return n, nil
		}
		cr.offset = 0
		buf = buf[n:]
	}
	// mustRead reads from input and compares against provided slice.
	mustRead := func(b ...byte) error {
		for _, want := range b {
			got, err := cr.reader.ReadByte()
			if err == io.EOF {
				return io.ErrUnexpectedEOF
			}
			if got != want {
				if cr.debug {
					fmt.Printf("mustread: want: %q got: %q\n", string(want), string(got))
				}