ImplPtr.h

/*
  Copyright (C) 2000-2012 Novell, Inc
  This library 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) version 3.0 of the License. This library
  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 library; if not, write
  to the Free Software Foundation, Inc., 51 Franklin Street, Fifth
  Floor, Boston, MA 02110-1301 USA
*/


/*-/

  File:       ImplPtr.h

  Author:     Michael Andres <ma@suse.de>

/-*/

#ifndef ImplPtr_h
#define ImplPtr_h

#include <boost/noncopyable.hpp>
#include <boost/scoped_ptr.hpp>

/**
 * Helper template class for implementation pointers (pointers to a private
 * class or structure that hold the member variables of a higher-level class
 * that is part of a public API).
 *
 * This pointer class maintains constness of its parent class, i.e. if it is
 * used in a const class the class this pointer points to will also be const.
 *
 * This class automatically deletes the class it points to in its destructor.
 **/
template<class _Impl>
class ImplPtr : private boost::noncopyable
{
    typedef typename boost::scoped_ptr<_Impl>::unspecified_bool_type unspecified_bool_type;

public:
    typedef _Impl element_type;

    explicit
    ImplPtr( _Impl * impl_r = 0 )    : _impl( impl_r ) {}

public:
    void reset( _Impl * impl_r = 0 ) { _impl.reset( impl_r ); }

    void swap( ImplPtr rhs )         { _impl.swap( rhs._impl ); }

public:
    operator unspecified_bool_type() const { return _impl; }

    const _Impl & operator*()  const { return *_impl; }
    const _Impl * operator->() const { return _impl.get(); }
    const _Impl * get()        const { return _impl.get(); }

    _Impl &       operator*()        { return *_impl; }
    _Impl *       operator->()       { return _impl.get(); }
    _Impl *       get()              { return _impl.get(); }

private:
    boost::scoped_ptr<_Impl> _impl;
};

template<class _Impl>
inline bool operator==( ImplPtr<_Impl> & lhs, ImplPtr<_Impl> & rhs ) { return lhs.get() == rhs.get(); }

template<class _Impl>
inline bool operator!=( ImplPtr<_Impl> & lhs, ImplPtr<_Impl> & rhs ) { return lhs.get() != rhs.get(); }

template<class _Impl>
inline bool operator< ( ImplPtr<_Impl> & lhs, ImplPtr<_Impl> & rhs ) { return lhs.get() <  rhs.get(); }

#endif // ImplPtr_h