hash_filo.h
上传用户:romrleung
上传日期:2022-05-23
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文件大小:3k
- /* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
- 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; either version 2 of the License, or
- (at your option) any later version.
- 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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
- class hash_filo_element
- {
- hash_filo_element *next_used,*prev_used;
- public:
- hash_filo_element() {}
- friend class hash_filo;
- };
- class hash_filo
- {
- const uint size, key_offset, key_length;
- const hash_get_key get_key;
- hash_free_key free_element;
- bool init;
- CHARSET_INFO *hash_charset;
- hash_filo_element *first_link,*last_link;
- public:
- pthread_mutex_t lock;
- HASH cache;
- hash_filo(uint size_arg, uint key_offset_arg , uint key_length_arg,
- hash_get_key get_key_arg, hash_free_key free_element_arg,
- CHARSET_INFO *hash_charset_arg)
- :size(size_arg), key_offset(key_offset_arg), key_length(key_length_arg),
- get_key(get_key_arg), free_element(free_element_arg),init(0),
- hash_charset(hash_charset_arg)
- {
- bzero((char*) &cache,sizeof(cache));
- }
- ~hash_filo()
- {
- if (init)
- {
- if (cache.array.buffer) /* Avoid problems with thread library */
- (void) hash_free(&cache);
- pthread_mutex_destroy(&lock);
- }
- }
- void clear(bool locked=0)
- {
- if (!init)
- {
- init=1;
- (void) pthread_mutex_init(&lock,MY_MUTEX_INIT_FAST);
- }
- if (!locked)
- (void) pthread_mutex_lock(&lock);
- (void) hash_free(&cache);
- (void) hash_init(&cache,hash_charset,size,key_offset,
- key_length, get_key, free_element,0);
- if (!locked)
- (void) pthread_mutex_unlock(&lock);
- first_link=last_link=0;
- }
- hash_filo_element *search(gptr key,uint length)
- {
- hash_filo_element *entry=(hash_filo_element*)
- hash_search(&cache,(byte*) key,length);
- if (entry)
- { // Found; link it first
- if (entry != first_link)
- { // Relink used-chain
- if (entry == last_link)
- last_link=entry->prev_used;
- else
- {
- entry->next_used->prev_used = entry->prev_used;
- entry->prev_used->next_used = entry->next_used;
- }
- if ((entry->next_used= first_link))
- first_link->prev_used=entry;
- first_link=entry;
- }
- }
- return entry;
- }
- my_bool add(hash_filo_element *entry)
- {
- if (cache.records == size)
- {
- hash_filo_element *tmp=last_link;
- last_link=last_link->prev_used;
- hash_delete(&cache,(byte*) tmp);
- }
- if (my_hash_insert(&cache,(byte*) entry))
- {
- if (free_element)
- (*free_element)(entry); // This should never happen
- return 1;
- }
- if ((entry->next_used=first_link))
- first_link->prev_used=entry;
- else
- last_link=entry;
- first_link=entry;
- return 0;
- }
- };
- #endif