Fix #57 by using core.hash_node_position for reliable indexing

The previously used minetest.serialize function may provide different
results for the same table in certain circumstances, thus it is not
suitable for generating strings to index tables with.

lua/api.lua

@@ -89,8 +89,8 @@ function drawers.drawer_on_destruct(pos)
 	drawers.remove_visuals(pos)
 
 	-- clean up visual cache
-	if drawers.drawer_visuals[core.serialize(pos)] then
-		drawers.drawer_visuals[core.serialize(pos)] = nil
+	if drawers.drawer_visuals[core.hash_node_position(pos)] then
+		drawers.drawer_visuals[core.hash_node_position(pos)] = nil
 	end
 end
 
@@ -193,7 +193,7 @@ end
 	Inserts an incoming stack into a drawer and uses all slots.
 ]]
 function drawers.drawer_insert_object_from_tube(pos, node, stack, direction)
-	local drawer_visuals = drawers.drawer_visuals[core.serialize(pos)]
+	local drawer_visuals = drawers.drawer_visuals[core.hash_node_position(pos)]
 	if not drawer_visuals then
         return stack
     end
@@ -231,7 +231,7 @@ end
 	Returns whether a stack can be (partially) inserted to any slot of a drawer.
 ]]
 function drawers.drawer_can_insert_stack_from_tube(pos, node, stack, direction)
-	local drawer_visuals = drawers.drawer_visuals[core.serialize(pos)]
+	local drawer_visuals = drawers.drawer_visuals[core.hash_node_position(pos)]
 	if not drawer_visuals then
 		return false
 	end
@@ -245,7 +245,7 @@ function drawers.drawer_can_insert_stack_from_tube(pos, node, stack, direction)
 end
 
 function drawers.drawer_take_item(pos, itemstack)
-	local drawer_visuals = drawers.drawer_visuals[core.serialize(pos)]
+	local drawer_visuals = drawers.drawer_visuals[core.hash_node_position(pos)]
 
 	if not drawer_visuals then
 		return ItemStack("")

lua/controller.lua

@@ -274,7 +274,7 @@ local function controller_insert_to_drawers(pos, stack)
 		-- will put the items in the drawer
 		if content.name == stack:get_name() and
 				content.count < content.maxCount and
-				drawers.drawer_visuals[core.serialize(drawer_pos)] then
+				drawers.drawer_visuals[core.hash_node_position(drawer_pos)] then
 			return drawers.drawer_insert_object(drawer_pos, stack, visualid)
 		end
 	elseif drawer_net_index["empty"] then
@@ -284,7 +284,7 @@ local function controller_insert_to_drawers(pos, stack)
 
 		-- If the drawer is still empty and the drawer entity is loaded, we will
 		-- put the items in the drawer
-		if content.name == "" and drawers.drawer_visuals[core.serialize(drawer_pos)] then
+		if content.name == "" and drawers.drawer_visuals[core.hash_node_position(drawer_pos)] then
 			local leftover = drawers.drawer_insert_object(drawer_pos, stack, visualid)
 
 			-- Add the item to the drawers table index and set the empty one to nil

lua/helpers.lua

@@ -215,7 +215,7 @@ end
 	visualid can be: "", "1", "2", ... or 1, 2, ...
 ]]
 function drawers.get_visual(pos, visualid)
-	local drawer_visuals = drawers.drawer_visuals[core.serialize(pos)]
+	local drawer_visuals = drawers.drawer_visuals[core.hash_node_position(pos)]
 	if not drawer_visuals then
 		return nil
 	end
@@ -256,7 +256,7 @@ function drawers.update_drawer_upgrades(pos)
 	stackMaxFactor = stackMaxFactor / drawerType
 
 	-- set the new stack max factor in all visuals
-	local drawer_visuals = drawers.drawer_visuals[core.serialize(pos)]
+	local drawer_visuals = drawers.drawer_visuals[core.hash_node_position(pos)]
 	if not drawer_visuals then return end
 
 	for _,visual in pairs(drawer_visuals) do

lua/visual.lua

@@ -89,7 +89,7 @@ core.register_entity("drawers:visual", {
 		-- PLEASE contact me, if this is wrong
 		local vId = self.visualId
 		if vId == "" then vId = 1 end
-		local posstr = core.serialize(self.drawer_pos)
+		local posstr = core.hash_node_position(self.drawer_pos)
 		if not drawers.drawer_visuals[posstr] then
 			drawers.drawer_visuals[posstr] = {[vId] = self}
 		else