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MySQL 5.1: mysql/src/5.1-dbg/sql/hash_filo.h Source File
mysql/src/5.1-dbg/sql/hash_filo.h

00001 /* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
00002 
00003    This program is free software; you can redistribute it and/or modify
00004    it under the terms of the GNU General Public License as published by
00005    the Free Software Foundation; either version 2 of the License, or
00006    (at your option) any later version.
00007 
00008    This program is distributed in the hope that it will be useful,
00009    but WITHOUT ANY WARRANTY; without even the implied warranty of
00010    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00011    GNU General Public License for more details.
00012 
00013    You should have received a copy of the GNU General Public License
00014    along with this program; if not, write to the Free Software
00015    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
00016 
00017 
00018 /*
00019 ** A class for static sized hash tables where old entries are deleted in
00020 ** first-in-last-out to usage.
00021 */
00022 
00023 #ifndef  HASH_FILO_H
00024 #define  HASH_FILO_H
00025 
00026 #ifdef USE_PRAGMA_INTERFACE
00027 #pragma interface                       /* gcc class interface */
00028 #endif
00029 
00030 class hash_filo_element
00031 {
00032   hash_filo_element *next_used,*prev_used;
00033  public:
00034   hash_filo_element() {}
00035   friend class hash_filo;
00036 };
00037 
00038 
00039 class hash_filo
00040 {
00041   const uint size, key_offset, key_length;
00042   const hash_get_key get_key;
00043   hash_free_key free_element;
00044   bool init;
00045   CHARSET_INFO *hash_charset;
00046 
00047   hash_filo_element *first_link,*last_link;
00048 public:
00049   pthread_mutex_t lock;
00050   HASH cache;
00051 
00052   hash_filo(uint size_arg, uint key_offset_arg , uint key_length_arg,
00053             hash_get_key get_key_arg, hash_free_key free_element_arg,
00054             CHARSET_INFO *hash_charset_arg)
00055     :size(size_arg), key_offset(key_offset_arg), key_length(key_length_arg),
00056     get_key(get_key_arg), free_element(free_element_arg),init(0),
00057     hash_charset(hash_charset_arg)
00058   {
00059     bzero((char*) &cache,sizeof(cache));
00060   }
00061 
00062   ~hash_filo()
00063   {
00064     if (init)
00065     {
00066       if (cache.array.buffer)   /* Avoid problems with thread library */
00067         (void) hash_free(&cache);
00068       pthread_mutex_destroy(&lock);
00069     }
00070   }
00071   void clear(bool locked=0)
00072   {
00073     if (!init)
00074     {
00075       init=1;
00076       (void) pthread_mutex_init(&lock,MY_MUTEX_INIT_FAST);
00077     }
00078     if (!locked)
00079       (void) pthread_mutex_lock(&lock);
00080     (void) hash_free(&cache);
00081     (void) hash_init(&cache,hash_charset,size,key_offset, 
00082                      key_length, get_key, free_element,0);
00083     if (!locked)
00084       (void) pthread_mutex_unlock(&lock);
00085     first_link=last_link=0;
00086   }
00087 
00088   hash_filo_element *search(gptr key,uint length)
00089   {
00090     hash_filo_element *entry=(hash_filo_element*)
00091       hash_search(&cache,(byte*) key,length);
00092     if (entry)
00093     {                                           // Found; link it first
00094       if (entry != first_link)
00095       {                                         // Relink used-chain
00096         if (entry == last_link)
00097           last_link=entry->prev_used;
00098         else
00099         {
00100           entry->next_used->prev_used = entry->prev_used;
00101           entry->prev_used->next_used = entry->next_used;
00102         }
00103         if ((entry->next_used= first_link))
00104           first_link->prev_used=entry;
00105         first_link=entry;
00106       }
00107     }
00108     return entry;
00109   }
00110 
00111   my_bool add(hash_filo_element *entry)
00112   {
00113     if (cache.records == size)
00114     {
00115       hash_filo_element *tmp=last_link;
00116       last_link=last_link->prev_used;
00117       hash_delete(&cache,(byte*) tmp);
00118     }
00119     if (my_hash_insert(&cache,(byte*) entry))
00120     {
00121       if (free_element)
00122         (*free_element)(entry);         // This should never happen
00123       return 1;
00124     }
00125     if ((entry->next_used=first_link))
00126       first_link->prev_used=entry;
00127     else
00128       last_link=entry;
00129     first_link=entry;
00130     return 0;
00131   }
00132 };
00133 
00134 #endif
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