def pad_after( length )
      before = stream_position
      pad = Padding.padding_for(length)
      pad.times do
        @stream.write_unsigned_int_8(0)
      end
      after = stream_position
      log.debug "padded 0x#{length.to_s(16)} with 0x#{pad.to_s(16)} stream #{before.to_s(16)}/#{after.to_s(16)}"
    end
def pad_after( length )
      before = stream_position
      pad = Padding.padding_for(length)
      pad.times do
        @stream.write_unsigned_int_8(0)
      end
      after = stream_position
      log.debug "padded 0x#{length.to_s(16)} with 0x#{pad.to_s(16)} stream #{before.to_s(16)}/#{after.to_s(16)}"
    end
pad_after is always in bytes and pads (writes 0's) up to the next 8 word boundary