geometry/views/segment_view.hpp

0001 // Boost.Geometry (aka GGL, Generic Geometry Library)
0002
0003 // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
0004 // Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
0005 // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
0006
0007 // This file was modified by Oracle on 2020-2021.
0008 // Modifications copyright (c) 2020-2021 Oracle and/or its affiliates.
0009 // Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
0010
0011 // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
0012 // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
0013
0014 // Use, modification and distribution is subject to the Boost Software License,
0015 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
0016 // http://www.boost.org/LICENSE_1_0.txt)
0017
0018 #ifndef BOOST_GEOMETRY_VIEWS_SEGMENT_VIEW_HPP
0019 #define BOOST_GEOMETRY_VIEWS_SEGMENT_VIEW_HPP
0020
0021
0022 #include <array>
0023
0024 #include <boost/geometry/algorithms/detail/assign_indexed_point.hpp>
0025 #include <boost/geometry/core/point_type.hpp>
0026 #include <boost/geometry/core/tag.hpp>
0027
0028
0029 namespace boost { namespace geometry
0030 {
0031
0032 // NOTE: This is equivalent to the previous implementation with detail::points_view.
0033 //       Technically this should not be called a view because it owns the elements.
0034 //       It's also not a borrowed_range because of dangling iterators after the
0035 //       destruction.
0036 //       It's a container or more specifically a linestring of some sort, e.g. static_linestring.
0037 // NOTE: It would be possible to implement a borrowed_range or a view.
0038 //       The iterators would have to store copies of points.
0039 //       Another possibility is to store the original Segment or reference/pointer
0040 //       to Segment and index. But then the reference would be the value type
0041 //       so technically they would be InputIterators not RandomAccessIterators.
0042
0043
0044 /*!
0045 \brief Makes a segment behave like a linestring or a range
0046 \details Adapts a segment to the Boost.Range concept, enabling the user to
0047     iterate the two segment points. The segment_view is registered as a LineString Concept
0048 \tparam Segment \tparam_geometry{Segment}
0049 \ingroup views
0050
0051 \qbk{before.synopsis,
0052 [heading Model of]
0053 [link geometry.reference.concepts.concept_linestring LineString Concept]
0054 }
0055
0056 \qbk{[include reference/views/segment_view.qbk]}
0057
0058 */
0059 template <typename Segment>
0060 struct segment_view
0061 {
0062     using array_t = std::array<typename geometry::point_type<Segment>::type, 2>;
0063
0064     using iterator = typename array_t::const_iterator;
0065     using const_iterator = typename array_t::const_iterator;
0066
0067     /// Constructor accepting the segment to adapt
0068     explicit segment_view(Segment const& segment)
0069     {
0070         geometry::detail::assign_point_from_index<0>(segment, m_array[0]);
0071         geometry::detail::assign_point_from_index<1>(segment, m_array[1]);
0072     }
0073
0074     const_iterator begin() const noexcept { return m_array.begin(); }
0075     const_iterator end() const noexcept { return m_array.end(); }
0076
0077 private:
0078     array_t m_array;
0079 };
0080
0081
0082 #ifndef DOXYGEN_NO_TRAITS_SPECIALIZATIONS
0083
0084 // All segment ranges can be handled as linestrings
0085 namespace traits
0086 {
0087
0088 template<typename Segment>
0089 struct tag<segment_view<Segment> >
0090 {
0091     typedef linestring_tag type;
0092 };
0093
0094 }
0095
0096 #endif // DOXYGEN_NO_TRAITS_SPECIALIZATIONS
0097
0098
0099 }} // namespace boost::geometry
0100
0101
0102 #endif // BOOST_GEOMETRY_VIEWS_SEGMENT_VIEW_HPP