osrm-backend/include/osmium/geom/wkb.hpp

#ifndef OSMIUM_GEOM_WKB_HPP
#define OSMIUM_GEOM_WKB_HPP

/*

This file is part of Osmium (http://osmcode.org/libosmium).

Copyright 2013-2015 Jochen Topf <jochen@topf.org> and others (see README).

Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
obtaining a copy of the software and accompanying documentation covered by
this license (the "Software") to use, reproduce, display, distribute,
execute, and transmit the Software, and to prepare derivative works of the
Software, and to permit third-parties to whom the Software is furnished to
do so, all subject to the following:

The copyright notices in the Software and this entire statement, including
the above license grant, this restriction and the following disclaimer,
must be included in all copies of the Software, in whole or in part, and
all derivative works of the Software, unless such copies or derivative
works are solely in the form of machine-executable object code generated by
a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.

*/

#include <cstddef>
#include <cstdint>
#include <string>

// Windows is only available for little endian architectures
// http://stackoverflow.com/questions/6449468/can-i-safely-assume-that-windows-installations-will-always-be-little-endian
#if !defined(_WIN32) && !defined(__APPLE__)
# include <endian.h>
#else
# define __LITTLE_ENDIAN 1234
# define __BYTE_ORDER __LITTLE_ENDIAN
#endif

#include <osmium/geom/coordinates.hpp>
#include <osmium/geom/factory.hpp>
#include <osmium/util/cast.hpp>

namespace osmium {

    namespace geom {

        enum class wkb_type : bool {
            wkb  = false,
            ewkb = true
        }; // enum class wkb_type

        enum class out_type : bool {
            binary = false,
            hex    = true
        }; // enum class out_type

        namespace detail {

            template <typename T>
            inline void str_push(std::string& str, T data) {
                size_t size = str.size();
                str.resize(size + sizeof(T));
                std::copy_n(reinterpret_cast<char*>(&data), sizeof(T), &str[size]);
            }

            inline std::string convert_to_hex(const std::string& str) {
                static const char* lookup_hex = "0123456789ABCDEF";
                std::string out;

                for (char c : str) {
                    out += lookup_hex[(c >> 4) & 0xf];
                    out += lookup_hex[c & 0xf];
                }

                return out;
            }

            class WKBFactoryImpl {

                /// OSM data always uses SRID 4326 (WGS84).
                static constexpr uint32_t srid = 4326;

                /**
                * Type of WKB geometry.
                * These definitions are from
                * 99-049_OpenGIS_Simple_Features_Specification_For_SQL_Rev_1.1.pdf (for WKB)
                * and http://trac.osgeo.org/postgis/browser/trunk/doc/ZMSgeoms.txt (for EWKB).
                * They are used to encode geometries into the WKB format.
                */
                enum wkbGeometryType : uint32_t {
                    wkbPoint               = 1,
                    wkbLineString          = 2,
                    wkbPolygon             = 3,
                    wkbMultiPoint          = 4,
                    wkbMultiLineString     = 5,
                    wkbMultiPolygon        = 6,
                    wkbGeometryCollection  = 7,

                    // SRID-presence flag (EWKB)
                    wkbSRID                = 0x20000000
                }; // enum wkbGeometryType

                /**
                * Byte order marker in WKB geometry.
                */
                enum class wkb_byte_order_type : uint8_t {
                    XDR = 0,         // Big Endian
                    NDR = 1          // Little Endian
                }; // enum class wkb_byte_order_type

                std::string m_data;
                uint32_t m_points {0};
                wkb_type m_wkb_type;
                out_type m_out_type;

                size_t m_linestring_size_offset = 0;
                size_t m_polygons = 0;
                size_t m_rings = 0;
                size_t m_multipolygon_size_offset = 0;
                size_t m_polygon_size_offset = 0;
                size_t m_ring_size_offset = 0;

