Function parseDisplayString

displaystring.go:48–94

parseDisplayString parses as defined in https://httpwg.org/specs/rfc9651.html#parse-display.

(s *scanner)

// parseDisplayString parses as defined in
// https://httpwg.org/specs/rfc9651.html#parse-display.
func parseDisplayString(s *scanner) (DisplayString, error) {
	if s.eof() || len(s.data[s.off:]) < 2 || s.data[s.off:2] != `%"` {
		return "", &UnmarshalError{s.off, ErrInvalidDisplayString}
	}
	s.off += 2

	var b strings.Builder
	for !s.eof() {
		c := s.data[s.off]
		s.off++

		switch c {
		case '%':
			if len(s.data[s.off:]) < 2 {
				return "", &UnmarshalError{s.off, ErrInvalidDisplayString}
			}
			c0 := unhex(s.data[s.off])
			if c0 == 0 {
				return "", &UnmarshalError{s.off, ErrInvalidDisplayString}
			}

			c1 := unhex(s.data[s.off+1])
			if c1 == 0 {
				return "", &UnmarshalError{s.off, ErrInvalidDisplayString}
			}

			b.WriteByte(c0<<4 | c1)
			s.off += 2
		case '"':
			r := b.String()
			if !utf8.ValidString(r) {
				return "", ErrInvalidDisplayString
			}

			return DisplayString(r), nil

		default:
			if unicode.Is(notVcharOrSp, rune(c)) {
				return "", &UnmarshalError{s.off, ErrInvalidDisplayString}
			}

			b.WriteByte(c)
		}
	}

	return "", &UnmarshalError{s.off, ErrInvalidDisplayString}
}

func unhex(c byte) byte {
	switch {