add net and wire struct; move net update into its file

sim/group.lua

@@ -1,6 +1,19 @@
 
 Group = {}
 
+FFI.cdef[[
+	struct Port;
+	struct Net {
+		bool state;
+		bool fxstate;
+		int updatetick;
+		int internal_ref;
+		int state_num;
+		int num_in_ports_update;
+		struct Port* in_ports_update[1];
+	};
+]]
+
 function Group.new(self, sim)
 	local o = {
 		state = false,
@@ -9,6 +22,8 @@ function Group.new(self, sim)
 		wires = {},
 		out_ports = {},
 		in_ports = {},
+		
+		state_num = 0,
 	
 		nwires = 0,
 		nout_ports = 0,
@@ -154,3 +169,15 @@ end
 function Group.getsim(group)
 	return group.sim
 end
+
+function Group.update(group)
+	local newstate = false
+	for j, port in pairs(group.out_ports) do
+		newstate = newstate or Port.getstate(port)
+		if newstate then
+			break
+		end
+	end
+	
+	Group.setstate(group, newstate)
+end