96 lines
3.6 KiB
C++
96 lines
3.6 KiB
C++
#ifndef SQL_GIS_RING_FLIP_VISITOR_H_INCLUDED
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#define SQL_GIS_RING_FLIP_VISITOR_H_INCLUDED
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// Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License, version 2.0,
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// as published by the Free Software Foundation.
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//
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// This program is also distributed with certain software (including
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// but not limited to OpenSSL) that is licensed under separate terms,
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// as designated in a particular file or component or in included license
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// documentation. The authors of MySQL hereby grant you an additional
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// permission to link the program and your derivative works with the
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// separately licensed software that they have included with MySQL.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License, version 2.0, for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#include <boost/geometry.hpp>
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#include <memory> // std::unique_ptr
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#include "sql/dd/types/spatial_reference_system.h" // dd::Spatial_reference_system
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#include "sql/gis/geometries_cs.h"
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#include "sql/gis/geometries_traits.h"
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#include "sql/gis/geometry_visitor.h"
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namespace gis {
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/// A visitor that flips polygon rings so that exterior rings are in a
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/// counter-clockwise direction and interior rings in a clockwise direction.
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///
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/// Invalid polygon rings are not guaranteed to be flipped to the correct
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/// direction.
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class Ring_flip_visitor : public Nop_visitor {
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private:
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/// Strategy used for geographic SRSs.
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std::unique_ptr<boost::geometry::strategy::area::geographic<>>
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m_geographic_strategy;
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/// Whether the geometry is invalid. That happens either if the ellipsoid of
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/// a geographic SRS is invalid or if we encounter a ring with unknown
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/// direction.
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bool m_invalid;
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public:
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/// Construct a new ring flip visitor.
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///
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/// @param[in] semi_major The semi-major axis of the ellipsoid.
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/// @param[in] semi_minor The semi-minor axis of the ellipsoid.
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Ring_flip_visitor(double semi_major, double semi_minor) {
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try {
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m_geographic_strategy.reset(
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new boost::geometry::strategy::area::geographic<>(
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boost::geometry::srs::spheroid<double>(semi_major, semi_minor)));
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m_invalid = false;
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} catch (...) {
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// Spheroid construction may fail if the axes are invalid.
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m_invalid = true;
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}
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}
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/// Check if anything wrong has been detected, either an invalid ellipsoid or
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/// a ring with an unknown direction.
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///
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/// Polygon rings which direction can't be determined are invalid. This is the
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/// only way this visitor detects invalid rings. Other invalid rings, e.g.,
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/// rings crossing themselves, are not necessarily detected.
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///
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/// @retval true Invalid SRS ellipsoid or invalid polygon ring.
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/// @retval false No invalid rings detected, but the geometry may still be
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/// invalid.
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bool invalid() const { return m_invalid; }
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using Nop_visitor::visit_enter;
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bool visit_enter(Polygon *py) override;
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bool visit_enter(Multipolygon *py) override;
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bool visit_enter(Multipoint *) override {
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return true; // Don't descend into each point.
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}
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bool visit_enter(Multilinestring *) override {
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return true; // Don't descend into each linestring.
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}
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};
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} // namespace gis
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#endif // SQL_GIS_RING_FLIP_VISITOR_H_INCLUDED
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