text: //
  // UniqueExpireStrategy.h
  //
  // $Id: //poco/1.3/Foundation/include/Poco/UniqueExpireStrategy.h#2 $
  //
  // Library: Foundation
  // Package: Cache
  // Module:  UniqueExpireStrategy
  //
  // Definition of the UniqueExpireStrategy 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_UniqueExpireStrategy_INCLUDED
  #define  Foundation_UniqueExpireStrategy_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 UniqueExpireStrategy: 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& getExpiration() const;
  	///    
  	/// which returns the absolute timepoint when the entry will be invalidated.
  {
  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:
  	UniqueExpireStrategy()
  		/// Create an unique expire strategy.
  	{
  	}
  
  	~UniqueExpireStrategy()
  	{
  	}
  
  	void onAdd(const void*, const KeyValueArgs <TKey, TValue>& args)
  	{
  		// note: we have to insert even if the expire timepoint is in the past (for StrategyCollection classes to avoid inconsistency with LRU)
  		// no problem: will be removed with next get
  		const Timestamp& expire = args.value().getExpiration();
  		IndexIterator it = _keyIndex.insert(std::make_pair(expire, args.key()));
  		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;
  		}
  	}
  
  	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())
  		{
  			Timestamp now;
  			if (it->second->first <= now)
  			{
  				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();
  		Timestamp now;
  		while (it != _keyIndex.end() && it->first < now)
  		{
  			elemsToRemove.insert(it->second);
  			++it;
  		}
  	}
  
  protected:
  	Keys      _keys;     /// For faster replacement of keys, the iterator points to the _keyIndex map
  	TimeIndex _keyIndex; /// Maps time to key value
  };
  
  
  } // namespace Poco
  
  
  #endif
  