}

func indexBytePortable(s []byte, c byte) int {
	for i, b := range s {
		if b == c {
			return i
		}
	}
	return -1
}

// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
func LastIndex(s, sep []byte) int {
	n := len(sep)
	switch {
	case n == 0:
		return len(s)
	case n == 1:
		return bytealg.LastIndexByte(s, sep[0])
	case n == len(s):