ClickHouse/base/poco/Foundation/include/Poco/AbstractStrategy.h

//
// AbstractStrategy.h
//
// Library: Foundation
// Package: Cache
// Module:  AbstractCache
//
// Definition of the AbstractStrategy class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_AbstractStrategy_INCLUDED
#define Foundation_AbstractStrategy_INCLUDED


#include <set>
#include "Poco/EventArgs.h"
#include "Poco/KeyValueArgs.h"
#include "Poco/ValidArgs.h"


namespace Poco
{


template <class TKey, class TValue>
class AbstractStrategy
/// An AbstractStrategy is the interface for all strategies.
{
public:
    AbstractStrategy() { }

    virtual ~AbstractStrategy() { }

    virtual void onUpdate(const void * pSender, const KeyValueArgs<TKey, TValue> & args)
    /// Updates an existing entry.
    {
        onRemove(pSender, args.key());
        onAdd(pSender, args);
    }

    virtual void onAdd(const void * pSender, const KeyValueArgs<TKey, TValue> & key) = 0;
    /// Adds the key to the strategy.
    /// If for the key already an entry exists, an exception will be thrown.

    virtual void onRemove(const void * pSender, const TKey & key) = 0;
    /// Removes an entry from the strategy. If the entry is not found
    /// the remove is ignored.

    virtual void onGet(const void * pSender, const TKey & key) = 0;
    /// Informs the strategy that a read-access happens to an element.

    virtual void onClear(const void * pSender, const EventArgs & args) = 0;
    /// Removes all elements from the cache.

    virtual void onIsValid(const void * pSender, ValidArgs<TKey> & key) = 0;
    /// Used to query if a key is still valid (i.e. cached).

    virtual void onReplace(const void * pSender, std::set<TKey> & elemsToRemove) = 0;
    /// Used by the Strategy to indicate which elements should be removed from
    /// the cache. Note that onReplace does not change the current list of keys.
    /// The cache object is responsible to remove the elements.
};


} // namespace Poco


#endif // Foundation_AbstractStrategy_INCLUDED