Merged pull request php-geospatial#20

.travis.yml

@@ -16,7 +16,7 @@ env:
 before_script:
   - phpize
   - EXTRA_LDFLAGS="-precious-files-regex .libs/geospatial.gcno" LDFLAGS="-lgcov" CFLAGS="-Wall -ggdb3 -fno-strict-aliasing -coverage -O0" ./configure --enable-geospatial
-  - make -j 5 test && if ls tests/*.diff >/dev/null 2>&1; then echo "Tests failed" && exit 1; fi
+  - make -j 5 test && if ls tests/*.diff >/dev/null 2>&1; then echo "Tests failed" && cat tests/*.diff && exit 1; fi
   - gcov --object-directory .libs *.c
   - bash <(curl -s https://codecov.io/bash)
 

README.rst

@@ -170,3 +170,32 @@ you would use::
 	$point2 = [ 'type' => 'Point', 'coordinates' => [ 15, 10 ] ];
 
 	var_dump(fraction_along_gc_line($point1, $point2, 0.25));
+
+Geohashing
+----------
+
+The `geohash_encode` function can be used to convert GeoJSON Point to a
+geohash of a specific length (in this case, 12)::
+
+	$point = [ 'type' => 'Point', 'coordinates' => [ 16.4, 48.2 ] ];
+	echo geohash_encode( $point, 12 );
+
+Which outputs::
+    
+	u2edjnw17enr
+
+Similarly, a hashed coordinates pair can be decoded using `geohash_decode`
+function::
+
+	var_dump(geohash_decode('u2edjnw17enr'));
+	array(2) {
+	  ["type"]=>
+	  string(5) "Point"
+	  ["coordinates"]=>
+	  array(2) {
+		[0]=>
+		float(16.40000006184)
+		[1]=>
+		float(48.199999993667)
+	  }
+	}

config.m4

@@ -5,5 +5,5 @@ PHP_ARG_ENABLE(geospatial, whether to enable geospatial support,
 [  --enable-geospatial           Enable geospatial support])
 
 if test "$PHP_GEOSPATIAL" != "no"; then
-  PHP_NEW_EXTENSION(geospatial, geospatial.c geo_array.c, $ext_shared)
+  PHP_NEW_EXTENSION(geospatial, geospatial.c geo_array.c geohash.c, $ext_shared)
 fi

geo_array.h

@@ -18,6 +18,8 @@
   |          Marcus Deglos <[email protected]>                           |
   +----------------------------------------------------------------------+
 */
+#ifndef PHP_GEO_ARRAY_H
+#define PHP_GEO_ARRAY_H
 
 typedef struct geo_array {
 	double  *x;
@@ -30,3 +32,4 @@ typedef struct geo_array {
 geo_array *geo_array_ctor(int element_count);
 void geo_array_add(geo_array *points, double lat, double lon);
 void geo_array_dtor(geo_array *points);
+#endif /* PHP_GEO_ARRAY_H */

geo_lat_long.h

@@ -0,0 +1,27 @@
+/*
+  +----------------------------------------------------------------------+
+  | PHP Version 7                                                        |
+  +----------------------------------------------------------------------+
+  | Copyright (c) 2017 The PHP Group                                     |
+  +----------------------------------------------------------------------+
+  | This source file is subject to version 3.01 of the PHP license,      |
+  | that is bundled with this package in the file LICENSE, and is        |
+  | available through the world-wide-web at the following url:           |
+  | http://www.php.net/license/3_01.txt                                  |
+  | If you did not receive a copy of the PHP license and are unable to   |
+  | obtain it through the world-wide-web, please send a note to          |
+  | [email protected] so we can mail you a copy immediately.               |
+  +----------------------------------------------------------------------+
+  | Authors: Emir Beganovic <[email protected]>                               |
+  +----------------------------------------------------------------------+
+*/
+#ifndef PHP_GEO_LAT_LONG_H
+#define PHP_GEO_LAT_LONG_H
+
+typedef struct {
+	double x;
+	double y;
+	double z;
+} geo_lat_long;
+
+#endif

