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// 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
|
