1 //-----------------------------------------------------------------------------
2 // boost detail/reference_content.hpp header file
3 // See http://www.boost.org for updates, documentation, and revision history.
4 //-----------------------------------------------------------------------------
5 //
6 // Copyright (c) 2003
7 // Eric Friedman
8 //
9 // Distributed under the Boost Software License, Version 1.0. (See
10 // accompanying file LICENSE_1_0.txt or copy at
11 // http://www.boost.org/LICENSE_1_0.txt)
12 
13 #ifndef BOOST_DETAIL_REFERENCE_CONTENT_HPP
14 #define BOOST_DETAIL_REFERENCE_CONTENT_HPP
15 
16 #include "boost/config.hpp"
17 
18 #   include "boost/type_traits/integral_constant.hpp"
19 #   include "boost/type_traits/has_nothrow_copy.hpp"
20 
21 namespace boost {
22 
23 namespace detail {
24 
25 struct void_type {};
26 
27 ///////////////////////////////////////////////////////////////////////////////
28 // (detail) class template reference_content
29 //
30 // Non-Assignable wrapper for references.
31 //
32 template <typename RefT>
33 class reference_content
34 {
35 private: // representation
36 
37     RefT content_;
38 
39 public: // structors
40 
~reference_content()41     ~reference_content()
42     {
43     }
44 
reference_content(RefT r)45     reference_content(RefT r)
46         : content_( r )
47     {
48     }
49 
reference_content(const reference_content & operand)50     reference_content(const reference_content& operand)
51         : content_( operand.content_ )
52     {
53     }
54 
55 private: // non-Assignable
56 
57     reference_content& operator=(const reference_content&);
58 
59 public: // queries
60 
get() const61     RefT get() const
62     {
63         return content_;
64     }
65 
66 };
67 
68 ///////////////////////////////////////////////////////////////////////////////
69 // (detail) metafunction make_reference_content
70 //
71 // Wraps with reference_content if specified type is reference.
72 //
73 
74 template <typename T = void_type> struct make_reference_content;
75 
76 
77 template <typename T>
78 struct make_reference_content
79 {
80     typedef T type;
81 };
82 
83 template <typename T>
84 struct make_reference_content< T& >
85 {
86     typedef reference_content<T&> type;
87 };
88 
89 
90 template <>
91 struct make_reference_content< void_type >
92 {
93     template <typename T>
94     struct apply
95         : make_reference_content<T>
96     {
97     };
98 
99     typedef void_type type;
100 };
101 
102 } // namespace detail
103 
104 ///////////////////////////////////////////////////////////////////////////////
105 // reference_content<T&> type traits specializations
106 //
107 
108 
109 template <typename T>
110 struct has_nothrow_copy<
111       ::boost::detail::reference_content< T& >
112     >
113     : boost::true_type
114 {
115 };
116 
117 
118 } // namespace boost
119 
120 #endif // BOOST_DETAIL_REFERENCE_CONTENT_HPP
121