ceph/src/boost/libs/geometry/include/boost/geometry/algorithms/detail/direction_code.hpp

   1 // Boost.Geometry (aka GGL, Generic Geometry Library)
   2
   3 // Copyright (c) 2015 Barend Gehrels, Amsterdam, the Netherlands.
   4
   5 // This file was modified by Oracle on 2015.
   6 // Modifications copyright (c) 2015 Oracle and/or its affiliates.
   7
   8 // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
   9
  10 // Use, modification and distribution is subject to the Boost Software License,
  11 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
  12 // http://www.boost.org/LICENSE_1_0.txt)
  13
  14 #ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_DIRECITON_CODE_HPP
  15 #define BOOST_GEOMETRY_ALGORITHMS_DETAIL_DIRECITON_CODE_HPP
  16
  17
  18 #include <boost/geometry/core/access.hpp>
  19 #include <boost/geometry/util/math.hpp>
  20
  21 namespace boost { namespace geometry
  22 {
  23
  24 #ifndef DOXYGEN_NO_DETAIL
  25 namespace detail
  26 {
  27
  28 template <std::size_t Index, typename Point1, typename Point2>
  29 inline int sign_of_difference(Point1 const& point1, Point2 const& point2)
  30 {
  31     return
  32         math::equals(geometry::get<Index>(point1), geometry::get<Index>(point2))
  33         ?
  34         0
  35         :
  36         (geometry::get<Index>(point1) > geometry::get<Index>(point2) ? 1 : -1);
  37 }
  38
  39
  40 // Gives sense of direction for point p, collinear w.r.t. segment (a,b)
  41 // Returns -1 if p goes backward w.r.t (a,b), so goes from b in direction of a
  42 // Returns 1 if p goes forward, so extends (a,b)
  43 // Returns 0 if p is equal with b, or if (a,b) is degenerate
  44 // Note that it does not do any collinearity test, that should be done before
  45 template <typename Point1, typename Point2>
  46 inline int direction_code(Point1 const& segment_a, Point1 const& segment_b,
  47                           const Point2& p)
  48 {
  49     // Suppose segment = (4 3,4 4) and p =(4 2)
  50     // Then sign_a1 = 1 and sign_p1 = 1 -> goes backward -> return -1
  51
  52     int const sign_a0 = sign_of_difference<0>(segment_b, segment_a);
  53     int const sign_a1 = sign_of_difference<1>(segment_b, segment_a);
  54
  55     if (sign_a0 == 0 && sign_a1 == 0)
  56     {
  57         return 0;
  58     }
  59
  60     int const sign_p0 = sign_of_difference<0>(segment_b, p);
  61     int const sign_p1 = sign_of_difference<1>(segment_b, p);
  62
  63     if (sign_p0 == 0 && sign_p1 == 0)
  64     {
  65         return 0;
  66     }
  67
  68     return sign_a0 == sign_p0 && sign_a1 == sign_p1 ? -1 : 1;
  69 }
  70
  71
  72 } // namespace detail
  73 #endif //DOXYGEN_NO_DETAIL
  74
  75
  76
  77 }} // namespace boost::geometry
  78
  79 #endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_DIRECITON_CODE_HPP