w.line[w.i+1] = upperhex[b>>4]
	w.line[w.i+2] = upperhex[b&0x0f]
	w.i += 3

	return nil
}

const upperhex = "0123456789ABCDEF"

// checkLastByte encodes the last buffered byte if it is a space or a tab.
func (w *Writer) checkLastByte() error {
	if w.i == 0 {
		return nil
	}

	b := w.line[w.i-1]
	if isWhitespace(b) {
		w.i--
		if err := w.encode(b); err != nil {
			return err