text: // Copyright (c) 2009-2016 Vladimir Batov.
  // Use, modification and distribution are subject to the Boost Software License,
  // Version 1.0. See http://www.boost.org/LICENSE_1_0.txt.
  
  #ifndef BOOST_CONVERT_DETAIL_RANGE_HPP
  #define BOOST_CONVERT_DETAIL_RANGE_HPP
  
  #include <boost/convert/detail/has_member.hpp>
  #include <boost/convert/detail/char.hpp>
  #include <boost/utility/enable_if.hpp>
  #include <boost/range/iterator.hpp>
  
  namespace boost { namespace cnv
  {
      namespace detail
      {
          template<typename T, bool is_class> struct is_range : std::false_type {};
  
          template<typename T> struct is_range<T, /*is_class=*/true>
          {
              BOOST_DECLARE_HAS_MEMBER(has_begin, begin);
              BOOST_DECLARE_HAS_MEMBER(  has_end, end);
  
              static bool const value = has_begin<T>::value && has_end<T>::value;
          };
      }
      template<typename T> struct is_range : detail::is_range<typename boost::remove_const<T>::type, boost::is_class<T>::value> {};
      template<typename T, typename enable =void> struct range;
      template<typename T, typename enable =void> struct iterator;
  
      template<typename T>
      struct iterator<T, typename enable_if<is_range<T> >::type>
      {
          typedef typename boost::range_iterator<T>::type             type;
          typedef typename boost::range_iterator<T const>::type const_type;
          typedef typename boost::iterator_value<type>::type    value_type;
      };
      template<typename T>
      struct iterator<T*, void>
      {
          typedef typename boost::remove_const<T>::type value_type;
          typedef T*                                        type;
          typedef value_type const*                   const_type;
      };
      template<typename T>
      struct range_base
      {
          typedef typename cnv::iterator<T>::value_type     value_type;
          typedef typename cnv::iterator<T>::type             iterator;
          typedef typename cnv::iterator<T>::const_type const_iterator;
          typedef const_iterator                           sentry_type;
  
          iterator       begin () { return begin_; }
          const_iterator begin () const { return begin_; }
          void      operator++ () { ++begin_; }
  //      void      operator-- () { --end_; }
  
          protected:
  
          range_base (iterator b, iterator e) : begin_(b), end_(e) {}
  
          iterator       begin_;
          iterator mutable end_;
      };
  
      template<typename T>
      struct range<T, typename enable_if<is_range<T> >::type> : public range_base<T>
      {
          typedef range                                   this_type;
          typedef range_base<T>                           base_type;
          typedef typename base_type::iterator             iterator;
          typedef typename base_type::const_iterator const_iterator;
          typedef const_iterator                        sentry_type;
  
          range (T& r) : base_type(r.begin(), r.end()) {}
  
          iterator       end () { return base_type::end_; }
          const_iterator end () const { return base_type::end_; }
          sentry_type sentry () const { return base_type::end_; }
          std::size_t   size () const { return base_type::end_ - base_type::begin_; }
          bool         empty () const { return base_type::begin_ == base_type::end_; }
      };
  
      template<typename T>
      struct range<T*, typename enable_if<cnv::is_char<T> >::type> : public range_base<T*>
      {
          using      this_type = range;
          using      base_type = range_base<T*>;
          using     value_type = typename boost::remove_const<T>::type;
          using       iterator = T*;
          using const_iterator = value_type const*;
  
          struct sentry_type
          {
              friend bool operator!=(iterator it, sentry_type) { return !!*it; }
          };
  
          range (iterator b, iterator e =0) : base_type(b, e) {}
  
          iterator       end ()       { return base_type::end_ ? base_type::end_ : (base_type::end_ = base_type::begin_ + size()); }
          const_iterator end () const { return base_type::end_ ? base_type::end_ : (base_type::end_ = base_type::begin_ + size()); }
          sentry_type sentry () const { return sentry_type(); }
          std::size_t   size () const { return std::char_traits<value_type>::length(base_type::begin_); }
          bool         empty () const { return !*base_type::begin_; }
      };
      template<typename T>
      struct range<T* const, void> : public range<T*>
      {
          range (T* b, T* e =0) : range<T*>(b, e) {}
      };
      template <typename T, std::size_t N>
      struct range<T [N], void> : public range<T*>
      {
          range (T* b, T* e =0) : range<T*>(b, e) {}
      };
  }}
  
  #endif // BOOST_CONVERT_DETAIL_RANGE_HPP
  