replace trackdb by nodedb

- trackdb is kept for large rail networks to still work but not saved anymore
- saving node name and param2 instead of track connections, so also signals can be saved.
- small serialization format
- fast access times, almost no redundancy

10 files changed, 484 insertions, 241 deletions

diff --git a/advtrains/advtrains/atc.lua b/advtrains/advtrains/atc.lua
index e015d47..ece7075 100644
--- a/advtrains/advtrains/atc.lua
+++ b/advtrains/advtrains/atc.lua
@@ -3,7 +3,13 @@
 
 local atc={}
 -- ATC persistence table. advtrains.atc is created by init.lua when it loads the save file.
-atc.controllers = advtrains.atc.controllers
+atc.controllers = {}
+function atc.load_data(data)
+	atc.controllers = data and data.controllers or {}
+end
+function atc.save_data()
+	return atc.controllers
+end
 --contents: {command="...", arrowconn=0-15 where arrow points}
 
 --call from advtrains.detector subprogram
@@ -52,8 +58,8 @@ end
 
 --nodes
 local idxtrans={static=1, mesecon=2, digiline=3}
-local apn_func=function(pos)
-	advtrains.reset_trackdb_position(pos)
+local apn_func=function(pos, node)
+	advtrains.ndb.update(pos, node)
 	local meta=minetest.get_meta(pos)
 	if meta then
 		meta:set_string("infotext", "ATC controller, unconfigured.")
@@ -72,10 +78,9 @@ advtrains.register_tracks("default", {
 	get_additional_definiton = function(def, preset, suffix, rotation)
 		return {
 			after_place_node=apn_func,
-			on_place_rail=apn_func,
 			after_dig_node=function(pos)
 				advtrains.invalidate_all_paths()
-				advtrains.reset_trackdb_position(pos)
+				advtrains.ndb.clear(pos)
 				local pts=minetest.pos_to_string(pos)
 				atc.controllers[pts]=nil
 			end,
diff --git a/advtrains/advtrains/debugitems.lua b/advtrains/advtrains/debugitems.lua
index b3164ff..dcc95d9 100644
--- a/advtrains/advtrains/debugitems.lua
+++ b/advtrains/advtrains/debugitems.lua
@@ -24,13 +24,5 @@ minetest.register_tool("advtrains:tunnelborer",
 			end
 		end
 	end,
---[[
-^  default: nil
-^ Function must return either nil if no item shall be removed from
-inventory, or an itemstack to replace the original itemstack.
-e.g. itemstack:take_item(); return itemstack
-^ Otherwise, the function is free to do what it wants.
-^ The default functions handle regular use cases.
-]]
 }
-) 
+)
diff --git a/advtrains/advtrains/init.lua b/advtrains/advtrains/init.lua
index 74201b5..c8c4b56 100644
--- a/advtrains/advtrains/init.lua
+++ b/advtrains/advtrains/init.lua
@@ -1,7 +1,6 @@
 --advtrains
 
---create the base table structure.
-advtrains={atc={controllers={}}, detector={}, trackplacer={}, trains={}, trackdb={}, wagon_save={}}
+advtrains = {trains={}, wagon_save={}}
 
 advtrains.modpath = minetest.get_modpath("advtrains")
 
@@ -57,7 +56,21 @@ advtrains.meseconrules =
  {x=0,  y=-1, z=-1},
  {x=0, y=-2, z=0}}
  
+dofile(advtrains.modpath.."/trainlogic.lua")
+dofile(advtrains.modpath.."/trainhud.lua")
+dofile(advtrains.modpath.."/trackplacer.lua")
+dofile(advtrains.modpath.."/tracks.lua")
+dofile(advtrains.modpath.."/atc.lua")
+dofile(advtrains.modpath.."/wagons.lua")
 
+dofile(advtrains.modpath.."/trackdb_legacy.lua")
+dofile(advtrains.modpath.."/nodedb.lua")
+dofile(advtrains.modpath.."/couple.lua")
+dofile(advtrains.modpath.."/damage.lua")
+
+dofile(advtrains.modpath.."/signals.lua")
+dofile(advtrains.modpath.."/misc_nodes.lua")
+dofile(advtrains.modpath.."/crafting.lua")
 
 --load/save
 
@@ -70,9 +83,11 @@ else
 	if type(tbl) == "table" then
 		if tbl.version then
 			--congrats, we have the new save format.
-			advtrains.atc.controllers = tbl.atc_controllers
 			advtrains.trains = tbl.trains
 			advtrains.wagon_save = tbl.wagon_save
+			advtrains.ndb.load_data(tbl.ndb)
+			advtrains.atc.load_data(tbl.atc)
+			--advtrains.latc.load_data(tbl.latc)
 		else
 			--oh no, its the old one...
 			advtrains.trains=tbl
@@ -110,7 +125,7 @@ else
 end
 
 advtrains.save = function()
-	atprint("saving")
+	--atprint("saving")
 	advtrains.invalidate_all_paths()
 	
 	-- update wagon saves
@@ -134,14 +149,15 @@ advtrains.save = function()
 			data.discouple=nil
 		end
 	end
-	--atprint(dump(advtrains.wagon_save))
 	
