1// boost utility/base_from_member.hpp header file --------------------------//
2
3// Copyright 2001, 2003, 2004, 2012 Daryle Walker. Use, modification, and
4// distribution are subject to the Boost Software License, Version 1.0. (See
5// accompanying file LICENSE_1_0.txt or a copy at
6// <http://www.boost.org/LICENSE_1_0.txt>.)
7
8// See <http://www.boost.org/libs/utility/> for the library's home page.
9
10#ifndef BOOST_UTILITY_BASE_FROM_MEMBER_HPP
11#define BOOST_UTILITY_BASE_FROM_MEMBER_HPP
12
13#include <boost/config.hpp>
14#include <boost/preprocessor/arithmetic/inc.hpp>
15#include <boost/preprocessor/repetition/enum_binary_params.hpp>
16#include <boost/preprocessor/repetition/enum_params.hpp>
17#include <boost/preprocessor/repetition/repeat_from_to.hpp>
18#include <boost/type_traits/is_same.hpp>
19#include <boost/type_traits/remove_cv.hpp>
20#include <boost/type_traits/remove_reference.hpp>
21#include <boost/utility/enable_if.hpp>
22
23
24// Base-from-member arity configuration macro ------------------------------//
25
26// The following macro determines how many arguments will be in the largest
27// constructor template of base_from_member. Constructor templates will be
28// generated from one argument to this maximum. Code from other files can read
29// this number if they need to always match the exact maximum base_from_member
30// uses. The maximum constructor length can be changed by overriding the
31// #defined constant. Make sure to apply the override, if any, for all source
32// files during project compiling for consistency.
33
34// Contributed by Jonathan Turkanis
35
36#ifndef BOOST_BASE_FROM_MEMBER_MAX_ARITY
37#define BOOST_BASE_FROM_MEMBER_MAX_ARITY 10
38#endif
39
40
41// An iteration of a constructor template for base_from_member -------------//
42
43// A macro that should expand to:
44// template < typename T1, ..., typename Tn >
45// base_from_member( T1 x1, ..., Tn xn )
46// : member( x1, ..., xn )
47// {}
48// This macro should only persist within this file.
49
50#define BOOST_PRIVATE_CTR_DEF( z, n, data ) \
51 template < BOOST_PP_ENUM_PARAMS(n, typename T) > \
52 base_from_member( BOOST_PP_ENUM_BINARY_PARAMS(n, T, x) ) \
53 : member( BOOST_PP_ENUM_PARAMS(n, x) ) \
54 {} \
55 /**/
56
57
58namespace boost
59{
60
61namespace detail
62{
63
64// Type-unmarking class template -------------------------------------------//
65
66// Type-trait to get the raw type, i.e. the type without top-level reference nor
67// cv-qualification, from a type expression. Mainly for function arguments, any
68// reference part is stripped first.
69
70// Contributed by Daryle Walker
71
72template < typename T >
73struct remove_cv_ref
74{
75 typedef typename ::boost::remove_cv<typename
76 ::boost::remove_reference<T>::type>::type type;
77
78}; // boost::detail::remove_cv_ref
79
80// Unmarked-type comparison class template ---------------------------------//
81
82// Type-trait to check if two type expressions have the same raw type.
83
84// Contributed by Daryle Walker, based on a work-around by Luc Danton
85
86template < typename T, typename U >
87struct is_related
88 : public ::boost::is_same<
89 typename ::boost::detail::remove_cv_ref<T>::type,
90 typename ::boost::detail::remove_cv_ref<U>::type >
91{};
92
93// Enable-if-on-unidentical-unmarked-type class template -------------------//
94
95// Enable-if on the first two type expressions NOT having the same raw type.
96
97// Contributed by Daryle Walker, based on a work-around by Luc Danton
98
99#ifndef BOOST_NO_CXX11_VARIADIC_TEMPLATES
100template<typename ...T>
101struct enable_if_unrelated
102 : public ::boost::enable_if_c<true>
103{};
104
105template<typename T, typename U, typename ...U2>
106struct enable_if_unrelated<T, U, U2...>
107 : public ::boost::disable_if< ::boost::detail::is_related<T, U> >
108{};
109#endif
110
111} // namespace boost::detail
112
113
114// Base-from-member class template -----------------------------------------//
115
116// Helper to initialize a base object so a derived class can use this
117// object in the initialization of another base class. Used by
118// Dietmar Kuehl from ideas by Ron Klatcho to solve the problem of a
119// base class needing to be initialized by a member.
120
121// Contributed by Daryle Walker
122
123template < typename MemberType, int UniqueID = 0 >
124class base_from_member
125{
126protected:
127 MemberType member;
128
129#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES) && \
130 !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) && \
131 !defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS) && \
132 !(defined(__GNUC__) && (__GNUC__ == 4) && (__GNUC_MINOR__ < 4))
133 template <typename ...T, typename EnableIf = typename
134 ::boost::detail::enable_if_unrelated<base_from_member, T...>::type>
135 explicit BOOST_CONSTEXPR base_from_member( T&& ...x )
136 BOOST_NOEXCEPT_IF( BOOST_NOEXCEPT_EXPR(::new ((void*) 0) MemberType(
137 static_cast<T&&>(x)... )) ) // no std::is_nothrow_constructible...
138 : member( static_cast<T&&>(x)... ) // ...nor std::forward needed
139 {}
140#else
141 base_from_member()
142 : member()
143 {}
144
145 template < typename T0 > explicit base_from_member( T0 x0 ) : member( x0 ) {}
146 BOOST_PP_REPEAT_FROM_TO( 2, BOOST_PP_INC(BOOST_BASE_FROM_MEMBER_MAX_ARITY),
147 BOOST_PRIVATE_CTR_DEF, _ )
148#endif
149
150}; // boost::base_from_member
151
152template < typename MemberType, int UniqueID >
153class base_from_member<MemberType&, UniqueID>
154{
155protected:
156 MemberType& member;
157
158 explicit BOOST_CONSTEXPR base_from_member( MemberType& x )
159 BOOST_NOEXCEPT
160 : member( x )
161 {}
162
163}; // boost::base_from_member
164
165} // namespace boost
166
167
168// Undo any private macros
169#undef BOOST_PRIVATE_CTR_DEF
170
171
172#endif // BOOST_UTILITY_BASE_FROM_MEMBER_HPP
173

source code of include/boost/utility/base_from_member.hpp