make nets keep list of updated gates instead of ports

sim/port.lua

@@ -15,20 +15,6 @@ PortDirections = {
 
 Port = {}
 
-FFI.cdef[[
-	struct Gate;
-	struct Net;
-	struct Port {
-		bool state;
-		char type;
-		char direction;
-		bool causeupdate;
-		int position[3];
-		struct Gate* gate;
-		struct Net* group;
-	};
-]]
-
 function Port.new(type, direction, position, causeupdate)
 	local o = {
 		type = type,
@@ -44,13 +30,13 @@ end
 
 function Port.setstate(port, state) -- output state
 	if state ~= port.state then
+		local group = port.group
+		group.state_num = group.state_num - (port.state and 1 or 0) + (state and 1 or 0)
 		port.state = state
-		if state then
-			Port.getgroup(port).state_num = Port.getgroup(port).state_num + 1
-		else
-			Port.getgroup(port).state_num = Port.getgroup(port).state_num - 1
+		
+		if (group.state_num>0) ~= group.state then
+			Simulation.queuegroup(GSim, group)
 		end
-		Simulation.queuegroup(GSim, Port.getgroup(port))
 	end
 end