local MEMSIZE=16 -- does this still apply?
local SHUTUP = false
if not digiline then
 print("Digilines not found.")
 return
end
local path = minetest.get_modpath(minetest.get_current_modname())
local t400 = dofile(path.."/t400.lua")
local oldprint=print
local function print(...)
 if SHUTUP then return end
 for k,v in ipairs({...}) do
  oldprint("[Test3D:T400] "..tostring(v))
 end
end
print("Loading.")

local function pos2string(pos)
 return tostring(pos.x)..","..tostring(pos.y)..","..tostring(pos.z)
end

local function push(pos,val)
 local meta = minetest.get_meta(pos)
 local sstring = ""
 local sstab = string.split(meta:get_string("stack"),"\n")
 sstab[#sstab+1] = tostring(tonumber(val) % 4096)
 if #sstab > MEMSIZE then
  table.remove(sstab,1)
 end
 for k,v in ipairs(sstab) do
  sstring = sstring .. v .. "\n"
 end
 meta:set_string("stack",sstring)
end

function rqaddr(pos,addr,tp)
 local meta = minetest.get_meta(pos)
 meta:set_string("state","waiting"..tostring(tp))
 meta:set_string("addr",addr)
 print("rqaddr: "..addr.." "..tp)
 digiline:receptor_send(pos,digiline.rules.default,meta:get_string("channel")..string.format("%X",tonumber(addr)),"get")
end

local function t400_set_meta(pos)
 local meta = minetest.get_meta(pos)
 local stab = {}
 stab.stack,stab.rstack = {},{}
 for i = 1, MEMSIZE do
  stab.stack[#stab.stack+1] = 0
  stab.rstack[#stab.stack+1] = 0
 end
 stab.cins = 0
 stab.pc = 0
 meta:set_string("stab",minetest.serialize(stab))
 meta:set_string("channel","")
 meta:set_string("rw","")
 meta:set_string("state","running")
 meta:set_int("pc",0)
 meta:set_string("formspec","size[5,5]\nlabel[0.4,0.5;T400 Execution Node]\nfield[0.5,2;4,1;channel;Channel prefix;${channel}]\nfield[0.5,3;4,1;pc;Program Counter;${pc}]field[0.5,4;4,1;state;State;${state}]")
 print("Set metadata for a T400 node at "..pos2string(pos))
end

minetest.register_node("test3d_t400:t400", {
 description = "T400 Execution Node",
 tiles = {
  {
   image="t400.png",
   animation={
    type = "vertical_frames",
    aspect_w=16,
    aspect_h=16,
    length=18,
    length=1.8,
   },
  },
 },
 groups = {snappy=1,choppy=2,oddly_breakable_by_hand=2,flammable=3},
 on_construct = t400_set_meta,
 on_receive_fields = function(pos,_,fields,sender)
  print("Received fields for a T400 node at "..pos2string(pos))
  for k,v in pairs(fields) do print(tostring(k).." = "..tostring(v)) end
  local meta = minetest.get_meta(pos)
  if fields.channel ~= nil then
   meta:set_string("channel",fields.channel)
  end
  if fields.pc ~= nil then
   local stab = minetest.deserialize(meta:get_string("stab"))
   stab.pc = tonumber(fields.pc)
   meta:set_int("pc",fields.pc) -- for display only
   meta:set_string("stab",minetest.serialize(stab))
  end
  if fields.state ~= nil then
   meta:set_string("state",fields.state)
  end
 end,
 digiline = {
  receptor = {},
  effector = {
   action = function(pos,node,channel,msg)
    local meta = minetest.get_meta(pos)
    local stab = minetest.deserialize(meta:get_string("stab"))
    print(meta:get_string("state").." "..meta:get_string("addr"),channel.." "..msg.." = "..meta:get_string("channel")..string.format("%X",meta:get_string("addr")))
    if meta:get_string("state") == "waitingread" and meta:get_string("channel")..string.format("%X",meta:get_string("addr")) == channel then
     push(pos,tonumber(msg)%4096)
     rqaddr(pos,stab.pc,"ins")
    elseif meta:get_string("state") == "waitingins" and meta:get_string("channel")..string.format("%X",meta:get_string("addr")) == channel then
     stab.ins = (tonumber(msg)%4096)
     meta:set_string("state","running")
    end
   end
  }
 }
})
print("T400 node registered")
minetest.register_abm({
 nodenames={"test3d_t400:t400"},
 interval=1,
 chance=1,
 action = function(pos)
  local meta = minetest.get_meta(pos)
  if meta:get_string("state") ~= "running" then return false end
  local stab = minetest.deserialize(meta:get_string("stab"))
  local stab, rw, addr, dat = t400.run(stab)
  meta:set_int("pc",stab.pc)
  meta:set_string("stab",minetest.serialize(stab))
  print(minetest.serialize(stab))
  if rw == "read" then
   rqaddr(pos,addr,rw)
  else
   if rw == "write" then
    digiline:receptor_send(pos,digiline.rules.default,meta:get_string("channel")..string.format("%X",addr),dat)
   end
   rqaddr(pos,stab.pc,"ins")
  end
 end
})