boost/move/detail/meta_utils.hpp
//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2012-2015.
// 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)
//
// See http://www.boost.org/libs/move for documentation.
//
//////////////////////////////////////////////////////////////////////////////
//! \file
#ifndef BOOST_MOVE_DETAIL_META_UTILS_HPP
#define BOOST_MOVE_DETAIL_META_UTILS_HPP
#ifndef BOOST_CONFIG_HPP
# include <boost/config.hpp>
#endif
#
#if defined(BOOST_HAS_PRAGMA_ONCE)
# pragma once
#endif
#include <boost/move/detail/meta_utils_core.hpp>
#include <cstddef> //for std::size_t
//Small meta-typetraits to support move
namespace boost {
//Forward declare boost::rv
template <class T> class rv;
namespace move_detail {
//////////////////////////////////////
// nat
//////////////////////////////////////
struct nat{};
//////////////////////////////////////
// natify
//////////////////////////////////////
template <class T> struct natify{};
//////////////////////////////////////
// remove_reference
//////////////////////////////////////
template<class T>
struct remove_reference
{
typedef T type;
};
template<class T>
struct remove_reference<T&>
{
typedef T type;
};
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template<class T>
struct remove_reference<T&&>
{
typedef T type;
};
#else
template<class T>
struct remove_reference< rv<T> >
{
typedef T type;
};
template<class T>
struct remove_reference< rv<T> &>
{
typedef T type;
};
template<class T>
struct remove_reference< const rv<T> &>
{
typedef T type;
};
#endif
//////////////////////////////////////
// add_const
//////////////////////////////////////
template<class T>
struct add_const
{
typedef const T type;
};
template<class T>
struct add_const<T&>
{
typedef const T& type;
};
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template<class T>
struct add_const<T&&>
{
typedef T&& type;
};
#endif
//////////////////////////////////////
// add_lvalue_reference
//////////////////////////////////////
template<class T>
struct add_lvalue_reference
{ typedef T& type; };
template<class T> struct add_lvalue_reference<T&> { typedef T& type; };
template<> struct add_lvalue_reference<void> { typedef void type; };
template<> struct add_lvalue_reference<const void> { typedef const void type; };
template<> struct add_lvalue_reference<volatile void> { typedef volatile void type; };
template<> struct add_lvalue_reference<const volatile void>{ typedef const volatile void type; };
template<class T>
struct add_const_lvalue_reference
{
typedef typename remove_reference<T>::type t_unreferenced;
typedef typename add_const<t_unreferenced>::type t_unreferenced_const;
typedef typename add_lvalue_reference
<t_unreferenced_const>::type type;
};
//////////////////////////////////////
// is_lvalue_reference
//////////////////////////////////////
template<class T>
struct is_lvalue_reference
{
static const bool value = false;
};
template<class T>
struct is_lvalue_reference<T&>
{
static const bool value = true;
};
//////////////////////////////////////
// is_class_or_union
//////////////////////////////////////
template<class T>
struct is_class_or_union
{
struct twochar { char dummy[2]; };
template <class U>
static char is_class_or_union_tester(void(U::*)(void));
template <class U>
static twochar is_class_or_union_tester(...);
static const bool value = sizeof(is_class_or_union_tester<T>(0)) == sizeof(char);
};
//////////////////////////////////////
// addressof
//////////////////////////////////////
template<class T>
struct addr_impl_ref
{
T & v_;
inline addr_impl_ref( T & v ): v_( v ) {}
inline operator T& () const { return v_; }
private:
addr_impl_ref & operator=(const addr_impl_ref &);
};
template<class T>
struct addressof_impl
{
static inline T * f( T & v, long )
{
return reinterpret_cast<T*>(
&const_cast<char&>(reinterpret_cast<const volatile char &>(v)));
}
static inline T * f( T * v, int )
{ return v; }
};
template<class T>
inline T * addressof( T & v )
{
return ::boost::move_detail::addressof_impl<T>::f
( ::boost::move_detail::addr_impl_ref<T>( v ), 0 );
}
//////////////////////////////////////
// has_pointer_type
//////////////////////////////////////
template <class T>
struct has_pointer_type
{
struct two { char c[2]; };
template <class U> static two test(...);
template <class U> static char test(typename U::pointer* = 0);
static const bool value = sizeof(test<T>(0)) == 1;
};
//////////////////////////////////////
// is_convertible
//////////////////////////////////////
#if defined(_MSC_VER) && (_MSC_VER >= 1400)
//use intrinsic since in MSVC
//overaligned types can't go through ellipsis
template <class T, class U>
