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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 <[email protected]>
+ * Keith Packard <[email protected]>
+ */
+
+/**
+ * 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 "hash_table.h"
+#include "main/macros.h"
+#include "ralloc.h"
+
+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;
+} hash_sizes[] = {
+ { 2, 5, 3 },
+ { 4, 7, 5 },
+ { 8, 13, 11 },
+ { 16, 19, 17 },
+ { 32, 43, 41 },
+ { 64, 73, 71 },
+ { 128, 151, 149 },
+ { 256, 283, 281 },
+ { 512, 571, 569 },
+ { 1024, 1153, 1151 },
+ { 2048, 2269, 2267 },
+ { 4096, 4519, 4517 },
+ { 8192, 9013, 9011 },
+ { 16384, 18043, 18041 },
+ { 32768, 36109, 36107 },
+ { 65536, 72091, 72089 },
+ { 131072, 144409, 144407 },
+ { 262144, 288361, 288359 },
+ { 524288, 576883, 576881 },
+ { 1048576, 1153459, 1153457 },
+ { 2097152, 2307163, 2307161 },
+ { 4194304, 4613893, 4613891 },
+ { 8388608, 9227641, 9227639 },
+ { 16777216, 18455029, 18455027 },
+ { 33554432, 36911011, 36911009 },
+ { 67108864, 73819861, 73819859 },
+ { 134217728, 147639589, 147639587 },
+ { 268435456, 295279081, 295279079 },
+ { 536870912, 590559793, 590559791 },
+ { 1073741824, 1181116273, 1181116271},
+ { 2147483648ul, 2362232233ul, 2362232231ul}
+};
+
+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;
+}
+
+struct hash_table *
+_mesa_hash_table_create(void *mem_ctx,
+ bool (*key_equals_function)(const void *a,
+ const void *b))
+{
+ struct hash_table *ht;
+
+ ht = ralloc(mem_ctx, struct hash_table);
+ if (ht == NULL)
+ return NULL;
+
+ ht->size_index = 0;
+ ht->size = hash_sizes[ht->size_index].size;
+ ht->rehash = hash_sizes[ht->size_index].rehash;
+ ht->max_entries = hash_sizes[ht->size_index].max_entries;
+ ht->key_equals_function = key_equals_function;
+ ht->table = rzalloc_array(ht, struct hash_entry, ht->size);
+ ht->entries = 0;
+ ht->deleted_entries = 0;
+ ht->deleted_key = &deleted_key_value;
+
+ if (ht->table == NULL) {
+ ralloc_free(ht);
+ return NULL;
+ }
+
+ return ht;
+}
+
+/**
+ * Frees the given hash table.
+ *
+ * If delete_function is passed, it gets called on each entry present before
+ * freeing.
+ */
+void
+_mesa_hash_table_destroy(struct hash_table *ht,
+ void (*delete_function)(struct hash_entry *entry))
+{
+ if (!ht)
+ return;
+
+ if (delete_function) {
+ struct hash_entry *entry;
+
+ hash_table_foreach(ht, entry) {
+ delete_function(entry);
+ }
+ }
+ ralloc_free(ht);
+}
+
+/** Sets the value of the key pointer used for deleted entries in the table.
+ *
+ * The assumption is that usually keys are actual pointers, so we use a
+ * default value of a pointer to an arbitrary piece of storage in the library.
+ * But in some cases a consumer wants to store some other sort of value in the
+ * table, like a uint32_t, in which case that pointer may conflict with one of
+ * their valid keys. This lets that user select a safe value.
+ *
+ * This must be called before any keys are actually deleted from the table.