 	--versions:
 	-- 1 - Initial new save format.
 	local save_tbl={
 		trains = advtrains.trains,
 		wagon_save = advtrains.wagon_save,
-		atc_controllers = advtrains.atc.controllers,
+		atc = advtrains.atc.save_data(),
+		--latc = advtrains.latc.save_data(),
+		ndb = advtrains.ndb.save_data(),
 		version = 1,
 	}
 	local datastr = minetest.serialize(save_tbl)
@@ -160,18 +176,5 @@ end
 minetest.register_on_shutdown(advtrains.save)
 
 
-dofile(advtrains.modpath.."/trainlogic.lua")
-dofile(advtrains.modpath.."/trainhud.lua")
-dofile(advtrains.modpath.."/trackplacer.lua")
-dofile(advtrains.modpath.."/tracks.lua")
-dofile(advtrains.modpath.."/atc.lua")
-dofile(advtrains.modpath.."/wagons.lua")
 
-dofile(advtrains.modpath.."/pseudoload.lua")
-dofile(advtrains.modpath.."/couple.lua")
-dofile(advtrains.modpath.."/damage.lua")
-
-dofile(advtrains.modpath.."/signals.lua")
-dofile(advtrains.modpath.."/misc_nodes.lua")
-dofile(advtrains.modpath.."/crafting.lua")
 
