// 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/ref.hpp> # include <boost/python/detail/value_arg.hpp> # include <boost/python/detail/type_traits.hpp> # include <boost/python/detail/copy_ctor_mutates_rhs.hpp> # include <boost/mpl/or.hpp> 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 boost::python::detail::add_lvalue_reference<typename boost::python::detail::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_< mpl::or_<python::detail::copy_ctor_mutates_rhs<T>, boost::python::detail::is_scalar<T> > , T , reference_to_value<T> > { }; 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> > : boost::python::detail::add_lvalue_reference<typename boost::python::detail::add_const<T>::type> { }; 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