advtrains_netmapper/nodedb.lua

--nodedb.lua
--database of all nodes that have 'save_in_at_nodedb' field set to true in node definition

ndb_nodes_notrack = 0

--serialization format:
--(2byte z) (2byte y) (2byte x) (2byte contentid)
--contentid := (14bit nodeid, 2bit param2)

local function int_to_bytes(i)
	local x=i+32768--clip to positive integers
	local cH = math.floor(x /           256) % 256;
	local cL = math.floor(x                ) % 256;
	return(string.char(cH, cL));
end
local function bytes_to_int(bytes)
	local t={string.byte(bytes,1,-1)}
	local n = 
		t[1] *           256 +
		t[2]
    return n-32768
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={}
local ndb_ver

local function ndbget(x,y,z)
	local ny=ndb_nodes[y]
	if ny then
		local nx=ny[x]
		if nx then
			return nx[z]
		end
	end
	return nil
end
local function ndbset(x,y,z,v)
	if not ndb_nodes[y] then
		ndb_nodes[y]={}
	end
	if not ndb_nodes[y][x] then
		ndb_nodes[y][x]={}
	end
	ndb_nodes[y][x][z]=v
end

-- load/save

local path_pre_v4=datapath.."advtrains_ndb2"
--load pre_v4 format
--nodeids get loaded by advtrains init.lua and passed here
function ndb.load_data_pre_v4(data)
	print("nodedb: Loading pre v4 format")

	ndb_nodeids = data and data.nodeids or {}
	ndb_ver = data and data.ver or 0
	if ndb_ver < 1 then
		for k,v in pairs(ndb_nodeids) do
			if v == "advtrains:dtrack_xing4590_st" then
				cidDepr = k
			elseif v == "advtrains:dtrack_xing90plusx_45l" then
				cidNew = k
			end
		end
	end
	local file, err = io.open(path_pre_v4, "rb")
	if not file then
		print("Couldn't load the node database: ", err or "Unknown Error")
	else
		-- Note: code duplication because of weird coordinate order in ndb2 format (z,y,x)
		local cnt=0
		local hst_z=file:read(2)
		local hst_y=file:read(2)
		local hst_x=file:read(2)
		local cid=file:read(2)
		while hst_z and hst_y and hst_x and cid and #hst_z==2 and #hst_y==2 and #hst_x==2 and #cid==2 do
			if (ndb_ver < 1 and cid == cidDepr) then
				cid = cidNew
			end
			ndbset(bytes_to_int(hst_x), bytes_to_int(hst_y), bytes_to_int(hst_z), bytes_to_int(cid))
			cnt=cnt+1
			hst_z=file:read(2)
			hst_y=file:read(2)
			hst_x=file:read(2)
			cid=file:read(2)
		end
		print("nodedb (ndb2 format): read", cnt, "nodes.")
		ndb_nodes_total = cnt
		file:close()
	end
	ndb_ver = 1
end

-- the new ndb file format is backported from cellworld, and stores the cids also in the ndb file.
-- These functions have the form of a serialize_lib atomic load/save callback and are called from avt_save/avt_load.
function ndb.load_callback(file)
	-- read version
	local vers_byte = file:read(1)
	local version = string.byte(vers_byte)
	if version~=1 then
		file:close()
		error("Doesn't support v4 nodedb file of version "..version)
	end
	
	-- read cid mappings
	local nstr_byte = file:read(2)
	local nstr = bytes_to_int(nstr_byte)
	for i = 1,nstr do
		local stid_byte = file:read(2)
		local stid = bytes_to_int(stid_byte)
		local stna = file:read("*l")
		--atdebug("content id:", stid, "->", stna)
		ndb_nodeids[stid] = stna
	end
	print("[nodedb] read", nstr, "node content ids.")

	-- read nodes
	local cnt=0
	local hst_x=file:read(2)
	local hst_y=file:read(2)
	local hst_z=file:read(2)
	local cid=file:read(2)
	local cidi
	while hst_z and hst_y and hst_x and cid and #hst_z==2 and #hst_y==2 and #hst_x==2 and #cid==2 do
		cidi = bytes_to_int(cid)
		-- prevent file corruption already here
		if not ndb_nodeids[u14b(cidi)] then
			-- clear the ndb data, to reinitialize it
			-- in strict loading mode, doesn't matter as starting will be interrupted anyway
			ndb_nodeids = {}
			ndb_nodes = {}
			error("NDB file is corrupted (found entry with invalid cid)")
		end
		ndbset(bytes_to_int(hst_x), bytes_to_int(hst_y), bytes_to_int(hst_z), cidi)
		cnt=cnt+1
		hst_x=file:read(2)
		hst_y=file:read(2)
		hst_z=file:read(2)
		cid=file:read(2)
	end
	print("[nodedb] read", cnt, "nodes.")
	ndb_nodes_total = cnt
	file:close()
end


--function to get node. track database is not helpful here.
function ndb.get_node_or_nil(pos)
	-- FIX for bug found on linuxworks server:
	-- a loaded node might get read before the LBM has updated its state, resulting in wrongly set signals and switches
	-- -> Using the saved node prioritarily.
	local node = ndb.get_node_raw(pos)
	if node then
		return node
	else
		-- no minetest here
		return nil
	end
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.get_node_raw(pos)
	local cid=ndbget(pos.x, pos.y, pos.z)
	if cid then
		local nodeid = ndb_nodeids[u14b(cid)]
		if nodeid then
			return {name=nodeid, param2 = l2b(cid)}
		end
	end
	return nil
end

function ndb.clear(pos)
	ndbset(pos.x, pos.y, pos.z, 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)
advtrains = advtrains or {}
function advtrains.get_rail_info_at(pos)
	local rdp=advtrains.round_vector_floor_y(pos)
	
	local node=ndb.get_node_or_nil(rdp)
	if not node then return end
	
	local nodename=node.name
	
	local conns, railheight, tracktype=advtrains.get_track_connections(node.name, node.param2)
	
	if not conns then
		return false
	end
	
	return true, conns, railheight
end


-- mapper-specific

function ndb.mapper_find_starting_point()
	for y, ty in pairs(ndb_nodes) do
		for x, tx in pairs(ty) do
			for z, v in pairs(tx) do
				local pos = {x=x, y=y, z=z}
				local node_ok, conns, _ = advtrains.get_rail_info_at(pos)
				if node_ok then
					return pos, conns
				else
					-- this is a signal or something similar, ignore.
					tx[z]=nil
					ndb_nodes_notrack = ndb_nodes_notrack + 1
				end
			end
		end
	end
end


advtrains.ndb = ndb