Encoded polyline to google polyline

Polyline.dart

static List<LatLng> decodeEncodedPolyline(String encoded) {
    List<LatLng> poly = [];
    int index = 0, len = encoded.length;
    int lat = 0, lng = 0;

    while (index < len) {
      int b, shift = 0, result = 0;
      do {
        b = encoded.codeUnitAt(index++) - 63;
        result |= (b & 0x1f) << shift;
        shift += 5;
      } while (b >= 0x20);
      int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
      lat += dlat;

      shift = 0;
      result = 0;
      do {
        b = encoded.codeUnitAt(index++) - 63;
        result |= (b & 0x1f) << shift;
        shift += 5;
      } while (b >= 0x20);
      int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
      lng += dlng;
      LatLng p = new LatLng(
        (lat / 1E5).toDouble(),
        (lng / 1E5).toDouble(),
      );
      poly.add(p);
    }
    return poly;
  }