/* Copyright (C) 2003 KSVG Team This file is part of the KDE project This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This library 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 Library General Public License for more details. You should have received a copy of the GNU Library General Public License aint with this library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ #ifndef LRUCACHE_H #define LRUCACHE_H #include <tqvaluelist.h> namespace KSVG { // A value-based LRU cache with a maximum total cost constraint, but with the exception that the // most recently added item is kept in the cache even if its cost exceeds the maximum total cost. template<class keyType, class valueType> class MinOneLRUCache { public: MinOneLRUCache(int maxTotalCost = 0) : m_maxTotalCost(maxTotalCost), m_totalCost(0) {} virtual ~MinOneLRUCache() {} void insert(const keyType& key, const valueType& value, int cost); bool tqfind(const keyType& key, valueType& result); void setMaxTotalCost(int maxTotalCost); int maxTotalCost() const { return m_maxTotalCost; } int totalCost() const { return m_totalCost; } void clear(); protected: class CacheItem { public: CacheItem() : m_cost(0) {} CacheItem(const keyType& key, const valueType& value, int cost) : m_key(key), m_value(value), m_cost(cost) {} const keyType& key() const { return m_key; } const valueType& value() const { return m_value; } int cost() const { return m_cost; } private: keyType m_key; valueType m_value; int m_cost; }; typedef TQValueList<CacheItem> CacheItemList; typename CacheItemList::iterator tqfind(const keyType& key); void enforceCostConstraint(); CacheItemList m_items; int m_maxTotalCost; int m_totalCost; }; template<class keyType, class valueType> void MinOneLRUCache<keyType, valueType>::insert(const keyType& key, const valueType& value, int cost) { typename CacheItemList::iterator it = tqfind(key); if(it != m_items.end()) { // Replace the existing item. m_totalCost -= (*it).cost(); m_items.erase(it); } // We always hold the most recently added item in the cache, even if it exceeds // the maximum total cost. m_items.push_front(CacheItem(key, value, cost)); m_totalCost += cost; enforceCostConstraint(); } template<class keyType, class valueType> bool MinOneLRUCache<keyType, valueType>::tqfind(const keyType& key, valueType& result) { bool foundKey = false; typename CacheItemList::iterator it = tqfind(key); if(it != m_items.end()) { CacheItem item = *it; result = item.value(); if(it != m_items.begin()) { // This is now the most recently used item. m_items.erase(it); m_items.push_front(item); } foundKey = true; } return foundKey; } template<class keyType, class valueType> typename MinOneLRUCache<keyType, valueType>::CacheItemList::iterator MinOneLRUCache<keyType, valueType>::tqfind(const keyType& key) { typename CacheItemList::iterator it; for(it = m_items.begin(); it != m_items.end(); it++) { if((*it).key() == key) break; } return it; } template<class keyType, class valueType> void MinOneLRUCache<keyType, valueType>::enforceCostConstraint() { if(m_totalCost > m_maxTotalCost && m_items.size() > 1) { typename CacheItemList::iterator it = m_items.begin(); m_totalCost = (*it).cost(); ++it; while(it != m_items.end() && m_totalCost + (*it).cost() <= m_maxTotalCost) { m_totalCost += (*it).cost(); ++it; } // Remove the remainder while(it != m_items.end()) it = m_items.erase(it); } } template<class keyType, class valueType> void MinOneLRUCache<keyType, valueType>::setMaxTotalCost(int maxTotalCost) { m_maxTotalCost = maxTotalCost; enforceCostConstraint(); } template<class keyType, class valueType> void MinOneLRUCache<keyType, valueType>::clear() { m_items.clear(); m_totalCost = 0; } } #endif