geohash.c

@@ -0,0 +1,140 @@
+/*
+  +----------------------------------------------------------------------+
+  | PHP Version 7                                                        |
+  +----------------------------------------------------------------------+
+  | Copyright (c) 2017 The PHP Group                                     |
+  +----------------------------------------------------------------------+
+  | This source file is subject to version 3.01 of the PHP license,      |
+  | that is bundled with this package in the file LICENSE, and is        |
+  | available through the world-wide-web at the following url:           |
+  | http://www.php.net/license/3_01.txt                                  |
+  | If you did not receive a copy of the PHP license and are unable to   |
+  | obtain it through the world-wide-web, please send a note to          |
+  | [email protected] so we can mail you a copy immediately.               |
+  +----------------------------------------------------------------------+
+  | Authors: Emir Beganovic <[email protected]>                               |
+  +----------------------------------------------------------------------+
+*/
+
+#include <stdlib.h>
+
+#include "php.h"
+#include "geo_lat_long.h"
+#include "geohash.h"
+
+#define MAX_LAT   90.0
+#define MIN_LAT  -90.0
+
+#define MAX_LONG  180.0
+#define MIN_LONG -180.0
+
+typedef struct interval_string {
+	double high;
+	double low;
+} interval_struct;
+
+static char char_map[32] = "0123456789bcdefghjkmnpqrstuvwxyz";
+static size_t char_map_size = sizeof(char_map);
+
+char *php_geo_geohash_encode(double latitude, double longitude, int precision)
+{
+	char            *hash;
+	int              steps;
+	double           coord, mid;
+	int              is_even = 1;
+	unsigned int     hash_char = 0;
+	int              i;
+	interval_struct  lat_interval = { MAX_LAT, MIN_LAT };
+	interval_struct  lng_interval = { MAX_LONG, MIN_LONG };
+	interval_struct *interval;
+
+	hash = (char*)safe_emalloc(precision, sizeof(char), 1);
+
+	hash[precision] = '\0';
+	steps = precision * 5.0;
+
+	for (i = 1; i <= steps; i++) {
+		if (is_even) {
+			interval = &lng_interval;
+			coord = longitude;
+		} else {
+			interval = &lat_interval;
+			coord = latitude;
+		}
+
+		mid = (interval->low + interval->high) / 2.0;
+		hash_char = hash_char << 1;
+
+		if (coord > mid) {
+			interval->low = mid;
+			hash_char |= 0x01;
+		} else {
+			interval->high = mid;
+		}
+
+		if (!(i % 5)) {
+			hash[(i - 1) / 5] = char_map[hash_char];
+			hash_char = 0;
+		}
+
+		is_even = !is_even;
+	}
+
+	return hash;
+}
+
+static unsigned int index_for_char(char c, char *string, size_t string_amount)
+{
+	unsigned int index = -1;
+	int          i;
+
+	for (i = 0; i < string_amount; i++) {
+		if (c == string[i]) {
+			index = i;
+			break;
+		}
+	}
+
+	return index;
+}
+
+geo_lat_long php_geo_geohash_decode(char *hash, size_t char_amount)
+{
+	geo_lat_long coordinate;
+
+	if (char_amount) {
+		int              charmap_index;
+		double           delta;
+		int              i, j;
+		interval_struct  lat_interval = { MAX_LAT, MIN_LAT };
+		interval_struct  lng_interval = { MAX_LONG, MIN_LONG };
+		interval_struct *interval;
+
+		int is_even = 1;
+
+		for (i = 0; i < char_amount; i++) {
+			charmap_index = index_for_char(hash[i], char_map, char_map_size);
+
+			/* 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 ((charmap_index << j) & 0x0010) {
+					interval->low += delta;
+				} else {
+					interval->high -= delta;
+				}
+
+				is_even = !is_even;
+			}
+		}
+
+		coordinate.x = lat_interval.high - ((lat_interval.high - lat_interval.low) / 2.0);
+		coordinate.y = lng_interval.high - ((lng_interval.high - lng_interval.low) / 2.0);
+		coordinate.z = 0;
+	}
+
+	return coordinate;
+}

geohash.h

@@ -0,0 +1,24 @@
+/*
+  +----------------------------------------------------------------------+
+  | PHP Version 5/7                                                      |
+  +----------------------------------------------------------------------+
+  | Copyright (c) 2017 The PHP Group                                     |
+  +----------------------------------------------------------------------+
+  | This source file is subject to version 3.01 of the PHP license,      |
+  | that is bundled with this package in the file LICENSE, and is        |
+  | available through the world-wide-web at the following url:           |
+  | http://www.php.net/license/3_01.txt                                  |
+  | If you did not receive a copy of the PHP license and are unable to   |
+  | obtain it through the world-wide-web, please send a note to          |
+  | [email protected] so we can mail you a copy immediately.               |
+  +----------------------------------------------------------------------+
+  | Authors: Emir Beganovic <[email protected]>                               |
+  +----------------------------------------------------------------------+
+*/
+#ifndef PHP_GEOHASH_H
+#define PHP_GEOHASH_H
+
+char *php_geo_geohash_encode(double lat, double lng, int precision);
+geo_lat_long php_geo_geohash_decode(char *hash, size_t hash_len);
+
+#endif /* PHP_GEOHASH_H */