for i := 0; i < b.N; i++ {
			j := index(buf, '世')
			if j != n-3 {
				b.Fatal("bad index", j)
			}
		}
		buf[n-3] = '\x00'
		buf[n-2] = '\x00'
		buf[n-1] = '\x00'
	}
}

func BenchmarkEqual(b *testing.B) {
	b.Run("0", func(b *testing.B) {
		var buf [4]byte
		buf1 := buf[0:0]
		buf2 := buf[1:1]
		for i := 0; i < b.N; i++ {
			eq := Equal(buf1, buf2)
			if !eq {
				b.Fatal("bad equal")