rr := rand.New(rand.NewSource(1))
	rr.Shuffle(len(rs), func(i, j int) {
		rs[i], rs[j] = rs[j], rs[i]
	})
	uchars := string(rs)

	return func(b *testing.B, n int) {
		buf := bmbuf[0:n]
		o := copy(buf, uchars)
		for o < len(buf) {
			o += copy(buf[o:], uchars)
		}

		// Make space for the needle rune at the end of buf.
		m := utf8.RuneLen(needle)
		for o := m; o > 0; {