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80 lines
2.2 KiB
C++
80 lines
2.2 KiB
C++
// -*- C++ -*-
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/**
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* \file Cache.h
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* This file is part of LyX, the document processor.
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* Licence details can be found in the file COPYING.
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*
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* \author Guillaume Munch
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*
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* Full author contact details are available in file CREDITS.
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*/
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#ifndef CACHE_H
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#define CACHE_H
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#include <QCache>
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#include <list>
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#include <type_traits>
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namespace lyx {
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/**
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* Cache<Key, T> implements a cache where objects are stored by copy.
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*
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* This is a wrapper for QCache. See the documentation of QCache:
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* <https://doc.qt.io/qt-5/qcache.html>.
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*
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* It is especially useful for storing shared pointers. This turns QCache into a
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* shared-ownership cache with no risks of dangling pointer. It is also useful
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* for small copyable objects.
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*
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* Use this rather than QCache directly, to avoid naked pointers.
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*/
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template <class Key, class Val>
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class Cache : private QCache<Key, Val> {
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#if !(defined(__GNUC__) && (__GNUC__ == 4) && (__GNUC_MINOR__ == 6))
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static_assert(std::is_copy_constructible<Val>::value,
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"lyx::Cache only stores copyable objects!");
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static_assert(std::is_default_constructible<Val>::value,
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"lyx::Cache only stores default-constructible objects!");
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using Q = QCache<Key, Val>;
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#else
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typedef QCache<Key, Val> Q;
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#endif
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public:
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///
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Cache(int max_cost = 100) : Q(max_cost) {}
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///
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bool insert(Key const & key, Val object, int cost = 1)
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{
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return Q::insert(key, new Val(std::move(object)), cost);
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}
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// Returns the default value (e.g. null pointer) before using the result. If
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// this is not convenient for your type, check if it exists beforehand with
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// Cache::contains.
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Val object(Key const & key) const
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{
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if (Val * obj = Q::object(key))
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return *obj;
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return Val();
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}
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/// Everything from QCache except QCache::take.
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using Q::clear;
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using Q::contains;
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using Q::count;
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using Q::remove;
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using Q::size;
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bool empty() const { return Q::isEmpty(); }
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std::list<Key> keys() { return Q::keys().toStdList(); }
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int max_cost() const { return Q::maxCost(); }
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void set_max_cost(int cost) { Q::setMaxCost(cost); }
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int total_cost() const { return Q::totalCost(); }
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Val operator[](Key const & key) const { return object(key); }
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};
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} // namespace lyx
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#endif
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