t.pExt = uint16(p)
		p += appendTokens(buf[p:], b.extensions...)
		t.str = string(buf[:p])
		// We may not always need to remake the string, but when or when not
		// to do so is rather tricky.
		scan := makeScanner(buf[:p])
		t, _ = parse(&scan, "")
		return t

	} else if b.private != "" {
		t.str = b.private
		t.RemakeString()
	}
	return t
}

		scan.b = scan.bytes[:copy(scan.bytes[:], s)]
	} else {
		scan.b = []byte(s)
	}
	scan.init()
	return scan
}

// makeScanner returns a scanner using b as the input buffer.
// b is not copied and may be modified by the scanner routines.
func makeScanner(b []byte) scanner {
	scan := scanner{b: b}
	scan.init()
	return scan
}

func (s *scanner) init() {
	for i, c := range s.b {

		buf[uStart] = '-'
		uStart++
	}

	// Create new key-type pair and parse it to verify.
	b := buf[uStart:]
	copy(b, "u-")
	copy(b[2:], key)
	b[4] = '-'
	b = b[:5+copy(b[5:], value)]
	scan := makeScanner(b)
	if parseExtensions(&scan); scan.err != nil {
		return t, scan.err
	}

	// Assemble the replacement string.
	if t.str == "" {
		t.pVariant, t.pExt = byte(uStart-1), uint16(uStart-1)