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+/*
+ * Copyright (c) 2013-2014, yinqiwen <yinqiwen@gmail.com>
+ * Copyright (c) 2014, Matt Stancliff <matt@genges.com>.
+ * Copyright (c) 2015-2016, 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.
+ */
+#include "geohash.h"
+
+/**
+ * Hashing works like this:
+ * Divide the world into 4 buckets. Label each one as such:
+ * -----------------
+ * | | |
+ * | | |
+ * | 0,1 | 1,1 |
+ * -----------------
+ * | | |
+ * | | |
+ * | 0,0 | 1,0 |
+ * -----------------
+ */
+
+/* Interleave lower bits of x and y, so the bits of x
+ * are in the even positions and bits from y in the odd;
+ * x and y must initially be less than 2**32 (4294967296).
+ * From: https://graphics.stanford.edu/~seander/bithacks.html#InterleaveBMN
+ */
+static inline uint64_t interleave64(uint32_t xlo, uint32_t ylo) {
+ static const uint64_t B[] = {0x5555555555555555ULL, 0x3333333333333333ULL,
+ 0x0F0F0F0F0F0F0F0FULL, 0x00FF00FF00FF00FFULL,
+ 0x0000FFFF0000FFFFULL};
+ static const unsigned int S[] = {1, 2, 4, 8, 16};
+
+ uint64_t x = xlo;
+ uint64_t y = ylo;
+
+ x = (x | (x << S[4])) & B[4];
+ y = (y | (y << S[4])) & B[4];
+
+ x = (x | (x << S[3])) & B[3];
+ y = (y | (y << S[3])) & B[3];
+
+ x = (x | (x << S[2])) & B[2];
+ y = (y | (y << S[2])) & B[2];
+
+ x = (x | (x << S[1])) & B[1];
+ y = (y | (y << S[1])) & B[1];
+
+ x = (x | (x << S[0])) & B[0];
+ y = (y | (y << S[0])) & B[0];
+
+ return x | (y << 1);
+}
+
+/* reverse the interleave process
+ * derived from http://stackoverflow.com/questions/4909263
+ */
+static inline uint64_t deinterleave64(uint64_t interleaved) {
+ static const uint64_t B[] = {0x5555555555555555ULL, 0x3333333333333333ULL,
+ 0x0F0F0F0F0F0F0F0FULL, 0x00FF00FF00FF00FFULL,
+ 0x0000FFFF0000FFFFULL, 0x00000000FFFFFFFFULL};
+ static const unsigned int S[] = {0, 1, 2, 4, 8, 16};
+
+ uint64_t x = interleaved;
+ uint64_t y = interleaved >> 1;
+
+ x = (x | (x >> S[0])) & B[0];
+ y = (y | (y >> S[0])) & B[0];
+
+ x = (x | (x >> S[1])) & B[1];
+ y = (y | (y >> S[1])) & B[1];
+
+ x = (x | (x >> S[2])) & B[2];
+ y = (y | (y >> S[2])) & B[2];
+
+ x = (x | (x >> S[3])) & B[3];
+ y = (y | (y >> S[3])) & B[3];
+
+ x = (x | (x >> S[4])) & B[4];
+ y = (y | (y >> S[4])) & B[4];
+
+ x = (x | (x >> S[5])) & B[5];
+ y = (y | (y >> S[5])) & B[5];
+
+ return x | (y << 32);
+}
+
+void geohashGetCoordRange(GeoHashRange *long_range, GeoHashRange *lat_range) {
+ /* These are constraints from EPSG:900913 / EPSG:3785 / OSGEO:41001 */
+ /* We can't geocode at the north/south pole. */
+ long_range->max = GEO_LONG_MAX;
+ long_range->min = GEO_LONG_MIN;
+ lat_range->max = GEO_LAT_MAX;
+ lat_range->min = GEO_LAT_MIN;
+}
+
+int geohashEncode(const GeoHashRange *long_range, const GeoHashRange *lat_range,
+ double longitude, double latitude, uint8_t step,
+ GeoHashBits *hash) {
+ /* Check basic arguments sanity. */
+ if (hash == NULL || step > 32 || step == 0 ||
+ RANGEPISZERO(lat_range) || RANGEPISZERO(long_range)) return 0;
+
+ /* Return an error when trying to index outside the supported
+ * constraints. */
+ if (longitude > GEO_LONG_MAX || longitude < GEO_LONG_MIN ||
+ latitude > GEO_LAT_MAX || latitude < GEO_LAT_MIN) return 0;
+
+ hash->bits = 0;
+ hash->step = step;
+
+ if (latitude < lat_range->min || latitude > lat_range->max ||
+ longitude < long_range->min || longitude > long_range->max) {
+ return 0;
+ }
+
+ double lat_offset =
+ (latitude - lat_range->min) / (lat_range->max - lat_range->min);
+ double long_offset =
+ (longitude - long_range->min) / (long_range->max - long_range->min);
+
+ /* convert to fixed point based on the step size */
+ lat_offset *= (1ULL << step);
+ long_offset *= (1ULL << step);
+ hash->bits = interleave64(lat_offset, long_offset);
+ return 1;
+}
+
+int geohashEncodeType(double longitude, double latitude, uint8_t step, GeoHashBits *hash) {
+ GeoHashRange r[2] = {{0}};
+ geohashGetCoordRange(&r[0], &r[1]);
+ return geohashEncode(&r[0], &r[1], longitude, latitude, step, hash);
+}
+
+int geohashEncodeWGS84(double longitude, double latitude, uint8_t step,
+ GeoHashBits *hash) {
+ return geohashEncodeType(longitude, latitude, step, hash);
+}
+
+int geohashDecode(const GeoHashRange long_range, const GeoHashRange lat_range,
+ const GeoHashBits hash, GeoHashArea *area) {
+ if (HASHISZERO(hash) || NULL == area || RANGEISZERO(lat_range) ||
+ RANGEISZERO(long_range)) {
+ return 0;
+ }
+
+ area->hash = hash;
+ uint8_t step = hash.step;
+ uint64_t hash_sep = deinterleave64(hash.bits); /* hash = [LAT][LONG] */
+
+ double lat_scale = lat_range.max - lat_range.min;
+ double long_scale = long_range.max - long_range.min;
+
+ uint32_t ilato = hash_sep; /* get lat part of deinterleaved hash */
+ uint32_t ilono = hash_sep >> 32; /* shift over to get long part of hash */
+
+ /* divide by 2**step.
