convert/detail/range.hpp

0001 // Copyright (c) 2009-2020 Vladimir Batov.
0002 // Use, modification and distribution are subject to the Boost Software License,
0003 // Version 1.0. See http://www.boost.org/LICENSE_1_0.txt.
0004
0005 #ifndef BOOST_CONVERT_DETAIL_RANGE_HPP
0006 #define BOOST_CONVERT_DETAIL_RANGE_HPP
0007
0008 #include <boost/convert/detail/has_member.hpp>
0009 #include <boost/convert/detail/char.hpp>
0010 #include <boost/range/iterator.hpp>
0011
0012 namespace boost { namespace cnv
0013 {
0014     namespace detail
0015     {
0016         template<typename T, bool is_class> struct is_range : std::false_type {};
0017
0018         template<typename T> struct is_range<T, /*is_class=*/true>
0019         {
0020             BOOST_DECLARE_HAS_MEMBER(has_begin, begin);
0021             BOOST_DECLARE_HAS_MEMBER(  has_end, end);
0022
0023             static bool BOOST_CONSTEXPR_OR_CONST value = has_begin<T>::value && has_end<T>::value;
0024         };
0025     }
0026     template<typename T> struct is_range : detail::is_range<typename boost::remove_const<T>::type, boost::is_class<T>::value> {};
0027     template<typename T, typename enable =void> struct range;
0028     template<typename T, typename enable =void> struct iterator;
0029
0030     template<typename T>
0031     struct iterator<T, typename std::enable_if<is_range<T>::value>::type>
0032     {
0033         using       type = typename boost::range_iterator<T>::type;
0034         using const_type = typename boost::range_iterator<T const>::type;
0035         using value_type = typename boost::iterator_value<type>::type;
0036     };
0037     template<typename T>
0038     struct iterator<T*, void>
0039     {
0040         using value_type = typename boost::remove_const<T>::type;
0041         using       type = T*;
0042         using const_type = value_type const*;
0043     };
0044     template<typename T>
0045     struct range_base
0046     {
0047         using     value_type = typename cnv::iterator<T>::value_type;
0048         using       iterator = typename cnv::iterator<T>::type;
0049         using const_iterator = typename cnv::iterator<T>::const_type;
0050         using    sentry_type = const_iterator;
0051
0052         iterator       begin () { return begin_; }
0053         const_iterator begin () const { return begin_; }
0054         void      operator++ () { ++begin_; }
0055 //      void      operator-- () { --end_; }
0056
0057         protected:
0058
0059         range_base (iterator b, iterator e) : begin_(b), end_(e) {}
0060
0061         iterator       begin_;
0062         iterator mutable end_;
0063     };
0064
0065     template<typename T>
0066     struct range<T, typename std::enable_if<is_range<T>::value>::type> : public range_base<T>
0067     {
0068         using      this_type = range;
0069         using      base_type = range_base<T>;
0070         using       iterator = typename base_type::iterator;
0071         using const_iterator = typename base_type::const_iterator;
0072         using    sentry_type = const_iterator;
0073
0074         range (T& r) : base_type(r.begin(), r.end()) {}
0075
0076         iterator       end ()       { return base_type::end_; }
0077         const_iterator end () const { return base_type::end_; }
0078         sentry_type sentry () const { return base_type::end_; }
0079         std::size_t   size () const { return base_type::end_ - base_type::begin_; }
0080         bool         empty () const { return base_type::begin_ == base_type::end_; }
0081     };
0082
0083     template<typename T>
0084     struct range<T*, typename std::enable_if<cnv::is_char<T>::value>::type> : public range_base<T*>
0085     {
0086         using      this_type = range;
0087         using      base_type = range_base<T*>;
0088         using     value_type = typename boost::remove_const<T>::type;
0089         using       iterator = T*;
0090         using const_iterator = value_type const*;
0091
0092         struct sentry_type
0093         {
0094             friend bool operator!=(iterator it, sentry_type) { return !!*it; }
0095         };
0096
0097         range (iterator b, iterator e =0) : base_type(b, e) {}
0098
0099         iterator       end ()       { return base_type::end_ ? base_type::end_ : (base_type::end_ = base_type::begin_ + size()); }
0100         const_iterator end () const { return base_type::end_ ? base_type::end_ : (base_type::end_ = base_type::begin_ + size()); }
0101         sentry_type sentry () const { return sentry_type(); }
0102         std::size_t   size () const { return std::char_traits<value_type>::length(base_type::begin_); }
0103         bool         empty () const { return !*base_type::begin_; }
0104     };
0105     template<typename T>
0106     struct range<T* const, void> : public range<T*>
0107     {
0108         range (T* b, T* e =0) : range<T*>(b, e) {}
0109     };
0110     template <typename T, std::size_t N>
0111     struct range<T [N], void> : public range<T*>
0112     {
0113         range (T* b, T* e =0) : range<T*>(b, e) {}
0114     };
0115 }}
0116
0117 #endif // BOOST_CONVERT_DETAIL_RANGE_HPP