GCEdge.hpp

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/*CXXR $Id: GCEdge.hpp 1353 2013-03-18 16:59:38Z arr $
 *CXXR
 *CXXR This file is part of CXXR, a project to refactor the R interpreter
 *CXXR into C++.  It may consist in whole or in part of program code and
 *CXXR documentation taken from the R project itself, incorporated into
 *CXXR CXXR (and possibly MODIFIED) under the terms of the GNU General Public
 *CXXR Licence.
 *CXXR 
 *CXXR CXXR is Copyright (C) 2008-13 Andrew R. Runnalls, subject to such other
 *CXXR copyrights and copyright restrictions as may be stated below.
 *CXXR 
 *CXXR CXXR is not part of the R project, and bugs and other issues should
 *CXXR not be reported via r-bugs or other R project channels; instead refer
 *CXXR to the CXXR website.
 *CXXR */

/*
 *  R : A Computer Language for Statistical Data Analysis
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation; either version 2.1 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, a copy is available at
 *  http://www.r-project.org/Licenses/
 */

#ifndef GCEDGE_HPP
#define GCEDGE_HPP 1

#include "CXXR/GCNode.hpp"
#include "CXXR/GCStackRoot.hpp"

namespace CXXR {
    class RObject;

    class GCEdgeBase {
    public:
        void detach();
    protected:
        GCEdgeBase()
            : m_target(0)
        {}

        GCEdgeBase(const GCNode* target)
            : m_target(target)
        {
            GCNode::maybeCheckExposed(m_target);
            GCNode::incRefCount(m_target);
        }

        GCEdgeBase(const GCEdgeBase& source)
            : m_target(source.m_target)
        {
            GCNode::incRefCount(m_target);
        }
            
        ~GCEdgeBase()
        {
            GCNode::decRefCount(m_target);
        }

        const GCNode* target() const
        {
            return m_target;
        }
    protected:
        void retarget(const GCNode* newtarget)
        {
            GCEdgeBase tmp(newtarget);
            std::swap(m_target, tmp.m_target);
        }
    private:
        const GCNode* m_target;

        static void abortIfNotExposed(const GCNode* target);
    };

    template <class T = RObject>
    class GCEdge : public GCEdgeBase {
    public:
        typedef T type;

        GCEdge()
        {}

        explicit GCEdge(T* target)
            : GCEdgeBase(target)
        {}

        GCEdge(const GCEdge<T>& source)
            : GCEdgeBase(source)
        {}

        GCEdge<T>& operator=(const GCEdge<T>& source)
        {
            retarget(source);
            return *this;
        }

        GCEdge<T>& operator=(T* newtarget)
        {
            retarget(newtarget);
            return *this;
        }

        T* operator->() const
        {
            return get();
        }

        operator T*() const
        {
            return get();
        }

        T* get() const
        {
            return static_cast<T*>(const_cast<GCNode*>(target()));
        }
    };
} // namespace CXXR

#endif  // GCEDGE_HPP