Python/hashtable.c - platform/external/python/cpython3 - Git at Google

 /* The implementation of the hash table (_Py_hashtable_t) is based on the
    cfuhash project:
    http://sourceforge.net/projects/libcfu/

    Copyright of cfuhash:
    ----------------------------------
    Creation date: 2005-06-24 21:22:40
    Authors: Don
    Change log:

    Copyright (c) 2005 Don Owens
    All rights reserved.

    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
        copyright notice, this list of conditions and the following
        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
    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
    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);
 }
	/* The implementation of the hash table (_Py_hashtable_t) is based on the
	cfuhash project:
	http://sourceforge.net/projects/libcfu/

	Copyright of cfuhash:
	----------------------------------
	Creation date: 2005-06-24 21:22:40
	Authors: Don
	Change log:

	Copyright (c) 2005 Don Owens
	All rights reserved.

	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
	copyright notice, this list of conditions and the following
	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
	COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
	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);
	}