                size_t header(std::string& str, wkbGeometryType type, bool add_length) const {
#if __BYTE_ORDER == __LITTLE_ENDIAN
                    str_push(str, wkb_byte_order_type::NDR);
#else
                    str_push(str, wkb_byte_order_type::XDR);
#endif
                    if (m_wkb_type == wkb_type::ewkb) {
                        str_push(str, type | wkbSRID);
                        str_push(str, srid);
                    } else {
                        str_push(str, type);
                    }
                    size_t offset = str.size();
                    if (add_length) {
                        str_push(str, static_cast<uint32_t>(0));
                    }
                    return offset;
                }

                void set_size(const size_t offset, const size_t size) {
                    *reinterpret_cast<uint32_t*>(&m_data[offset]) = static_cast_with_assert<uint32_t>(size);
                }

            public:

                typedef std::string point_type;
                typedef std::string linestring_type;
                typedef std::string polygon_type;
                typedef std::string multipolygon_type;
                typedef std::string ring_type;

                explicit WKBFactoryImpl(wkb_type wtype = wkb_type::wkb, out_type otype = out_type::binary) :
                    m_wkb_type(wtype),
                    m_out_type(otype) {
                }

                /* Point */

                point_type make_point(const osmium::geom::Coordinates& xy) const {
                    std::string data;
                    header(data, wkbPoint, false);
                    str_push(data, xy.x);
                    str_push(data, xy.y);

                    if (m_out_type == out_type::hex) {
                        return convert_to_hex(data);
                    } else {
                        return data;
                    }
                }

                /* LineString */

                void linestring_start() {
                    m_data.clear();
                    m_linestring_size_offset = header(m_data, wkbLineString, true);
                }

                void linestring_add_location(const osmium::geom::Coordinates& xy) {
                    str_push(m_data, xy.x);
                    str_push(m_data, xy.y);
                }

                linestring_type linestring_finish(size_t num_points) {
                    set_size(m_linestring_size_offset, num_points);
                    std::string data;
                    std::swap(data, m_data);

                    if (m_out_type == out_type::hex) {
                        return convert_to_hex(data);
                    } else {
                        return data;
                    }
                }

                /* MultiPolygon */

                void multipolygon_start() {
                    m_data.clear();
                    m_polygons = 0;
                    m_multipolygon_size_offset = header(m_data, wkbMultiPolygon, true);
                }

                void multipolygon_polygon_start() {
                    ++m_polygons;
                    m_rings = 0;
                    m_polygon_size_offset = header(m_data, wkbPolygon, true);
                }

                void multipolygon_polygon_finish() {
                    set_size(m_polygon_size_offset, m_rings);
                }

                void multipolygon_outer_ring_start() {
                    ++m_rings;
                    m_points = 0;
                    m_ring_size_offset = m_data.size();
                    str_push(m_data, static_cast<uint32_t>(0));
                }

                void multipolygon_outer_ring_finish() {
                    set_size(m_ring_size_offset, m_points);
                }

                void multipolygon_inner_ring_start() {
                    ++m_rings;
                    m_points = 0;
                    m_ring_size_offset = m_data.size();
                    str_push(m_data, static_cast<uint32_t>(0));
                }

                void multipolygon_inner_ring_finish() {
                    set_size(m_ring_size_offset, m_points);
                }

                void multipolygon_add_location(const osmium::geom::Coordinates& xy) {
                    str_push(m_data, xy.x);
                    str_push(m_data, xy.y);
                    ++m_points;
                }

                multipolygon_type multipolygon_finish() {
                    set_size(m_multipolygon_size_offset, m_polygons);
                    std::string data;
                    std::swap(data, m_data);

                    if (m_out_type == out_type::hex) {
                        return convert_to_hex(data);
                    } else {
                        return data;
                    }
                }

            }; // class WKBFactoryImpl

        } // namespace detail

        template <class TProjection = IdentityProjection>
        using WKBFactory = GeometryFactory<osmium::geom::detail::WKBFactoryImpl, TProjection>;

    } // namespace geom

} // namespace osmium

#endif // OSMIUM_GEOM_WKB_HPP