76 строки
2.3 KiB
C++
76 строки
2.3 KiB
C++
//
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// UniqueAccessExpireCache.h
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//
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// $Id: //poco/1.4/Foundation/include/Poco/UniqueAccessExpireCache.h#1 $
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//
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// Library: Foundation
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// Package: Cache
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// Module: UniqueAccessExpireCache
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//
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// Definition of the UniqueAccessExpireCache 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_UniqueAccessExpireCache_INCLUDED
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#define Foundation_UniqueAccessExpireCache_INCLUDED
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#include "Poco/AbstractCache.h"
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#include "Poco/UniqueAccessExpireStrategy.h"
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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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class TMutex = FastMutex,
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class TEventMutex = FastMutex
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>
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class UniqueAccessExpireCache: public AbstractCache<TKey, TValue, UniqueAccessExpireStrategy<TKey, TValue>, TMutex, TEventMutex>
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/// An UniqueAccessExpireCache caches entries for a given time span. In contrast
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/// to ExpireCache 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::Timespan& getTimeout() const;
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///
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/// which returns the relative timespan for how long the entry should be valid without being accessed!
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/// The absolute expire timepoint is calculated as now() + getTimeout().
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/// Accessing an object will update this absolute expire timepoint.
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/// You can use the Poco::AccessExpirationDecorator to add the getExpiration
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/// method to values that do not have a getExpiration function.
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///
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/// Be careful when using an UniqueAccessExpireCache. A cache is often used
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/// like cache.has(x) followed by cache.get x). Note that it could happen
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/// that the "has" call works, then the current execution thread gets descheduled, time passes,
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/// the entry gets invalid, thus leading to an empty SharedPtr being returned
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/// when "get" is invoked.
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{
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public:
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UniqueAccessExpireCache():
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AbstractCache<TKey, TValue, UniqueAccessExpireStrategy<TKey, TValue>, TMutex, TEventMutex>(UniqueAccessExpireStrategy<TKey, TValue>())
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{
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}
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~UniqueAccessExpireCache()
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{
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}
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private:
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UniqueAccessExpireCache(const UniqueAccessExpireCache& aCache);
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UniqueAccessExpireCache& operator = (const UniqueAccessExpireCache& aCache);
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};
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} // namespace Poco
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#endif // Foundation_UniqueAccessExpireCache_INCLUDED
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