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