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262 lines
8.2 KiB
C
262 lines
8.2 KiB
C
/*
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* Copyright (c) 2013-2014, yinqiwen <yinqiwen@gmail.com>
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* Copyright (c) 2014, Matt Stancliff <matt@genges.com>.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Redis nor the names of its contributors may be used
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* to endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "geohash.h"
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/**
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* Hashing works like this:
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* Divide the world into 4 buckets. Label each one as such:
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* -----------------
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* | | |
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* | | |
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* | 0,1 | 1,1 |
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* -----------------
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* | | |
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* | | |
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* | 0,0 | 1,0 |
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* -----------------
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*/
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void geohashGetCoordRange(GeoHashRange *lat_range, GeoHashRange *long_range) {
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/* These are constraints from EPSG:900913 / EPSG:3785 / OSGEO:41001 */
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/* We can't geocode at the north/south pole. */
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lat_range->max = 85.05112878;
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lat_range->min = -85.05112878;
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long_range->max = 180.0;
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long_range->min = -180.0;
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}
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int geohashEncode(GeoHashRange *lat_range, GeoHashRange *long_range,
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double latitude, double longitude, uint8_t step,
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GeoHashBits *hash) {
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uint8_t i;
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if (NULL == hash || step > 32 || step == 0 || RANGEPISZERO(lat_range) ||
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RANGEPISZERO(long_range)) {
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return 0;
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}
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hash->bits = 0;
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hash->step = step;
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if (latitude < lat_range->min || latitude > lat_range->max ||
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longitude < long_range->min || longitude > long_range->max) {
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return 0;
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}
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for (i = 0; i < step; i++) {
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uint8_t lat_bit, long_bit;
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if (lat_range->max - latitude >= latitude - lat_range->min) {
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lat_bit = 0;
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lat_range->max = (lat_range->max + lat_range->min) / 2;
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} else {
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lat_bit = 1;
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lat_range->min = (lat_range->max + lat_range->min) / 2;
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}
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if (long_range->max - longitude >= longitude - long_range->min) {
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long_bit = 0;
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long_range->max = (long_range->max + long_range->min) / 2;
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} else {
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long_bit = 1;
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long_range->min = (long_range->max + long_range->min) / 2;
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}
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hash->bits <<= 1;
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hash->bits += long_bit;
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hash->bits <<= 1;
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hash->bits += lat_bit;
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}
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return 1;
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}
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int geohashEncodeType(double latitude, double longitude, uint8_t step, GeoHashBits *hash) {
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GeoHashRange r[2] = { { 0 } };
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geohashGetCoordRange(&r[0], &r[1]);
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return geohashEncode(&r[0], &r[1], latitude, longitude, step, hash);
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}
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int geohashEncodeWGS84(double latitude, double longitude, uint8_t step,
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GeoHashBits *hash) {
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return geohashEncodeType(latitude, longitude, step, hash);
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}
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static inline uint8_t get_bit(uint64_t bits, uint8_t pos) {
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return (bits >> pos) & 0x01;
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}
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int geohashDecode(const GeoHashRange lat_range, const GeoHashRange long_range,
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const GeoHashBits hash, GeoHashArea *area) {
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uint8_t i;
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if (HASHISZERO(hash) || NULL == area || RANGEISZERO(lat_range) ||
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RANGEISZERO(long_range)) {
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return 0;
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}
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area->hash = hash;
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area->latitude.min = lat_range.min;
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area->latitude.max = lat_range.max;
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area->longitude.min = long_range.min;
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area->longitude.max = long_range.max;
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for (i = 0; i < hash.step; i++) {
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uint8_t lat_bit, long_bit;
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long_bit = get_bit(hash.bits, (hash.step - i) * 2 - 1);
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lat_bit = get_bit(hash.bits, (hash.step - i) * 2 - 2);
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if (lat_bit == 0) {
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area->latitude.max = (area->latitude.max + area->latitude.min) / 2;
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} else {
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area->latitude.min = (area->latitude.max + area->latitude.min) / 2;
