--[[
function luaU:make_setF(filename)
  local buff = {}
        buff.h = io.open(filename, "wb")
  if not buff.h then return nil end
  local writer =
    function(s, buff)  -- chunk writer
      if not buff.h then return 0 end
      if not s then
        if buff.h:close() then return 0 end
      else
        if buff.h:write(s) then return 0 end
      end
      return 1
    end
  return writer, buff
end--]]