QuadTile infrastructure.

lib/quad_tile/extconf.rb

@@ -0,0 +1,3 @@
+require "mkmf"
+
+create_makefile("quad_tile_so")

lib/quad_tile/quad_tile.c

@@ -0,0 +1,47 @@
+#include "ruby.h"
+#include "quad_tile.h"
+
+static VALUE tile_for_point(VALUE self, VALUE lat, VALUE lon)
+{
+   unsigned int x = lon2x(NUM2DBL(lon));
+   unsigned int y = lat2y(NUM2DBL(lat));
+
+   return UINT2NUM(xy2tile(x, y));
+}
+
+static VALUE tiles_for_area(VALUE self, VALUE minlat, VALUE minlon, VALUE maxlat, VALUE maxlon)
+{
+   unsigned int minx = lon2x(NUM2DBL(minlon));
+   unsigned int maxx = lon2x(NUM2DBL(maxlon));
+   unsigned int miny = lat2y(NUM2DBL(minlat));
+   unsigned int maxy = lat2y(NUM2DBL(maxlat));
+   VALUE        tiles = rb_ary_new();
+   unsigned int x;
+   unsigned int y;
+
+   for (x = minx; x <= maxx; x++)
+   {
+      for (y = miny; y <= maxy; y++)
+      {
+         rb_ary_push(tiles, UINT2NUM(xy2tile(x, y)));
+      }
+   }
+
+   return tiles;
+}
+
+static VALUE tile_for_xy(VALUE self, VALUE x, VALUE y)
+{
+   return UINT2NUM(xy2tile(NUM2UINT(x), NUM2UINT(y)));
+}
+
+void Init_quad_tile_so(void)
+{
+   VALUE m = rb_define_module("QuadTile");
+
+   rb_define_module_function(m, "tile_for_point", tile_for_point, 2);
+   rb_define_module_function(m, "tiles_for_area", tiles_for_area, 4);
+   rb_define_module_function(m, "tile_for_xy", tile_for_xy, 2);
+
+   return;
+}

lib/quad_tile/quad_tile.h

@@ -0,0 +1,25 @@
+#include <math.h>
+
+inline unsigned int xy2tile(unsigned int x, unsigned int y)
+{
+   unsigned int tile = 0;
+   int          i;
+
+   for (i = 15; i >= 0; i--)
+   {
+      tile = (tile << 1) | ((x >> i) & 1);
+      tile = (tile << 1) | ((y >> i) & 1);
+   }
+
+   return tile;
+}
+
+inline unsigned int lon2x(double lon)
+{
+   return round((lon + 180.0) * 65535.0 / 360.0);
+}
+
+inline unsigned int lat2y(double lat)
+{
+   return round((lat + 90.0) * 65535.0 / 180.0);
+}