// for a k-rune slice.
func ReplaceAll(s, old, new []byte) []byte {
	return Replace(s, old, new, -1)
}

// EqualFold reports whether s and t, interpreted as UTF-8 strings,
// are equal under simple Unicode case-folding, which is a more general
// form of case-insensitivity.
func EqualFold(s, t []byte) bool {
	// ASCII fast path
	i := 0
	for ; i < len(s) && i < len(t); i++ {
		sr := s[i]