boost/detail/reference_content.hpp

   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
  46     ~reference_content()
  47     {
  48     }
  49
  50     reference_content(RefT r)
  51         : content_( r )
  52     {
  53     }
  54
  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
  66     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