//-----------------------------------------------------------------------------

// boost variant/detail/move.hpp header file

// See http://www.boost.org for updates, documentation, and revision history.

//-----------------------------------------------------------------------------

//

//  Copyright (c) 2002-2003 Eric Friedman

//  Copyright (c) 2002 by Andrei Alexandrescu

//

//  Use, modification and distribution are subject to the

//  Boost Software License, Version 1.0. (See accompanying file

//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

//

//  This file derivative of MoJO. Much thanks to Andrei for his initial work.

//  See <http://www.cuj.com/experts/2102/alexandr.htm> for information on MOJO.

//  Re-issued here under the Boost Software License, with permission of the original

//  author (Andrei Alexandrescu).

#ifndef BOOST_VARIANT_DETAIL_MOVE_HPP

#define BOOST_VARIANT_DETAIL_MOVE_HPP

#include <iterator> // for iterator_traits

#include <new> // for placement new

#include "boost/config.hpp"

#include "boost/detail/workaround.hpp"

#include "boost/mpl/if.hpp"

#include "boost/type_traits/is_base_and_derived.hpp"

namespace boost {

namespace detail { namespace variant {

//////////////////////////////////////////////////////////////////////////

// forward declares

//

// NOTE: Incomplete until (if?) Boost.Move becomes part of Boost.

//

template <typename Deriving> class moveable;

template <typename T>        class move_source;

template <typename T>        class move_return;

namespace detail {

// (detail) moveable_tag

//

// Concrete type from which moveable<T> derives.

//

// TODO: Move into moveable_fwd.hpp and define has_move_constructor.

//

template <typename Deriving>

struct moveable_tag

{

};

} // namespace detail

//////////////////////////////////////////////////////////////////////////

// function template move

//

// Takes a T& and returns, if T derives moveable<T>, a move_source<T> for

// the object; else, returns the T&.

//

namespace detail {

// (detail) class template move_type

//

// Metafunction that, given moveable T, provides move_source<T>, else T&.

//

template <typename T>

struct move_type

{

public: // metafunction result

    typedef typename mpl::if_<

          is_base_and_derived<detail::moveable_tag<T>, T>

        , move_source<T>

        , T&

        >::type type;

};

} // namespace detail

template <typename T>

inline

    typename detail::move_type<T>::type

move(T& source)

{

    typedef typename detail::move_type<T>::type

        move_t;

    return move_t(source);

}

//////////////////////////////////////////////////////////////////////////

// class template return_t

//

// Metafunction that, given moveable T, provides move_return<T>, else T.

//

template <typename T>

struct return_t

{

public: // metafunction result

    typedef typename mpl::if_<

          is_base_and_derived<moveable<T>, T>

        , move_return<T>

        , T

        >::type type;

};

//////////////////////////////////////////////////////////////////////////

// function template move_swap

//

// Swaps using Koenig lookup but falls back to move-swap for primitive

// types and on non-conforming compilers.

//

#if   defined(BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP)   \

 ||   BOOST_WORKAROUND(__GNUC__, BOOST_TESTED_AT(2))

// [Indicate that move_swap by overload is disabled...]

#define BOOST_NO_MOVE_SWAP_BY_OVERLOAD

// [...and provide straight swap-by-move implementation:]

template <typename T>

inline void move_swap(T& lhs, T& rhs)

{

    T tmp( boost::detail::variant::move(lhs) );

    lhs = boost::detail::variant::move(rhs);

    rhs = boost::detail::variant::move(tmp);

}

#else// !workaround

namespace detail { namespace move_swap {

template <typename T>

inline void swap(T& lhs, T& rhs)

{

    T tmp( boost::detail::variant::move(lhs) );

    lhs = boost::detail::variant::move(rhs);

    rhs = boost::detail::variant::move(tmp);

}

}} // namespace detail::move_swap

template <typename T>

inline void move_swap(T& lhs, T& rhs)

{

    using detail::move_swap::swap;

    swap(lhs, rhs);

}

#endif // workaround

}} // namespace detail::variant

} // namespace boost

#endif // BOOST_VARIANT_DETAIL_MOVE_HPP