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+/*
+ * Copyright © 2009,2012 Intel Corporation
+ * Copyright © 1988-2004 Keith Packard and Bart Massey.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the names of the authors
+ * or their institutions shall not be used in advertising or
+ * otherwise to promote the sale, use or other dealings in this
+ * Software without prior written authorization from the
+ * authors.
+ *
+ * Authors:
+ * Eric Anholt <eric@anholt.net>
+ * Keith Packard <keithp@keithp.com>
+ */
+
+/**
+ * Implements an open-addressing, linear-reprobing hash table.
+ *
+ * For more information, see:
+ *
+ * http://cgit.freedesktop.org/~anholt/hash_table/tree/README
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "fast_urem_by_const.h"
+#include "hash_table.h"
+
+# define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
+static const uint32_t deleted_key_value;
+
+/**
+ * From Knuth -- a good choice for hash/rehash values is p, p-2 where
+ * p and p-2 are both prime. These tables are sized to have an extra 10%
+ * free to avoid exponential performance degradation as the hash table fills
+ */
+static const struct {
+ uint32_t max_entries, size, rehash;
+ uint64_t size_magic, rehash_magic;
+} hash_sizes[] = {
+#define ENTRY(max_entries, size, rehash) \
+ { max_entries, size, rehash, \
+ REMAINDER_MAGIC(size), REMAINDER_MAGIC(rehash) }
+
+ ENTRY(2, 5, 3 ),
+ ENTRY(4, 7, 5 ),
+ ENTRY(8, 13, 11 ),
+ ENTRY(16, 19, 17 ),
+ ENTRY(32, 43, 41 ),
+ ENTRY(64, 73, 71 ),
+ ENTRY(128, 151, 149 ),
+ ENTRY(256, 283, 281 ),
+ ENTRY(512, 571, 569 ),
+ ENTRY(1024, 1153, 1151 ),
+ ENTRY(2048, 2269, 2267 ),
+ ENTRY(4096, 4519, 4517 ),
+ ENTRY(8192, 9013, 9011 ),
+ ENTRY(16384, 18043, 18041 ),
+ ENTRY(32768, 36109, 36107 ),
+ ENTRY(65536, 72091, 72089 ),
+ ENTRY(131072, 144409, 144407 ),
+ ENTRY(262144, 288361, 288359 ),
+ ENTRY(524288, 576883, 576881 ),
+ ENTRY(1048576, 1153459, 1153457 ),
+ ENTRY(2097152, 2307163, 2307161 ),
+ ENTRY(4194304, 4613893, 4613891 ),
+ ENTRY(8388608, 9227641, 9227639 ),
+ ENTRY(16777216, 18455029, 18455027 ),
+ ENTRY(33554432, 36911011, 36911009 ),
+ ENTRY(67108864, 73819861, 73819859 ),
+ ENTRY(134217728, 147639589, 147639587 ),
+ ENTRY(268435456, 295279081, 295279079 ),
+ ENTRY(536870912, 590559793, 590559791 ),
+ ENTRY(1073741824, 1181116273, 1181116271 ),
+ ENTRY(2147483648ul, 2362232233ul, 2362232231ul )
+};
+
+static inline bool
+key_pointer_is_reserved(const struct hash_table *ht, const void *key)
+{
+ return key == NULL || key == ht->deleted_key;
+}
+
+static int
+entry_is_free(const struct hash_entry *entry)
+{
+ return entry->key == NULL;
+}
+
+static int
+entry_is_deleted(const struct hash_table *ht, struct hash_entry *entry)
+{
+ return entry->key == ht->deleted_key;
+}
+
+static int
+entry_is_present(const struct hash_table *ht, struct hash_entry *entry)
+{
+ return entry->key != NULL && entry->key != ht->deleted_key;
+}
+
+static bool
+hash_table_init(struct hash_table *ht,
+ uint32_t (*key_hash_function)(const void *key),
+ bool (*key_equals_function)(const void *a,
+ const void *b))
+{
+ ht->size_index = 0;
+ ht->size = hash_sizes[ht->size_index].size;
+ ht->rehash = hash_sizes[ht->size_index].rehash;
+ ht->size_magic = hash_sizes[ht->size_index].size_magic;
+ ht->rehash_magic = hash_sizes[ht->size_index].rehash_magic;
+ ht->max_entries = hash_sizes[ht->size_index].max_entries;
+ ht->key_hash_function = key_hash_function;
+ ht->key_equals_function = key_equals_function;
+ ht->table = calloc(sizeof(struct hash_entry), ht->size);
