288 lines
9.8 KiB
C++
288 lines
9.8 KiB
C++
/*************************************************************************
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*
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* OpenOffice.org - a multi-platform office productivity suite
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*
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* $RCSfile: lru_cache.h,v $
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*
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* $Revision: 1.4 $
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*
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* last change: $Author: rt $ $Date: 2005-09-08 08:09:57 $
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*
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* The Contents of this file are made available subject to
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* the terms of GNU Lesser General Public License Version 2.1.
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*
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*
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* GNU Lesser General Public License Version 2.1
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* =============================================
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* Copyright 2005 by Sun Microsystems, Inc.
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* 901 San Antonio Road, Palo Alto, CA 94303, USA
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License version 2.1, as published by the Free Software Foundation.
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*
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* This library 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 GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
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* MA 02111-1307 USA
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*
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************************************************************************/
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#ifndef _STOC_SEC_LRU_CACHE_H_
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#define _STOC_SEC_LRU_CACHE_H_
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#include <hash_map>
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// __CACHE_DIAGNOSE works only for OUString keys
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#ifdef __CACHE_DIAGNOSE
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#include <osl/diagnose.h>
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#include <rtl/ustrbuf.hxx>
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#include <rtl/ustring.hxx>
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#include <rtl/string.hxx>
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#endif
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namespace stoc_sec
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{
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/** Implementation of a least recently used (lru) cache.
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*/
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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class lru_cache
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{
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struct Entry
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{
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t_key m_key;
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t_val m_val;
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Entry * m_pred;
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Entry * m_succ;
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};
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typedef ::std::hash_map< t_key, Entry *, t_hashKey, t_equalKey > t_key2element;
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t_key2element m_key2element;
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::std::size_t m_size;
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Entry * m_block;
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mutable Entry * m_head;
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mutable Entry * m_tail;
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inline void toFront( Entry * entry ) const SAL_THROW( () );
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public:
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/** Default Ctor. Does not cache.
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*/
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inline lru_cache() SAL_THROW( () );
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/** Ctor.
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@param size number of elements to be cached; default param set to 128
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*/
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inline lru_cache( ::std::size_t size ) SAL_THROW( () );
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/** Destructor: releases all cached elements and keys.
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*/
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inline ~lru_cache() SAL_THROW( () );
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/** Retrieves a pointer to value in cache. Returns 0, if none was found.
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@param key a key
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@return pointer to value or 0
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*/
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inline t_val const * lookup( t_key const & key ) const SAL_THROW( () );
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/** Sets a value to be cached for given key.
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@param key a key
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@param val a value
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*/
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inline void set( t_key const & key, t_val const & val ) SAL_THROW( () );
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/** Tests whether a value is cached for given key.
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@param key a key
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@return true, if value is cached
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*/
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inline bool has( t_key const & key ) const SAL_THROW( () );
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/** Clears the cache, releasing all cached elements and keys.
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*/
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inline void clear() SAL_THROW( () );
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/** Sets the number of elements to be cached. This will clear previous entries.
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@param cacheSize number of elements to be cached
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*/
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inline void setSize( ::std::size_t size ) SAL_THROW( () );
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};
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::setSize(
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::std::size_t size ) SAL_THROW( () )
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{
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m_key2element.clear();
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delete [] m_block;
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m_block = 0;
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m_size = size;
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if (0 < m_size)
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{
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m_block = new Entry[ m_size ];
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m_head = m_block;
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m_tail = m_block + m_size -1;
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for ( ::std::size_t nPos = m_size; nPos--; )
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{
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m_block[ nPos ].m_pred = m_block + nPos -1;
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m_block[ nPos ].m_succ = m_block + nPos +1;
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}
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}
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache(
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::std::size_t size ) SAL_THROW( () )
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: m_size( 0 )
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, m_block( 0 )
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{
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setSize( size );
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache() SAL_THROW( () )
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: m_size( 0 )
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, m_block( 0 )
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{
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::~lru_cache()
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SAL_THROW( () )
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{
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delete [] m_block;
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::toFront(
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Entry * entry ) const SAL_THROW( () )
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{
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if (entry != m_head)
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{
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// cut out element
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if (entry == m_tail)
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{
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m_tail = entry->m_pred;
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}
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else
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{
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entry->m_succ->m_pred = entry->m_pred;
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entry->m_pred->m_succ = entry->m_succ;
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}
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// push to front
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m_head->m_pred = entry;
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entry->m_succ = m_head;
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m_head = entry;
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}
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline bool lru_cache< t_key, t_val, t_hashKey, t_equalKey >::has(
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t_key const & key ) const SAL_THROW( () )
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{
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typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
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return (iFind != m_key2element.end());
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline t_val const * lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lookup(
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t_key const & key ) const SAL_THROW( () )
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{
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if (0 < m_size)
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{
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typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
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if (iFind != m_key2element.end())
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{
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Entry * entry = iFind->second;
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toFront( entry );
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#ifdef __CACHE_DIAGNOSE
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::rtl::OUStringBuffer buf( 48 );
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buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> retrieved element \"") );
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buf.append( entry->m_key );
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buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
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::rtl::OString str( ::rtl::OUStringToOString(
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buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
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OSL_TRACE( str.getStr() );
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#endif
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return &entry->m_val;
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}
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}
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return 0;
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::set(
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t_key const & key, t_val const & val ) SAL_THROW( () )
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{
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if (0 < m_size)
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{
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typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
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Entry * entry;
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if (iFind == m_key2element.end())
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{
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entry = m_tail; // erase last element
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#ifdef __CACHE_DIAGNOSE
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if (entry->m_key.getLength())
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{
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::rtl::OUStringBuffer buf( 48 );
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buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> kicking element \"") );
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buf.append( entry->m_key );
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buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
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::rtl::OString str( ::rtl::OUStringToOString(
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buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
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OSL_TRACE( str.getStr() );
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}
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#endif
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m_key2element.erase( entry->m_key );
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entry->m_key = key;
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::std::pair< typename t_key2element::iterator, bool > insertion(
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m_key2element.insert( typename t_key2element::value_type( key, entry ) ) );
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#ifdef __CACHE_DIAGNOSE
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OSL_ENSURE( insertion.second, "### inserting new cache entry failed?!" );
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#endif
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}
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else
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{
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entry = iFind->second;
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#ifdef __CACHE_DIAGNOSE
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::rtl::OUStringBuffer buf( 48 );
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buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> replacing element \"") );
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buf.append( entry->m_key );
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buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" in cache") );
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::rtl::OString str( ::rtl::OUStringToOString(
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buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
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OSL_TRACE( str.getStr() );
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#endif
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}
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entry->m_val = val;
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toFront( entry );
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}
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}
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//__________________________________________________________________________________________________
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template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
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inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::clear() SAL_THROW( () )
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{
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m_key2element.clear();
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for ( ::std::size_t nPos = m_size; nPos--; )
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{
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m_block[ nPos ].m_key = t_key();
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m_block[ nPos ].m_val = t_val();
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}
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#ifdef __CACHE_DIAGNOSE
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OSL_TRACE( "> cleared cache\n" );
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#endif
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}
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}
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#endif
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