func calcCheckNum(code string) rune { x3 := len(code) == 7 sum := 0 for _, r := range code { curNum := utils.RuneToInt(r) if curNum < 0 || curNum > 9 { return 'B' } if x3 { curNum = curNum * 3 } x3 = !x3 sum += curNum } return utils.IntToRune((10 - (sum % 10)) % 10) }
// AddCheckSum calculates the correct check-digit and appends it to the given content. func AddCheckSum(content string) (string, error) { if content == "" { return "", errors.New("content is empty") } even := len(content)%2 == 1 sum := 0 for _, r := range content { if _, ok := encodingTable[r]; ok { value := utils.RuneToInt(r) if even { sum += value * 3 } else { sum += value } even = !even } else { return "", fmt.Errorf("can not encode \"%s\"", content) } } return content + string(utils.IntToRune(sum%10)), nil }