struct is_convertible
{
static const bool value = __is_convertible_to(T, U);
};
#else
template <class T, class U>
class is_convertible
{
typedef typename add_lvalue_reference<T>::type t_reference;
typedef char true_t;
class false_t { char dummy[2]; };
static false_t dispatch(...);
static true_t dispatch(U);
static t_reference trigger();
public:
static const bool value = sizeof(dispatch(trigger())) == sizeof(true_t);
};
#endif
//////////////////////////////////////////////////////////////////////////////
//
// has_move_emulation_enabled_impl
//
//////////////////////////////////////////////////////////////////////////////
template<class T>
struct has_move_emulation_enabled_impl
: is_convertible< T, ::boost::rv<T>& >
{};
template<class T>
struct has_move_emulation_enabled_impl<T&>
{ static const bool value = false; };
template<class T>
struct has_move_emulation_enabled_impl< ::boost::rv<T> >
{ static const bool value = false; };
//////////////////////////////////////////////////////////////////////////////
//
// is_rv_impl
//
//////////////////////////////////////////////////////////////////////////////
template <class T>
struct is_rv_impl
{ static const bool value = false; };
template <class T>
struct is_rv_impl< rv<T> >
{ static const bool value = true; };
template <class T>
struct is_rv_impl< const rv<T> >
{ static const bool value = true; };
// Code from Jeffrey Lee Hellrung, many thanks
template< class T >
struct is_rvalue_reference
{ static const bool value = false; };
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template< class T >
struct is_rvalue_reference< T&& >
{ static const bool value = true; };
#else // #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template< class T >
struct is_rvalue_reference< boost::rv<T>& >
{ static const bool value = true; };
template< class T >
struct is_rvalue_reference< const boost::rv<T>& >
{ static const bool value = true; };
#endif // #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template< class T >
struct add_rvalue_reference
{ typedef T&& type; };
#else // #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
namespace detail_add_rvalue_reference
{
template< class T
, bool emulation = has_move_emulation_enabled_impl<T>::value
, bool rv = is_rv_impl<T>::value >
struct add_rvalue_reference_impl { typedef T type; };
template< class T, bool emulation>
struct add_rvalue_reference_impl< T, emulation, true > { typedef T & type; };
template< class T, bool rv >
struct add_rvalue_reference_impl< T, true, rv > { typedef ::boost::rv<T>& type; };
} // namespace detail_add_rvalue_reference
template< class T >
struct add_rvalue_reference
: detail_add_rvalue_reference::add_rvalue_reference_impl<T>
{ };
template< class T >
struct add_rvalue_reference<T &>
{ typedef T & type; };
#endif // #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template< class T > struct remove_rvalue_reference { typedef T type; };
#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template< class T > struct remove_rvalue_reference< T&& > { typedef T type; };
#else // #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
template< class T > struct remove_rvalue_reference< rv<T> > { typedef T type; };
template< class T > struct remove_rvalue_reference< const rv<T> > { typedef T type; };
template< class T > struct remove_rvalue_reference< volatile rv<T> > { typedef T type; };
template< class T > struct remove_rvalue_reference< const volatile rv<T> > { typedef T type; };
template< class T > struct remove_rvalue_reference< rv<T>& > { typedef T type; };
template< class T > struct remove_rvalue_reference< const rv<T>& > { typedef T type; };
template< class T > struct remove_rvalue_reference< volatile rv<T>& > { typedef T type; };
template< class T > struct remove_rvalue_reference< const volatile rv<T>& >{ typedef T type; };
#endif // #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
// Ideas from Boost.Move review, Jeffrey Lee Hellrung:
//
//- TypeTraits metafunctions is_lvalue_reference, add_lvalue_reference, and remove_lvalue_reference ?
// Perhaps add_reference and remove_reference can be modified so that they behave wrt emulated rvalue
// references the same as wrt real rvalue references, i.e., add_reference< rv<T>& > -> T& rather than
// rv<T>& (since T&& & -> T&).
//
//- Add'l TypeTraits has_[trivial_]move_{constructor,assign}...?
//
//- An as_lvalue(T& x) function, which amounts to an identity operation in C++0x, but strips emulated
// rvalue references in C++03. This may be necessary to prevent "accidental moves".
} //namespace move_detail {
} //namespace boost {
#endif //#ifndef BOOST_MOVE_DETAIL_META_UTILS_HPP