presto-geospatial/src/main/java/io/prestosql/plugin/geospatial/BingTile.java/BingTile/toQuadKey
class BingTile:    public String toQuadKey()
    {
        char[] quadKey = new char[this.zoomLevel];
        for (int i = this.zoomLevel; i > 0; i--) {
            char digit = '0';
            int mask = 1 << (i - 1);
            if ((this.x & mask) != 0) {
                digit++;
            }
            if ((this.y & mask) != 0) {
                digit += 2;
            }
            quadKey[this.zoomLevel - i] = digit;
        }
        return String.valueOf(quadKey);
    }