diff --git a/advtrains/advtrains/lua_atc.lua b/advtrains/advtrains/lua_atc.lua
new file mode 100644
index 0000000..313d70d
--- /dev/null
+++ b/advtrains/advtrains/lua_atc.lua
@@ -0,0 +1,166 @@
+-------------
+--LUA ATC controllers
+
+local latc={}
+
+function latc.load_data(data)
+end
+function latc.save_data()
+	return stuff
+end
+
+latc.data
+latc.env_cdata
+latc.init_code=""
+latc.step_code=""
+
+advtrains.fpath_latc=minetest.get_worldpath().."/advtrains_latc"
+local file, err = io.open(advtrains.fpath_atc, "r")
+if not file then
+	local er=err or "Unknown Error"
+	atprint("Failed loading advtrains latc save file "..er)
+else
+	local tbl = minetest.deserialize(file:read("*a"))
+	if type(tbl) == "table" then
+		atc.controllers=tbl.controllers
+	end
+	file:close()
+end
+function latc.save()
+	
+	local datastr = minetest.serialize({controllers = atc.controllers})
+	if not datastr then
+		minetest.log("error", " Failed to serialize latc data!")
+		return
+	end
+	local file, err = io.open(advtrains.fpath_atc, "w")
+	if err then
+		return err
+	end
+	file:write(datastr)
+	file:close()
+end
+
+--Privilege
+--Only trusted players should be enabled to build stuff which can break the server.
+--If I later decide to have multiple environments ('data' tables), I better store an owner for every controller for future reference.
+
+minetest.register_privilege("advtrains_lua_atc", { description = "Player can place and modify LUA ATC components. Grant with care! Allows to execute bad LUA code.", give_to_singleplayer = false, default= false })
+
+--Environment
+--Code from mesecons_luacontroller (credit goes to Jeija and mesecons contributors)
+
+local safe_globals = {
+	"assert", "error", "ipairs", "next", "pairs", "select",
+	"tonumber", "tostring", "type", "unpack", "_VERSION"
+}
+local function safe_print(param)
+	print(dump(param))
+end
+
+local function safe_date()
+	return(os.date("*t",os.time()))
+end
+
+-- string.rep(str, n) with a high value for n can be used to DoS
+-- the server. Therefore, limit max. length of generated string.
+local function safe_string_rep(str, n)
+	if #str * n > mesecon.setting("luacontroller_string_rep_max", 64000) then
+		debug.sethook() -- Clear hook
+		error("string.rep: string length overflow", 2)
+	end
+
+	return string.rep(str, n)
+end
+
+-- string.find with a pattern can be used to DoS the server.
+-- Therefore, limit string.find to patternless matching.
+local function safe_string_find(...)
+	if (select(4, ...)) ~= true then
+		debug.sethook() -- Clear hook
+		error("string.find: 'plain' (fourth parameter) must always be true in a LuaController")
+	end
+
+	return string.find(...)
+end
+
+latc.static_env = {
+	print = safe_print,
+	string = {
+		byte = string.byte,
+		char = string.char,
+		format = string.format,
+		len = string.len,
+		lower = string.lower,
+		upper = string.upper,
+		rep = safe_string_rep,
+		reverse = string.reverse,
+		sub = string.sub,
+		find = safe_string_find,
+	},
+	math = {
+		abs = math.abs,
+		acos = math.acos,
+		asin = math.asin,
+		atan = math.atan,
+		atan2 = math.atan2,
+		ceil = math.ceil,
+		cos = math.cos,
+		cosh = math.cosh,
+		deg = math.deg,
+		exp = math.exp,
+		floor = math.floor,
+		fmod = math.fmod,
+		frexp = math.frexp,
+		huge = math.huge,
+		ldexp = math.ldexp,
+		log = math.log,
+		log10 = math.log10,
+		max = math.max,
+		min = math.min,
+		modf = math.modf,
+		pi = math.pi,
+		pow = math.pow,
+		rad = math.rad,
+		random = math.random,
+		sin = math.sin,
+		sinh = math.sinh,
+		sqrt = math.sqrt,
+		tan = math.tan,
+		tanh = math.tanh,
+	},
+	table = {
+		concat = table.concat,
+		insert = table.insert,
+		maxn = table.maxn,
+		remove = table.remove,
+		sort = table.sort,
+	},
+	os = {
+		clock = os.clock,
+		difftime = os.difftime,
+		time = os.time,
+		datetable = safe_date,
+	},
+}
+latc.static_env._G = env
+
+for _, name in pairs(safe_globals) do
+	latc.static_env[name] = _G[name]
+end
+
+
+--The environment all code calls get is a proxy table with a metatable.
+--When an index is read:
+-- Look in static_env
+-- Look in volatile_env (user_written functions and userdata)
+-- Look in saved_env (everything that's not a function or userdata)
+--when an index is written:
+-- If in static_env, do not allow
+-- if function or userdata, volatile_env
+-- if table, see below
+-- else, save in saved_env
+
+
+
+advtrains.latc=latc
diff --git a/advtrains/advtrains/nodedb.lua b/advtrains/advtrains/nodedb.lua
new file mode 100644
index 0000000..0e1d836
--- /dev/null
+++ b/advtrains/advtrains/nodedb.lua
@@ -0,0 +1,232 @@
+--nodedb.lua
+--database of all nodes that have 'save_in_nodedb' field set to true in node definition
+
+
+
+--serialization format:
+--(6byte poshash) (2byte contentid)
+--contentid := (14bit nodeid, 2bit param2)
+
+local function hash_to_bytes(x)
+	local aH = math.floor(x / 1099511627776) % 256;
+	local aL = math.floor(x /    4294967296) % 256;
+	local bH = math.floor(x /      16777216) % 256;
+	local bL = math.floor(x /         65536) % 256;
+	local cH = math.floor(x /           256) % 256;
+	local cL = math.floor(x                ) % 256;
+	return(string.char(aH, aL, bH, bL, cH, cL));
+end
+local function cid_to_bytes(x)
+	local cH = math.floor(x /           256) % 256;
+	local cL = math.floor(x                ) % 256;
+	return(string.char(cH, cL));
+end
+local function bytes_to_hash(bytes)
+	local t={string.byte(bytes,1,-1)}
+	local n = 
+		t[1] * 1099511627776 +
+		t[2] *    4294967296 +
+		t[3] *      16777216 +
+		t[4] *         65536 +
+		t[5] *           256 +
+		t[6]
+    return n
+end
+local function bytes_to_cid(bytes)
