private String padOutput(int value) {
    String result = Integer.toString(value);
    for (int i = result.length(); i < codeLength; i++) {
      result = "0" + result;
    }
    return result;
  }
@param mac A {@link Mac} used to generate passcodes
@param passCodeLength The length of the decimal passcode
java/com/google/android/apps/authenticator/otp/PasscodeGenerator.java