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}
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if (long_bit == 0) {
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area->longitude.max =
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(area->longitude.max + area->longitude.min) / 2;
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} else {
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area->longitude.min =
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(area->longitude.max + area->longitude.min) / 2;
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}
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}
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return 1;
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}
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int geohashDecodeType(const GeoHashBits hash, GeoHashArea *area) {
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GeoHashRange r[2] = { { 0 } };
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geohashGetCoordRange(&r[0], &r[1]);
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return geohashDecode(r[0], r[1], hash, area);
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}
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int geohashDecodeWGS84(const GeoHashBits hash, GeoHashArea *area) {
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return geohashDecodeType(hash, area);
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}
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int geohashDecodeAreaToLatLong(const GeoHashArea *area, double *latlong) {
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double y, x;
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if (!latlong) return 0;
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y = (area->latitude.min + area->latitude.max) / 2;
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x = (area->longitude.min + area->longitude.max) / 2;
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latlong[0] = y;
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latlong[1] = x;
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return 1;
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}
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int geohashDecodeToLatLongType(const GeoHashBits hash, double *latlong) {
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GeoHashArea area = { { 0 } };
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if (!latlong || !geohashDecodeType(hash, &area))
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return 0;
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return geohashDecodeAreaToLatLong(&area, latlong);
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}
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int geohashDecodeToLatLongWGS84(const GeoHashBits hash, double *latlong) {
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return geohashDecodeToLatLongType(hash, latlong);
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}
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int geohashDecodeToLatLongMercator(const GeoHashBits hash, double *latlong) {
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return geohashDecodeToLatLongType(hash, latlong);
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}
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static void geohash_move_x(GeoHashBits *hash, int8_t d) {
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if (d == 0)
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return;
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uint64_t x = hash->bits & 0xaaaaaaaaaaaaaaaaLL;
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uint64_t y = hash->bits & 0x5555555555555555LL;
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uint64_t zz = 0x5555555555555555LL >> (64 - hash->step * 2);
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if (d > 0) {
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x = x + (zz + 1);
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} else {
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x = x | zz;
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x = x - (zz + 1);
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}
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x &= (0xaaaaaaaaaaaaaaaaLL >> (64 - hash->step * 2));
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hash->bits = (x | y);
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}
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static void geohash_move_y(GeoHashBits *hash, int8_t d) {
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if (d == 0)
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return;
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uint64_t x = hash->bits & 0xaaaaaaaaaaaaaaaaLL;
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uint64_t y = hash->bits & 0x5555555555555555LL;
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uint64_t zz = 0xaaaaaaaaaaaaaaaaLL >> (64 - hash->step * 2);
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if (d > 0) {
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y = y + (zz + 1);
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} else {
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y = y | zz;
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y = y - (zz + 1);
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}
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y &= (0x5555555555555555LL >> (64 - hash->step * 2));
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hash->bits = (x | y);
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}
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void geohashNeighbors(const GeoHashBits *hash, GeoHashNeighbors *neighbors) {
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neighbors->east = *hash;
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neighbors->west = *hash;
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neighbors->north = *hash;
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neighbors->south = *hash;
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neighbors->south_east = *hash;
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neighbors->south_west = *hash;
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neighbors->north_east = *hash;
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neighbors->north_west = *hash;
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geohash_move_x(&neighbors->east, 1);
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geohash_move_y(&neighbors->east, 0);
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geohash_move_x(&neighbors->west, -1);
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geohash_move_y(&neighbors->west, 0);
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geohash_move_x(&neighbors->south, 0);
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geohash_move_y(&neighbors->south, -1);
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geohash_move_x(&neighbors->north, 0);
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geohash_move_y(&neighbors->north, 1);
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geohash_move_x(&neighbors->north_west, -1);
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geohash_move_y(&neighbors->north_west, 1);
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geohash_move_x(&neighbors->north_east, 1);
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geohash_move_y(&neighbors->north_east, 1);
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geohash_move_x(&neighbors->south_east, 1);
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geohash_move_y(&neighbors->south_east, -1);
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geohash_move_x(&neighbors->south_west, -1);
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geohash_move_y(&neighbors->south_west, -1);
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}
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