-
-
Notifications
You must be signed in to change notification settings - Fork 121
/
geohash.c
300 lines (210 loc) · 8.79 KB
/
geohash.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
/*
* geohash.c
* libgeohash
*
* Created by Derek Smith on 10/6/09.
* Copyright (c) 2010, SimpleGeo
* 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 the SimpleGeo 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 HOLDER 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"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#define MAX_LAT 90.0
#define MIN_LAT -90.0
#define MAX_LONG 180.0
#define MIN_LONG -180.0
#define NORTH 0
#define EAST 1
#define SOUTH 2
#define WEST 3
#define LENGTH_OF_DEGREE 111100 // meters
/*
* From Elasticsearch Guide:
* The highest-precision geohash of length 12 produces cells
* that cover less than a square metre of land.
*/
#define MAX_GEOHASH_LENGTH 12
typedef struct IntervalStruct {
double high;
double low;
} Interval;
/* Normal 32 characer map used for geohashing */
static char char_map[32] = "0123456789bcdefghjkmnpqrstuvwxyz";
/*
* The follow character maps were created by Dave Troy and used in his Javascript Geohashing
* library. http://github.com/davetroy/geohash-js
*/
static char *even_neighbors[] = {"p0r21436x8zb9dcf5h7kjnmqesgutwvy",
"bc01fg45238967deuvhjyznpkmstqrwx",
"14365h7k9dcfesgujnmqp0r2twvyx8zb",
"238967debc01fg45kmstqrwxuvhjyznp"
};
static char *odd_neighbors[] = {"bc01fg45238967deuvhjyznpkmstqrwx",
"p0r21436x8zb9dcf5h7kjnmqesgutwvy",
"238967debc01fg45kmstqrwxuvhjyznp",
"14365h7k9dcfesgujnmqp0r2twvyx8zb"
};
static char *even_borders[] = {"prxz", "bcfguvyz", "028b", "0145hjnp"};
static char *odd_borders[] = {"bcfguvyz", "prxz", "0145hjnp", "028b"};
unsigned int index_for_char(char c, char *string) {
int index = -1;
int string_amount = strlen(string);
int i;
for(i = 0; i < string_amount; i++) {
if(c == string[i]) {
index = i;
break;
}
}
return index;
}
char* get_neighbor(char *hash, int direction) {
int hash_length = strlen(hash);
char last_char = hash[hash_length - 1];
int is_odd = hash_length % 2;
char **border = is_odd ? odd_borders : even_borders;
char **neighbor = is_odd ? odd_neighbors : even_neighbors;
size_t geohash_b_size = MAX_GEOHASH_LENGTH + 1;
char *base = malloc(sizeof(char) * geohash_b_size);
snprintf(base, geohash_b_size, "%s", hash);
if(index_for_char(last_char, border[direction]) != -1)
base = get_neighbor(base, direction);
int neighbor_index = index_for_char(last_char, neighbor[direction]);
last_char = char_map[neighbor_index];
char *last_hash = malloc(sizeof(char) * 2);
last_hash[0] = last_char;
last_hash[1] = '\0';
strcat(base, last_hash);
free(last_hash);
return base;
}
char* geohash_encode(double lat, double lng, int precision) {
if(precision < 1 || precision > 12)
precision = 6;
char* hash = NULL;
if(lat <= 90.0 && lat >= -90.0 && lng <= 180.0 && lng >= -180.0) {
hash = (char*)malloc(sizeof(char) * (precision + 1));
hash[precision] = '\0';
precision *= 5.0;
Interval lat_interval = {MAX_LAT, MIN_LAT};
Interval lng_interval = {MAX_LONG, MIN_LONG};
Interval *interval;
double coord, mid;
int is_even = 1;
unsigned int hashChar = 0;
int i;
for(i = 1; i <= precision; i++) {
if(is_even) {
interval = &lng_interval;
coord = lng;
} else {
interval = &lat_interval;
coord = lat;
}
mid = (interval->low + interval->high) / 2.0;
hashChar = hashChar << 1;
if(coord > mid) {
interval->low = mid;
hashChar |= 0x01;
} else
interval->high = mid;
if(!(i % 5)) {
hash[(i - 1) / 5] = char_map[hashChar];
hashChar = 0;
}
is_even = !is_even;
}
}
return hash;
}
GeoCoord geohash_decode(char *hash) {
GeoCoord coordinate = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
if(hash) {
int char_amount = strlen(hash);
if(char_amount) {
unsigned int char_mapIndex;
Interval lat_interval = {MAX_LAT, MIN_LAT};
Interval lng_interval = {MAX_LONG, MIN_LONG};
Interval *interval;
int is_even = 1;
double delta;
int i, j;
for(i = 0; i < char_amount; i++) {
char_mapIndex = index_for_char(hash[i], (char*)char_map);
//JPM always false if(char_mapIndex < 0)
//JPM break;
// Interpret the last 5 bits of the integer
for(j = 0; j < 5; j++) {
interval = is_even ? &lng_interval : &lat_interval;
delta = (interval->high - interval->low) / 2.0;
if((char_mapIndex << j) & 0x0010)
interval->low += delta;
else
interval->high -= delta;
is_even = !is_even;
}
}
coordinate.latitude = lat_interval.high - ((lat_interval.high - lat_interval.low) / 2.0);
coordinate.longitude = lng_interval.high - ((lng_interval.high - lng_interval.low) / 2.0);
coordinate.north = lat_interval.high;
coordinate.east = lng_interval.high;
coordinate.south = lat_interval.low;
coordinate.west = lng_interval.low;
}
}
return coordinate;
}
char** geohash_neighbors(char *hash) {
char** neighbors = NULL;
if(hash) {
// N, NE, E, SE, S, SW, W, NW
neighbors = (char**)malloc(sizeof(char*) * 8);
neighbors[0] = get_neighbor(hash, NORTH);
neighbors[1] = get_neighbor(neighbors[0], EAST);
neighbors[2] = get_neighbor(hash, EAST);
neighbors[3] = get_neighbor(neighbors[2], SOUTH);
neighbors[4] = get_neighbor(hash, SOUTH);
neighbors[5] = get_neighbor(neighbors[4], WEST);
neighbors[6] = get_neighbor(hash, WEST);
neighbors[7] = get_neighbor(neighbors[6], NORTH);
}
return neighbors;
}
GeoBoxDimension geohash_dimensions_for_precision(int precision) {
GeoBoxDimension dimensions = {0.0, 0.0};
if(precision > 0) {
int lat_times_to_cut = precision * 5 / 2;
int lng_times_to_cut = precision * 5 / 2 + (precision % 2 ? 1 : 0);
double width = 360.0;
double height = 180.0;
int i;
for(i = 0; i < lat_times_to_cut; i++)
height /= 2.0;
for(i = 0; i < lng_times_to_cut; i++)
width /= 2.0;
dimensions.width = width;
dimensions.height = height;
}
return dimensions;
}