ceph/src/boost/boost/accumulators/framework/accumulators/reference_accumulator.hpp

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // reference_accumulator.hpp
   3 //
   4 //  Copyright 2005 Eric Niebler. Distributed under the Boost
   5 //  Software License, Version 1.0. (See accompanying file
   6 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7
   8 #ifndef BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_REFERENCE_ACCUMULATOR_HPP_EAN_03_23_2006
   9 #define BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_REFERENCE_ACCUMULATOR_HPP_EAN_03_23_2006
  10
  11 #include <boost/ref.hpp>
  12 #include <boost/mpl/always.hpp>
  13 #include <boost/parameter/keyword.hpp>
  14 #include <boost/accumulators/framework/depends_on.hpp> // for feature_tag
  15 #include <boost/accumulators/framework/accumulator_base.hpp>
  16 #include <boost/accumulators/framework/extractor.hpp>
  17
  18 namespace boost { namespace accumulators
  19 {
  20
  21 namespace impl
  22 {
  23     //////////////////////////////////////////////////////////////////////////
  24     // reference_accumulator_impl
  25     //
  26     template<typename Referent, typename Tag>
  27     struct reference_accumulator_impl
  28       : accumulator_base
  29     {
  30         typedef Referent &result_type;
  31
  32         template<typename Args>
  33         reference_accumulator_impl(Args const &args)
  34           : ref(args[parameter::keyword<Tag>::get()])
  35         {
  36         }
  37
  38         result_type result(dont_care) const
  39         {
  40             return this->ref;
  41         }
  42
  43     private:
  44         reference_wrapper<Referent> ref;
  45     };
  46 } // namespace impl
  47
  48 namespace tag
  49 {
  50     //////////////////////////////////////////////////////////////////////////
  51     // reference_tag
  52     template<typename Tag>
  53     struct reference_tag
  54     {
  55     };
  56
  57     //////////////////////////////////////////////////////////////////////////
  58     // reference
  59     template<typename Referent, typename Tag>
  60     struct reference
  61       : depends_on<>
  62     {
  63         /// INTERNAL ONLY
  64         ///
  65         typedef mpl::always<accumulators::impl::reference_accumulator_impl<Referent, Tag> > impl;
  66     };
  67 }
  68
  69 namespace extract
  70 {
  71     BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, reference, (typename)(typename))
  72     BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, reference_tag, (typename))
  73 }
  74
  75 using extract::reference;
  76 using extract::reference_tag;
  77
  78 // Map all reference<V,T> features to reference_tag<T> so
  79 // that references can be extracted using reference_tag<T>
  80 // without specifying the referent type.
  81 template<typename ValueType, typename Tag>
  82 struct feature_of<tag::reference<ValueType, Tag> >
  83   : feature_of<tag::reference_tag<Tag> >
  84 {
  85 };
  86
  87 }} // namespace boost::accumulators
  88
  89 #endif