Current File : //usr/include/mysql/server/private/hash_filo.h
/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
/*
** A class for static sized hash tables where old entries are deleted in
** first-in-last-out to usage.
*/
#ifndef HASH_FILO_H
#define HASH_FILO_H
#ifdef USE_PRAGMA_INTERFACE
#pragma interface /* gcc class interface */
#endif
#include "hash.h" /* my_hash_get_key, my_hash_free_key, HASH */
#include "m_string.h" /* bzero */
#include "mysqld.h" /* key_hash_filo_lock */
class hash_filo_element
{
private:
hash_filo_element *next_used,*prev_used;
public:
hash_filo_element() = default;
hash_filo_element *next()
{ return next_used; }
hash_filo_element *prev()
{ return prev_used; }
friend class hash_filo;
};
class hash_filo
{
private:
PSI_memory_key m_psi_key;
const uint key_offset, key_length;
const my_hash_get_key get_key;
/** Size of this hash table. */
uint m_size;
my_hash_free_key free_element;
bool init;
CHARSET_INFO *hash_charset;
hash_filo_element *first_link,*last_link;
public:
mysql_mutex_t lock;
HASH cache;
hash_filo(PSI_memory_key psi_key, uint size_arg, uint key_offset_arg,
uint key_length_arg, my_hash_get_key get_key_arg,
my_hash_free_key free_element_arg, CHARSET_INFO *hash_charset_arg)
: m_psi_key(psi_key), key_offset(key_offset_arg),
key_length(key_length_arg), get_key(get_key_arg), m_size(size_arg),
free_element(free_element_arg),init(0), hash_charset(hash_charset_arg),
first_link(NULL), last_link(NULL)
{
bzero((char*) &cache,sizeof(cache));
}
~hash_filo()
{
if (init)
{
if (cache.array.buffer) /* Avoid problems with thread library */
(void) my_hash_free(&cache);
mysql_mutex_destroy(&lock);
}
}
void clear(bool locked=0)
{
if (!init)
{
init=1;
mysql_mutex_init(key_hash_filo_lock, &lock, MY_MUTEX_INIT_FAST);
}
if (!locked)
mysql_mutex_lock(&lock);
first_link= NULL;
last_link= NULL;
(void) my_hash_free(&cache);
(void) my_hash_init(m_psi_key, &cache,hash_charset,m_size,key_offset,
key_length, get_key, free_element, 0);
if (!locked)
mysql_mutex_unlock(&lock);
}
hash_filo_element *first()
{
mysql_mutex_assert_owner(&lock);
return first_link;
}
hash_filo_element *last()
{
mysql_mutex_assert_owner(&lock);
return last_link;
}
hash_filo_element *search(uchar* key, size_t length)
{
mysql_mutex_assert_owner(&lock);
hash_filo_element *entry=(hash_filo_element*)
my_hash_search(&cache,(uchar*) key,length);
if (entry)
{ // Found; link it first
DBUG_ASSERT(first_link != NULL);
DBUG_ASSERT(last_link != NULL);
if (entry != first_link)
{ // Relink used-chain
if (entry == last_link)
{
last_link= last_link->prev_used;
/*
The list must have at least 2 elements,
otherwise entry would be equal to first_link.
*/
DBUG_ASSERT(last_link != NULL);
last_link->next_used= NULL;
}
else
{
DBUG_ASSERT(entry->next_used != NULL);
DBUG_ASSERT(entry->prev_used != NULL);
entry->next_used->prev_used = entry->prev_used;
entry->prev_used->next_used = entry->next_used;
}
entry->prev_used= NULL;
entry->next_used= first_link;
first_link->prev_used= entry;
first_link=entry;
}
}
return entry;
}
bool add(hash_filo_element *entry)
{
if (!m_size) return 1;
if (cache.records == m_size)
{
hash_filo_element *tmp=last_link;
last_link= last_link->prev_used;
if (last_link != NULL)
{
last_link->next_used= NULL;
}
else
{
/* Pathological case, m_size == 1 */
first_link= NULL;
}
my_hash_delete(&cache,(uchar*) tmp);
}
if (my_hash_insert(&cache,(uchar*) entry))
{
if (free_element)
(*free_element)(entry); // This should never happen
return 1;
}
entry->prev_used= NULL;
entry->next_used= first_link;
if (first_link != NULL)
first_link->prev_used= entry;
else
last_link= entry;
first_link= entry;
return 0;
}
uint size()
{ return m_size; }
void resize(uint new_size)
{
mysql_mutex_lock(&lock);
m_size= new_size;
clear(true);
mysql_mutex_unlock(&lock);
}
};
template <class T> class Hash_filo: public hash_filo
{
public:
Hash_filo(PSI_memory_key psi_key, uint size_arg, uint key_offset_arg, uint
key_length_arg, my_hash_get_key get_key_arg, my_hash_free_key
free_element_arg, CHARSET_INFO *hash_charset_arg) :
hash_filo(psi_key, size_arg, key_offset_arg, key_length_arg,
get_key_arg, free_element_arg, hash_charset_arg) {}
T* first() { return (T*)hash_filo::first(); }
T* last() { return (T*)hash_filo::last(); }
T* search(uchar* key, size_t len) { return (T*)hash_filo::search(key, len); }
};
#endif
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