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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
#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 "sal/log.hxx"
#include <boost/unordered_map.hpp>
/** 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 ::boost::unordered_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
SAL_INFO("stoc.tdmanager", "> retrieved element \"" );
SAL_INFO("stoc.tdmanager", "" << pEntry->aKey);
SAL_INFO("stoc.tdmanager", "\" from cache <" );
#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())
{
SAL_INFO("stoc.tdmanager", "> kicking element \"" );
SAL_INFO("stoc.tdmanager", "" << pEntry->aKey);
SAL_INFO("stoc.tdmanager", "\" from cache <" );
}
#endif
_aKey2Element.erase( pEntry->aKey );
_aKey2Element[ pEntry->aKey = rKey ] = pEntry;
}
else
{
pEntry = (*iFind).second;
#ifdef __CACHE_DIAGNOSE
SAL_INFO("stoc.tdmanager", "> replacing element \"" );
SAL_INFO("stoc.tdmanager", "" << pEntry->aKey);
SAL_INFO("stoc.tdmanager", "\" in cache <" );
#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
SAL_INFO("stoc.tdmanager", "> cleared cache <" );
#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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