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327 lines
8.5 KiB
C++
327 lines
8.5 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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//
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// Copyright Barend Gehrels 2009, Geodan, Amsterdam, the Netherlands.
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// Use, modification and distribution is subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// Custom polygon example
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#ifndef _MSC_VER
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#warning "Currently only works for MSVC"
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int main() { return 0; }
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#else
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#include <iostream>
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#include <boost/iterator.hpp>
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#include <boost/iterator/iterator_adaptor.hpp>
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#include <boost/iterator/iterator_categories.hpp>
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#include <boost/iterator/iterator_facade.hpp>
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#include <boost/geometry/geometry.hpp>
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#include <boost/geometry/geometries/register/point.hpp>
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#include <boost/geometry/geometries/register/ring.hpp>
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#include <boost/geometry/util/add_const_if_c.hpp>
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// Sample point, having x/y
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struct my_point
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{
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my_point(double a = 0, double b = 0)
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: x(a), y(b)
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{}
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double x,y;
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};
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// Sample polygon, having legacy methods
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// (similar to e.g. COM objects)
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class my_polygon
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{
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std::vector<my_point> points;
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public :
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void add_point(my_point const& p) { points.push_back(p); }
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my_point const& get_point(std::size_t i) const
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{
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assert(i < points.size());
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return points[i];
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}
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// Non const access
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my_point & get_point(std::size_t i)
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{
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assert(i < points.size());
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return points[i];
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}
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int point_count() const { return points.size(); }
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void erase_all() { points.clear(); }
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// Note: it IS possible to have different method names;
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// however, there should (probably) be two different
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// iterators then or an iterator with a specified policy).
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// Note 2: if there is a set_point function, the iterator
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// does not have a way to dereference and non-const
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// iterators will not work!
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};
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// ----------------------------------------------------------------------------
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// Adaption: implement iterator and range-extension, and register with GGL
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// 1) implement iterator (const and non-const versions)
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template <bool IsConst>
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struct custom_iterator : public boost::iterator_facade
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<
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custom_iterator<IsConst>,
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my_point,
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boost::random_access_traversal_tag,
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typename boost::geometry::add_const_if_c<IsConst, my_point>::type&
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>
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{
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// Constructor for begin()
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explicit custom_iterator(typename boost::geometry::add_const_if_c<IsConst, my_polygon>::type& polygon)
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: m_polygon(&polygon)
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, m_index(0)
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{}
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// Constructor for end()
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explicit custom_iterator(bool, typename boost::geometry::add_const_if_c<IsConst, my_polygon>::type& polygon)
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: m_polygon(&polygon)
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, m_index(polygon.point_count())
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{}
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private:
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friend class boost::iterator_core_access;
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typedef boost::iterator_facade
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<
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custom_iterator<IsConst>,
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my_point,
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boost::random_access_traversal_tag,
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typename boost::geometry::add_const_if_c<IsConst, my_point>::type&
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> facade;
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typename boost::geometry::add_const_if_c<IsConst, my_polygon>::type* m_polygon;
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int m_index;
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bool equal(custom_iterator const& other) const
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{
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return this->m_index == other.m_index;
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}
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typename facade::difference_type distance_to(custom_iterator const& other) const
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{
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return other.m_index - this->m_index;
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}
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void advance(typename facade::difference_type n)
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{
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m_index += n;
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if(m_polygon != NULL
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&& (m_index >= m_polygon->point_count()
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|| m_index < 0)
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)
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{
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m_index = m_polygon->point_count();
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}
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}
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void increment()
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{
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advance(1);
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}
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void decrement()
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{
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advance(-1);
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}
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// const and non-const dereference of this iterator
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typename boost::geometry::add_const_if_c<IsConst, my_point>::type& dereference() const
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{
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return m_polygon->get_point(m_index);
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}
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};
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// 2) Implement Boost.Range const functionality
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// using method 2, "provide free-standing functions and specialize metafunctions"
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// 2a) meta-functions
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namespace boost
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{
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template<> struct range_iterator<my_polygon>
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{
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typedef custom_iterator<false> type;
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};
