mirror of https://github.com/JakubMelka/PDF4QT.git
70 lines
1.9 KiB
C++
70 lines
1.9 KiB
C++
// Copyright (C) 2019 Jakub Melka
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//
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// This file is part of PdfForQt.
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//
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// PdfForQt is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// PdfForQt is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with PDFForQt. If not, see <https://www.gnu.org/licenses/>.
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#ifndef PDFUTILS_H
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#define PDFUTILS_H
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namespace pdf
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{
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/// Class for easy storing of cached item. This class is not thread safe,
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/// and for this reason, access function are not constant (they can modify the
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/// object).
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template<typename T>
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class PDFCachedItem
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{
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public:
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explicit inline PDFCachedItem() :
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m_dirty(true),
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m_object()
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{
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}
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/// Returns the cached object. If object is dirty, then cached object is refreshed.
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/// \param holder Holder object, which owns the cached item
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/// \param function Refresh function
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template<typename H>
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inline const T& get(const H* holder, T(H::* function)(void) const)
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{
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if (m_dirty)
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{
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m_object = (holder->*function)();
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m_dirty = false;
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}
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return m_object;
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}
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/// Invalidates the cached item, so it must be refreshed from the cache next time,
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/// if it is accessed.
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inline void dirty()
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{
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m_dirty = true;
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m_object = T();
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}
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private:
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bool m_dirty;
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T m_object;
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};
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} // namespace pdf
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#endif // PDFUTILS_H
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