public static GeoHashQuery queryForGeoHash(GeoHash geohash, int bits)
{
string hash = geohash.getGeoHashString();
int precision = (int)Math.Ceiling((double)bits / Base32Utils.BITS_PER_BASE32_CHAR);
if (hash.Length < precision)
{
return(new GeoHashQuery(hash, hash + "~"));
}
hash = hash.Substring(0, precision);
string baseS = hash.Substring(0, hash.Length - 1);
int lastValue = Base32Utils.base32CharToValue(hash[(hash.Length - 1)]);
int significantBits = bits - (baseS.Length * Base32Utils.BITS_PER_BASE32_CHAR);
int unusedBits = (Base32Utils.BITS_PER_BASE32_CHAR - significantBits);
// delete unused bits
int startValue = (lastValue >> unusedBits) << unusedBits;
int endValue = startValue + (1 << unusedBits);
string startHash = baseS + Base32Utils.valueToBase32Char(startValue);
string endHash;
if (endValue > 31)
{
endHash = baseS + "~";
}
else
{
endHash = baseS + Base32Utils.valueToBase32Char(endValue);
}
return(new GeoHashQuery(startHash, endHash));
}
public GeoHash(double latitude, double longitude, int precision)
{
if (precision < 1)
{
throw new System.Exception("Precision of GeoHash must be larger than zero!");
}
if (precision > MAX_PRECISION)
{
throw new System.Exception("Precision of a GeoHash must be less than " + (MAX_PRECISION + 1) + "!");
}
if (!GeoLocation.coordinatesValid(latitude, longitude))
{
throw new System.Exception(string.Format("Not valid location coordinates: [{0}, {1}]", latitude, longitude));
}
double[] longitudeRange = { -180, 180 };
double[] latitudeRange = { -90, 90 };
char[] buffer = new char[precision];
for (int i = 0; i < precision; i++)
{
int hashValue = 0;
for (int j = 0; j < Base32Utils.BITS_PER_BASE32_CHAR; j++)
{
bool even = (((i * Base32Utils.BITS_PER_BASE32_CHAR) + j) % 2) == 0;
double val = even ? longitude : latitude;
double[] range = even ? longitudeRange : latitudeRange;
double mid = (range[0] + range[1]) / 2;
if (val > mid)
{
hashValue = (hashValue << 1) + 1;
range[0] = mid;
}
else
{
hashValue = (hashValue << 1);
range[1] = mid;
}
}
buffer[i] = Base32Utils.valueToBase32Char(hashValue);
}
this.geoHash = new string(buffer);
}