if !alg.IsSet() {
		return nil
	}
	wantParts := 0
	if strings.ContainsRune(value, '-') {
		valSplit := strings.Split(value, "-")
		if len(valSplit) != 2 {
			return nil
		}
		value = valSplit[0]
		nParts, err := strconv.Atoi(valSplit[1])
		if err != nil {
			return nil
		}
		alg |= ChecksumMultipart
		wantParts = nParts
	}