+	local t={string.byte(bytes,1,-1)}
+	local n = 
+		t[1] *           256 +
+		t[2]
+    return n
+end
+local function l2b(x)
+	return x%4
+end
+local function u14b(x)
+	return math.floor(x/4)
+end
+local ndb={}
+
+--local variables for performance
+local ndb_nodeids={}
+local ndb_nodes={}
+
+--load
+--nodeids get loaded by advtrains init.lua and passed here
+function ndb.load_data(data)
+	ndb_nodeids = data and data.nodeids or {}
+end
+
+local path=minetest.get_worldpath().."/advtrains_ndb"
+
+local file, err = io.open(path, "r")
+if not file then
+	atprint("load ndb failed: ", err or "Unknown Error")
+else
+	local cnt=0
+	local hst=file:read(6)
+	local cid=file:read(2)
+	while hst and #hst==6 and cid and #cid==2 do
+		ndb_nodes[bytes_to_hash(hst)]=bytes_to_cid(cid)
+		cnt=cnt+1
+		hst=file:read(6)
+		cid=file:read(2)
+	end
+	atprint("nodedb: read", cnt, "nodes.")
+	file:close()
+end
+
+--save
+function ndb.save_data()
+	local file, err = io.open(path, "w")
+	if not file then
+		atprint("load ndb failed: ", err or "Unknown Error")
+	else
+		for hash, cid in pairs(ndb_nodes) do
+			file:write(hash_to_bytes(hash))
+			file:write(cid_to_bytes(cid))
+		end
+		file:close()
+	end
+	return {nodeids = ndb_nodeids}
+end
+
+--function to get node. track database is not helpful here.
+function ndb.get_node_or_nil(pos)
+	local node=minetest.get_node_or_nil(pos)
+	if node then
+		return node
+	else
+		--maybe we have the node in the database...
+		local cid=ndb_nodes[minetest.hash_node_position(pos)]
+		if cid then
+			local nodeid = ndb_nodeids[u14b(cid)]
+			if nodeid then
+				--atprint("ndb.get_node_or_nil",pos,"found node",nodeid,"cid",cid,"par2",l2b(cid))
+				return {name=nodeid, param2 = l2b(cid)}
+			end
+		end
+	end
+	atprint("ndb.get_node_or_nil",pos,"not found")
+end
+function ndb.get_node(pos)
+	local n=ndb.get_node_or_nil(pos)
+	if not n then
+		return {name="ignore", param2=0}
+	end
+	return n
+end
+
+function ndb.swap_node(pos, node)
+	minetest.swap_node(pos, node)
+	ndb.update(pos, node)
+end
+
+function ndb.update(pos, pnode)
+	local node = pnode or minetest.get_node_or_nil(pos)
+	if not node or node.name=="ignore" then return end
+	if minetest.registered_nodes[node.name] and minetest.registered_nodes[node.name].groups.save_in_nodedb then
+		local nid
+		for tnid, nname in pairs(ndb_nodeids) do
+			if nname==node.name then
+				nid=tnid
+			end
+		end
+		if not nid then
+			nid=#ndb_nodeids+1
+			ndb_nodeids[nid]=node.name
+		end
+		local hash = minetest.hash_node_position(pos)
+		ndb_nodes[hash] = (nid * 4) + (l2b(node.param2 or 0))
+		--atprint("nodedb: updating node", pos, "stored nid",nid,"assigned",ndb_nodeids[nid],"resulting cid",ndb_nodes[hash])
+	else
+		--at this position there is no longer a node that needs to be tracked.
+		local hash = minetest.hash_node_position(pos)
+		ndb_nodes[hash] = nil
+	end
+end
+
+function ndb.clear(pos)
+	local hash = minetest.hash_node_position(pos)
+	ndb_nodes[hash] = nil
+end
+
+
+--get_node with pseudoload. now we only need track data, so we can use the trackdb as second fallback
+--nothing new will be saved inside the trackdb.
+--returns:
+--true, conn1, conn2, rely1, rely2, railheight   in case everything's right.
+--false  if it's not a rail or the train does not drive on this rail, but it is loaded or
+--nil    if the node is neither loaded nor in trackdb
+--the distraction between false and nil will be needed only in special cases.(train initpos)
+function advtrains.get_rail_info_at(pos, drives_on)
+	local rdp=advtrains.round_vector_floor_y(pos)
+	
+	local node=ndb.get_node_or_nil(rdp)
+	
+	--still no node?
+	--advtrains.trackdb is nil when there's no data available.
+	if not node then
+		if advtrains.trackdb then
+			--try raildb (see trackdb_legacy.lua)
+			local dbe=(advtrains.trackdb[rdp.y] and advtrains.trackdb[rdp.y][rdp.x] and advtrains.trackdb[rdp.y][rdp.x][rdp.z])
+			if dbe then
+				for tt,_ in pairs(drives_on) do
+					if not dbe.tracktype or tt==dbe.tracktype then
+						return true, dbe.conn1, dbe.conn2, dbe.rely1 or 0, dbe.rely2 or 0, dbe.railheight or 0
+					end
+				end
+			end
+		end
+		return nil
+	end
+	local nodename=node.name
+	if(not advtrains.is_track_and_drives_on(nodename, drives_on)) then
+		return false
+	end
+	local conn1, conn2, rely1, rely2, railheight, tracktype=advtrains.get_track_connections(node.name, node.param2)
+	
+	return true, conn1, conn2, rely1, rely2, railheight
+end
+
+
+minetest.register_abm({
+        name = "advtrains:nodedb_on_load_update",
+        nodenames = {"group:save_in_nodedb"},
+        run_at_every_load = true,
+        action = function(pos, node)
+			local cid=ndb_nodes[minetest.hash_node_position(pos)]
+			if cid then
+				--if in database, detect changes and apply.
+				local nodeid = ndb_nodeids[u14b(cid)]
+				local param2 = l2b(cid)
+				if not nodeid then
+					--something went wrong
+					atprint("nodedb: lbm nid not found", pos, "with nid", u14b(cid), "param2", param2, "cid is", cid)
+					ndb.update(pos, node)
+				else
+					if (nodeid~=node.name or param2~=node.param2) then
+						atprint("nodedb: lbm replaced", pos, "with nodeid", nodeid, "param2", param2, "cid is", cid)
+						minetest.swap_node(pos, {name=nodeid, param2 = param2})
+					end
+				end
+			else
+				--if not in database, take it.
+				atprint("nodedb: ", pos, "not in database")
+				ndb.update(pos, node)
+			end
+        end,
+        interval=10,
+        chance=1,
+    })
+    
+minetest.register_on_dignode(function(pos, oldnode, digger)
+	ndb.clear(pos)
+end)
+
+function ndb.t()
+	return ndb_nodes[141061759008906]
+end
+
+advtrains.ndb=ndb