+ * Then, for 0-1 coordinate, multiply times scale and add
+ to the min to get the absolute coordinate. */
+ area->latitude.min =
+ lat_range.min + (ilato * 1.0 / (1ull << step)) * lat_scale;
+ area->latitude.max =
+ lat_range.min + ((ilato + 1) * 1.0 / (1ull << step)) * lat_scale;
+ area->longitude.min =
+ long_range.min + (ilono * 1.0 / (1ull << step)) * long_scale;
+ area->longitude.max =
+ long_range.min + ((ilono + 1) * 1.0 / (1ull << step)) * long_scale;
+
+ return 1;
+}
+
+int geohashDecodeType(const GeoHashBits hash, GeoHashArea *area) {
+ GeoHashRange r[2] = {{0}};
+ geohashGetCoordRange(&r[0], &r[1]);
+ return geohashDecode(r[0], r[1], hash, area);
+}
+
+int geohashDecodeWGS84(const GeoHashBits hash, GeoHashArea *area) {
+ return geohashDecodeType(hash, area);
+}
+
+int geohashDecodeAreaToLongLat(const GeoHashArea *area, double *xy) {
+ if (!xy) return 0;
+ xy[0] = (area->longitude.min + area->longitude.max) / 2;
+ if (xy[0] > GEO_LONG_MAX) xy[0] = GEO_LONG_MAX;
+ if (xy[0] < GEO_LONG_MIN) xy[0] = GEO_LONG_MIN;
+ xy[1] = (area->latitude.min + area->latitude.max) / 2;
+ if (xy[1] > GEO_LAT_MAX) xy[1] = GEO_LAT_MAX;
+ if (xy[1] < GEO_LAT_MIN) xy[1] = GEO_LAT_MIN;
+ return 1;
+}
+
+int geohashDecodeToLongLatType(const GeoHashBits hash, double *xy) {
+ GeoHashArea area = {{0}};
+ if (!xy || !geohashDecodeType(hash, &area))
+ return 0;
+ return geohashDecodeAreaToLongLat(&area, xy);
+}
+
+int geohashDecodeToLongLatWGS84(const GeoHashBits hash, double *xy) {
+ return geohashDecodeToLongLatType(hash, xy);
+}
+
+static void geohash_move_x(GeoHashBits *hash, int8_t d) {
+ if (d == 0)
+ return;
+
+ uint64_t x = hash->bits & 0xaaaaaaaaaaaaaaaaULL;
+ uint64_t y = hash->bits & 0x5555555555555555ULL;
+
+ uint64_t zz = 0x5555555555555555ULL >> (64 - hash->step * 2);
+
+ if (d > 0) {
+ x = x + (zz + 1);
+ } else {
+ x = x | zz;
+ x = x - (zz + 1);
+ }
+
+ x &= (0xaaaaaaaaaaaaaaaaULL >> (64 - hash->step * 2));
+ hash->bits = (x | y);
+}
+
+static void geohash_move_y(GeoHashBits *hash, int8_t d) {
+ if (d == 0)
+ return;
+
+ uint64_t x = hash->bits & 0xaaaaaaaaaaaaaaaaULL;
+ uint64_t y = hash->bits & 0x5555555555555555ULL;
+
+ uint64_t zz = 0xaaaaaaaaaaaaaaaaULL >> (64 - hash->step * 2);
+ if (d > 0) {
+ y = y + (zz + 1);
+ } else {
+ y = y | zz;
+ y = y - (zz + 1);
+ }
+ y &= (0x5555555555555555ULL >> (64 - hash->step * 2));
+ hash->bits = (x | y);
+}
+
+void geohashNeighbors(const GeoHashBits *hash, GeoHashNeighbors *neighbors) {
+ neighbors->east = *hash;
+ neighbors->west = *hash;
+ neighbors->north = *hash;
+ neighbors->south = *hash;
+ neighbors->south_east = *hash;
+ neighbors->south_west = *hash;
+ neighbors->north_east = *hash;
+ neighbors->north_west = *hash;
+
+ geohash_move_x(&neighbors->east, 1);
+ geohash_move_y(&neighbors->east, 0);
+
+ geohash_move_x(&neighbors->west, -1);
+ geohash_move_y(&neighbors->west, 0);
+
+ geohash_move_x(&neighbors->south, 0);
+ geohash_move_y(&neighbors->south, -1);
+
+ geohash_move_x(&neighbors->north, 0);
+ geohash_move_y(&neighbors->north, 1);
+
+ geohash_move_x(&neighbors->north_west, -1);
+ geohash_move_y(&neighbors->north_west, 1);
+
+ geohash_move_x(&neighbors->north_east, 1);
+ geohash_move_y(&neighbors->north_east, 1);
+
+ geohash_move_x(&neighbors->south_east, 1);
+ geohash_move_y(&neighbors->south_east, -1);
+
+ geohash_move_x(&neighbors->south_west, -1);
+ geohash_move_y(&neighbors->south_west, -1);
+}
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