cpython/Python/hashtable.c at 3.11 · python/cpython · GitHub

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/* The implementation of the hash table (_Py_hashtable_t) is based on the

cfuhash project:

http://sourceforge.net/projects/libcfu/

----------------------------------

Creation date: 2005-06-24 21:22:40

Authors: Don

Change log:

This code is released under the BSD license:

Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions

are met:

* Redistributions of source code must retain the above copyright

notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above

disclaimer in the documentation and/or other materials provided

with the distribution.

* Neither the name of the author nor the names of its

contributors may be used to endorse or promote products derived

from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS

FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE

INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

OF THE POSSIBILITY OF SUCH DAMAGE.

----------------------------------

#include "Python.h"

#include "pycore_hashtable.h"

#define HASHTABLE_MIN_SIZE 16

#define HASHTABLE_HIGH 0.50

#define HASHTABLE_LOW 0.10

#define HASHTABLE_REHASH_FACTOR 2.0 / (HASHTABLE_LOW + HASHTABLE_HIGH)

#define BUCKETS_HEAD(SLIST) \

((_Py_hashtable_entry_t *)_Py_SLIST_HEAD(&(SLIST)))

#define TABLE_HEAD(HT, BUCKET) \

((_Py_hashtable_entry_t *)_Py_SLIST_HEAD(&(HT)->buckets[BUCKET]))

#define ENTRY_NEXT(ENTRY) \

((_Py_hashtable_entry_t *)_Py_SLIST_ITEM_NEXT(ENTRY))

/* Forward declaration */

static int hashtable_rehash(_Py_hashtable_t *ht);

static void

_Py_slist_init(_Py_slist_t *list)

{

list->head = NULL;

}

static void

_Py_slist_prepend(_Py_slist_t *list, _Py_slist_item_t *item)

{

item->next = list->head;

list->head = item;

}

static void

_Py_slist_remove(_Py_slist_t *list, _Py_slist_item_t *previous,

_Py_slist_item_t *item)

{

if (previous != NULL)

previous->next = item->next;

else

list->head = item->next;

}

Py_uhash_t

_Py_hashtable_hash_ptr(const void *key)

{

return (Py_uhash_t)_Py_HashPointerRaw(key);

}

int

_Py_hashtable_compare_direct(const void *key1, const void *key2)

{

return (key1 == key2);

}

/* makes sure the real size of the buckets array is a power of 2 */

static size_t

round_size(size_t s)

{

size_t i;

if (s < HASHTABLE_MIN_SIZE)

return HASHTABLE_MIN_SIZE;

i = 1;

while (i < s)

i <<= 1;

return i;

}

size_t

_Py_hashtable_size(const _Py_hashtable_t *ht)

{

size_t size = sizeof(_Py_hashtable_t);

/* buckets */

size += ht->nbuckets * sizeof(_Py_hashtable_entry_t *);

/* entries */

size += ht->nentries * sizeof(_Py_hashtable_entry_t);

return size;

}

_Py_hashtable_entry_t *

_Py_hashtable_get_entry_generic(_Py_hashtable_t *ht, const void *key)

{

Py_uhash_t key_hash = ht->hash_func(key);

size_t index = key_hash & (ht->nbuckets - 1);

_Py_hashtable_entry_t *entry = TABLE_HEAD(ht, index);

while (1) {

if (entry == NULL) {

return NULL;

}

if (entry->key_hash == key_hash && ht->compare_func(key, entry->key)) {

break;

}

entry = ENTRY_NEXT(entry);

}

return entry;

}

// Specialized for:

// hash_func == _Py_hashtable_hash_ptr

// compare_func == _Py_hashtable_compare_direct

static _Py_hashtable_entry_t *

_Py_hashtable_get_entry_ptr(_Py_hashtable_t *ht, const void *key)

{

Py_uhash_t key_hash = _Py_hashtable_hash_ptr(key);

size_t index = key_hash & (ht->nbuckets - 1);

_Py_hashtable_entry_t *entry = TABLE_HEAD(ht, index);

while (1) {

if (entry == NULL) {

return NULL;

}

// Compare directly keys (ignore entry->key_hash)

if (entry->key == key) {

break;

}

entry = ENTRY_NEXT(entry);

}

return entry;

}

void*

_Py_hashtable_steal(_Py_hashtable_t *ht, const void *key)

{

Py_uhash_t key_hash = ht->hash_func(key);

size_t index = key_hash & (ht->nbuckets - 1);

_Py_hashtable_entry_t *entry = TABLE_HEAD(ht, index);

_Py_hashtable_entry_t *previous = NULL;

while (1) {

if (entry == NULL) {

// not found

return NULL;

}

if (entry->key_hash == key_hash && ht->compare_func(key, entry->key)) {

break;

}

previous = entry;

entry = ENTRY_NEXT(entry);

}

_Py_slist_remove(&ht->buckets[index], (_Py_slist_item_t *)previous,

(_Py_slist_item_t *)entry);

ht->nentries--;

void *value = entry->value;

ht->alloc.free(entry);

if ((float)ht->nentries / (float)ht->nbuckets < HASHTABLE_LOW) {

// Ignore failure: error cannot be reported to the caller

hashtable_rehash(ht);

}

return value;

}

int

_Py_hashtable_set(_Py_hashtable_t *ht, const void *key, void *value)

{

_Py_hashtable_entry_t *entry;

#ifndef NDEBUG

/* Don't write the assertion on a single line because it is interesting

to know the duplicated entry if the assertion failed. The entry can

be read using a debugger. */

entry = ht->get_entry_func(ht, key);

assert(entry == NULL);

#endif

entry = ht->alloc.malloc(sizeof(_Py_hashtable_entry_t));

if (entry == NULL) {

/* memory allocation failed */

return -1;