+
diff --git a/advtrains/advtrains/pseudoload.lua b/advtrains/advtrains/pseudoload.lua
deleted file mode 100644
index 818808d..0000000
--- a/advtrains/advtrains/pseudoload.lua
+++ /dev/null
@@ -1,180 +0,0 @@
---pseudoload.lua
---responsible for keeping up a database of all rail nodes existant in the world, regardless of whether the mapchunk is loaded.
-
-advtrains.trackdb={}
---trackdb[tt][y][x][z]={conn1, conn2, rely1, rely2, railheight}
---serialization format:
---(2byte x)(2byte y)(2byte z)(4bits conn1, 4bits conn2)[(plain rely1)|(plain rely2)|(plain railheight)]\n
---[] may be missing if 0,0,0
-
---load initially
-
---[[ TODO temporary outcomment
-
---delayed since all traintypes need to be registered
-minetest.after(0, function()
-
-for tt, _ in pairs(advtrains.all_traintypes) do
-	local pl_fpath=minetest.get_worldpath().."/advtrains_trackdb_"..tt
-	advtrains.trackdb[tt]={}
-	local file, err = io.open(pl_fpath, "r")
-	if not file then
-		local er=err or "Unknown Error"
-		atprint("Failed loading advtrains trackdb save file "..er)
-	else
-		--custom format to save memory
-		while true do
-			local xbytes=file:read(2)
-			if not xbytes or #xbytes<2 then
-				break --eof reached
-			end
-			atprint(xbytes)
-			local ybytes=file:read(2)
-			local zbytes=file:read(2)
-			local x=(string.byte(xbytes[1])-128)*256+(string.byte(xbytes[2]))
-			local y=(string.byte(ybytes[1])-128)*256+(string.byte(ybytes[2]))
-			local z=(string.byte(zbytes[1])-128)*256+(string.byte(zbytes[2]))
-			
-			local conn1=string.byte(file:read(1))
-			local conn1=string.byte(file:read(1))
-			
-			if not advtrains.trackdb[tt][y] then advtrains.trackdb[tt][y]={} end
-			if not advtrains.trackdb[tt][y][x] then advtrains.trackdb[tt][y][x]={} end
-			
-			local rest=file.read("*l")
-			if rest~="" then
-				local rely1, rely2, railheight=string.match(rest, "([^|]+)|([^|]+)|([^|]+)")
-				if rely1 and rely2 and railheight then
-					advtrains.trackdb[tt][y][x][z]={
-						conn1=conn1, conn2=conn2,
-						rely1=rely1, rely2=rely2,
-						railheight=railheight
-					}
-				else
-					advtrains.trackdb[tt][y][x][z]={
-						conn1=conn1, conn2=conn2
-					}
-				end
-			else
-				advtrains.trackdb[tt][y][x][z]={
-					conn1=conn1, conn2=conn2
-				}
-			end
-		end
-		file:close()
-	end
-end
-
---end minetest.after
-end)
-
-function advtrains.save_trackdb()
-	for tt, _ in pairs(advtrains.all_traintypes) do
-		local pl_fpath=minetest.get_worldpath().."/advtrains_trackdb_"..tt
-		local file, err = io.open(pl_fpath, "w")
-		if not file then
-			local er=err or "Unknown Error"
-			atprint("Failed saving advtrains trackdb save file "..er)
-		else
-			--custom format to save memory
-			for y,tyl in pairs(advtrains.trackdb[tt]) do
-				for x,txl in pairs(tyl) do
-					for z,rail in pairs(txl) do
-						atprint("write "..x.." "..y.." "..z.." "..minetest.serialize(rail))
-						file:write(string.char(math.floor(x/256)+128)..string.char((x%256)))
-						file:write(string.char(math.floor(y/256)+128)..string.char((y%256)))
-						file:write(string.char(math.floor(z/256)+128)..string.char((z%256)))
-						file:write(string.char(rail.conn1))
-						file:write(string.char(rail.conn2))
-						if (rail.rely1 and rail.rely1~=0) or (rail.rely2 and rail.rely2~=0) or (rail.railheight and rail.railheight~=0) then
-							file:write(rail.rely1.."|"..rail.rely2.."|"..rail.railheight)
-						end
-						file:write("\n")
-					end
-				end
-			end
-			file:close()
-		end
-	end
-end
-]]--end temp outcomment
-
---trackdb keeps its own save file.
-advtrains.fpath_tdb=minetest.get_worldpath().."/advtrains_trackdb2"
-local file, err = io.open(advtrains.fpath_tdb, "r")
-if not file then
-	local er=err or "Unknown Error"
-	atprint("Failed loading advtrains save file "..er)
-else
-	local tbl = minetest.deserialize(file:read("*a"))
-	if type(tbl) == "table" then
-		advtrains.trackdb=tbl
-	end
-	file:close()
-end
-function advtrains.save_trackdb()
-	local datastr = minetest.serialize(advtrains.trackdb)
-	if not datastr then
-		minetest.log("error", " Failed to serialize trackdb data!")
-		return
-	end
-	local file, err = io.open(advtrains.fpath_tdb, "w")
-	if err then
-		return err
-	end
-	file:write(datastr)
-	file:close()
-end
-
---get_node with pseudoload.
---returns:
---true, conn1, conn2, rely1, rely2, railheight   in case everything's right.
---false  if it's not a rail or the train does not drive on this rail, but it is loaded or
---nil    if the node is neither loaded nor in trackdb
---the distraction between false and nil will be needed only in special cases.(train initpos)
-function advtrains.get_rail_info_at(pos, drives_on)
-	local rdp=advtrains.round_vector_floor_y(pos)
-	local node=minetest.get_node_or_nil(rdp)
-	if not node then
-		--try raildb
-		local dbe=(advtrains.trackdb[rdp.y] and advtrains.trackdb[rdp.y][rdp.x] and advtrains.trackdb[rdp.y][rdp.x][rdp.z])
-		if dbe then
-			for tt,_ in pairs(drives_on) do
-				if not dbe.tracktype or tt==dbe.tracktype then
-					return true, dbe.conn1, dbe.conn2, dbe.rely1 or 0, dbe.rely2 or 0, dbe.railheight or 0
-				end
-			end
-		else
-			return nil
-		end
-	end
-	local nodename=node.name
-	if(not advtrains.is_track_and_drives_on(nodename, drives_on)) then
-		return false
-	end
-	local conn1, conn2, rely1, rely2, railheight, tracktype=advtrains.get_track_connections(node.name, node.param2)
-	
-	--already in trackdb?
-	if not (advtrains.trackdb and advtrains.trackdb[rdp.y] and advtrains.trackdb[rdp.y][rdp.x] and advtrains.trackdb[rdp.y][rdp.x][rdp.z]) then--TODO is this necessary?
-		if not advtrains.trackdb then advtrains.trackdb={} end
