2048, 2269, 2267 },
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{ 4096, 4519, 4517 },
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{ 8192, 9013, 9011 },
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{ 16384, 18043, 18041 },
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{ 32768, 36109, 36107 },
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{ 65536, 72091, 72089 },
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{ 131072, 144409, 144407 },
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{ 262144, 288361, 288359 },
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{ 524288, 576883, 576881 },
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{ 1048576, 1153459, 1153457 },
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{ 2097152, 2307163, 2307161 },
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{ 4194304, 4613893, 4613891 },
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{ 8388608, 9227641, 9227639 },
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{ 16777216, 18455029, 18455027 },
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{ 33554432, 36911011, 36911009 },
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{ 67108864, 73819861, 73819859 },
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{ 134217728, 147639589, 147639587 },
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{ 268435456, 295279081, 295279079 },
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{ 536870912, 590559793, 590559791 },
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{ 1073741824, 1181116273, 1181116271},
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{ 2147483648ul, 2362232233ul, 2362232231ul}
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};
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static int
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entry_is_free(const HashEntry *entry)
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{
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return entry->key == NULL;
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}
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static int
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entry_is_deleted(const HashEntry *entry)
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{
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return entry->key == deleted_key;
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}
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static int
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entry_is_present(const HashEntry *entry)
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{
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return entry->key != NULL && entry->key != deleted_key;
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}
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HashTable *
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raviX_hash_table_create(uint32_t (*hash_function)(const void *key),
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int (*key_equals_function)(const void *a,
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const void *b))
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{
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HashTable *ht;
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ht = (HashTable *) raviX_malloc(sizeof(*ht));
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ht->size_index = 0;
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ht->size = hash_sizes[ht->size_index].size;
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ht->rehash = hash_sizes[ht->size_index].rehash;
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ht->max_entries = hash_sizes[ht->size_index].max_entries;
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ht->hash_function = hash_function;
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ht->key_equals_function = key_equals_function;
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ht->table = (HashEntry *) raviX_calloc(ht->size, sizeof(*ht->table));
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ht->entries = 0;
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ht->deleted_entries = 0;
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if (ht->table == NULL) {
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raviX_free(ht);
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return NULL;
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}
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return ht;
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}
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/**
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* Frees the given hash table.
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*
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* If delete_function is passed, it gets called on each entry present before
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* freeing.
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*/
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void
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raviX_hash_table_destroy(HashTable *ht,
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void (*delete_function)(HashEntry *entry))
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{
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if (!ht)
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return;
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if (delete_function) {
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HashEntry *entry;
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hash_table_foreach(ht, entry) {
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delete_function(entry);
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}
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}
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raviX_free(ht->table);
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raviX_free(ht);
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}
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/**
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* Finds a hash table entry with the given key.
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*
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* Returns NULL if no entry is found. Note that the data pointer may be
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* modified by the user.
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*/
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HashEntry *
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raviX_hash_table_search(HashTable *ht, const void *key)
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{
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uint32_t hash = ht->hash_function(key);
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return raviX_hash_table_search_pre_hashed(ht, hash, key);
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}
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/**
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* Finds a hash table entry with the given key and hash of that key.
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*
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* Returns NULL if no entry is found. Note that the data pointer may be
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* modified by the user.
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*/
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HashEntry *
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raviX_hash_table_search_pre_hashed(HashTable *ht, uint32_t hash,
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const void *key)
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{
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uint32_t start_hash_address = hash % ht->size;
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uint32_t hash_address = start_hash_address;
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do {
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uint32_t double_hash;
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HashEntry *entry = ht->table + hash_address;
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if (entry_is_free(entry)) {
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return NULL;
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} else if (entry_is_present(entry) && entry->hash == hash) {
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if (ht->key_equals_function(key, entry->key)) {
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return entry;
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}
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}
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double_hash = 1 + hash % ht->rehash;
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hash_address = (hash_address + double_hash) % ht->size;
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} while (hash_address != start_hash_address);
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return NULL;
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}
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static void
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hash_table_rehash(HashTable *ht, int new_size_index)
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{
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HashTable old_ht;
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HashEntry *table, *entry;
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if (new_size_index >= ARRAY_SIZE(hash_sizes))
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return;
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table = (HashEntry *) raviX_calloc(hash_sizes[new_size_index].size, sizeof(*ht->table));
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old_ht = *ht;
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ht->table = table;
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ht->size_index = new_size_index;
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ht->size = hash_sizes[ht->size_index].size;
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ht->rehash = hash_sizes[ht->size_index].rehash;
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ht->max_entries = hash_sizes[ht->size_index].max_entries;
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ht->entries = 0;
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ht->deleted_entries = 0;
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hash_table_foreach(&old_ht, entry) {
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raviX_hash_table_insert_pre_hashed(ht, entry->hash,
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entry->key, entry->data);
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}
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raviX_free(old_ht.table);
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}
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/**
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* Inserts the key into the table.
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*
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* Note that insertion may rearrange the table on a resize or rehash,
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* so previously found hash_entries are no longer valid after this function.
