private static void divideRangeDecode(GeoHash geoHash, double[] range, boolean isOnBit) {
double mid = (range[0] + range[1]) / 2;
if (isOnBit) {
geoHash.addOnBitToEnd();
range[0] = mid;
} else {
geoHash.addOffBitToEnd();
range[1] = mid;
}
}
private static void divideRangeEncode(GeoHash geoHash, double value, double[] range) {
double mid = (range[0] + range[1]) / 2;
if (value >= mid) {
geoHash.addOnBitToEnd();
range[0] = mid;
} else {
geoHash.addOffBitToEnd();
range[1] = mid;
}
}
public static GeoHash fromCoordinate(double latitude, double longitude, int precision) {
GeoHash geoHash = new GeoHash();
geoHash.coordinate = new Coordinate(latitude, longitude);
boolean isEvenBit = true;
double[] latitudeRange = {-90, 90};
double[] longitudeRange = {-180, 180};
while (geoHash.significantBits < precision) {
if (isEvenBit) {
divideRangeEncode(geoHash, longitude, longitudeRange);
} else {
divideRangeEncode(geoHash, latitude, latitudeRange);
}
isEvenBit = !isEvenBit;
}
geoHash.bits <<= (MAX_PRECISION - precision);
return geoHash;
}
public static GeoHash fromLong(long longValue, int significantBits) {
double[] latitudeRange = {-90.0, 90.0};
double[] longitudeRange = {-180.0, 180.0};
boolean isEvenBit = true;
GeoHash geoHash = new GeoHash();
String binaryString = Long.toBinaryString(longValue);
while (binaryString.length() < MAX_PRECISION) {
binaryString = "0" + binaryString;
}
for (int j = 0; j < significantBits; j++) {
if (isEvenBit) {
divideRangeDecode(geoHash, longitudeRange, binaryString.charAt(j) != '0');
} else {
divideRangeDecode(geoHash, latitudeRange, binaryString.charAt(j) != '0');
}
isEvenBit = !isEvenBit;
}
double latitude = (latitudeRange[0] + latitudeRange[1]) / 2;
double longitude = (longitudeRange[0] + longitudeRange[1]) / 2;
geoHash.coordinate = new Coordinate(latitude, longitude);
geoHash.bits <<= (MAX_PRECISION - geoHash.significantBits);
return geoHash;
}
private GeoHash recombineLatLonBitsToHash(long[] latBits, long[] lonBits) {
GeoHash geoHash = new GeoHash();
boolean isEvenBit = false;
latBits[0] <<= (MAX_PRECISION - latBits[1]);
lonBits[0] <<= (MAX_PRECISION - lonBits[1]);
double[] latitudeRange = {-90.0, 90.0};
double[] longitudeRange = {-180.0, 180.0};
for (int i = 0; i < latBits[1] + lonBits[1]; i++) {
if (isEvenBit) {
divideRangeDecode(
geoHash, latitudeRange, (latBits[0] & FIRST_BIT_FLAGGED) == FIRST_BIT_FLAGGED);
latBits[0] <<= 1;
} else {
divideRangeDecode(
geoHash, longitudeRange, (lonBits[0] & FIRST_BIT_FLAGGED) == FIRST_BIT_FLAGGED);
lonBits[0] <<= 1;
}
isEvenBit = !isEvenBit;
}
geoHash.bits <<= (MAX_PRECISION - geoHash.significantBits);
geoHash.coordinate = getCenterCoordinate(latitudeRange, longitudeRange);
return geoHash;
}
public List<GeoHash> getAdjacent() {
GeoHash northern = getNorthernNeighbour();
GeoHash eastern = getEasternNeighbour();
GeoHash southern = getSouthernNeighbour();
GeoHash western = getWesternNeighbour();
return Arrays.asList(
northern,
northern.getEasternNeighbour(),
eastern,
southern.getEasternNeighbour(),
southern,
southern.getWesternNeighbour(),
western,
northern.getWesternNeighbour(),
this);
}