New version 3 save system.

This new save system exists to split up the save file into several
smaller ones, to bypass lua limitations.

advtrains/init.lua

@@ -206,14 +206,64 @@ local MDS_interlocking, MDS_lines
 
 advtrains.fpath=minetest.get_worldpath().."/advtrains"
 dofile(advtrains.modpath.."/log.lua")
+function advtrains.read_component(name)
+	local path = advtrains.fpath.."_"..name
+	minetest.log("action", "[advtrains] loading "..path)
+	local file, err = io.open(path, "r")
+	if not file then
+		minetest.log("warning", " Failed to read advtrains save data from file "..path..": "..(err or "Unknown Error"))
+		minetest.log("warning", " (this is normal when first enabling advtrains on this world)")
+		return
+	end
+	local tbl =  minetest.deserialize(file:read("*a"))
+	file:close()
+	return tbl
+end
 
 function advtrains.avt_load()
+	-- check for new, split advtrains save file
+	
+	local version = advtrains.read_component("version")
+	local tbl
+	if version and version == 3 then
+		-- we are dealing with the new, split-up system
+		minetest.log("action", "[advtrains] loading savefiles version 3")
+		local il_save = {
+			tcbs = true,
+			ts = true,
+			signalass = true,
+			rs_locks = true,
+			rs_callbacks = true,
+			influence_points = true,
+			npr_rails = true,
+		}
+		tbl={
+			trains = true,
+			wagon_save = true,
+			ptmap = true,
+			atc = true,
+			ndb = true,		
+			lines = true,
+			version = 2,
+		}
+		for i,k in pairs(il_save) do
+			il_save[i] = advtrains.read_component("interlocking_"..i)
+		end
+		for i,k in pairs(tbl) do
+			tbl[i] = advtrains.read_component(i)
+		end
+		tbl["interlocking"] = il_save
+	else	
 		local file, err = io.open(advtrains.fpath, "r")
 		if not file then
 			minetest.log("warning", " Failed to read advtrains save data from file "..advtrains.fpath..": "..(err or "Unknown Error"))
 			minetest.log("warning", " (this is normal when first enabling advtrains on this world)")
+			return
 		else
-		local tbl = minetest.deserialize(file:read("*a"))
+			tbl = minetest.deserialize(file:read("*a"))
+			file:close()
+		end
+	end
 	if type(tbl) == "table" then
 		if tbl.version then
 			--congrats, we have the new save format.
@@ -281,8 +331,28 @@ function advtrains.avt_load()
 	else
 		minetest.log("error", " Failed to deserialize advtrains save data: Not a table!")
 	end
-		file:close()
+end
+
+advtrains.save_component = function (tbl, name)
+	-- Saves each component of the advtrains file separately
+	--
+	-- required for now to shrink the advtrains db to overcome lua
+	-- limitations.
+	local datastr = minetest.serialize(tbl)
+	if not datastr then
+		minetest.log("error", " Failed to serialize advtrains save data!")
+		return
 	end
+	local temppath = advtrains.fpath.."_"..name.."~"
+	local file, err = io.open(temppath, "w")
+	if err then
+		minetest.log("error", " Failed to write advtrains save data to file "..temppath..": "..(err or "Unknown Error"))
+		return
+	end
+	file:write(datastr)
+	file:close()
+	os.rename(temppath, advtrains.fpath.."_"..name)
+	
 end
 
 advtrains.avt_save = function(remove_players_from_wagons)
@@ -343,30 +413,24 @@ advtrains.avt_save = function(remove_players_from_wagons)
 	else
 		ln_save = MDS_lines
 	end
+
 	local save_tbl={
 		trains = tmp_trains,
 		wagon_save = advtrains.wagons,
 		ptmap = advtrains.player_to_train_mapping,
 		atc = advtrains.atc.save_data(),
 		ndb = advtrains.ndb.save_data(),
-		interlocking = il_save,
 		lines = ln_save,
-		version = 2,
+		version = 3,
 	}
-	local datastr = minetest.serialize(save_tbl)
-	if not datastr then
-		minetest.log("error", " Failed to serialize advtrains save data!")
-		return
+	for i,k in pairs(save_tbl) do
+		advtrains.save_component(k,i)
 	end
-	local temppath = advtrains.fpath.."~"
-	local file, err = io.open(temppath, "w")
-	if err then
-		minetest.log("error", " Failed to write advtrains save data to file "..temppath..": "..(err or "Unknown Error"))
-		return
+	
+	for i,k in pairs(il_save) do
+		advtrains.save_component(k,"interlocking_"..i)
 	end
-	file:write(datastr)
-	file:close()
-	os.rename(temppath, advtrains.fpath)
+	
 	if DUMP_DEBUG_SAVE then
 		local file, err = io.open(advtrains.fpath.."_DUMP", "w")
 		if err then