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*/
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HashEntry *
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raviX_hash_table_insert(HashTable *ht, const void *key, void *data)
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{
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uint32_t hash = ht->hash_function(key);
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/* Make sure nobody tries to add one of the magic values as a
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* key. If you need to do so, either do so in a wrapper, or
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* store keys with the magic values separately in the struct
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* hash_table.
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*/
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assert(key != NULL);
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return raviX_hash_table_insert_pre_hashed(ht, hash, key, data);
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}
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/**
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* Inserts the key with the given hash into the table.
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*
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* Note that insertion may rearrange the table on a resize or rehash,
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* so previously found hash_entries are no longer valid after this function.
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*/
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HashEntry *
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raviX_hash_table_insert_pre_hashed(HashTable *ht, uint32_t hash,
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const void *key, void *data)
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{
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uint32_t start_hash_address, hash_address;
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HashEntry *available_entry = NULL;
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if (ht->entries >= ht->max_entries) {
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hash_table_rehash(ht, ht->size_index + 1);
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} else if (ht->deleted_entries + ht->entries >= ht->max_entries) {
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hash_table_rehash(ht, ht->size_index);
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}
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start_hash_address = hash % ht->size;
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hash_address = start_hash_address;
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do {
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HashEntry *entry = ht->table + hash_address;
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uint32_t double_hash;
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if (!entry_is_present(entry)) {
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/* Stash the first available entry we find */
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if (available_entry == NULL)
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available_entry = entry;
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if (entry_is_free(entry))
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break;
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}
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/* Implement replacement when another insert happens
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* with a matching key. This is a relatively common
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* feature of hash tables, with the alternative
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* generally being "insert the new value as well, and
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* return it first when the key is searched for".
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*
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* Note that the hash table doesn't have a delete
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* callback. If freeing of old data pointers is
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* required to avoid memory leaks, perform a search
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* before inserting.
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*/
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if (!entry_is_deleted(entry) &&
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entry->hash == hash &&
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ht->key_equals_function(key, entry->key)) {
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entry->key = key;
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entry->data = data;
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return entry;
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}
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double_hash = 1 + hash % ht->rehash;
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hash_address = (hash_address + double_hash) % ht->size;
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} while (hash_address != start_hash_address);
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if (available_entry) {
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if (entry_is_deleted(available_entry))
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ht->deleted_entries--;
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available_entry->hash = hash;
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available_entry->key = key;
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available_entry->data = data;
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ht->entries++;
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return available_entry;
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}
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/* We could hit here if a required resize failed. An unchecked-malloc
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* application could ignore this result.
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*/
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return NULL;
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}
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/**
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* This function searches for, and removes an entry from the hash table.
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*
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* If the caller has previously found a HashEntry pointer,
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* (from calling hash_table_search or remembering it from
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* hash_table_insert), then hash_table_remove_entry can be called
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* instead to avoid an extra search.
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*/
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void
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raviX_hash_table_remove(HashTable *ht, const void *key)
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{
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HashEntry *entry;
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entry = raviX_hash_table_search(ht, key);
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raviX_hash_table_remove_entry(ht, entry);
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}
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/**
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* This function deletes the given hash table entry.
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*
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* Note that deletion doesn't otherwise modify the table, so an iteration over
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* the table deleting entries is safe.
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*/
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void
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raviX_hash_table_remove_entry(HashTable *ht, HashEntry *entry)
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{
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if (!entry)
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return;
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entry->key = deleted_key;
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ht->entries--;
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ht->deleted_entries++;
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}
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/**
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* This function is an iterator over the hash table.
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*
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* Pass in NULL for the first entry, as in the start of a for loop. Note that
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* an iteration over the table is O(table_size) not O(entries).
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*/
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HashEntry *
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raviX_hash_table_next_entry(HashTable *ht, HashEntry *entry)
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{
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if (entry == NULL)
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entry = ht->table;
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else
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entry = entry + 1;
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for (; entry != ht->table + ht->size; entry++) {
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if (entry_is_present(entry)) {
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return entry;
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}
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}
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return NULL;
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}
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#if 0
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#ifndef _WIN32
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/**
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* Returns a random entry from the hash table.
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*
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* This may be useful in implementing random replacement (as opposed
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* to just removing everything) in caches based on this hash table
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* implementation. @predicate may be used to filter entries, or may
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* be set to NULL for no filtering.
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*/
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HashEntry *
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hash_table_random_entry(HashTable *ht,
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int (*predicate)(HashEntry *entry))
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{
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HashEntry *entry;
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uint32_t i = random() % ht->size;
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if (ht->entries == 0)
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return NULL;
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for (entry = ht->table + i; entry != ht->table + ht->size; entry++) {
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if (entry_is_present(entry) &&
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(!predicate || predicate(entry))) {
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return entry;
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}
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}
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for (entry = ht->table; entry != ht->table + i; entry++) {
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if (entry_is_present(entry) &&
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(!predicate || predicate(entry))) {
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return entry;
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}
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}
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return NULL;
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}
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#endif
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#endif
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