+ ht->entries = 0;
+ ht->deleted_entries = 0;
+ ht->deleted_key = &deleted_key_value;
+
+ return ht->table != NULL;
+}
+
+struct hash_table *
+hash_table_create(uint32_t (*key_hash_function)(const void *key),
+ bool (*key_equals_function)(const void *a,
+ const void *b))
+{
+ struct hash_table *ht;
+
+ ht = malloc(sizeof(struct hash_table));
+ if (ht == NULL)
+ return NULL;
+
+ if (!hash_table_init(ht, key_hash_function, key_equals_function)) {
+ free(ht);
+ return NULL;
+ }
+
+ return ht;
+}
+
+struct hash_table *
+hash_table_clone(struct hash_table *src)
+{
+ struct hash_table *ht;
+
+ ht = malloc(sizeof(struct hash_table));
+ if (ht == NULL)
+ return NULL;
+
+ memcpy(ht, src, sizeof(struct hash_table));
+
+ ht->table = calloc(sizeof(struct hash_entry), ht->size);
+ if (ht->table == NULL) {
+ free(ht);
+ return NULL;
+ }
+
+ memcpy(ht->table, src->table, ht->size * sizeof(struct hash_entry));
+
+ return ht;
+}
+
+/**
+ * Frees the given hash table.
+ */
+void
+hash_table_destroy(struct hash_table *ht,
+ void (*delete_function)(struct hash_entry *entry))
+{
+ if (!ht)
+ return;
+
+ if (delete_function) {
+ hash_table_foreach(ht, entry) {
+ delete_function(entry);
+ }
+ }
+ free(ht->table);
+ free(ht);
+}
+
+static struct hash_entry *
+hash_table_search(struct hash_table *ht, uint32_t hash, const void *key)
+{
+ assert(!key_pointer_is_reserved(ht, key));
+
+ uint32_t size = ht->size;
+ uint32_t start_hash_address = util_fast_urem32(hash, size, ht->size_magic);
+ uint32_t double_hash = 1 + util_fast_urem32(hash, ht->rehash,
+ ht->rehash_magic);
+ uint32_t hash_address = start_hash_address;
+
+ do {
+ struct hash_entry *entry = ht->table + hash_address;
+
+ if (entry_is_free(entry)) {
+ return NULL;
+ } else if (entry_is_present(ht, entry) && entry->hash == hash) {
+ if (ht->key_equals_function(key, entry->key)) {
+ return entry;
+ }
+ }
+
+ hash_address += double_hash;
+ if (hash_address >= size)
+ hash_address -= size;
+ } while (hash_address != start_hash_address);
+
+ return NULL;
+}
+
+/**
+ * Finds a hash table entry with the given key and hash of that key.
+ *
+ * Returns NULL if no entry is found. Note that the data pointer may be
+ * modified by the user.
+ */
+struct hash_entry *
+hash_table_search_pre_hashed(struct hash_table *ht, uint32_t hash,
+ const void *key)
+{
+ assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
+ return hash_table_search(ht, hash, key);
+}
+
+static void
+hash_table_insert_rehash(struct hash_table *ht, uint32_t hash,
+ const void *key, void *data)
+{
+ uint32_t size = ht->size;
+ uint32_t start_hash_address = util_fast_urem32(hash, size, ht->size_magic);
+ uint32_t double_hash = 1 + util_fast_urem32(hash, ht->rehash,
+ ht->rehash_magic);
+ uint32_t hash_address = start_hash_address;
+ do {
+ struct hash_entry *entry = ht->table + hash_address;
+
+ if (entry->key == NULL) {
+ entry->hash = hash;
+ entry->key = key;
+ entry->data = data;
+ return;
+ }
+
+ hash_address += double_hash;
+ if (hash_address >= size)
+ hash_address -= size;
+ } while (true);
+}
+
+static void
+hash_table_rehash(struct hash_table *ht, unsigned new_size_index)
+{
+ struct hash_table old_ht;
+ struct hash_entry *table;
+
+ if (new_size_index >= ARRAY_SIZE(hash_sizes))
+ return;
+
+ table = calloc(sizeof(struct hash_entry), hash_sizes[new_size_index].size);
+ if (table == NULL)
+ return;
+
+ old_ht = *ht;
+
+ ht->table = table;
+ ht->size_index = new_size_index;
+ ht->size = hash_sizes[ht->size_index].size;
