// 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 |