93 lines
2.6 KiB
C++
93 lines
2.6 KiB
C++
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/*
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VISITOR.hpp - Acyclic Visitor library
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Copyright (C) CinelerraCV
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2007, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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This program 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 General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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====================================================================
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This code is heavily inspired by
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The Loki Library (loki-lib/trunk/include/loki/Visitor.h)
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Copyright (c) 2001 by Andrei Alexandrescu
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This Loki code accompanies the book:
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Alexandrescu, Andrei. "Modern C++ Design: Generic Programming
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and Design Patterns Applied".
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Copyright (c) 2001. Addison-Wesley. ISBN 0201704315
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*/
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#ifndef CINELERRA_VISITORPOLICIES_H
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#define CINELERRA_VISITORPOLICIES_H
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#include "common/error.hpp"
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namespace cinelerra
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{
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namespace visitor
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{
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/* == several Policies usable in conjunction with cinelerra::visitor::Visitable == */
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/**
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* Policy returning just the default return value in case
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* of encountering an unknown Visitor (typically caused by
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* adding a new class to the visitable hierarchy)
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*/
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template<typename RET, class TOOL>
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struct UseDefault
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{
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template<class TAR>
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static RET onUnknown (TAR&, TOOL&)
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{
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return RET();
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}
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};
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/**
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* Policy to throw when encountering an unknown visiting tool
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*/
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template<typename RET, class TOOL>
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struct ThrowException
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{
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template<class TAR>
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static RET onUnknown (TAR&, TOOL&)
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{
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throw cinelerra::error::Config("unable to decide what tool operation to call");
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}
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};
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/**
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* Policy invoking an catch-all function for processing
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* an unknown tool / target pair
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*/
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template<typename RET, class TOOL>
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struct InvokeCatchAllFunction
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{
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template<class TAR>
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static RET onUnknown (TAR& target,TOOL& tool)
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{
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target.apply (static_cast<TOOL&> (tool));
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}
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};
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} // namespace visitor
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} // namespace cinelerra
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#endif
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