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90 lines
3.5 KiB
C++
90 lines
3.5 KiB
C++
//
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// UniqueAccessExpireCache.h
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//
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// $Id: //poco/Main/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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// Permission is hereby granted, free of charge, to any person or organization
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// obtaining a copy of the software and accompanying documentation covered by
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// this license (the "Software") to use, reproduce, display, distribute,
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// execute, and transmit the Software, and to prepare derivative works of the
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// Software, and to permit third-parties to whom the Software is furnished to
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// do so, all subject to the following:
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//
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// The copyright notices in the Software and this entire statement, including
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// the above license grant, this restriction and the following disclaimer,
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// must be included in all copies of the Software, in whole or in part, and
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// all derivative works of the Software, unless such copies or derivative
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// works are solely in the form of machine-executable object code generated by
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// a source language processor.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
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// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
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// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
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// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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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 <class TKey, class TValue>
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class UniqueAccessExpireCache: public AbstractCache<TKey, TValue, UniqueAccessExpireStrategy<TKey, TValue> >
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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> >(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
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