LuaC: add lightweight interrupts (#449)

mesecons_luacontroller/init.lua

@@ -266,13 +266,26 @@ local function remove_functions(x)
 	return x
 end
 
--- itbl: Flat table of functions to run after sandbox cleanup, used to prevent various security hazards
+-- The setting affects API so is not intended to be changeable at runtime
-local function get_interrupt(pos, itbl, send_warning)
+local get_interrupt
+if mesecon.setting("luacontroller_lightweight_interrupts", false) then
+	-- use node timer
+	get_interrupt = function(pos, itbl, send_warning)
+		return (function(time, iid)
+			if type(time) ~= "number" then error("Delay must be a number") end
+			if iid ~= nil then send_warning("Interrupt IDs are disabled on this server") end
+			table.insert(itbl, function() minetest.get_node_timer(pos):start(time) end)
+		end)
+	end
+else
+	-- use global action queue
+	-- itbl: Flat table of functions to run after sandbox cleanup, used to prevent various security hazards
+	get_interrupt = function(pos, itbl, send_warning)
 		-- iid = interrupt id
 		local function interrupt(time, iid)
 			-- NOTE: This runs within string metatable sandbox, so don't *rely* on anything of the form (""):y
 			-- Hence the values get moved out. Should take less time than original, so totally compatible
-		if type(time) ~= "number" then return end
+			if type(time) ~= "number" then error("Delay must be a number") end
 			table.insert(itbl, function ()
 				-- Outside string metatable sandbox, can safely run this now
 				local luac_id = minetest.get_meta(pos):get_int("luac_id")
@@ -289,9 +302,9 @@ local function get_interrupt(pos, itbl, send_warning)
 			end)
 		end
 		return interrupt
+	end
 end
 
-
 -- Given a message object passed to digiline_send, clean it up into a form
 -- which is safe to transmit over the network and compute its "cost" (a very
 -- rough estimate of its memory usage).
@@ -414,7 +427,6 @@ local function get_digiline_send(pos, itbl, send_warning)
 	end
 end
 
-
 local safe_globals = {
 	-- Don't add pcall/xpcall unless willing to deal with the consequences (unless very careful, incredibly likely to allow killing server indirectly)
 	"assert", "error", "ipairs", "next", "pairs", "select",
@@ -651,6 +663,14 @@ local function reset(pos)
 	set_port_states(pos, {a=false, b=false, c=false, d=false})
 end
 
+local function node_timer(pos)
+	if minetest.registered_nodes[minetest.get_node(pos).name].is_burnt then
+		return false
+	end
+	run(pos, {type="interrupt"})
+	return false
+end
+
 -----------------------
 -- A.Queue callbacks --
 -----------------------
@@ -823,6 +843,7 @@ for d = 0, 1 do
 			mesecon.receptor_off(pos, output_rules)
 		end,
 		is_luacontroller = true,
+		on_timer = node_timer,
 		on_blast = mesecon.on_blastnode,
 	})
 end

settingtypes.txt

@@ -24,6 +24,10 @@ mesecon.luacontroller_digiline_maxlen (Digiline message size limit) int 50000 10
 mesecon.luacontroller_maxevents (Controller execution time limit) int 10000 1000 100000
 mesecon.luacontroller_memsize (Controller memory limit) int 100000 10000 1000000
 
+# Use node timer for interrupts (runs in active blocks only).
+# IID is ignored and at most one interrupt may be queued if this setting is enabled.
+mesecon.luacontroller_lightweight_interrupts (Lightweight interrupts) bool false
+
 
 [mesecons_movestones]