class BinData::DelayedIO

def write_now!

The writing is delayed until this method is called.
DelayedIO objects aren't written when #write is called. 
def write_now!
  return unless include_obj?
  raise IOError, "write to where?" unless @write_io
  @write_io.seek_to_abs_offset(abs_offset)
  @type.do_write(@write_io)
end