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/*
* Copyright (c) 2013-2014, yinqiwen <yinqiwen@gmail.com>
* Copyright (c) 2014, Matt Stancliff <matt@genges.com>.
* Copyright (c) 2015, Salvatore Sanfilippo <antirez@gmail.com>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
/* This is a C++ to C conversion from the ardb project.
* This file started out as:
* https://github.com/yinqiwen/ardb/blob/d42503/src/geo/geohash_helper.cpp
*/
#include "geohash_helper.h"
#define D_R (M_PI / 180.0)
#define R_MAJOR 6378137.0
#define R_MINOR 6356752.3142
#define RATIO (R_MINOR / R_MAJOR)
#define ECCENT (sqrt(1.0 - (RATIO *RATIO)))
#define COM (0.5 * ECCENT)
/// @brief The usual PI/180 constant
const double DEG_TO_RAD = 0.017453292519943295769236907684886;
/// @brief Earth's quatratic mean radius for WGS-84
const double EARTH_RADIUS_IN_METERS = 6372797.560856;
const double MERCATOR_MAX = 20037726.37;
const double MERCATOR_MIN = -20037726.37;
static inline double deg_rad(double ang) { return ang * D_R; }
static inline double rad_deg(double ang) { return ang / D_R; }
/* You must *ONLY* estimate steps when you are encoding.
* If you are decoding, always decode to GEO_STEP_MAX (26). */
uint8_t geohashEstimateStepsByRadius(double range_meters, double lat) {
if (range_meters == 0) return 26;
int step = 1;
while (range_meters < MERCATOR_MAX) {
range_meters *= 2;
step++;
}
step -= 2; /* Make sure range is included in the worst case. */
/* Wider range torwards the poles... Note: it is possible to do better
* than this approximation by computing the distance between meridians
* at this latitude, but this does the trick for now. */
if (lat > 67 || lat < -67) step--;
if (lat > 80 || lat < -80) step--;
/* Frame to valid range. */
if (step < 1) step = 1;
if (step > 26) step = 25;
return step;
}
int geohashBitsComparator(const GeoHashBits *a, const GeoHashBits *b) {
/* If step not equal, compare on step. Else, compare on bits. */
return a->step != b->step ? a->step - b->step : a->bits - b->bits;
}
int geohashBoundingBox(double longitude, double latitude, double radius_meters,
double *bounds) {
if (!bounds) return 0;
double lonr, latr;
lonr = deg_rad(longitude);
latr = deg_rad(latitude);
double distance = radius_meters / EARTH_RADIUS_IN_METERS;
double min_latitude = latr - distance;
double max_latitude = latr + distance;
/* Note: we're being lazy and not accounting for coordinates near poles */
double min_longitude, max_longitude;
double difference_longitude = asin(sin(distance) / cos(latr));
min_longitude = lonr - difference_longitude;
max_longitude = lonr + difference_longitude;
bounds[0] = rad_deg(min_longitude);
bounds[1] = rad_deg(min_latitude);
bounds[2] = rad_deg(max_longitude);
bounds[3] = rad_deg(max_latitude);
return 1;
}
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;
}
GeoHashRadius geohashGetAreasByRadiusWGS84(double longitude, double latitude,
double radius_meters) {
return geohashGetAreasByRadius(longitude, latitude, radius_meters);
}
GeoHashFix52Bits geohashAlign52Bits(const GeoHashBits hash) {
uint64_t bits = hash.bits;
bits <<= (52 - hash.step * 2);
return bits;
}
/* Calculate distance using haversin great circle distance formula. */
double geohashGetDistance(double lon1d, double lat1d, double lon2d, double lat2d) {
double lat1r, lon1r, lat2r, lon2r, u, v;
lat1r = deg_rad(lat1d);
lon1r = deg_rad(lon1d);
lat2r = deg_rad(lat2d);
lon2r = deg_rad(lon2d);
u = sin((lat2r - lat1r) / 2);
v = sin((lon2r - lon1r) / 2);
return 2.0 * EARTH_RADIUS_IN_METERS *
asin(sqrt(u * u + cos(lat1r) * cos(lat2r) * v * v));
}
int geohashGetDistanceIfInRadius(double x1, double y1,
double x2, double y2, double radius,
double *distance) {
*distance = geohashGetDistance(x1, y1, x2, y2);
if (*distance > radius) return 0;
return 1;
}
int geohashGetDistanceIfInRadiusWGS84(double x1, double y1, double x2,
double y2, double radius,
double *distance) {
return geohashGetDistanceIfInRadius(x1, y1, x2, y2, radius, distance);
}
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