/*
* 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 "hash_table.h"
#include "ralloc.h"
#include "macros.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,
uint32_t (*key_hash_function)(const void *key),
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_hash_function = key_hash_function;
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;
}
static struct hash_entry *
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;
}
/**
* 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, const void *key)
{
assert(ht
->key_hash_function
); return hash_table_search(ht, ht->key_hash_function(key), key);
}
struct hash_entry *
_mesa_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 struct hash_entry *
hash_table_insert(struct hash_table *ht, uint32_t hash,
const void *key, void *data);
static void
_mesa_hash_table_rehash(struct hash_table *ht, unsigned 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) {
hash_table_insert(ht, entry->hash, entry->key, entry->data);
}
ralloc_free(old_ht.table);
}
static struct hash_entry *
hash_table_insert(struct hash_table *ht, uint32_t hash,
const void *key, void *data)
{
uint32_t start_hash_address, hash_address;
struct hash_entry *available_entry = NULL;
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)) {
/* 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->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);
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 *
_mesa_hash_table_insert(struct hash_table *ht, const void *key, void *data)
{
assert(ht
->key_hash_function
); return hash_table_insert(ht, ht->key_hash_function(key), key, data);
}
struct hash_entry *
_mesa_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 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-1a hash implementation based on:
* http://www.isthe.com/chongo/tech/comp/fnv/
*
* FNV-1a 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)
{
return _mesa_fnv32_1a_accumulate_block(_mesa_fnv32_1a_offset_bias,
data, size);
}
/** FNV-1a string hash implementation */
uint32_t
_mesa_hash_string(const char *key)
{
uint32_t hash = _mesa_fnv32_1a_offset_bias;
while (*key != 0) {
hash = _mesa_fnv32_1a_accumulate(hash, *key);
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)
{
}
bool
_mesa_key_pointer_equal(const void *a, const void *b)
{
return a == b;
}