Fixes reversed: true.

Hey crystal, why don’t you have reversed ranges?

spec/test.cr

@@ -166,13 +166,17 @@ describe "DODB::DataBase" do
 				db << ship
 			end
 
+			# The two #each test iteration.
 			db.each_with_index do |item, index|
 				item.should eq Ship.all_ships[index]
 			end
 
 			db.each_with_index(reversed: true) do |item, index|
-				item.should eq Ship.all_ships.reverse[index]
+				item.should eq Ship.all_ships[index]
 			end
+
+			# Actual reversal is tested here.
+			db.to_a(reversed: true).should eq db.to_a.reverse
 		end
 
 		it "respects the provided offsets if any" do

src/dodb.cr

@@ -179,18 +179,25 @@ class DODB::DataBase(V)
 	end
 
 	private def each_key(reversed = false)
-		range = if reversed
-					(last_index..0)
-				else
-					(0..last_index)
-				end
+		start = 0
+		_end = last_index
+		step = 1
 
-		range.each do |key|
+		if reversed
+			start = _end
+			_end = 0
+			step = -1
+		end
+
+		key = start
+		while step == 1 ? key <= _end : key >= _end
 			full_path = file_path key
 
-			next unless File.exists? full_path
+			if File.exists? full_path
+				yield key, full_path
+			end
 
-			yield key, full_path
+			key = key + step
 		end
 	end