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       1             : //-----------------------------------------------------------------------------
       2             : // boost variant/detail/initializer.hpp header file
       3             : // See http://www.boost.org for updates, documentation, and revision history.
       4             : //-----------------------------------------------------------------------------
       5             : //
       6             : // Copyright (c) 2002-2003
       7             : // Eric Friedman, Itay Maman
       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_VARIANT_DETAIL_INITIALIZER_HPP
      14             : #define BOOST_VARIANT_DETAIL_INITIALIZER_HPP
      15             : 
      16             : #include <new> // for placement new
      17             : 
      18             : #include <boost/config.hpp>
      19             : 
      20             : #include <boost/call_traits.hpp>
      21             : #include <boost/detail/reference_content.hpp>
      22             : #include <boost/variant/recursive_wrapper_fwd.hpp>
      23             : #include <boost/variant/detail/move.hpp>
      24             : 
      25             : #   include <boost/mpl/aux_/value_wknd.hpp>
      26             : #   include <boost/mpl/int.hpp>
      27             : #   include <boost/mpl/iter_fold.hpp>
      28             : #   include <boost/mpl/next.hpp>
      29             : #   include <boost/mpl/deref.hpp>
      30             : #   include <boost/mpl/pair.hpp>
      31             : #   include <boost/mpl/protect.hpp>
      32             : 
      33             : 
      34             : namespace boost {
      35             : namespace detail { namespace variant {
      36             : 
      37             : ///////////////////////////////////////////////////////////////////////////////
      38             : // (detail) support to simulate standard overload resolution rules
      39             : //
      40             : // The below initializers allows variant to follow standard overload
      41             : // resolution rules over the specified set of bounded types.
      42             : //
      43             : // On compilers where using declarations in class templates can correctly
      44             : // avoid name hiding, use an optimal solution based on the variant's typelist.
      45             : //
      46             : // Otherwise, use a preprocessor workaround based on knowledge of the fixed
      47             : // size of the variant's psuedo-variadic template parameter list.
      48             : //
      49             : 
      50             : // (detail) quoted metafunction make_initializer_node
      51             : //
      52             : // Exposes a pair whose first type is a node in the initializer hierarchy.
      53             : //
      54             : struct make_initializer_node
      55             : {
      56             :     template <typename BaseIndexPair, typename Iterator>
      57             :     struct apply
      58             :     {
      59             :     private: // helpers, for metafunction result (below)
      60             : 
      61             :         typedef typename BaseIndexPair::first
      62             :             base;
      63             :         typedef typename BaseIndexPair::second
      64             :             index;
      65             : 
      66             :         class initializer_node
      67             :             : public base
      68             :         {
      69             :         private: // helpers, for static functions (below)
      70             : 
      71             :             typedef typename mpl::deref<Iterator>::type
      72             :                 recursive_enabled_T;
      73             :             typedef typename unwrap_recursive<recursive_enabled_T>::type
      74             :                 public_T;
      75             : 
      76             :             typedef boost::is_reference<public_T> 
      77             :                 is_reference_content_t;
      78             : 
      79             :             typedef typename boost::mpl::if_<is_reference_content_t, public_T, const public_T& >::type 
      80             :                 param_T;
      81             : 
      82             :             template <class T> struct disable_overload{};
      83             : 
      84             :             typedef typename boost::mpl::if_<is_reference_content_t, disable_overload<public_T>, public_T&& >::type 
      85             :                 param2_T;
      86             : 
      87             :         public: // static functions
      88             : 
      89             :             using base::initialize;
      90             : 
      91             :             static int initialize(void* dest, param_T operand)
      92             :             {
      93             :                 typedef typename boost::detail::make_reference_content<
      94             :                       recursive_enabled_T
      95             :                     >::type internal_T;
      96             : 
      97             :                 new(dest) internal_T(operand);
      98             :                 return BOOST_MPL_AUX_VALUE_WKND(index)::value; // which
      99             :             }
     100             : 
     101      111230 :             static int initialize(void* dest, param2_T operand)
     102             :             {
     103             :                 // This assert must newer trigger, because all the reference contents are
     104             :                 // handled by the initilize(void* dest, param_T operand) function above
     105             :                 BOOST_ASSERT(!is_reference_content_t::value);
     106             : 
     107             :                 typedef typename boost::mpl::if_<is_reference_content_t, param2_T, recursive_enabled_T>::type value_T;
     108      111230 :                 new(dest) value_T( boost::detail::variant::move(operand) );
     109      111230 :                 return BOOST_MPL_AUX_VALUE_WKND(index)::value; // which
     110             :             }
     111             :         };
     112             : 
     113             :         friend class initializer_node;
     114             : 
     115             :     public: // metafunction result
     116             : 
     117             :         typedef mpl::pair<
     118             :               initializer_node
     119             :             , typename mpl::next< index >::type
     120             :             > type;
     121             : 
     122             :     };
     123             : };
     124             : 
     125             : // (detail) class initializer_root
     126             : //
     127             : // Every level of the initializer hierarchy must expose the name
     128             : // "initialize," so initializer_root provides a dummy function:
     129             : //
     130             : class initializer_root
     131             : {
     132             : public: // static functions
     133             : 
     134             :     static void initialize();
     135             : 
     136             : };
     137             : 
     138             : }} // namespace detail::variant
     139             : } // namespace boost
     140             : 
     141             : ///////////////////////////////////////////////////////////////////////////////
     142             : // macro BOOST_VARIANT_AUX_INITIALIZER_T
     143             : //
     144             : // Given both the variant's typelist and a basename for forming the list of
     145             : // bounded types (i.e., T becomes T1, T2, etc.), exposes the initializer
     146             : // most appropriate to the current compiler.
     147             : //
     148             : 
     149             : #define BOOST_VARIANT_AUX_INITIALIZER_T( mpl_seq, typename_base ) \
     150             :     ::boost::mpl::iter_fold< \
     151             :           mpl_seq \
     152             :         , ::boost::mpl::pair< \
     153             :               ::boost::detail::variant::initializer_root \
     154             :             , ::boost::mpl::int_<0> \
     155             :             > \
     156             :         , ::boost::mpl::protect< \
     157             :               ::boost::detail::variant::make_initializer_node \
     158             :             > \
     159             :         >::type::first \
     160             :     /**/
     161             : 
     162             : #endif // BOOST_VARIANT_DETAIL_INITIALIZER_HPP