source: XMLIO_V2/external/src/POCO/Foundation.save/Poco/ExpireStrategy.h @ 80

//
// ExpireStrategy.h
//
// $Id: //poco/1.3/Foundation/include/Poco/ExpireStrategy.h#3 $
//
// Library: Foundation
// Package: Cache
// Module:  ExpireStrategy
//
// Definition of the ExpireStrategy class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef  Foundation_ExpireStrategy_INCLUDED
#define  Foundation_ExpireStrategy_INCLUDED


#include "Poco/KeyValueArgs.h"
#include "Poco/ValidArgs.h"
#include "Poco/AbstractStrategy.h"
#include "Poco/Bugcheck.h"
#include "Poco/Timestamp.h"
#include "Poco/EventArgs.h"
#include <set>
#include <map>


namespace Poco {


template < 
        class TKey,
        class TValue
>
class ExpireStrategy: public AbstractStrategy<TKey, TValue>
        /// An ExpireStrategy implements time based expiration of cache entries
{
public:
        typedef std::multimap<Timestamp, TKey>     TimeIndex;
        typedef typename TimeIndex::iterator       IndexIterator;
        typedef typename TimeIndex::const_iterator ConstIndexIterator;
        typedef std::map<TKey, IndexIterator>      Keys;
        typedef typename Keys::iterator            Iterator;

public:
        ExpireStrategy(Timestamp::TimeDiff expireTimeInMilliSec): _expireTime(expireTimeInMilliSec * 1000)
                /// Create an expire strategy. Note that the smallest allowed caching time is 25ms.
                /// Anything lower than that is not useful with current operating systems.
        {
                if (_expireTime < 25000) throw InvalidArgumentException("expireTime must be at least 25 ms");  
        }

        ~ExpireStrategy()
        {
        }

        void onAdd(const void*, const KeyValueArgs <TKey, TValue>& args)
        {
                Timestamp now;
                IndexIterator it = _keyIndex.insert(typename TimeIndex::value_type(now, args.key()));
                std::pair<Iterator, bool> stat = _keys.insert(typename Keys::value_type(args.key(), it));
                if (!stat.second)
                {
                        _keyIndex.erase(stat.first->second);
                        stat.first->second = it;
                }
        }

        void onRemove(const void*, const TKey& key)
        {
                Iterator it = _keys.find(key);
                if (it != _keys.end())
                {
                        _keyIndex.erase(it->second);
                        _keys.erase(it);
                }
        }

        void onGet(const void*, const TKey& key)
        {
                // get triggers no changes in an expire
        }

        void onClear(const void*, const EventArgs& args)
        {
                _keys.clear();
                _keyIndex.clear();
        }

        void onIsValid(const void*, ValidArgs<TKey>& args)
        {
                Iterator it = _keys.find(args.key());
                if (it != _keys.end())
                {
                        if (it->second->first.isElapsed(_expireTime))
                        {
                                args.invalidate();
                        }
                }
                else //not found: probably removed by onReplace
                        args.invalidate();
        }

        void onReplace(const void*, std::set<TKey>& elemsToRemove)
        {
                // Note: replace only informs the cache which elements
                // it would like to remove!
                // it does not remove them on its own!
                IndexIterator it = _keyIndex.begin();
                while (it != _keyIndex.end() && it->first.isElapsed(_expireTime))
                {
                        elemsToRemove.insert(it->second);
                        ++it;
                }
        }

protected:
        Timestamp::TimeDiff _expireTime;
        Keys      _keys;     /// For faster replacement of keys, the iterator points to the _keyIndex map
        TimeIndex _keyIndex; /// Maps time to key value
};


} // namespace Poco


#endif