j := index(buf, 'x')
			if j != n-1 {
				b.Fatal("bad index", j)
			}
		}
		buf[n-1] = '\x00'
	}
}

func BenchmarkIndexRune(b *testing.B) {
	benchBytes(b, indexSizes, bmIndexRune(IndexRune))
}

func BenchmarkIndexRuneASCII(b *testing.B) {
	benchBytes(b, indexSizes, bmIndexRuneASCII(IndexRune))
}

func bmIndexRuneASCII(index func([]byte, rune) int) func(b *testing.B, n int) {