python/include/boost/python/object/forward.hpp at python313 · boostorg/python · GitHub

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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/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

python/include/boost/python/object/forward.hpp at python313 · boostorg/python · GitHub

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