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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 _STOC_SEC_LRU_CACHE_H_
#define _STOC_SEC_LRU_CACHE_H_
#include <boost/unordered_map.hpp>
// __CACHE_DIAGNOSE works only for OUString keys
#ifdef __CACHE_DIAGNOSE
#include <osl/diagnose.h>
#include <rtl/ustrbuf.hxx>
#include <rtl/ustring.hxx>
#include <rtl/string.hxx>
#endif
namespace stoc_sec
{
/** Implementation of a least recently used (lru) cache.
*/
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
class lru_cache
{
struct Entry
{
t_key m_key;
t_val m_val;
Entry * m_pred;
Entry * m_succ;
};
typedef ::boost::unordered_map< t_key, Entry *, t_hashKey, t_equalKey > t_key2element;
t_key2element m_key2element;
::std::size_t m_size;
Entry * m_block;
mutable Entry * m_head;
mutable Entry * m_tail;
inline void toFront( Entry * entry ) const SAL_THROW( () );
public:
/** Default Ctor. Does not cache.
*/
inline lru_cache() SAL_THROW( () );
/** Ctor.
@param size number of elements to be cached; default param set to 128
*/
inline lru_cache( ::std::size_t size ) SAL_THROW( () );
/** Destructor: releases all cached elements and keys.
*/
inline ~lru_cache() SAL_THROW( () );
/** Retrieves a pointer to value in cache. Returns 0, if none was found.
@param key a key
@return pointer to value or 0
*/
inline t_val const * lookup( t_key const & key ) const SAL_THROW( () );
/** Sets a value to be cached for given key.
@param key a key
@param val a value
*/
inline void set( t_key const & key, t_val const & val ) SAL_THROW( () );
/** Tests whether a value is cached for given key.
@param key a key
@return true, if value is cached
*/
inline bool has( t_key const & key ) const SAL_THROW( () );
/** Clears the cache, releasing all cached elements and keys.
*/
inline void clear() SAL_THROW( () );
/** Sets the number of elements to be cached. This will clear previous entries.
@param cacheSize number of elements to be cached
*/
inline void setSize( ::std::size_t size ) SAL_THROW( () );
};
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::setSize(
::std::size_t size ) SAL_THROW( () )
{
m_key2element.clear();
delete [] m_block;
m_block = 0;
m_size = size;
if (0 < m_size)
{
m_block = new Entry[ m_size ];
m_head = m_block;
m_tail = m_block + m_size -1;
for ( ::std::size_t nPos = m_size; nPos--; )
{
m_block[ nPos ].m_pred = m_block + nPos -1;
m_block[ nPos ].m_succ = m_block + nPos +1;
}
}
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache(
::std::size_t size ) SAL_THROW( () )
: m_size( 0 )
, m_block( 0 )
{
setSize( size );
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lru_cache() SAL_THROW( () )
: m_size( 0 )
, m_block( 0 )
{
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline lru_cache< t_key, t_val, t_hashKey, t_equalKey >::~lru_cache()
SAL_THROW( () )
{
delete [] m_block;
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::toFront(
Entry * entry ) const SAL_THROW( () )
{
if (entry != m_head)
{
// cut out element
if (entry == m_tail)
{
m_tail = entry->m_pred;
}
else
{
entry->m_succ->m_pred = entry->m_pred;
entry->m_pred->m_succ = entry->m_succ;
}
// push to front
m_head->m_pred = entry;
entry->m_succ = m_head;
m_head = entry;
}
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline bool lru_cache< t_key, t_val, t_hashKey, t_equalKey >::has(
t_key const & key ) const SAL_THROW( () )
{
typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
return (iFind != m_key2element.end());
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline t_val const * lru_cache< t_key, t_val, t_hashKey, t_equalKey >::lookup(
t_key const & key ) const SAL_THROW( () )
{
if (0 < m_size)
{
typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
if (iFind != m_key2element.end())
{
Entry * entry = iFind->second;
toFront( entry );
#ifdef __CACHE_DIAGNOSE
::rtl::OUStringBuffer buf( 48 );
buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> retrieved element \"") );
buf.append( entry->m_key );
buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
::rtl::OString str( ::rtl::OUStringToOString(
buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
OSL_TRACE( "%s", str.getStr() );
#endif
return &entry->m_val;
}
}
return 0;
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::set(
t_key const & key, t_val const & val ) SAL_THROW( () )
{
if (0 < m_size)
{
typename t_key2element::const_iterator const iFind( m_key2element.find( key ) );
Entry * entry;
if (iFind == m_key2element.end())
{
entry = m_tail; // erase last element
#ifdef __CACHE_DIAGNOSE
if (entry->m_key.getLength())
{
::rtl::OUStringBuffer buf( 48 );
buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> kicking element \"") );
buf.append( entry->m_key );
buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" from cache") );
::rtl::OString str( ::rtl::OUStringToOString(
buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
OSL_TRACE( "%s", str.getStr() );
}
#endif
m_key2element.erase( entry->m_key );
entry->m_key = key;
::std::pair< typename t_key2element::iterator, bool > insertion(
m_key2element.insert( typename t_key2element::value_type( key, entry ) ) );
#ifdef __CACHE_DIAGNOSE
OSL_ENSURE( insertion.second, "### inserting new cache entry failed?!" );
#endif
}
else
{
entry = iFind->second;
#ifdef __CACHE_DIAGNOSE
::rtl::OUStringBuffer buf( 48 );
buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("> replacing element \"") );
buf.append( entry->m_key );
buf.appendAscii( RTL_CONSTASCII_STRINGPARAM("\" in cache") );
::rtl::OString str( ::rtl::OUStringToOString(
buf.makeStringAndClear(), RTL_TEXTENCODING_ASCII_US ) );
OSL_TRACE( "%s", str.getStr() );
#endif
}
entry->m_val = val;
toFront( entry );
}
}
//__________________________________________________________________________________________________
template< typename t_key, typename t_val, typename t_hashKey, typename t_equalKey >
inline void lru_cache< t_key, t_val, t_hashKey, t_equalKey >::clear() SAL_THROW( () )
{
m_key2element.clear();
for ( ::std::size_t nPos = m_size; nPos--; )
{
m_block[ nPos ].m_key = t_key();
m_block[ nPos ].m_val = t_val();
}
#ifdef __CACHE_DIAGNOSE
OSL_TRACE( "> cleared cache\n" );
#endif
}
}
#endif
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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