GeoHash C#版 找到周围8个区域的GeoHash编码

using System;

namespace sharonjl.utils
{
public static class Geohash
{
#region Direction enum

public enum Direction
{
Top = 0,
Right = 1,
Bottom = 2,
Left = 3
}

#endregion

private const string Base32 = "0123456789bcdefghjkmnpqrstuvwxyz";
private static readonly int[] Bits = new[] {16, 8, 4, 2, 1};

private static readonly string[][] Neighbors = {
new[]
{
"p0r21436x8zb9dcf5h7kjnmqesgutwvy", // Top
"bc01fg45238967deuvhjyznpkmstqrwx", // Right
"14365h7k9dcfesgujnmqp0r2twvyx8zb", // Bottom
"238967debc01fg45kmstqrwxuvhjyznp", // Left
}, new[]
{
"bc01fg45238967deuvhjyznpkmstqrwx", // Top
"p0r21436x8zb9dcf5h7kjnmqesgutwvy", // Right
"238967debc01fg45kmstqrwxuvhjyznp", // Bottom
"14365h7k9dcfesgujnmqp0r2twvyx8zb", // Left
}
};

private static readonly string[][] Borders = {
new[] {"prxz", "bcfguvyz", "028b", "0145hjnp"},
new[] {"bcfguvyz", "prxz", "0145hjnp", "028b"}
};
/// <summary>
/// 计算相邻
/// </summary>
/// <param name="hash"></param>
/// <param name="direction"></param>
/// <returns></returns>
public static String CalculateAdjacent(String hash, Direction direction)
{
hash = hash.ToLower();

char lastChr = hash[hash.Length - 1];
int type = hash.Length%2;
var dir = (int) direction;
string nHash = hash.Substring(0, hash.Length - 1);

if (Borders[type][dir].IndexOf(lastChr) != -1)
{
nHash = CalculateAdjacent(nHash, (Direction) dir);
}
return nHash + Base32[Neighbors[type][dir].IndexOf(lastChr)];
}
/// <summary>
/// 细化间隔
/// </summary>
/// <param name="interval"></param>
/// <param name="cd"></param>
/// <param name="mask"></param>
public static void RefineInterval(ref double[] interval, int cd, int mask)
{
if ((cd & mask) != 0)
{
interval[0] = (interval[0] + interval[1])/2;
}
else
{
interval[1] = (interval[0] + interval[1])/2;
}
}

/// <summary>
/// 解码
/// </summary>
/// <param name="geohash"></param>
/// <returns></returns>
public static double[] Decode(String geohash)
{
bool even = true;
double[] lat = {-90.0, 90.0};
double[] lon = {-180.0, 180.0};

foreach (char c in geohash)
{
int cd = Base32.IndexOf(c);
for (int j = 0; j < 5; j++)
{
int mask = Bits[j];
if (even)
{
RefineInterval(ref lon, cd, mask);
}
else
{
RefineInterval(ref lat, cd, mask);
}
even = !even;
}
}

return new[] {(lat[0] + lat[1])/2, (lon[0] + lon[1])/2};
}
/// <summary>
/// 编码
/// </summary>
/// <param name="latitude">纬度</param>
/// <param name="longitude">经度</param>
/// <param name="precision">精度</param>
/// <returns></returns>
public static String Encode(double latitude, double longitude, int precision = 12)
{
bool even = true;
int bit = 0;
int ch = 0;
string geohash = "";

double[] lat = {-90.0, 90.0};
double[] lon = {-180.0, 180.0};

if (precision < 1 || precision > 20) precision = 12;

while (geohash.Length < precision)
{
double mid;

if (even)
{
mid = (lon[0] + lon[1])/2;
if (longitude > mid)
{
ch |= Bits[bit];
lon[0] = mid;
}
else
lon[1] = mid;
}
else
{
mid = (lat[0] + lat[1])/2;
if (latitude > mid)
{
ch |= Bits[bit];
lat[0] = mid;
}
else
lat[1] = mid;
}

even = !even;
if (bit < 4)
bit++;
else
{
geohash += Base32[ch];
bit = 0;
ch = 0;
}
}
return geohash;
}

/// <summary>
/// 获取九个格子 顺序 本身 上、下、左、右、 左上、 右上、 左下、右下
/// </summary>
/// <param name="geohash"></param>
/// <returns></returns>
public static String[] getGeoHashExpand(String geohash)
{

try {
String geohashTop = CalculateAdjacent(geohash, Direction.Top);//上

String geohashBottom = CalculateAdjacent(geohash, Direction.Bottom);//下

String geohashLeft = CalculateAdjacent(geohash, Direction.Left);//左

String geohashRight = CalculateAdjacent(geohash, Direction.Right);//右

String geohashTopLeft = CalculateAdjacent(geohashLeft, Direction.Top);//左上

String geohashTopRight = CalculateAdjacent(geohashRight, Direction.Top);//右上

String geohashBottomLeft = CalculateAdjacent(geohashLeft, Direction.Bottom);//左下

String geohashBottomRight = CalculateAdjacent(geohashRight, Direction.Bottom);//右下

String[] expand = { geohash, geohashTop, geohashBottom, geohashLeft, geohashRight, geohashTopLeft, geohashTopRight,  geohashBottomLeft, geohashBottomRight};
return expand;
} catch (Exception e) {
return null;
}
}

///// <summary>
///// test
///// </summary>
///// <param name="args"></param>
//public  void main()
//{
//    double lat = 39.90403;
//    double lon = 116.407526; //需要查询经纬度，目前指向的是BeiJing
//    string hash = Geohash.Encode(lat, lon);
//    int geohashLen = 6;
//    /*获取中心点的geohash*/
//    String geohash = hash.Substring(0, geohashLen);
//    /*获取所有的矩形geohash， 一共是九个 ，包含中心点,打印顺序请参考参数*/
//    String[] result = Geohash.getGeoHashExpand(geohash);
//}
}
}