| // 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 |