243 lines
8.4 KiB
C++
243 lines
8.4 KiB
C++
/*************************************************************************
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*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* Copyright 2000, 2010 Oracle and/or its affiliates.
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*
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* OpenOffice.org - a multi-platform office productivity suite
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*
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* This file is part of OpenOffice.org.
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*
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* OpenOffice.org is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 3
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* only, as published by the Free Software Foundation.
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*
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* OpenOffice.org 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 Lesser General Public License version 3 for more details
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* (a copy is included in the LICENSE file that accompanied this code).
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*
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* You should have received a copy of the GNU Lesser General Public License
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* version 3 along with OpenOffice.org. If not, see
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* <http://www.openoffice.org/license.html>
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* for a copy of the LGPLv3 License.
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*
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************************************************************************/
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#ifndef _LRU_CACHE_HXX_
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#define _LRU_CACHE_HXX_
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// __CACHE_DIAGNOSE forces cache size to 4 and works only for OUString keys
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// #define __CACHE_DIAGNOSE 1
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#include <osl/mutex.hxx>
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#include "rtl/ustring.hxx"
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#include <hash_map>
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/** Implementation of a least recently used (lru) cache.
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<br>
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@author Daniel Boelzle
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*/
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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class LRU_Cache
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{
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struct CacheEntry
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{
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t_Key aKey;
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t_Val aVal;
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CacheEntry * pPred;
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CacheEntry * pSucc;
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};
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typedef ::std::hash_map< t_Key, CacheEntry *, t_KeyHash, t_KeyEqual > t_Key2Element;
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mutable ::osl::Mutex _aCacheMutex;
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sal_Int32 _nCachedElements;
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t_Key2Element _aKey2Element;
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CacheEntry * _pBlock;
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mutable CacheEntry * _pHead;
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mutable CacheEntry * _pTail;
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inline void toFront( CacheEntry * pEntry ) const;
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public:
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/** Constructor:
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<br>
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@param nCachedElements number of elements to be cached; default param set to 128
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*/
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inline LRU_Cache( sal_Int32 nCachedElements = 128 );
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/** Destructor: releases all cached elements and keys.
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<br>
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*/
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inline ~LRU_Cache();
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/** Retrieves a value from the cache. Returns default constructed value,
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if none was found.
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<br>
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@param rKey a key
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@return value
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*/
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inline t_Val getValue( const t_Key & rKey ) const;
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/** Sets a value to be cached for given key.
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<br>
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@param rKey a key
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@param rValue a value
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*/
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inline void setValue( const t_Key & rKey, const t_Val & rValue );
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/** Tests whether a value is cached for given key.
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<br>
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@param rKey a key
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@return true, if value is cached
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*/
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inline sal_Bool hasValue( const t_Key & rKey ) const;
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/** Clears the cache, thus releasing all cached elements and keys.
