// Copyright David Abrahams 2001.

// Distributed under 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)

#ifndef FORWARD_DWA20011215_HPP

# define FORWARD_DWA20011215_HPP



# include <boost/mpl/if.hpp>

# include <boost/type_traits/is_scalar.hpp>

# include <boost/type_traits/add_const.hpp>

# include <boost/type_traits/add_reference.hpp>

# include <boost/ref.hpp>

# include <boost/python/detail/value_arg.hpp>

# include <boost/python/detail/copy_ctor_mutates_rhs.hpp>

# if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

#  include <boost/type_traits/is_enum.hpp>

#  include <boost/mpl/and.hpp>

#  include <boost/mpl/not.hpp>

# else

#  include <boost/mpl/or.hpp>

# endif 



namespace boost { namespace python { namespace objects { 



// Very much like boost::reference_wrapper<T>, except that in this

// case T can be a reference already without causing a

// reference-to-reference error.

template <class T>

struct reference_to_value

{

    typedef typename add_reference<typename add_const<T>::type>::type reference;

    

    reference_to_value(reference x) : m_value(x) {}

    reference get() const { return m_value; }

 private:

    reference m_value;

};



// A little metaprogram which selects the type to pass through an

// intermediate forwarding function when the destination argument type

// is T.

template <class T>

struct forward

    : mpl::if_<

# if BOOST_WORKAROUND(BOOST_MSVC, < 1300)

          // vc6 chokes on unforwarding enums nested in classes

          mpl::and_<

              is_scalar<T>

            , mpl::not_< 

                  is_enum<T>

              >

          >

# else 

          mpl::or_<python::detail::copy_ctor_mutates_rhs<T>, is_scalar<T> >

# endif 

        , T

        , reference_to_value<T>

      >

{

};



# ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

template<typename T>

struct unforward

{

    typedef typename unwrap_reference<T>::type& type;

};



template<typename T>

struct unforward<reference_to_value<T> >

{

    typedef T type;

};



template <typename T>

struct unforward_cref

  : python::detail::value_arg<

        typename unwrap_reference<T>::type

    >

{

};



template<typename T>

struct unforward_cref<reference_to_value<T> >

  : add_reference<typename add_const<T>::type>

{

};



# else // no partial specialization



namespace detail

{

  typedef char (&yes_reference_to_value_t)[1];

  typedef char (&no_reference_to_value_t)[2];

      

  no_reference_to_value_t is_reference_to_value_test(...);



  template<typename T>

  yes_reference_to_value_t is_reference_to_value_test(boost::type< reference_to_value<T> >);



  template<bool wrapped>

  struct unforwarder

  {

      template <class T>

      struct apply

      {

          typedef typename unwrap_reference<T>::type& type;

      };

  };



  template<>

  struct unforwarder<true>

  {

      template <class T>

      struct apply

      {

          typedef typename T::reference type;

      };

  };



  template<bool wrapped = false>

  struct cref_unforwarder

  {

      template <class T>

      struct apply

        : python::detail::value_arg<

              typename unwrap_reference<T>::type

          >

      {          

      };

  };

      

  template<>

  struct cref_unforwarder<true>

  {

      template <class T>

      struct apply

        : python::detail::value_arg<

              typename T::reference

          >

      {

      };

  };



  template<typename T>

  struct is_reference_to_value

  {

      BOOST_STATIC_CONSTANT(

          bool, value = (

              sizeof(is_reference_to_value_test(boost::type<T>()))

              == sizeof(yes_reference_to_value_t)));

      typedef mpl::bool_<value> type;

  };

}



template <typename T>

struct unforward

    : public detail::unforwarder<

        detail::is_reference_to_value<T>::value

      >::template apply<T>

{};



template <typename T>

struct unforward_cref

    : public detail::cref_unforwarder<

        detail::is_reference_to_value<T>::value

      >::template apply<T>

{};



# endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION



template <class T>

typename reference_to_value<T>::reference

do_unforward(reference_to_value<T> const& x, int)

{

    return x.get();

}



template <class T>

typename reference_wrapper<T>::type&

do_unforward(reference_wrapper<T> const& x, int)

{

    return x.get();

}



template <class T>

T const& do_unforward(T const& x, ...)

{

    return x;

}



}}} // namespace boost::python::objects



#endif // FORWARD_DWA20011215_HPP

