159 строки
3.9 KiB
C++
159 строки
3.9 KiB
C++
//
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// UniqueAccessExpireStrategy.h
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//
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// $Id: //poco/1.4/Foundation/include/Poco/UniqueAccessExpireStrategy.h#1 $
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//
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// Library: Foundation
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// Package: Cache
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// Module: UniqueAccessExpireStrategy
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//
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// Definition of the UniqueAccessExpireStrategy class.
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//
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// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Foundation_UniqueAccessExpireStrategy_INCLUDED
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#define Foundation_UniqueAccessExpireStrategy_INCLUDED
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#include "Poco/KeyValueArgs.h"
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#include "Poco/ValidArgs.h"
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#include "Poco/AbstractStrategy.h"
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#include "Poco/Bugcheck.h"
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#include "Poco/Timestamp.h"
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#include "Poco/Timespan.h"
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#include "Poco/EventArgs.h"
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#include "Poco/UniqueExpireStrategy.h"
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#include <set>
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#include <map>
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namespace Poco {
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template <
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class TKey,
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class TValue
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>
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class UniqueAccessExpireStrategy: public AbstractStrategy<TKey, TValue>
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/// An UniqueExpireStrategy implements time based expiration of cache entries. In contrast
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/// to ExpireStrategy which only allows to set a per cache expiration value, it allows to define
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/// expiration per CacheEntry.
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/// Each TValue object must thus offer the following method:
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///
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/// const Poco::Timestamp& getTimeout() const;
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///
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/// which returns the timespan for how long an object will be valid without being accessed.
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{
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public:
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typedef std::pair<TKey, Timespan> KeyExpire;
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typedef std::multimap<Timestamp, KeyExpire> TimeIndex;
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typedef typename TimeIndex::iterator IndexIterator;
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typedef typename TimeIndex::const_iterator ConstIndexIterator;
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typedef std::map<TKey, IndexIterator> Keys;
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typedef typename Keys::iterator Iterator;
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public:
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UniqueAccessExpireStrategy()
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/// Create an unique expire strategy.
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{
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}
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~UniqueAccessExpireStrategy()
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{
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}
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void onAdd(const void*, const KeyValueArgs <TKey, TValue>& args)
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{
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// the expire value defines how many millisecs in the future the
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// value will expire, even insert negative values!
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Timestamp expire;
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expire += args.value().getTimeout().totalMicroseconds();
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IndexIterator it = _keyIndex.insert(std::make_pair(expire, std::make_pair(args.key(), args.value().getTimeout())));
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std::pair<Iterator, bool> stat = _keys.insert(std::make_pair(args.key(), it));
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if (!stat.second)
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{
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_keyIndex.erase(stat.first->second);
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stat.first->second = it;
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}
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}
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void onRemove(const void*, const TKey& key)
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{
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Iterator it = _keys.find(key);
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if (it != _keys.end())
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{
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_keyIndex.erase(it->second);
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_keys.erase(it);
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}
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}
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void onGet(const void*, const TKey& key)
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{
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// get updates the expiration time stamp
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Iterator it = _keys.find(key);
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if (it != _keys.end())
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{
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KeyExpire ke = it->second->second;
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// gen new absolute expire value
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Timestamp expire;
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expire += ke.second.totalMicroseconds();
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// delete old index
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_keyIndex.erase(it->second);
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IndexIterator itt = _keyIndex.insert(std::make_pair(expire, ke));
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// update iterator
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it->second = itt;
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}
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}
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void onClear(const void*, const EventArgs& args)
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{
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_keys.clear();
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_keyIndex.clear();
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}
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void onIsValid(const void*, ValidArgs<TKey>& args)
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{
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Iterator it = _keys.find(args.key());
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if (it != _keys.end())
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{
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Timestamp now;
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if (it->second->first <= now)
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{
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args.invalidate();
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}
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}
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else //not found: probably removed by onReplace
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args.invalidate();
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}
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void onReplace(const void*, std::set<TKey>& elemsToRemove)
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{
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// Note: replace only informs the cache which elements
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// it would like to remove!
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// it does not remove them on its own!
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IndexIterator it = _keyIndex.begin();
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Timestamp now;
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while (it != _keyIndex.end() && it->first < now)
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{
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elemsToRemove.insert(it->second.first);
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++it;
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}
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}
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protected:
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Keys _keys; /// For faster replacement of keys, the iterator points to the _keyIndex map
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TimeIndex _keyIndex; /// Maps time to key value
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};
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} // namespace Poco
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#endif // Foundation_UniqueAccessExpireStrategy_INCLUDED
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