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Optimise encodePolyline function (#6940)

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This commit is contained in:
Siarhei Fedartsou
2024-06-22 20:04:32 +02:00
committed by GitHub
parent 3d01d96036
commit 7d72dfebf7
4 changed files with 122 additions and 47 deletions
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include/engine/polyline_compressor.hpp
+17 -20
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@@ -12,7 +12,7 @@ namespace osrm::engine
{
namespace detail
{
std::string encode(std::vector<int> &numbers);
void encode(int number_to_encode, std::string &output);
std::int32_t decode_polyline_integer(std::string::const_iterator &first,
std::string::const_iterator last);
} // namespace detail
@@ -30,27 +30,24 @@ std::string encodePolyline(CoordVectorForwardIter begin, CoordVectorForwardIter
return {};
}
std::vector<int> delta_numbers;
BOOST_ASSERT(size > 0);
delta_numbers.reserve((size - 1) * 2);
std::string output;
// just a guess that we will need ~4 bytes per coordinate to avoid reallocations
output.reserve(size * 4);
int current_lat = 0;
int current_lon = 0;
std::for_each(
begin,
end,
[&delta_numbers, &current_lat, &current_lon, coordinate_to_polyline](
const util::Coordinate loc)
{
const int lat_diff =
std::round(static_cast<int>(loc.lat) * coordinate_to_polyline) - current_lat;
const int lon_diff =
std::round(static_cast<int>(loc.lon) * coordinate_to_polyline) - current_lon;
delta_numbers.emplace_back(lat_diff);
delta_numbers.emplace_back(lon_diff);
current_lat += lat_diff;
current_lon += lon_diff;
});
return detail::encode(delta_numbers);
for (auto it = begin; it != end; ++it)
{
const int lat_diff =
std::round(static_cast<int>(it->lat) * coordinate_to_polyline) - current_lat;
const int lon_diff =
std::round(static_cast<int>(it->lon) * coordinate_to_polyline) - current_lon;
detail::encode(lat_diff, output);
detail::encode(lon_diff, output);
current_lat += lat_diff;
current_lon += lon_diff;
}
return output;
}
// Decodes geometry from polyline format