Move projection and tile arithmetic to its own file

projection.c

@@ -0,0 +1,68 @@
+#include <math.h>
+#include "projection.h"
+
+// http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
+void latlon2tile(double lat, double lon, int zoom, unsigned int *x, unsigned int *y) {
+	double lat_rad = lat * M_PI / 180;
+	unsigned long long n = 1LL << zoom;
+
+	long long llx = n * ((lon + 180) / 360);
+	long long lly = n * (1 - (log(tan(lat_rad) + 1/cos(lat_rad)) / M_PI)) / 2;
+
+	if (lat >= 85.0511) {
+		lly = 0;
+	}
+	if (lat <= -85.0511) {
+		lly = n - 1;
+	}
+
+	if (llx < 0) {
+		llx = 0;
+	}
+	if (lly < 0) {
+		lly = 0;
+	}
+	if (llx >= n) {
+		llx = n - 1;
+	}
+	if (lly >= n) {
+		lly = n - 1;
+	}
+
+	*x = llx;
+	*y = lly;
+}
+
+// http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
+void tile2latlon(unsigned int x, unsigned int y, int zoom, double *lat, double *lon) {
+	unsigned long long n = 1LL << zoom;
+	*lon = 360.0 * x / n - 180.0;
+	float lat_rad = atan(sinh(M_PI * (1 - 2.0 * y / n)));
+	*lat = lat_rad * 180 / M_PI;
+}
+
+unsigned long long encode(unsigned int wx, unsigned int wy) {
+	long long out = 0;
+
+	int i;
+	for (i = 0; i < 32; i++) {
+		long long v = ((wx >> (32 - (i + 1))) & 1) << 1;
+		v |= (wy >> (32 - (i + 1))) & 1;
+		v = v << (64 - 2 * (i + 1));
+
+		out |= v;
+	}
+
+
+	return out;
+}
+
+void decode(unsigned long long index, unsigned *wx, unsigned *wy) {
+	*wx = *wy = 0;
+
+	int i;
+	for (i = 0; i < 32; i++) {
+		*wx |= ((index >> (64 - 2 * (i + 1) + 1)) & 1) << (32 - (i + 1));
+		*wy |= ((index >> (64 - 2 * (i + 1) + 0)) & 1) << (32 - (i + 1));
+	}
+}