docs: private int advanceChar() throws JsonParserException {
      if (eof)
        return -1;
      int c = string.charAt(index);
      if (c == '\n') {
        linePos++;
        rowPos = index + 1;
        utf8adjust = 0;
      }
  
      index++;
      if (index >= bufferLength)
        eof = true;
  
      return c;
    }