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<br>
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*/
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inline void clear();
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};
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//__________________________________________________________________________________________________
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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inline LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::LRU_Cache( sal_Int32 nCachedElements )
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#ifdef __CACHE_DIAGNOSE
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: _nCachedElements( 4 )
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#else
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: _nCachedElements( nCachedElements )
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#endif
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, _pBlock( 0 )
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{
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if (_nCachedElements > 0)
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{
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_pBlock = new CacheEntry[_nCachedElements];
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_pHead = _pBlock;
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_pTail = _pBlock + _nCachedElements -1;
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for ( sal_Int32 nPos = _nCachedElements; nPos--; )
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{
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_pBlock[nPos].pPred = _pBlock + nPos -1;
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_pBlock[nPos].pSucc = _pBlock + nPos +1;
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}
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}
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}
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//__________________________________________________________________________________________________
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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inline LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::~LRU_Cache()
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{
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delete [] _pBlock;
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}
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//__________________________________________________________________________________________________
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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inline void LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::toFront( CacheEntry * pEntry ) const
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{
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if (pEntry != _pHead)
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{
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// cut out element
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if (pEntry == _pTail)
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{
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_pTail = pEntry->pPred;
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}
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else
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{
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pEntry->pSucc->pPred = pEntry->pPred;
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pEntry->pPred->pSucc = pEntry->pSucc;
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}
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// push to front
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_pHead->pPred = pEntry;
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pEntry->pSucc = _pHead;
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_pHead = pEntry;
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}
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}
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//__________________________________________________________________________________________________
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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inline sal_Bool LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::hasValue( const t_Key & rKey ) const
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{
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::osl::MutexGuard aGuard( _aCacheMutex );
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const typename t_Key2Element::const_iterator iFind( _aKey2Element.find( rKey ) );
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return (iFind != _aKey2Element.end());
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}
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//__________________________________________________________________________________________________
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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inline t_Val LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::getValue( const t_Key & rKey ) const
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{
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::osl::MutexGuard aGuard( _aCacheMutex );
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const typename t_Key2Element::const_iterator iFind( _aKey2Element.find( rKey ) );
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if (iFind != _aKey2Element.end())
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{
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CacheEntry * pEntry = (*iFind).second;
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toFront( pEntry );
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#ifdef __CACHE_DIAGNOSE
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OSL_TRACE( "> retrieved element \"" );
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OSL_TRACE( ::rtl::OUStringToOString( pEntry->aKey, RTL_TEXTENCODING_ASCII_US ).getStr() );
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OSL_TRACE( "\" from cache <\n" );
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#endif
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return pEntry->aVal;
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}
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return t_Val();
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}
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//__________________________________________________________________________________________________
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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inline void LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::setValue(
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const t_Key & rKey, const t_Val & rValue )
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{
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if (_nCachedElements > 0)
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{
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::osl::MutexGuard aGuard( _aCacheMutex );
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const typename t_Key2Element::const_iterator iFind( _aKey2Element.find( rKey ) );
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CacheEntry * pEntry;
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if (iFind == _aKey2Element.end())
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{
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pEntry = _pTail; // erase last element
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#ifdef __CACHE_DIAGNOSE
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if (pEntry->aKey.getLength())
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{
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OSL_TRACE( "> kicking element \"" );
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OSL_TRACE( ::rtl::OUStringToOString( pEntry->aKey, RTL_TEXTENCODING_ASCII_US ).getStr() );
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OSL_TRACE( "\" from cache <\n" );
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}
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#endif
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_aKey2Element.erase( pEntry->aKey );
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_aKey2Element[ pEntry->aKey = rKey ] = pEntry;
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}
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else
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{
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pEntry = (*iFind).second;
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#ifdef __CACHE_DIAGNOSE
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OSL_TRACE( "> replacing element \"" );
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OSL_TRACE( ::rtl::OUStringToOString( pEntry->aKey, RTL_TEXTENCODING_ASCII_US ).getStr() );
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OSL_TRACE( "\" in cache <\n" );
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#endif
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}
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pEntry->aVal = rValue;
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toFront( pEntry );
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}
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}
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//__________________________________________________________________________________________________
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template< class t_Key, class t_Val, class t_KeyHash, class t_KeyEqual >
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inline void LRU_Cache< t_Key, t_Val, t_KeyHash, t_KeyEqual >::clear()
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{
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::osl::MutexGuard aGuard( _aCacheMutex );
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_aKey2Element.clear();
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for ( sal_Int32 nPos = _nCachedElements; nPos--; )
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{
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_pBlock[nPos].aKey = t_Key();
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_pBlock[nPos].aVal = 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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struct FctHashOUString : public ::std::unary_function< const ::rtl::OUString &, size_t >
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{
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size_t operator()( const ::rtl::OUString & rKey ) const
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{ return rKey.hashCode(); }
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};
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/** Template instance for OUString keys, Any values.<br>
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*/
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typedef LRU_Cache< ::rtl::OUString, ::com::sun::star::uno::Any,
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FctHashOUString, ::std::equal_to< ::rtl::OUString > >
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LRU_CacheAnyByOUString;
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#endif
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