87 lines
2.2 KiB
C++
87 lines
2.2 KiB
C++
/*
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OPTIONAL-REF.hpp - optional and switchable reference
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Copyright (C) Lumiera.org
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2010, 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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#ifndef LIB_OPTIONAL_REF_H
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#define LIB_OPTIONAL_REF_H
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#include "lib/error.hpp"
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#include "lib/bool-checkable.hpp"
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#include "lib/util.hpp"
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//#include <boost/type_traits/remove_const.hpp>
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//#include <boost/noncopyable.hpp>
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//#include <tr1/functional>
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namespace lib {
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using lumiera::error::LUMIERA_ERROR_BOTTOM_VALUE;
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/**
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* Reference wrapper implemented as constant function,
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* returning the (fixed) reference on invocation
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*/
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template<typename T>
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class ReturnRef
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{
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T& ref_;
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public:
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ReturnRef(T& target) : ref_(target) { }
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T& operator() () const { return ref_;}
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};
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template<typename T>
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ReturnRef<T>
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refFunction (T& target)
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{
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return ReturnRef<T> (target);
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}
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/**
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* Optional or switchable link to an existing object.
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* This reference wrapper normally behaves like a reference,
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* but has the ability to be \em disabled. This disabled state
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* is managed automatically by ctor and dtor, can be detected
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* through \c bool check and -- contrary to a \c NULL pointer
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* -- produces a real exception instead of crashing.
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* @note \em not taking ownership of the pointee
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*/
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template<typename T>
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class OptionalRef
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{
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T* ref_;
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public:
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OptionalRef() : ref_(0) { }
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OptionalRef(T& target) : ref_(&target) { }
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~OptionalRef() { ref_ = 0; }
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};
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} // namespace lib
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#endif
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