func (s *Scanner) Split(split SplitFunc) {
	if s.scanCalled {
		panic("Split called after Scan")
	}
	s.split = split
}

// Split functions

// ScanBytes is a split function for a [Scanner] that returns each byte as a token.
func ScanBytes(data []byte, atEOF bool) (advance int, token []byte, err error) {
	if atEOF && len(data) == 0 {
		return 0, nil, nil
	}
	return 1, data[0:1], nil
}

	"abcdefgh",
	"abc def\n\t\tgh    ",
	"abc¼☹\x81\uFFFD日本語\x82abc",
}

func TestScanByte(t *testing.T) {
	for n, test := range scanTests {
		buf := strings.NewReader(test)
		s := NewScanner(buf)
		s.Split(ScanBytes)
		var i int
		for i = 0; s.Scan(); i++ {
			if b := s.Bytes(); len(b) != 1 || b[0] != test[i] {
				t.Errorf("#%d: %d: expected %q got %q", n, i, test, b)
			}
		}
		if i != len(test) {