}

entry->key_hash = ht->hash_func(key);

entry->key = (void *)key;

entry->value = value;

ht->nentries++;

if ((float)ht->nentries / (float)ht->nbuckets > HASHTABLE_HIGH) {

if (hashtable_rehash(ht) < 0) {

ht->nentries--;

ht->alloc.free(entry);

return -1;

}

size_t index = entry->key_hash & (ht->nbuckets - 1);

_Py_slist_prepend(&ht->buckets[index], (_Py_slist_item_t*)entry);

return 0;

}

void*

_Py_hashtable_get(_Py_hashtable_t *ht, const void *key)

{

_Py_hashtable_entry_t *entry = ht->get_entry_func(ht, key);

if (entry != NULL) {

return entry->value;

}

else {

return NULL;

}

int

_Py_hashtable_foreach(_Py_hashtable_t *ht,

_Py_hashtable_foreach_func func,

void *user_data)

{

for (size_t hv = 0; hv < ht->nbuckets; hv++) {

_Py_hashtable_entry_t *entry = TABLE_HEAD(ht, hv);

while (entry != NULL) {

int res = func(ht, entry->key, entry->value, user_data);

if (res) {

return res;

}

entry = ENTRY_NEXT(entry);

}

return 0;

}

static int

hashtable_rehash(_Py_hashtable_t *ht)

{

size_t new_size = round_size((size_t)(ht->nentries * HASHTABLE_REHASH_FACTOR));

if (new_size == ht->nbuckets) {

return 0;

}

size_t buckets_size = new_size * sizeof(ht->buckets[0]);

_Py_slist_t *new_buckets = ht->alloc.malloc(buckets_size);

if (new_buckets == NULL) {

/* memory allocation failed */

return -1;

}

memset(new_buckets, 0, buckets_size);

for (size_t bucket = 0; bucket < ht->nbuckets; bucket++) {

_Py_hashtable_entry_t *entry = BUCKETS_HEAD(ht->buckets[bucket]);

while (entry != NULL) {

assert(ht->hash_func(entry->key) == entry->key_hash);

_Py_hashtable_entry_t *next = ENTRY_NEXT(entry);

size_t entry_index = entry->key_hash & (new_size - 1);

_Py_slist_prepend(&new_buckets[entry_index], (_Py_slist_item_t*)entry);

entry = next;

}

ht->alloc.free(ht->buckets);

ht->nbuckets = new_size;

ht->buckets = new_buckets;

return 0;

}

_Py_hashtable_t *

_Py_hashtable_new_full(_Py_hashtable_hash_func hash_func,

_Py_hashtable_compare_func compare_func,

_Py_hashtable_destroy_func key_destroy_func,

_Py_hashtable_destroy_func value_destroy_func,

_Py_hashtable_allocator_t *allocator)

{

_Py_hashtable_allocator_t alloc;

if (allocator == NULL) {

alloc.malloc = PyMem_Malloc;

alloc.free = PyMem_Free;

}

else {

alloc = *allocator;

}

_Py_hashtable_t *ht = (_Py_hashtable_t *)alloc.malloc(sizeof(_Py_hashtable_t));

if (ht == NULL) {

return ht;

}

ht->nbuckets = HASHTABLE_MIN_SIZE;

ht->nentries = 0;

size_t buckets_size = ht->nbuckets * sizeof(ht->buckets[0]);

ht->buckets = alloc.malloc(buckets_size);

if (ht->buckets == NULL) {

alloc.free(ht);

return NULL;

}

memset(ht->buckets, 0, buckets_size);

ht->get_entry_func = _Py_hashtable_get_entry_generic;

ht->hash_func = hash_func;

ht->compare_func = compare_func;

ht->key_destroy_func = key_destroy_func;

ht->value_destroy_func = value_destroy_func;

ht->alloc = alloc;

if (ht->hash_func == _Py_hashtable_hash_ptr

&& ht->compare_func == _Py_hashtable_compare_direct)

{

ht->get_entry_func = _Py_hashtable_get_entry_ptr;

}

return ht;

}

_Py_hashtable_t *

_Py_hashtable_new(_Py_hashtable_hash_func hash_func,

_Py_hashtable_compare_func compare_func)

{

return _Py_hashtable_new_full(hash_func, compare_func,

NULL, NULL, NULL);

}

static void

_Py_hashtable_destroy_entry(_Py_hashtable_t *ht, _Py_hashtable_entry_t *entry)

{

if (ht->key_destroy_func) {

ht->key_destroy_func(entry->key);

}

if (ht->value_destroy_func) {

ht->value_destroy_func(entry->value);

}

ht->alloc.free(entry);

}

void

_Py_hashtable_clear(_Py_hashtable_t *ht)

{

for (size_t i=0; i < ht->nbuckets; i++) {

_Py_hashtable_entry_t *entry = TABLE_HEAD(ht, i);

while (entry != NULL) {

_Py_hashtable_entry_t *next = ENTRY_NEXT(entry);

_Py_hashtable_destroy_entry(ht, entry);

entry = next;

}

_Py_slist_init(&ht->buckets[i]);

}

ht->nentries = 0;

// Ignore failure: clear function is not expected to fail

// because of a memory allocation failure.

(void)hashtable_rehash(ht);

}

void

_Py_hashtable_destroy(_Py_hashtable_t *ht)

{

for (size_t i = 0; i < ht->nbuckets; i++) {

_Py_hashtable_entry_t *entry = TABLE_HEAD(ht, i);

while (entry) {

_Py_hashtable_entry_t *entry_next = ENTRY_NEXT(entry);

_Py_hashtable_destroy_entry(ht, entry);

entry = entry_next;

}

ht->alloc.free(ht->buckets);

ht->alloc.free(ht);

}

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