82 lines
2.7 KiB
C++
82 lines
2.7 KiB
C++
#ifndef POLYLINECOMPRESSOR_H_
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#define POLYLINECOMPRESSOR_H_
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#include "util/coordinate.hpp"
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#include <algorithm>
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#include <boost/assert.hpp>
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#include <string>
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#include <vector>
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namespace osrm::engine
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{
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namespace detail
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{
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void encode(int number_to_encode, std::string &output);
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std::int32_t decode_polyline_integer(std::string::const_iterator &first,
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std::string::const_iterator last);
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} // namespace detail
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using CoordVectorForwardIter = std::vector<util::Coordinate>::const_iterator;
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// Encodes geometry into polyline format.
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// See: https://developers.google.com/maps/documentation/utilities/polylinealgorithm
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template <unsigned POLYLINE_PRECISION = 100000>
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std::string encodePolyline(CoordVectorForwardIter begin, CoordVectorForwardIter end)
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{
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double coordinate_to_polyline = POLYLINE_PRECISION / COORDINATE_PRECISION;
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auto size = std::distance(begin, end);
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if (size == 0)
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{
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return {};
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}
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std::string output;
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// just a guess that we will need ~4 bytes per coordinate to avoid reallocations
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output.reserve(size * 4);
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int current_lat = 0;
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int current_lon = 0;
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for (auto it = begin; it != end; ++it)
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{
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const int lat_diff =
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std::round(static_cast<int>(it->lat) * coordinate_to_polyline) - current_lat;
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const int lon_diff =
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std::round(static_cast<int>(it->lon) * coordinate_to_polyline) - current_lon;
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detail::encode(lat_diff, output);
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detail::encode(lon_diff, output);
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current_lat += lat_diff;
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current_lon += lon_diff;
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}
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return output;
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}
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// Decodes geometry from polyline format
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// See: https://developers.google.com/maps/documentation/utilities/polylinealgorithm
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template <unsigned POLYLINE_PRECISION = 100000>
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std::vector<util::Coordinate> decodePolyline(const std::string &polyline)
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{
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double polyline_to_coordinate = COORDINATE_PRECISION / POLYLINE_PRECISION;
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std::vector<util::Coordinate> coordinates;
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std::int32_t latitude = 0, longitude = 0;
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std::string::const_iterator first = polyline.begin();
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const std::string::const_iterator last = polyline.end();
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while (first != last)
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{
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const auto dlat = detail::decode_polyline_integer(first, last);
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const auto dlon = detail::decode_polyline_integer(first, last);
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latitude += dlat;
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longitude += dlon;
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coordinates.emplace_back(util::Coordinate{
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util::FixedLongitude{static_cast<std::int32_t>(longitude * polyline_to_coordinate)},
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util::FixedLatitude{static_cast<std::int32_t>(latitude * polyline_to_coordinate)}});
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}
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return coordinates;
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}
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} // namespace osrm::engine
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#endif /* POLYLINECOMPRESSOR_H_ */
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