}
			tw.curr = &sparseFileWriter{tw.curr, spd, 0}
		}
	*/
	return nil
}

func (tw *Writer) writeGNUHeader(hdr *Header) error {
	// Use long-link files if Name or Linkname exceeds the field size.
	const longName = "././@LongLink"
	if len(hdr.Name) > nameSize {
		data := hdr.Name + "\x00"
		if err := tw.writeRawFile(longName, data, TypeGNULongName, FormatGNU); err != nil {
			return err
		}
	}

	if err := writeHeader(w.cw, h); err != nil {
		return nil, err
	}
	// If we're creating a directory, fw is nil.
	w.last = fw
	return ow, nil
}

func writeHeader(w io.Writer, h *header) error {
	const maxUint16 = 1<<16 - 1
	if len(h.Name) > maxUint16 {
		return errLongName
	}
	if len(h.Extra) > maxUint16 {
		return errLongExtra
	}

	var buf [fileHeaderLen]byte
	b := writeBuf(buf[:])