boost/pointee.hpp

   1 #ifndef POINTEE_DWA200415_HPP
   2 # define POINTEE_DWA200415_HPP
   3
   4 //
   5 // Copyright David Abrahams 2004. Use, modification and distribution is
   6 // subject to the Boost Software License, Version 1.0. (See accompanying
   7 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   8 //
   9 // typename pointee<P>::type provides the pointee type of P.
  10 //
  11 // For example, it is T for T* and X for shared_ptr<X>.
  12 //
  13 // http://www.boost.org/libs/iterator/doc/pointee.html
  14 //
  15
  16 # include <boost/detail/is_incrementable.hpp>
  17 # include <boost/iterator/iterator_traits.hpp>
  18 # include <boost/type_traits/add_const.hpp>
  19 # include <boost/type_traits/remove_cv.hpp>
  20 # include <boost/mpl/if.hpp>
  21 # include <boost/mpl/eval_if.hpp>
  22
  23 namespace boost {
  24
  25 namespace detail
  26 {
  27   template <class P>
  28   struct smart_ptr_pointee
  29   {
  30       typedef typename P::element_type type;
  31   };
  32
  33   template <class Iterator>
  34   struct iterator_pointee
  35   {
  36       typedef typename iterator_traits<Iterator>::value_type value_type;
  37
  38       struct impl
  39       {
  40           template <class T>
  41           static char test(T const&);
  42
  43           static char (& test(value_type&) )[2];
  44
  45           static Iterator& x;
  46       };
  47
  48       BOOST_STATIC_CONSTANT(bool, is_constant = sizeof(impl::test(*impl::x)) == 1);
  49
  50       typedef typename mpl::if_c<
  51 #  if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
  52           ::boost::detail::iterator_pointee<Iterator>::is_constant
  53 #  else
  54           is_constant
  55 #  endif
  56         , typename add_const<value_type>::type
  57         , value_type
  58       >::type type;
  59   };
  60 }
  61
  62 template <class P>
  63 struct pointee
  64   : mpl::eval_if<
  65         detail::is_incrementable<P>
  66       , detail::iterator_pointee<P>
  67       , detail::smart_ptr_pointee<P>
  68     >
  69 {
  70 };
  71
  72 } // namespace boost
  73
  74 #endif // POINTEE_DWA200415_HPP