std::string data {"5020303000182306,,30502,,2,0,,,0"},str = data;
  std::regex re(",,");
  const std::string fmt = ", ,";
  do
  {
    str = std::regex_replace(str,re,fmt,std::regex_constants::match_prev_avail);
  }
  while(std::regex_search(str,re));
  std::cerr << str << std::endl;