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 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
19 #   include "boost/mpl/bool.hpp"
20 #   include "boost/type_traits/has_nothrow_copy.hpp"
21 #else
22 #   include "boost/mpl/if.hpp"
23 #   include "boost/type_traits/is_reference.hpp"
24 #endif
25 
26 #include "boost/mpl/void.hpp"
27 
28 namespace boost {
29 
30 namespace detail {
31 
32 ///////////////////////////////////////////////////////////////////////////////
33 // (detail) class template reference_content
34 //
35 // Non-Assignable wrapper for references.
36 //
37 template <typename RefT>
38 class reference_content
39 {
40 private: // representation
41 
42     RefT content_;
43 
44 public: // structors
45 
~reference_content()46     ~reference_content()
47     {
48     }
49 
reference_content(RefT r)50     reference_content(RefT r)
51         : content_( r )
52     {
53     }
54 
reference_content(const reference_content & operand)55     reference_content(const reference_content& operand)
56         : content_( operand.content_ )
57     {
58     }
59 
60 private: // non-Assignable
61 
62     reference_content& operator=(const reference_content&);
63 
64 public: // queries
65 
get() const66     RefT get() const
67     {
68         return content_;
69     }
70 
71 };
72 
73 ///////////////////////////////////////////////////////////////////////////////
74 // (detail) metafunction make_reference_content
75 //
76 // Wraps with reference_content if specified type is reference.
77 //
78 
79 template <typename T = mpl::void_> struct make_reference_content;
80 
81 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
82 
83 template <typename T>
84 struct make_reference_content
85 {
86     typedef T type;
87 };
88 
89 template <typename T>
90 struct make_reference_content< T& >
91 {
92     typedef reference_content<T&> type;
93 };
94 
95 #else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
96 
97 template <typename T>
98 struct make_reference_content
99     : mpl::if_<
100           is_reference<T>
101         , reference_content<T>
102         , T
103         >
104 {
105 };
106 
107 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
108 
109 template <>
110 struct make_reference_content< mpl::void_ >
111 {
112     template <typename T>
113     struct apply
114         : make_reference_content<T>
115     {
116     };
117 
118     typedef mpl::void_ type;
119 };
120 
121 } // namespace detail
122 
123 ///////////////////////////////////////////////////////////////////////////////
124 // reference_content<T&> type traits specializations
125 //
126 
127 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
128 
129 template <typename T>
130 struct has_nothrow_copy<
131       ::boost::detail::reference_content< T& >
132     >
133     : mpl::true_
134 {
135 };
136 
137 #endif // !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
138 
139 } // namespace boost
140 
141 #endif // BOOST_DETAIL_REFERENCE_CONTENT_HPP
142