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https://gitlab.freedesktop.org/wayland/weston
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![Bryce Harrington](/assets/img/avatar_default.png)
Signed-off-by: Bryce Harrington <bryce@osg.samsung.com> Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
310 lines
7.5 KiB
C
310 lines
7.5 KiB
C
/*
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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 "config.h"
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#include <stdlib.h>
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#include <stdint.h>
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#include "hash.h"
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struct hash_entry {
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uint32_t hash;
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void *data;
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};
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struct hash_table {
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struct hash_entry *table;
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uint32_t size;
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uint32_t rehash;
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uint32_t max_entries;
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uint32_t size_index;
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uint32_t entries;
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uint32_t deleted_entries;
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};
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#define ARRAY_SIZE(array) (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_data;
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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(struct hash_entry *entry)
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{
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return entry->data == NULL;
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}
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static int
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entry_is_deleted(struct hash_entry *entry)
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{
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return entry->data == &deleted_data;
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}
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static int
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entry_is_present(struct hash_entry *entry)
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{
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return entry->data != NULL && entry->data != &deleted_data;
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}
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struct hash_table *
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hash_table_create(void)
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{
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struct hash_table *ht;
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ht = malloc(sizeof(*ht));
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if (ht == NULL)
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return NULL;
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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->table = 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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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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void
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hash_table_destroy(struct hash_table *ht)
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{
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if (!ht)
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return;
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free(ht->table);
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free(ht);
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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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static void *
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hash_table_search(struct hash_table *ht, uint32_t hash)
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{
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uint32_t hash_address;
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hash_address = hash % ht->size;
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do {
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uint32_t double_hash;
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struct hash_entry *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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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 != hash % ht->size);
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return NULL;
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}
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void
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hash_table_for_each(struct hash_table *ht,
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hash_table_iterator_func_t func, void *data)
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{
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struct hash_entry *entry;
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uint32_t i;
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for (i = 0; i < ht->size; i++) {
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entry = ht->table + i;
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if (entry_is_present(entry))
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func(entry->data, data);
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}
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}
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void *
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hash_table_lookup(struct hash_table *ht, uint32_t hash)
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{
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struct hash_entry *entry;
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entry = hash_table_search(ht, hash);
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if (entry != NULL)
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return entry->data;
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return NULL;
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}
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static void
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hash_table_rehash(struct hash_table *ht, unsigned int new_size_index)
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{
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struct hash_table old_ht;
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struct hash_entry *table, *entry;
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if (new_size_index >= ARRAY_SIZE(hash_sizes))
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return;
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table = calloc(hash_sizes[new_size_index].size, sizeof(*ht->table));
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if (table == NULL)
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return;
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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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for (entry = old_ht.table;
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entry != old_ht.table + old_ht.size;
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entry++) {
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if (entry_is_present(entry)) {
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hash_table_insert(ht, entry->hash, entry->data);
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}
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}
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free(old_ht.table);
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}
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/**
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* Inserts the data 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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int
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hash_table_insert(struct hash_table *ht, uint32_t hash, void *data)
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{
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uint32_t hash_address;
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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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hash_address = hash % ht->size;
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do {
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struct hash_entry *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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if (entry_is_deleted(entry))
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ht->deleted_entries--;
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entry->hash = hash;
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entry->data = data;
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ht->entries++;
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return 0;
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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 != hash % ht->size);
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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 -1;
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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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hash_table_remove(struct hash_table *ht, uint32_t hash)
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{
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struct hash_entry *entry;
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entry = hash_table_search(ht, hash);
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if (entry != NULL) {
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entry->data = (void *) &deleted_data;
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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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