Moved reference_content to boost/detail from variant/detail.

[SVN r19884]

include/boost/detail/reference_content.hpp

@@ -0,0 +1,180 @@
+//-----------------------------------------------------------------------------
+// boost detail/reference_content.hpp header file
+// See http://www.boost.org for updates, documentation, and revision history.
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) 2003
+// Eric Friedman
+//
+// Permission to use, copy, modify, distribute and sell this software
+// and its documentation for any purpose is hereby granted without fee, 
+// provided that the above copyright notice appears in all copies and 
+// that both the copyright notice and this permission notice appear in 
+// supporting documentation. No representations are made about the 
+// suitability of this software for any purpose. It is provided "as is" 
+// without express or implied warranty.
+
+#ifndef BOOST_DETAIL_REFERENCE_CONTENT_HPP
+#define BOOST_DETAIL_REFERENCE_CONTENT_HPP
+
+#include "boost/config.hpp"
+
+#if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
+#   include "boost/utility/addressof.hpp"
+#   include "boost/type.hpp"
+#   include "boost/mpl/if.hpp"
+#   include "boost/type_traits/is_reference.hpp"
+#endif
+
+#include "boost/mpl/void.hpp"
+
+namespace boost {
+namespace detail {
+
+///////////////////////////////////////////////////////////////////////////////
+// (detail) class template reference_content
+//
+// Non-Assignable wrapper for references.
+//
+
+template <typename RefT> class reference_content;
+
+#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
+
+template <typename T>
+class reference_content< T& >
+{
+private: // representation
+
+    T& content_;
+
+public: // structors
+
+    ~reference_content()
+    {
+    }
+
+    reference_content(T& r)
+        : content_( r )
+    {
+    }
+
+    reference_content(const reference_content& operand)
+        : content_( operand.content_ )
+    {
+    }
+
+public: // non-Assignable
+
+    reference_content& operator=(const reference_content&);
+
+public: // queries
+
+    T& get() const
+    {
+        return content_;
+    }
+
+};
+
+#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
+
+template <typename RefT>
+class reference_content
+{
+private: // representation
+
+    void* content_;
+
+public: // structors
+
+    ~reference_content()
+    {
+    }
+
+    reference_content(RefT r)
+        : content_( boost::addressof(r) )
+    {
+    }
+
+    reference_content(const reference_content& operand)
+        : content_( operand.content_ )
+    {
+    }
+
+private: // non-Assignable
+
+    reference_content& operator=(const reference_content&);
+
+private: // helpers, for queries (below)
+
+    template <typename T>
+    RefT get_impl( boost::type<T&> ) const
+    {
+        return *static_cast<T*>( content_ );
+    }
+
+public: // queries
+
+    RefT get() const
+    {
+        boost::type<RefT> wknd_type;
+        return get_impl( wknd_type );
+    }
+
+};
+
+#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
+
+///////////////////////////////////////////////////////////////////////////////
+// (detail) metafunction make_reference_content
+//
+// Wraps with reference_content if specified type is reference.
+//
+
+template <typename T = mpl::void_> struct make_reference_content;
+
+#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
+
+template <typename T>
+struct make_reference_content
+{
+    typedef T type;
+};
+
+template <typename T>
+struct make_reference_content< T& >
+{
+    typedef reference_content<T&> type;
+};
+
+#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
+
+template <typename T>
+struct make_reference_content
+    : mpl::if_<
+          is_reference<T>
+        , reference_content<T>
+        , T
+        >
+{
+};
+
+#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
+
+template <>
+struct make_reference_content< mpl::void_ >
+{
+    template <typename T>
+    struct apply
+        : make_reference_content<T>
+    {
+    };
+
+    typedef mpl::void_ type;
+};
+
+} // namespace detail
+} // namespace boost
+
+#endif // BOOST_DETAIL_REFERENCE_CONTENT_HPP