boost/utility/base_from_member.hpp
// boost utility/base_from_member.hpp header file --------------------------//
// Copyright 2001, 2003, 2004, 2012 Daryle Walker. Use, modification, and
// distribution are subject to the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or a copy at
// <http://www.boost.org/LICENSE_1_0.txt>.)
// See <http://www.boost.org/libs/utility/> for the library's home page.
#ifndef BOOST_UTILITY_BASE_FROM_MEMBER_HPP
#define BOOST_UTILITY_BASE_FROM_MEMBER_HPP
#include <boost/config.hpp>
#include <boost/preprocessor/arithmetic/inc.hpp>
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/repetition/repeat_from_to.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/utility/enable_if.hpp>
// Base-from-member arity configuration macro ------------------------------//
// The following macro determines how many arguments will be in the largest
// constructor template of base_from_member. Constructor templates will be
// generated from one argument to this maximum. Code from other files can read
// this number if they need to always match the exact maximum base_from_member
// uses. The maximum constructor length can be changed by overriding the
// #defined constant. Make sure to apply the override, if any, for all source
// files during project compiling for consistency.
// Contributed by Jonathan Turkanis
#ifndef BOOST_BASE_FROM_MEMBER_MAX_ARITY
#define BOOST_BASE_FROM_MEMBER_MAX_ARITY 10
#endif
// An iteration of a constructor template for base_from_member -------------//
// A macro that should expand to:
// template < typename T1, ..., typename Tn >
// base_from_member( T1 x1, ..., Tn xn )
// : member( x1, ..., xn )
// {}
// This macro should only persist within this file.
#define BOOST_PRIVATE_CTR_DEF( z, n, data ) \
template < BOOST_PP_ENUM_PARAMS(n, typename T) > \
base_from_member( BOOST_PP_ENUM_BINARY_PARAMS(n, T, x) ) \
: member( BOOST_PP_ENUM_PARAMS(n, x) ) \
{} \
/**/
namespace boost
{
namespace detail
{
// Type-unmarking class template -------------------------------------------//
// Type-trait to get the raw type, i.e. the type without top-level reference nor
// cv-qualification, from a type expression. Mainly for function arguments, any
// reference part is stripped first.
// Contributed by Daryle Walker
template < typename T >
struct remove_cv_ref
{
typedef typename ::boost::remove_cv<typename
::boost::remove_reference<T>::type>::type type;
}; // boost::detail::remove_cv_ref
// Unmarked-type comparison class template ---------------------------------//
// Type-trait to check if two type expressions have the same raw type.
// Contributed by Daryle Walker, based on a work-around by Luc Danton
template < typename T, typename U >
struct is_related
: public ::boost::is_same<
typename ::boost::detail::remove_cv_ref<T>::type,
typename ::boost::detail::remove_cv_ref<U>::type >
{};
// Enable-if-on-unidentical-unmarked-type class template -------------------//
// Enable-if on the first two type expressions NOT having the same raw type.
// Contributed by Daryle Walker, based on a work-around by Luc Danton
#ifndef BOOST_NO_CXX11_VARIADIC_TEMPLATES
template<typename ...T>
struct enable_if_unrelated
: public ::boost::enable_if_c<true>
{};
template<typename T, typename U, typename ...U2>
struct enable_if_unrelated<T, U, U2...>
: public ::boost::disable_if< ::boost::detail::is_related<T, U> >
{};
#endif
} // namespace boost::detail
// Base-from-member class template -----------------------------------------//
// Helper to initialize a base object so a derived class can use this
// object in the initialization of another base class. Used by
// Dietmar Kuehl from ideas by Ron Klatcho to solve the problem of a
// base class needing to be initialized by a member.
// Contributed by Daryle Walker
template < typename MemberType, int UniqueID = 0 >
class base_from_member
{
protected:
MemberType member;
#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && \
!defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && \
!defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS) && \
!(defined(__GNUC__) && (__GNUC__ == 4) && (__GNUC_MINOR__ < 4))
template <typename ...T, typename EnableIf = typename
::boost::detail::enable_if_unrelated<base_from_member, T...>::type>
explicit BOOST_CONSTEXPR base_from_member( T&& ...x )
BOOST_NOEXCEPT_IF( BOOST_NOEXCEPT_EXPR(::new ((void*) 0) MemberType(
static_cast<T&&>(x)... )) ) // no std::is_nothrow_constructible...
: member( static_cast<T&&>(x)... ) // ...nor std::forward needed
{}
#else
base_from_member()
: member()
{}
template < typename T0 > explicit base_from_member( T0 x0 ) : member( x0 ) {}
BOOST_PP_REPEAT_FROM_TO( 2, BOOST_PP_INC(BOOST_BASE_FROM_MEMBER_MAX_ARITY),
BOOST_PRIVATE_CTR_DEF, _ )
#endif
}; // boost::base_from_member
template < typename MemberType, int UniqueID >
class base_from_member<MemberType&, UniqueID>
{
protected:
MemberType& member;
explicit BOOST_CONSTEXPR base_from_member( MemberType& x )
BOOST_NOEXCEPT
: member( x )
{}
}; // boost::base_from_member
} // namespace boost
// Undo any private macros
#undef BOOST_PRIVATE_CTR_DEF
#endif // BOOST_UTILITY_BASE_FROM_MEMBER_HPP