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template<> struct range_const_iterator<my_polygon>
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{
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typedef custom_iterator<true> type;
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};
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// RangeEx
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template<> struct range_size<my_polygon>
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{
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typedef std::size_t type;
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};
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} // namespace 'boost'
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// 2b) free-standing function for Boost.Range ADP
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inline custom_iterator<false> range_begin(my_polygon& polygon)
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{
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return custom_iterator<false>(polygon);
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}
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inline custom_iterator<true> range_begin(my_polygon const& polygon)
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{
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return custom_iterator<true>(polygon);
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}
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inline custom_iterator<false> range_end(my_polygon& polygon)
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{
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return custom_iterator<false>(true, polygon);
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}
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inline custom_iterator<true> range_end(my_polygon const& polygon)
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{
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return custom_iterator<true>(true, polygon);
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}
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// RangeEx
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inline std::size_t range_size(my_polygon const& polygon)
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{
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return polygon.point_count();
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}
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// 3) optional, for writable geometries only, implement back_inserter (=push_back)
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class custom_insert_iterator
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{
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my_polygon* m_polygon;
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public:
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typedef std::output_iterator_tag iterator_category;
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// Not relevant for output iterator
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typedef void value_type;
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typedef void difference_type;
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typedef void pointer;
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typedef void reference;
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typedef void const_reference;
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explicit custom_insert_iterator(my_polygon& x)
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: m_polygon(&x)
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{}
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custom_insert_iterator& operator=(my_point const & p)
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{
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m_polygon->add_point(p);
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return *this;
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}
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custom_insert_iterator& operator*() { return *this; }
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custom_insert_iterator& operator++() { return *this; }
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custom_insert_iterator& operator++(int) { return *this; }
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};
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namespace std
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{
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custom_insert_iterator back_inserter(my_polygon& polygon)
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{
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return custom_insert_iterator(polygon);
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}
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}
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// 4) register with GGL
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BOOST_GEOMETRY_REGISTER_POINT_2D(my_point, double, cs::cartesian, x, y)
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BOOST_GEOMETRY_REGISTER_RING(my_polygon)
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// end adaption
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// ----------------------------------------------------------------------------
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void walk_using_iterator(my_polygon const& polygon)
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{
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for (custom_iterator<true> it = custom_iterator<true>(polygon);
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it != custom_iterator<true>(true, polygon);
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++it)
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{
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std::cout << boost::geometry::dsv(*it) << std::endl;
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}
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std::cout << std::endl;
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}
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void walk_using_range(my_polygon const& polygon)
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{
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for (boost::range_iterator<const my_polygon>::type it
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= boost::begin(polygon);
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it != boost::end(polygon);
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++it)
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{
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std::cout << boost::geometry::dsv(*it) << std::endl;
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}
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std::cout << std::endl;
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}
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int main()
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{
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my_polygon container1;
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// Create (as an example) a regular polygon
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const int n = 5;
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const double d = (360 / n) * boost::geometry::math::d2r;
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double a = 0;
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for (int i = 0; i < n + 1; i++, a += d)
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{
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container1.add_point(my_point(sin(a), cos(a)));
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}
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std::cout << "Walk using Boost.Iterator derivative" << std::endl;
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walk_using_iterator(container1);
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std::cout << "Walk using Boost.Range extension" << std::endl << std::endl;
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walk_using_range(container1);
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std::cout << "Use it by GGL" << std::endl;
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std::cout << "Area: " << boost::geometry::area(container1) << std::endl;
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// Container 2 will be modified by GGL. Add all points but the last one.
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my_polygon container2;
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for (int i = 0; i < n; i++)
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{
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// Use here the std::/GGL way of inserting (but the my_polygon way of getting)
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*(std::back_inserter(container2)++) = container1.get_point(i);
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}
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std::cout << "Second container is not closed:" << std::endl;
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walk_using_range(container2);
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// Correct (= close it)
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boost::geometry::correct(container2);
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std::cout << "Now it is closed:" << std::endl;
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walk_using_range(container2);
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std::cout << "Area: " << boost::geometry::area(container2) << std::endl;
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// Use things from std:: using Boost.Range
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std::reverse(boost::begin(container2), boost::end(container2));
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std::cout << "Area reversed: " << boost::geometry::area(container2) << std::endl;
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return 0;
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}
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#endif
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