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141 lines
3.4 KiB
C++
141 lines
3.4 KiB
C++
//
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// UniqueExpireStrategy.h
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//
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// $Id: //poco/1.4/Foundation/include/Poco/UniqueExpireStrategy.h#1 $
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//
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// Library: Foundation
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// Package: Cache
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// Module: UniqueExpireStrategy
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//
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// Definition of the UniqueExpireStrategy 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_UniqueExpireStrategy_INCLUDED
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#define Foundation_UniqueExpireStrategy_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/EventArgs.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 UniqueExpireStrategy: 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& getExpiration() const;
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///
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/// which returns the absolute timepoint when the entry will be invalidated.
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{
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public:
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typedef std::multimap<Timestamp, TKey> 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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UniqueExpireStrategy()
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/// Create an unique expire strategy.
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{
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}
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~UniqueExpireStrategy()
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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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// note: we have to insert even if the expire timepoint is in the past (for StrategyCollection classes to avoid inconsistency with LRU)
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// no problem: will be removed with next get
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const Timestamp& expire = args.value().getExpiration();
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IndexIterator it = _keyIndex.insert(std::make_pair(expire, args.key()));
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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 triggers no changes in an expire
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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);
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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_UniqueExpireStrategy_INCLUDED
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