-		if not advtrains.trackdb[rdp.y] then advtrains.trackdb[rdp.y]={} end
-		if not advtrains.trackdb[rdp.y][rdp.x] then advtrains.trackdb[rdp.y][rdp.x]={} end
-		advtrains.trackdb[rdp.y][rdp.x][rdp.z]={
-			conn1=conn1, conn2=conn2,
-			rely1=rely1, rely2=rely2,
-			railheight=railheight, tracktype=tracktype
-		}
-	end
-	
-	return true, conn1, conn2, rely1, rely2, railheight
-end
-function advtrains.reset_trackdb_position(pos)
-	local rdp=advtrains.round_vector_floor_y(pos)
-	if not advtrains.trackdb then advtrains.trackdb={} end
-	if not advtrains.trackdb[rdp.y] then advtrains.trackdb[rdp.y]={} end
-	if not advtrains.trackdb[rdp.y][rdp.x] then advtrains.trackdb[rdp.y][rdp.x]={} end
-	advtrains.trackdb[rdp.y][rdp.x][rdp.z]=nil
-	advtrains.get_rail_info_at(pos, advtrains.all_tracktypes)--to restore it.
-end
-	
-
diff --git a/advtrains/advtrains/signals.lua b/advtrains/advtrains/signals.lua
index 8be65e0..59c5af1 100644
--- a/advtrains/advtrains/signals.lua
+++ b/advtrains/advtrains/signals.lua
@@ -29,14 +29,15 @@ for r,f in pairs({on="off", off="on"}) do
 				choppy=3,
 				not_blocking_trains=1,
 				not_in_creative_inventory=crea,
+				save_in_nodedb=1,
 			},
 			mesecons = {effector = {
 				["action_"..f] = function (pos, node)
-					minetest.swap_node(pos, {name = "advtrains:retrosignal_"..f..rotation, param2 = node.param2})
+					advtrains.np.swap_node(pos, {name = "advtrains:retrosignal_"..f..rotation, param2 = node.param2})
 				end
 			}},
 			on_rightclick=function(pos, node, clicker)
-				minetest.swap_node(pos, {name = "advtrains:retrosignal_"..f..rotation, param2 = node.param2})
+				advtrains.np.swap_node(pos, {name = "advtrains:retrosignal_"..f..rotation, param2 = node.param2})
 			end,
 		})
 		advtrains.trackplacer.add_worked("advtrains:retrosignal", r, rotation, nil)
@@ -59,6 +60,7 @@ for r,f in pairs({on="off", off="on"}) do
 				choppy=3,
 				not_blocking_trains=1,
 				not_in_creative_inventory=crea,
+				save_in_nodedb=1,
 			},
 			light_source = 1,
 			sunlight_propagates=true,
diff --git a/advtrains/advtrains/trackdb_legacy.lua b/advtrains/advtrains/trackdb_legacy.lua
new file mode 100644
index 0000000..99349e8
--- /dev/null
+++ b/advtrains/advtrains/trackdb_legacy.lua
@@ -0,0 +1,27 @@
+--trackdb_legacy.lua
+--loads the (old) track database. the only use for this is to provide data for rails that haven't been written into the ndb database.
+--nothing will be saved.
+--if the user thinks that he has loaded every track in his world at least once, he can delete the track database.
+
+--trackdb[[y][x][z]={conn1, conn2, rely1, rely2, railheight}
+
+
+--trackdb keeps its own save file.
+advtrains.fpath_tdb=minetest.get_worldpath().."/advtrains_trackdb2"
+local file, err = io.open(advtrains.fpath_tdb, "r")
+if not file then
+	atprint("Not loading a trackdb file.")
+else
+	local tbl = minetest.deserialize(file:read("*a"))
+	if type(tbl) == "table" then
+		advtrains.trackdb=tbl
+		atprint("Loaded trackdb file.")
+	end
+	file:close()
+end
+	
+
+
+
+
+
diff --git a/advtrains/advtrains/trackplacer.lua b/advtrains/advtrains/trackplacer.lua
index e40cb59..1cb7680 100644
--- a/advtrains/advtrains/trackplacer.lua
+++ b/advtrains/advtrains/trackplacer.lua
@@ -117,13 +117,13 @@ function tp.bend_rail(originpos, conn, nnpref)
 		return false--dont destroy existing track
 	elseif adj1 and not adj2 then
 		if tr.double_conn[adj1.."_"..newdir] then
-			minetest.set_node(pos, tr.double_conn[adj1.."_"..newdir])
+			advtrains.ndb.swap_node(pos, tr.double_conn[adj1.."_"..newdir])
 			return true--if exists, connect new rail and old end
 		end
 		return false
 	else
 		if tr.single_conn[newdir] then--just rotate old rail to right orientation
-			minetest.set_node(pos, tr.single_conn[newdir])
+			advtrains.ndb.swap_node(pos, tr.single_conn[newdir])
 			return true
 		end
 		return false
@@ -145,7 +145,7 @@ function tp.placetrack(pos, nnpref, placer, itemstack, pointed_thing)
 		end
 	elseif #p_rails==1 then
 		tp.bend_rail(pos, p_rails[1], nnpref)
-		minetest.set_node(pos, tr.single_conn[p_rails[1]])
+		advtrains.ndb.swap_node(pos, tr.single_conn[p_rails[1]])
 		local nname=tr.single_conn[p_rails[1]].name
 		if minetest.registered_nodes[nname] and minetest.registered_nodes[nname].after_place_node then
 			minetest.registered_nodes[nname].after_place_node(pos, placer, itemstack, pointed_thing)
@@ -158,7 +158,7 @@ function tp.placetrack(pos, nnpref, placer, itemstack, pointed_thing)
 					if (tr.double_conn[conn1.."_"..conn2]) then
 						tp.bend_rail(pos, conn1, nnpref)
 						tp.bend_rail(pos, conn2, nnpref)
-						minetest.set_node(pos, tr.double_conn[conn1.."_"..conn2])
+						advtrains.ndb.swap_node(pos, tr.double_conn[conn1.."_"..conn2])
 						local nname=tr.double_conn[conn1.."_"..conn2].name
 						if minetest.registered_nodes[nname] and minetest.registered_nodes[nname].after_place_node then
 							minetest.registered_nodes[nname].after_place_node(pos, placer, itemstack, pointed_thing)
@@ -170,7 +170,7 @@ function tp.placetrack(pos, nnpref, placer, itemstack, pointed_thing)
 		end
 		--not found
 		tp.bend_rail(pos, p_rails[1], nnpref)
-		minetest.set_node(pos, tr.single_conn[p_rails[1]])
+		advtrains.ndb.swap_node(pos, tr.single_conn[p_rails[1]])
 		local nname=tr.single_conn[p_rails[1]].name
 		if minetest.registered_nodes[nname] and minetest.registered_nodes[nname].after_place_node then
 			minetest.registered_nodes[nname].after_place_node(pos, placer, itemstack, pointed_thing)
@@ -245,7 +245,7 @@ minetest.register_craftitem("advtrains:trackworker",{
 			local modext=tp.tracks[nnprefix].twrotate[suffix]
 
