“区域”与“区域”之间的区别是什么？和“BoundingBox”来自Redis的源代码 [英] What's the difference between "area" and "BoundingBox" from Redis's source code

问题描述

http://download.redis.io/redis- stable / deps / geohash-int / geohash_helper.c
从上面的URL中，我们知道有两个概念，一个是geohashBoundingBox，另一个是区域，我的问题是它们之间的区别，以及为什么我们需要他们两个吗？
也为什么这样说句子geohashGetCoordRange（& long_range，& lat_range）;被调用两次？

  GeoHashRadius geohashGetAreasByRadius（双经度，双纬度，双radius_meters）{
 GeoHashRange long_range，lat_range ; 
 GeoHashRadius radius = {{0}}; 
 GeoHashBits hash = {0}; 
 GeoHashNeighbors neighbors = {{0}}; 
 GeoHashArea area = {{0}}; 
 double min_lon，max_lon，min_lat，max_lat; 
双边界[4]; 
 int步骤; 
 
 geohashBoundingBox（longitude，latitude，radius_meters，bounds）; 
 min_lon = bounds [0]; 
 min_lat = bounds [1]; 
 max_lon = bounds [2]; 
 max_lat = bounds [3]; 
 
 steps = geohashEstimateStepsByRadius（radius_meters，latitude）; 
 
 geohashGetCoordRange（& long_range，& lat_range）; 
 geohashEncode（& long_range，& lat_range，longitude，latitude，steps，& hash）; 
 geohashNeighbors（& hash，& neighbors）; 
 geohashGetCoordRange（& long_range，& lat_range）; 
 geohashDecode（long_range，lat_range，hash，& area）; 
 
 if（area.latitude.min< min_lat）{
 GZERO（neighbors.south）; 
 GZERO（neighbors.south_west）; 
 GZERO（neighbors.south_east）; 
} 
 if（area.latitude.max> max_lat）{
 GZERO（neighbors.north）; 
 GZERO（neighbors.north_east）; 
 GZERO（neighbors.north_west）; 
} 
 if（area.longitude.min< min_lon）{
 GZERO（neighbors.west）; 
 GZERO（neighbors.south_west）; 
 GZERO（neighbors.north_west）; 
} 
 if（area.longitude.max> max_lon）{
 GZERO（neighbors.east）; 
 GZERO（neighbors.south_east）; 
 GZERO（neighbors.north_east）; 
} 
 radius.hash = hash; 
 radius.neighbors = neighbors; 
 radius.area =面积; 
回报半径; 
  

}

解决方案 div>

一个粘合盒通常是包含一个物体的最小矩形框。我不能说在redis中GeoHashArea的确切功能，但是因为你暗示它们有相似的目的，如果它们都代表一个地理区域，那么GeoHashArea肯定是一个区域的更详细的多边形表示而不是简单的矩形像geohashBoundingBox。

对于第二个问题，可能是因为变量 long_range 和 lat_range 通过引用传递，有可能是

  geohashEncode（& long_range，& lat_range，经度，纬度，步数和散列）; 
  

会修改它们的值，所以函数 geohashGetCoordRange 再次调用不同的值。

http://download.redis.io/redis-stable/deps/geohash-int/geohash_helper.c From the URL above, we know there are two conceptions , one is geohashBoundingBox ,and another is area,My questions is what's the difference between them and why we need them both? Also why sentence "geohashGetCoordRange(&long_range, &lat_range);" is called two times?

GeoHashRadius geohashGetAreasByRadius(double longitude, double latitude,    double radius_meters) {
GeoHashRange long_range, lat_range;
GeoHashRadius radius = { { 0 } };
GeoHashBits hash = { 0 };
GeoHashNeighbors neighbors = { { 0 } };
GeoHashArea area = { { 0 } };
double min_lon, max_lon, min_lat, max_lat;
double bounds[4];
int steps;

geohashBoundingBox(longitude, latitude, radius_meters, bounds);
min_lon = bounds[0];
min_lat = bounds[1];
max_lon = bounds[2];
max_lat = bounds[3];

steps = geohashEstimateStepsByRadius(radius_meters,latitude);

geohashGetCoordRange(&long_range, &lat_range);
geohashEncode(&long_range, &lat_range, longitude, latitude, steps, &hash);
geohashNeighbors(&hash, &neighbors);
geohashGetCoordRange(&long_range, &lat_range);
geohashDecode(long_range, lat_range, hash, &area);

if (area.latitude.min < min_lat) {
    GZERO(neighbors.south);
    GZERO(neighbors.south_west);
    GZERO(neighbors.south_east);
}
if (area.latitude.max > max_lat) {
    GZERO(neighbors.north);
    GZERO(neighbors.north_east);
    GZERO(neighbors.north_west);
}
if (area.longitude.min < min_lon) {
    GZERO(neighbors.west);
    GZERO(neighbors.south_west);
    GZERO(neighbors.north_west);
}
if (area.longitude.max > max_lon) {
    GZERO(neighbors.east);
    GZERO(neighbors.south_east);
    GZERO(neighbors.north_east);
}
radius.hash = hash;
radius.neighbors = neighbors;
radius.area = area;
return radius;

}

解决方案

A bonding box in general is the smallest rectangular box that will contain an object. I can't speak to the exact function of GeoHashArea in redis, but since you imply that they have a similar purpose, if they both represent a geographic area then GeoHashArea will most certainly be a more detailed polygonal representation of an area than a simple rectangle like geohashBoundingBox.

For your second question, presumably, since the variables long_range and lat_range are passed by reference, there's a chance that

geohashEncode(&long_range, &lat_range, longitude, latitude, steps, &hash);

modifies their value and so the function geohashGetCoordRange is called again on the different values.

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