if !needsEncoding(s) {
		return s
	}
	return e.encodeWord(charset, s)
}

func needsEncoding(s string) bool {
	for _, b := range s {
		if (b < ' ' || b > '~') && b != '\t' {
			return true
		}
	}
	return false
}

// encodeWord encodes a string into an encoded-word.
func (e WordEncoder) encodeWord(charset, s string) string {
	var buf strings.Builder