 			if rotation==modext[#modext] then --increase param2
-				minetest.swap_node(pos, {name=nnprefix.."_"..suffix..modext[1], param2=(node.param2+1)%4})
+				advtrains.ndb.swap_node(pos, {name=nnprefix.."_"..suffix..modext[1], param2=(node.param2+1)%4})
 				return
 			else
 				local modpos
@@ -254,7 +254,7 @@ minetest.register_craftitem("advtrains:trackworker",{
 						minetest.chat_send_player(placer:get_player_name(), "This node can't be rotated using the trackworker!")
 					return
 				end
-				minetest.swap_node(pos, {name=nnprefix.."_"..suffix..modext[modpos+1], param2=node.param2})
+				advtrains.ndb.swap_node(pos, {name=nnprefix.."_"..suffix..modext[modpos+1], param2=node.param2})
 			end
 			advtrains.invalidate_all_paths()
 		end
@@ -284,7 +284,7 @@ minetest.register_craftitem("advtrains:trackworker",{
 			  end
 		    end
 			local nextsuffix=tp.tracks[nnprefix].twcycle[suffix]
-			minetest.swap_node(pos, {name=nnprefix.."_"..nextsuffix..rotation, param2=node.param2})
+			advtrains.ndb.swap_node(pos, {name=nnprefix.."_"..nextsuffix..rotation, param2=node.param2})
 			--invalidate trains
 			advtrains.invalidate_all_paths()
 		else
diff --git a/advtrains/advtrains/tracks.lua b/advtrains/advtrains/tracks.lua
index 671c861..1108a06 100644
--- a/advtrains/advtrains/tracks.lua
+++ b/advtrains/advtrains/tracks.lua
@@ -235,10 +235,7 @@ advtrains.trackpresets = ap
 function advtrains.register_tracks(tracktype, def, preset)

