QuadTile infrastructure.

[rails.git] / lib / quad_tile.rb

diff --git a/lib/quad_tile.rb b/lib/quad_tile.rb
new file mode 100644 (file)
index 0000000..cb1b5a0
--- /dev/null
+++ b/lib/quad_tile.rb
@@ -0,0 +1,81 @@
+module QuadTile
+  begin
+    require "quad_tile/quad_tile_so"
+  rescue MissingSourceFile
+    def self.tile_for_point(lat, lon)
+      x = ((lon + 180) * 65535 / 360).round
+      y = ((lat + 90) * 65535 / 180).round
+
+      return tile_for_xy(x, y)
+    end
+
+    def self.tiles_for_area(minlat, minlon, maxlat, maxlon)
+      minx = ((minlon + 180) * 65535 / 360).round
+      maxx = ((maxlon + 180) * 65535 / 360).round
+      miny = ((minlat + 90) * 65535 / 180).round
+      maxy = ((maxlat + 90) * 65535 / 180).round
+      tiles = []
+
+      minx.upto(maxx) do |x|
+        miny.upto(maxy) do |y|
+          tiles << tile_for_xy(x, y)
+        end
+      end
+
+      return tiles
+    end
+
+    def self.tile_for_xy(x, y)
+      t = 0
+
+      16.times do
+        t = t << 1
+        t = t | 1 unless (x & 0x8000).zero?
+        x <<= 1
+        t = t << 1
+        t = t | 1 unless (y & 0x8000).zero?
+        y <<= 1
+      end
+
+      return t
+    end
+  end
+
+  def self.sql_for_area(minlat, minlon, maxlat, maxlon)
+    sql = Array.new
+    single = Array.new
+
+    iterate_tiles_for_area(minlat, minlon, maxlat, maxlon) do |first,last|
+      if first == last
+        single.push(first)
+      else
+        sql.push("tile BETWEEN #{first} AND #{last}")
+      end
+    end
+
+    sql.push("tile IN (#{single.join(',')})") if single.size > 0
+
+    return "( " + sql.join(" OR ") + " )"
+  end
+
+  def self.iterate_tiles_for_area(minlat, minlon, maxlat, maxlon)
+    tiles = tiles_for_area(minlat, minlon, maxlat, maxlon)
+    first = last = nil
+
+    tiles.sort.each do |tile|
+      if last.nil?
+        first = last = tile
+      elsif tile == last + 1
+        last = tile
+      else
+        yield first, last
+
+        first = last = tile
+      end
+    end
+
+    yield first, last unless last.nil?
+  end
+
+  private_class_method :tile_for_xy, :iterate_tiles_for_area
+end