+ */
+void
+_mesa_hash_table_set_deleted_key(struct hash_table *ht, const void *deleted_key)
+{
+ ht->deleted_key = deleted_key;
+}
+
+/**
+ * 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 *
+_mesa_hash_table_search(struct hash_table *ht, uint32_t hash,
+ const void *key)
+{
+ uint32_t start_hash_address = hash % ht->size;
+ uint32_t hash_address = start_hash_address;
+
+ do {
+ uint32_t double_hash;
+
+ 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;
+ }
+ }
+
+ double_hash = 1 + hash % ht->rehash;
+
+ hash_address = (hash_address + double_hash) % ht->size;
+ } while (hash_address != start_hash_address);
+
+ return NULL;
+}
+
+static void
+_mesa_hash_table_rehash(struct hash_table *ht, int new_size_index)
+{
+ struct hash_table old_ht;
+ struct hash_entry *table, *entry;
+
+ if (new_size_index >= ARRAY_SIZE(hash_sizes))
+ return;
+
+ table = rzalloc_array(ht, 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->max_entries = hash_sizes[ht->size_index].max_entries;
+ ht->entries = 0;
+ ht->deleted_entries = 0;
+
+ hash_table_foreach(&old_ht, entry) {
+ _mesa_hash_table_insert(ht, entry->hash,
+ entry->key, entry->data);
+ }
+
+ ralloc_free(old_ht.table);
+}
+
+/**
+ * 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 *
+_mesa_hash_table_insert(struct hash_table *ht, uint32_t hash,
+ const void *key, void *data)
+{
+ uint32_t start_hash_address, hash_address;
+
+ if (ht->entries >= ht->max_entries) {
+ _mesa_hash_table_rehash(ht, ht->size_index + 1);
+ } else if (ht->deleted_entries + ht->entries >= ht->max_entries) {
+ _mesa_hash_table_rehash(ht, ht->size_index);
+ }
+
+ start_hash_address = hash % ht->size;
+ hash_address = start_hash_address;
+ do {
+ struct hash_entry *entry = ht->table + hash_address;
+ uint32_t double_hash;
+
+ if (!entry_is_present(ht, entry)) {
+ if (entry_is_deleted(ht, entry))
+ ht->deleted_entries--;
+ entry->hash = hash;
+ entry->key = key;
+ entry->data = data;
+ ht->entries++;
+ return entry;
+ }
+
+ /* 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->hash == hash &&
+ ht->key_equals_function(key, entry->key)) {
+ entry->key = key;
+ entry->data = data;
+ return entry;
+ }
+
+
+ double_hash = 1 + hash % ht->rehash;
+
+ hash_address = (hash_address + double_hash) % ht->size;
+ } while (hash_address != start_hash_address);
+
+ /* We could hit here if a required resize failed. An unchecked-malloc
+ * application could ignore this result.
+ */
+ return NULL;
+}
+
+/**
+ * This function deletes the given hash table entry.
+ *
+ * Note that deletion doesn't otherwise modify the table, so an iteration over
+ * the table deleting entries is safe.
+ */
+void
+_mesa_hash_table_remove(struct hash_table *ht,
+ struct hash_entry *entry)
+{
+ if (!entry)
+ return;
+
+ entry->key = ht->deleted_key;
+ ht->entries--;
+ ht->deleted_entries++;
+}
+
+/**
+ * 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 *
+_mesa_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;
+}
+
+/**
+ * Returns a random entry from the hash table.
+ *
+ * This may be useful in implementing random replacement (as opposed
+ * to just removing everything) in caches based on this hash table
+ * implementation. @predicate may be used to filter entries, or may
+ * be set to NULL for no filtering.
+ */
+struct hash_entry *
+_mesa_hash_table_random_entry(struct hash_table *ht,
+ bool (*predicate)(struct hash_entry *entry))
+{
+ struct hash_entry *entry;
+ uint32_t i = rand() % ht->size;
+
+ if (ht->entries == 0)
+ return NULL;
+
+ for (entry = ht->table + i; entry != ht->table + ht->size; entry++) {
+ if (entry_is_present(ht, entry) &&
+ (!predicate || predicate(entry))) {
+ return entry;
+ }
+ }
+
+ for (entry = ht->table; entry != ht->table + i; entry++) {
+ if (entry_is_present(ht, entry) &&
+ (!predicate || predicate(entry))) {
+ return entry;
+ }
+ }
+
+ return NULL;
+}
+
+
+/**
+ * Quick FNV-1 hash implementation based on:
+ * http://www.isthe.com/chongo/tech/comp/fnv/
+ *
+ * FNV-1 is not be the best hash out there -- Jenkins's lookup3 is supposed to
+ * be quite good, and it probably beats FNV. But FNV has the advantage that
+ * it involves almost no code. For an improvement on both, see Paul
+ * Hsieh's http://www.azillionmonkeys.com/qed/hash.html
+ */
+uint32_t
+_mesa_hash_data(const void *data, size_t size)
+{
+ uint32_t hash = 2166136261ul;
+ const uint8_t *bytes = data;
+
+ while (size-- != 0) {
+ hash ^= *bytes;
+ hash = hash * 0x01000193;
+ bytes++;
+ }
+
+ return hash;
+}
+
+/** FNV-1 string hash implementation */
+uint32_t
+_mesa_hash_string(const char *key)
+{
+ uint32_t hash = 2166136261ul;
+
+ while (*key != 0) {
+ hash ^= *key;
+ hash = hash * 0x01000193;
+ key++;
+ }
+
+ return hash;
+}
+
+/**
+ * String compare function for use as the comparison callback in
+ * _mesa_hash_table_create().
+ */
+bool
+_mesa_key_string_equal(const void *a, const void *b)
+{
+ return strcmp(a, b) == 0;
+}
+
+bool
+_mesa_key_pointer_equal(const void *a, const void *b)
+{
+ return a == b;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-17 17:01:57 +0000