 	local function make_switchfunc(suffix_target, mesecon_state)

 		local switchfunc=function(pos, node)

-			if advtrains.is_train_at_pos(pos) then return end

-			minetest.set_node(pos, {name=def.nodename_prefix.."_"..suffix_target, param2=node.param2})

-			advtrains.invalidate_all_paths()

-			advtrains.reset_trackdb_position(pos)

+			advtrains.ndb.swap_node(pos, {name=def.nodename_prefix.."_"..suffix_target, param2=node.param2})

 		end

 		return switchfunc, {effector = {

 			["action_"..mesecon_state] = switchfunc,

@@ -258,10 +255,12 @@ function advtrains.register_tracks(tracktype, def, preset)
 			rely1=conns.rely1 or 0,

 			rely2=conns.rely2 or 0,

 			railheight=conns.railheight or 0,

+			

 			on_rightclick=switchfunc,

 			groups = {

 				attached_node=1,

 				["advtrains_track_"..tracktype]=1,

+				save_in_nodedb=1,

 				dig_immediate=2,

 				not_in_creative_inventory=(not in_creative_inv and 1 or nil),

 				not_blocking_trains=1,

@@ -299,13 +298,10 @@ function advtrains.register_tracks(tracktype, def, preset)
 		end,

 		after_dig_node=function(pos)

 			advtrains.invalidate_all_paths()

-			advtrains.reset_trackdb_position(pos)

+			advtrains.ndb.update(pos)

 		end,

 		after_place_node=function(pos)

-			advtrains.reset_trackdb_position(pos)

-		end,

-		on_place_rail=function(pos)

-			advtrains.reset_trackdb_position(pos)

+			advtrains.ndb.update(pos)

 		end,

 	}, def.common or {})

 	--make trackplacer base def

@@ -398,10 +394,10 @@ advtrains.detector.clean_step_before = false
 --The entry already being contained in advtrains.detector.on_node_restore will not trigger an on_train_enter event on the node.  (when path is reset, this is saved).

 function advtrains.detector.enter_node(pos, train_id)

 	local pts = minetest.pos_to_string(advtrains.round_vector_floor_y(pos))

-	atprint("enterNode "..pts.." "..sid(train_id))

+	--atprint("enterNode "..pts.." "..sid(train_id))

 	if advtrains.detector.on_node[pts] then

 		if advtrains.trains[advtrains.detector.on_node[pts]] then

-			atprint(""..pts.." already occupied")

+			--atprint(""..pts.." already occupied")

 			return false

 		else

 			advtrains.detector.leave_node(pos, advtrains.detector.on_node[pts])

@@ -417,9 +413,9 @@ function advtrains.detector.enter_node(pos, train_id)
 end

 function advtrains.detector.leave_node(pos, train_id)

 	local pts = minetest.pos_to_string(advtrains.round_vector_floor_y(pos))

-	atprint("leaveNode "..pts.." "..sid(train_id))

+	--atprint("leaveNode "..pts.." "..sid(train_id))

 	if not advtrains.detector.on_node[pts] then

-		atprint(""..pts.." leave: nothing here")

+		--atprint(""..pts.." leave: nothing here")

 		return false

 	end

 	if advtrains.detector.on_node[pts]==train_id then

@@ -427,7 +423,7 @@ function advtrains.detector.leave_node(pos, train_id)
 		advtrains.detector.on_node[pts]=nil

 	else

 		if advtrains.trains[advtrains.detector.on_node[pts]] then

-			atprint(""..pts.." occupied by another train")

+			--atprint(""..pts.." occupied by another train")

 			return false

 		else

 			advtrains.detector.leave_node(pos, advtrains.detector.on_node[pts])

@@ -438,7 +434,7 @@ function advtrains.detector.leave_node(pos, train_id)
 end

 --called immediately before invalidating paths

 function advtrains.detector.setup_restore()

-	atprint("setup_restore")

+	--atprint("setup_restore")

 	-- don't execute if it already has been called. For some reason it gets called twice...

 	if advtrains.detector.clean_step_before then

 		return

@@ -452,7 +448,7 @@ function advtrains.detector.setup_restore()
 end

 --called one step after invalidating paths, when all trains have restored their path and called enter_node for their contents.

 function advtrains.detector.finalize_restore()

-	atprint("finalize_restore")

+	--atprint("finalize_restore")

 	for pts, train_id in pairs(advtrains.detector.on_node_restore) do

 		--atprint("called leave callback "..pts.." "..train_id)

 		advtrains.detector.call_leave_callback(minetest.string_to_pos(pts), train_id)

@@ -461,7 +457,7 @@ function advtrains.detector.finalize_restore()
 	advtrains.detector.clean_step_before = false

 end

 function advtrains.detector.call_enter_callback(pos, train_id)

-	atprint("instructed to call enter calback")

+	--atprint("instructed to call enter calback")

 

 	local node = minetest.get_node(pos) --this spares the check if node is nil, it has a name in any case

 	local mregnode=minetest.registered_nodes[node.name]

@@ -473,7 +469,7 @@ function advtrains.detector.call_enter_callback(pos, train_id)
 	advtrains.atc.trigger_controller_train_enter(pos, train_id)

 end

 function advtrains.detector.call_leave_callback(pos, train_id)

-	atprint("instructed to call leave calback")

+	--atprint("instructed to call leave calback")

 

 	local node = minetest.get_node(pos) --this spares the check if node is nil, it has a name in any case

 	local mregnode=minetest.registered_nodes[node.name]