fn write_buf(&mut self, buf: &[u8]) -> ByteIOResult<()>;
fn tell(&mut self) -> u64;
fn seek(&mut self, pos: SeekFrom) -> ByteIOResult<u64>;
fn write_buf(&mut self, buf: &[u8]) -> ByteIOResult<()>;
fn tell(&mut self) -> u64;
fn seek(&mut self, pos: SeekFrom) -> ByteIOResult<u64>;