+ ht->rehash = hash_sizes[ht->size_index].rehash;
+ ht->size_magic = hash_sizes[ht->size_index].size_magic;
+ ht->rehash_magic = hash_sizes[ht->size_index].rehash_magic;
+ ht->max_entries = hash_sizes[ht->size_index].max_entries;
+ ht->entries = 0;
+ ht->deleted_entries = 0;
+
+ hash_table_foreach(&old_ht, entry) {
+ hash_table_insert_rehash(ht, entry->hash, entry->key, entry->data);
+ }
+
+ ht->entries = old_ht.entries;
+
+ free(old_ht.table);
+}
+
+static struct hash_entry *
+hash_table_insert(struct hash_table *ht, uint32_t hash,
+ const void *key, void *data)
+{
+ struct hash_entry *available_entry = NULL;
+
+ assert(!key_pointer_is_reserved(ht, key));
+
+ if (ht->entries >= ht->max_entries) {
+ hash_table_rehash(ht, ht->size_index + 1);
+ } else if (ht->deleted_entries + ht->entries >= ht->max_entries) {
+ hash_table_rehash(ht, ht->size_index);
+ }
+
+ uint32_t size = ht->size;
+ uint32_t start_hash_address = util_fast_urem32(hash, size, ht->size_magic);
+ uint32_t double_hash = 1 + util_fast_urem32(hash, ht->rehash,
+ ht->rehash_magic);
+ uint32_t hash_address = start_hash_address;
+ do {
+ struct hash_entry *entry = ht->table + hash_address;
+
+ if (!entry_is_present(ht, entry)) {
+ /* Stash the first available entry we find */
+ if (available_entry == NULL)
+ available_entry = entry;
+ if (entry_is_free(entry))
+ break;
+ }
+
+ /* Implement replacement when another insert happens
+ * with a matching key. This is a relatively common
+ * feature of hash tables, with the alternative
+ * generally being "insert the new value as well, and
+ * return it first when the key is searched for".
+ *
+ * Note that the hash table doesn't have a delete
+ * callback. If freeing of old data pointers is
+ * required to avoid memory leaks, perform a search
+ * before inserting.
+ */
+ if (!entry_is_deleted(ht, entry) &&
+ entry->hash == hash &&
+ ht->key_equals_function(key, entry->key)) {
+ entry->key = key;
+ entry->data = data;
+ return entry;
+ }
+
+ hash_address += double_hash;
+ if (hash_address >= size)
+ hash_address -= size;
+ } while (hash_address != start_hash_address);
+
+ if (available_entry) {
+ if (entry_is_deleted(ht, available_entry))
+ ht->deleted_entries--;
+ available_entry->hash = hash;
+ available_entry->key = key;
+ available_entry->data = data;
+ ht->entries++;
+ return available_entry;
+ }
+
+ /* We could hit here if a required resize failed. An unchecked-malloc
+ * application could ignore this result.
+ */
+ return NULL;
+}
+
+/**
+ * Inserts the key with the given hash into the table.
+ *
+ * Note that insertion may rearrange the table on a resize or rehash,
+ * so previously found hash_entries are no longer valid after this function.
+ */
+struct hash_entry *
+hash_table_insert_pre_hashed(struct hash_table *ht, uint32_t hash,
+ const void *key, void *data)
+{
+ assert(ht->key_hash_function == NULL || hash == ht->key_hash_function(key));
+ return hash_table_insert(ht, hash, key, data);
+}
+
+/**
+ * This function is an iterator over the hash table.
+ *
+ * Pass in NULL for the first entry, as in the start of a for loop. Note that
+ * an iteration over the table is O(table_size) not O(entries).
+ */
+struct hash_entry *
+hash_table_next_entry(struct hash_table *ht,
+ struct hash_entry *entry)
+{
+ if (entry == NULL)
+ entry = ht->table;
+ else
+ entry = entry + 1;
+
+ for (; entry != ht->table + ht->size; entry++) {
+ if (entry_is_present(ht, entry)) {
+ return entry;
+ }
+ }
+
+ return NULL;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-11 01:47:50 +0000