root/libbase/ref_counted.h

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// 
//   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010,
//   2011 Free Software Foundation, Inc
// 
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 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 General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

#ifndef GNASH_REF_COUNTED_H
#define GNASH_REF_COUNTED_H

#include "dsodefs.h" // for DSOEXPORT

#include <cassert>
#include <boost/detail/atomic_count.hpp>

namespace gnash {

/// \brief
/// For stuff that's tricky to keep track of w/r/t ownership & cleanup.
/// The only use for this class seems to be for putting derived
/// classes in smart_ptr
///
class DSOEXPORT ref_counted
{

private:

        // We use an atomic counter to make ref-counting 
        // thread-safe. The drop_ref() method must be
        // carefully designed for this to be effective
        // (decrement & check in a single statement)
        //
        typedef boost::detail::atomic_count Counter;

        mutable Counter m_ref_count;
        
protected:

        // A ref-counted object only deletes self,
        // must never be explicitly deleted !
        virtual ~ref_counted()
        {
                assert(m_ref_count == 0);
        }

public:
        ref_counted()
                :
                m_ref_count(0)
        {
        }

        ref_counted(const ref_counted&)
                :
                m_ref_count(0)
        {
        }

        void add_ref() const {
                assert(m_ref_count >= 0);
                ++m_ref_count;
        }

        void drop_ref() const {

                assert(m_ref_count > 0);
                if (!--m_ref_count) {
                        // Delete me!
                        delete this;
                }
        }

        long get_ref_count() const { return m_ref_count; }
};

} // namespace gnash

#endif // GNASH_REF_COUNTED_H