com.yuweix.kuafu.core.geo.GeoHash Maven / Gradle / Ivy
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package com.yuweix.kuafu.core.geo;
import com.yuweix.kuafu.core.MathUtil;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* @author yuwei
*/
public class GeoHash {
private Location location;
/**
* 1 2500km; 2 630km; 3 78km; 4 30km; 5 2.4km;
* 6 610m; 7 76m; 8 19m; 9 2m; 10 60cm;
*/
public static final int DEFAULT_HASH_LENGTH = 10;
/**
* 纬度转化为二进制长度
*/
private int latLength = 25;
/**
* 经度转化为二进制长度
*/
private int lngLength = 25;
/**
* 每格纬度的单位大小
*/
private double minLat;
/**
* 每格经度的大小
*/
private double minLng;
private static final char[] CHARS = {'0', '1', '2', '3', '4', '5', '6', '7'
, '8', '9', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'm', 'n'
, 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
public GeoHash(double lat, double lng) {
this(DEFAULT_HASH_LENGTH, lat, lng);
}
private GeoHash(int hashLength, double lat, double lng) {
setHashLength(hashLength);
location = new Location(lat, lng);
setMinLatLng();
}
/**
* 设置经纬度的最小单位
*/
private void setMinLatLng() {
minLat = Location.MAX_LAT - Location.MIN_LAT;
for (int i = 0; i < latLength; i++) {
minLat = MathUtil.mul(minLat, 0.5);
}
minLng = Location.MAX_LNG - Location.MIN_LNG;
for (int i = 0; i < lngLength; i++) {
minLng = MathUtil.mul(minLng, 0.5);
}
}
/**
* 求所在坐标点及周围点组成的九个
*/
public List getGeoHashBase32For9() {
double leftLat = MathUtil.sub(location.getLat(), minLat);
double rightLat = MathUtil.add(location.getLat(), minLat);
double upLng = MathUtil.sub(location.getLng(), minLng);
double downLng = MathUtil.add(location.getLng(), minLng);
List base32For9 = new ArrayList();
//左侧从上到下 3个
String leftUp = getGeoHashBase32(leftLat, upLng);
if (!(leftUp == null || "".equals(leftUp))) {
base32For9.add(leftUp);
}
String leftMid = getGeoHashBase32(leftLat, location.getLng());
if (!(leftMid == null || "".equals(leftMid))) {
base32For9.add(leftMid);
}
String leftDown = getGeoHashBase32(leftLat, downLng);
if (!(leftDown == null || "".equals(leftDown))) {
base32For9.add(leftDown);
}
//中间从上到下 3个
String midUp = getGeoHashBase32(location.getLat(), upLng);
if (!(midUp == null || "".equals(midUp))) {
base32For9.add(midUp);
}
String midMid = getGeoHashBase32(location.getLat(), location.getLng());
if (!(midMid == null || "".equals(midMid))) {
base32For9.add(midMid);
}
String midDown = getGeoHashBase32(location.getLat(), downLng);
if (!(midDown == null || "".equals(midDown))) {
base32For9.add(midDown);
}
//右侧从上到下 3个
String rightUp = getGeoHashBase32(rightLat, upLng);
if (!(rightUp == null || "".equals(rightUp))) {
base32For9.add(rightUp);
}
String rightMid = getGeoHashBase32(rightLat, location.getLng());
if (!(rightMid == null || "".equals(rightMid))) {
base32For9.add(rightMid);
}
String rightDown = getGeoHashBase32(rightLat, downLng);
if (!(rightDown == null || "".equals(rightDown))) {
base32For9.add(rightDown);
}
return base32For9;
}
/**
* 设置经纬度转化为geohash长度
*/
private boolean setHashLength(int length) {
if (length < 1) {
return false;
}
latLength = (length * 5) / 2;
if (length % 2 == 0) {
lngLength = latLength;
} else {
lngLength = latLength + 1;
}
setMinLatLng();
return true;
}
/**
* 获取经纬度的base32字符串
*/
public String getGeoHashBase32() {
return getGeoHashBase32(location.getLat(), location.getLng());
}
/**
* 获取经纬度的base32字符串
*/
private String getGeoHashBase32(double lat, double lng) {
boolean[] bools = getGeoBinary(lat, lng);
if (bools == null) {
return null;
}
StringBuilder builder = new StringBuilder("");
for (int i = 0; i < bools.length; i = i + 5) {
boolean[] base32 = new boolean[5];
for (int j = 0; j < 5; j++) {
base32[j] = bools[i + j];
}
char cha = getBase32Char(base32);
if (' ' == cha) {
return null;
}
builder.append(cha);
}
return builder.toString();
}
/**
* 将五位二进制转化为base32
*/
private char getBase32Char(boolean[] base32) {
if (base32 == null || base32.length != 5) {
return ' ';
}
int num = 0;
for (boolean bool : base32) {
num <<= 1;
if (bool) {
num += 1;
}
}
return CHARS[num % CHARS.length];
}
/**
* 获取坐标的geo二进制字符串
*/
private boolean[] getGeoBinary(double lat, double lng) {
boolean[] latArray = getHashArray(lat, Location.MIN_LAT, Location.MAX_LAT, latLength);
boolean[] lngArray = getHashArray(lng, Location.MIN_LNG, Location.MAX_LNG, lngLength);
return merge(latArray, lngArray);
}
/**
* 合并经纬度二进制
*/
private boolean[] merge(boolean[] latArray, boolean[] lngArray) {
if (latArray == null || lngArray == null) {
return null;
}
boolean[] result = new boolean[lngArray.length + latArray.length];
Arrays.fill(result, false);
for (int i = 0; i < lngArray.length; i++) {
result[2 * i] = lngArray[i];
}
for (int i = 0; i < latArray.length; i++) {
result[2 * i + 1] = latArray[i];
}
return result;
}
/**
* 将数字转化为geohash二进制字符串
*/
private boolean[] getHashArray(double value, double min, double max, int length) {
if (value < min || value > max) {
return null;
}
if (length < 1) {
return null;
}
boolean[] result = new boolean[length];
for (int i = 0; i < length; i++) {
double mid = MathUtil.mul(MathUtil.add(min, max), 0.5);
if (value > mid) {
result[i] = true;
min = mid;
} else {
result[i] = false;
max = mid;
}
}
return result;
}
}