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UniqueAccessExpireStrategy.h
//
// UniqueAccessExpireStrategy.h
//
// $Id: //poco/1.4/Foundation/include/Poco/UniqueAccessExpireStrategy.h#1 $
//
// Library: Foundation
// Package: Cache
// Module:  UniqueAccessExpireStrategy
//
// Definition of the UniqueAccessExpireStrategy 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_UniqueAccessExpireStrategy_INCLUDED
#define Foundation_UniqueAccessExpireStrategy_INCLUDED


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


namespace Poco {


template < 
      class TKey,
      class TValue
>
00062 class UniqueAccessExpireStrategy: public AbstractStrategy<TKey, TValue>
      /// An UniqueExpireStrategy implements time based expiration of cache entries. In contrast
      /// to ExpireStrategy which only allows to set a per cache expiration value, it allows to define 
      /// expiration per CacheEntry.
      /// Each TValue object must thus offer the following method:
      ///    
      ///    const Poco::Timestamp& getTimeout() const;
      ///    
      /// which returns the timespan for how long an object will be valid without being accessed.
{
public:
      typedef std::pair<TKey, Timespan>           KeyExpire;
      typedef std::multimap<Timestamp, KeyExpire> TimeIndex;
      typedef typename TimeIndex::iterator        IndexIterator;
      typedef typename TimeIndex::const_iterator  ConstIndexIterator;
      typedef std::map<TKey, IndexIterator>       Keys;
      typedef typename Keys::iterator             Iterator;

public:
00081       UniqueAccessExpireStrategy()
            /// Create an unique expire strategy.
      {
      }

      ~UniqueAccessExpireStrategy()
      {
      }

      void onAdd(const void*, const KeyValueArgs <TKey, TValue>& args)
      {
            // the expire value defines how many millisecs in the future the
            // value will expire, even insert negative values!
            Timestamp expire;
            expire += args.value().getTimeout().totalMicroseconds();
            
            IndexIterator it = _keyIndex.insert(std::make_pair(expire, std::make_pair(args.key(), args.value().getTimeout())));
            std::pair<Iterator, bool> stat = _keys.insert(std::make_pair(args.key(), it));
            if (!stat.second)
            {
                  _keyIndex.erase(stat.first->second);
                  stat.first->second = it;
            }
      }

00106       void onRemove(const void*, const TKey& key)
      {
            Iterator it = _keys.find(key);
            if (it != _keys.end())
            {
                  _keyIndex.erase(it->second);
                  _keys.erase(it);
            }
      }

00116       void onGet(const void*, const TKey& key)
      {
            // get updates the expiration time stamp
            Iterator it = _keys.find(key);
            if (it != _keys.end())
            {
                  KeyExpire ke = it->second->second;
                  // gen new absolute expire value
                  Timestamp expire;
                  expire += ke.second.totalMicroseconds();
                  // delete old index
                  _keyIndex.erase(it->second);
                  IndexIterator itt = _keyIndex.insert(std::make_pair(expire, ke));
                  // update iterator
                  it->second = itt;
            }
      }

00134       void onClear(const void*, const EventArgs& args)
      {
            _keys.clear();
            _keyIndex.clear();
      }

00140       void onIsValid(const void*, ValidArgs<TKey>& args)
      {
            Iterator it = _keys.find(args.key());
            if (it != _keys.end())
            {
                  Timestamp now;
                  if (it->second->first <= now)
                  {
                        args.invalidate();
                  }
            }
            else //not found: probably removed by onReplace
                  args.invalidate();
      }

00155       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();
            Timestamp now;
            while (it != _keyIndex.end() && it->first < now)
            {
                  elemsToRemove.insert(it->second.first);
                  ++it;
            }
      }

protected:
      Keys      _keys;     /// For faster replacement of keys, the iterator points to the _keyIndex map
00171       TimeIndex _keyIndex; /// Maps time to key value
};


} // namespace Poco


#endif // Foundation_UniqueAccessExpireStrategy_INCLUDED

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