boost/typeof/dmc/typeof_impl.hpp

   1 // Copyright (C) 2007 Peder Holt
   2
   3 // Use, modification and distribution is subject to the Boost Software
   4 // License, Version 1.0. (http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #ifndef BOOST_TYPEOF_MSVC_TYPEOF_IMPL_HPP_INCLUDED
   7 # define BOOST_TYPEOF_MSVC_TYPEOF_IMPL_HPP_INCLUDED
   8
   9 # include <boost/config.hpp>
  10 # include <boost/detail/workaround.hpp>
  11 # include <boost/mpl/int.hpp>
  12
  13 namespace boost
  14 {
  15     namespace type_of
  16     {
  17
  18         template<int N> struct encode_counter : encode_counter<N - 1> {};
  19         template<> struct encode_counter<0> {};
  20
  21         char (*encode_index(...))[1];
  22
  23 # define BOOST_TYPEOF_INDEX(T) (sizeof(*boost::type_of::encode_index((boost::type_of::encode_counter<1000>*)0)))
  24 # define BOOST_TYPEOF_NEXT_INDEX(next) friend char (*encode_index(encode_counter<next>*))[next];
  25
  26
  27         //Typeof code
  28
  29         template<typename ID>
  30         struct msvc_extract_type
  31         {
  32             struct id2type;
  33         };
  34
  35         template<typename T, typename ID>
  36         struct msvc_register_type : msvc_extract_type<ID>
  37         {
  38             typedef msvc_extract_type<ID> base_type;
  39             struct base_type::id2type // This uses nice VC6.5 and VC7.1 bugfeature, also works for Digital Mars
  40             {
  41                 typedef T type;
  42             };
  43         };
  44
  45
  46         template<int ID>
  47         struct msvc_typeid_wrapper {
  48             typedef typename msvc_extract_type<mpl::int_<ID> >::id2type id2type;
  49             typedef typename id2type::type type;
  50         };
  51
  52         //Tie it all together
  53         template<typename T>
  54         struct encode_type
  55         {
  56             //Get the next available compile time constants index
  57             BOOST_STATIC_CONSTANT(unsigned,value=BOOST_TYPEOF_INDEX(T));
  58             //Instantiate the template
  59             typedef typename msvc_register_type<T,mpl::int_<value> >::id2type type;
  60             //Set the next compile time constants index
  61             BOOST_STATIC_CONSTANT(unsigned,next=value+1);
  62             //Increment the compile time constant (only needed when extensions are not active
  63             BOOST_TYPEOF_NEXT_INDEX(next);
  64         };
  65
  66         template<class T>
  67         struct sizer
  68         {
  69             typedef char(*type)[encode_type<T>::value];
  70         };
  71
  72         template<typename T>
  73             typename sizer<T>::type encode_start(T const&);
  74
  75         template<typename Organizer, typename T>
  76         msvc_register_type<T,Organizer> typeof_register_type(const T&,Organizer* =0);
  77
  78 # define BOOST_TYPEOF(expr) \
  79     boost::type_of::msvc_typeid_wrapper<sizeof(*boost::type_of::encode_start(expr))>::type
  80
  81 # define BOOST_TYPEOF_TPL(expr) typename BOOST_TYPEOF(expr)
  82
  83 # define BOOST_TYPEOF_NESTED_TYPEDEF_TPL(name,expr) \
  84     struct name {\
  85         BOOST_STATIC_CONSTANT(int,_typeof_register_value=sizeof(boost::type_of::typeof_register_type<name>(expr)));\
  86         typedef typename boost::type_of::msvc_extract_type<name>::id2type id2type;\
  87         typedef typename id2type::type type;\
  88     };
  89
  90 # define BOOST_TYPEOF_NESTED_TYPEDEF(name,expr) \
  91     struct name {\
  92         BOOST_STATIC_CONSTANT(int,_typeof_register_value=sizeof(boost::type_of::typeof_register_type<name>(expr)));\
  93         typedef boost::type_of::msvc_extract_type<name>::id2type id2type;\
  94         typedef id2type::type type;\
  95     };
  96
  97     }
  98 }
  99
 100 #endif//BOOST_TYPEOF_MSVC_TYPEOF_IMPL_HPP_INCLUDED