void GeohashGetCoordRange(ref GeoHashRange longRange, ref GeoHashRange latRange)
{
/* These are constraints from EPSG:900913 / EPSG:3785 / OSGEO:41001 */
/* We can't geocode at the north/south pole. */
longRange.Max = GeoLongMax;
longRange.Min = GeoLongMin;
latRange.Max = GeoLatMax;
latRange.Min = GeoLatMin;
}
int GeohashEncode(GeoHashRange longRange, GeoHashRange latRange, double longitude, double latitude,
ushort step, ref GeoHashBits hash)
{
/* Check basic arguments sanity. */
if (step > 32 || step == 0 ||
Rangepiszero(latRange) || Rangepiszero(longRange))
{
return(0);
}
/* Return an error when trying to index outside the supported
* constraints. */
if (longitude > GeoLongMax)
{
return(0);
}
if (longitude < GeoLongMin)
{
return(0);
}
if (latitude > GeoLatMax)
{
return(0);
}
if (latitude < GeoLatMin)
{
return(0);
}
hash.Bits = 0;
hash.Step = step;
if (latitude < latRange.Min || latitude > latRange.Max ||
longitude < longRange.Min || longitude > longRange.Max)
{
return(0);
}
double latOffset =
(latitude - latRange.Min) / (latRange.Max - latRange.Min);
double longOffset =
(longitude - longRange.Min) / (longRange.Max - longRange.Min);
/* convert to fixed point based on the step size */
latOffset *= (1UL << step);
longOffset *= (1UL << step);
hash.Bits = Interleave64((uint)latOffset, (uint)longOffset);
return(1);
}
private bool Rangeiszero(GeoHashRange r)
{
return(r.Max == 0.0 && r.Min == 0.0);
}
private bool Rangepiszero(GeoHashRange r)
{
return(Rangeiszero(r));
}
int GeohashDecodeType(GeoHashBits hash, GeoHashArea area)
{
GeoHashRange[] r = new GeoHashRange[2];
GeohashGetCoordRange(ref r[0], ref r[1]);
return(GeohashDecode(r[0], r[1], hash, area));
}
int GeohashEncodeType(double longitude, double latitude, ushort step, ref GeoHashBits hash)
{
GeoHashRange[] r = new GeoHashRange[2];
GeohashGetCoordRange(ref r[0], ref r[1]);
return(GeohashEncode(r[0], r[1], longitude, latitude, step, ref hash));
}
