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https://github.com/MariaDB/server.git
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143 lines
3.7 KiB
C++
143 lines
3.7 KiB
C++
/* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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/*
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** A class for static sized hash tables where old entries are deleted in
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** first-in-last-out to usage.
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*/
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#ifndef HASH_FILO_H
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#define HASH_FILO_H
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#ifdef USE_PRAGMA_INTERFACE
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#pragma interface /* gcc class interface */
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#endif
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#include "hash.h" /* my_hash_get_key, my_hash_free_key, HASH */
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#include "m_string.h" /* bzero */
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#include "mysqld.h" /* key_hash_filo_lock */
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class hash_filo_element
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{
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private:
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hash_filo_element *next_used,*prev_used;
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public:
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hash_filo_element() {}
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hash_filo_element *next()
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{ return next_used; }
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hash_filo_element *prev()
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{ return prev_used; }
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friend class hash_filo;
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};
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class hash_filo
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{
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const uint size, key_offset, key_length;
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const my_hash_get_key get_key;
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my_hash_free_key free_element;
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bool init;
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CHARSET_INFO *hash_charset;
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hash_filo_element *first_link,*last_link;
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public:
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mysql_mutex_t lock;
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HASH cache;
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hash_filo(uint size_arg, uint key_offset_arg , uint key_length_arg,
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my_hash_get_key get_key_arg, my_hash_free_key free_element_arg,
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CHARSET_INFO *hash_charset_arg)
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:size(size_arg), key_offset(key_offset_arg), key_length(key_length_arg),
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get_key(get_key_arg), free_element(free_element_arg),init(0),
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hash_charset(hash_charset_arg)
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{
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bzero((char*) &cache,sizeof(cache));
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}
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~hash_filo()
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{
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if (init)
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{
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if (cache.array.buffer) /* Avoid problems with thread library */
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(void) my_hash_free(&cache);
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mysql_mutex_destroy(&lock);
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}
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}
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void clear(bool locked=0)
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{
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if (!init)
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{
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init=1;
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mysql_mutex_init(key_hash_filo_lock, &lock, MY_MUTEX_INIT_FAST);
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}
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if (!locked)
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mysql_mutex_lock(&lock);
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(void) my_hash_free(&cache);
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(void) my_hash_init(&cache,hash_charset,size,key_offset,
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key_length, get_key, free_element,0);
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if (!locked)
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mysql_mutex_unlock(&lock);
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first_link=last_link=0;
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}
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hash_filo_element *search(uchar* key, size_t length)
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{
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hash_filo_element *entry=(hash_filo_element*)
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my_hash_search(&cache,(uchar*) key,length);
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if (entry)
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{ // Found; link it first
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if (entry != first_link)
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{ // Relink used-chain
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if (entry == last_link)
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last_link=entry->prev_used;
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else
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{
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entry->next_used->prev_used = entry->prev_used;
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entry->prev_used->next_used = entry->next_used;
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}
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if ((entry->next_used= first_link))
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first_link->prev_used=entry;
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first_link=entry;
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}
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}
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return entry;
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}
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bool add(hash_filo_element *entry)
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{
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if (cache.records == size)
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{
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hash_filo_element *tmp=last_link;
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last_link=last_link->prev_used;
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my_hash_delete(&cache,(uchar*) tmp);
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}
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if (my_hash_insert(&cache,(uchar*) entry))
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{
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if (free_element)
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(*free_element)(entry); // This should never happen
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return 1;
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}
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if ((entry->next_used=first_link))
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first_link->prev_used=entry;
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else
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last_link=entry;
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first_link=entry;
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return 0;
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}
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};
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#endif
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