anchor.diff:        int c = _decodeTable[input.codeUnitAt(i)];
         if (c < 0) {
           extrasLen++;
  -        if(c == -2 && !ignoreInvalidCharacters) {
  +        if(c == -2) {
             throw new FormatException('Invalid character: ${input[i]}');
           }
         }
  
positive.code:     return new String.fromCharCodes(out);
    }
  
    static List<int> base64StringToBytes(String input,
                                         [bool ignoreInvalidCharacters = true]) {
      int len = input.length;
      if (len == 0) {
        return new List<int>(0);
  
negative.code:           must be a multiple of 4. Input: $input''');
      }
  
      // Count pad characters.
      int padLength = 0;
      for (int i = len - 1; i >= 0; i--) {
        int currentCodeUnit = input.codeUnitAt(i);
  