list_files(this->fullpath_, [&](tinydir_file& f) {
        obs.write_bytes(f.is_dir ? "type=dir;"sv : "type=file;"sv);
        obs.write_bytes("modify="sv);
        struct stat st;
        if (0 == ::stat(f.path, &st))
        {
          struct tm tinfo;
          localtime_r(&st.st_mtime, &tinfo);

          char buf[96];
          strftime(buf, 96, "%Y%m%d%H%M%S", &tinfo);
          obs.write_bytes(buf);
          if (st.st_mode & S_IFREG)
          {
            obs.write_bytes(";size="sv);
            obs.write_bytes(std::to_string(st.st_size));
          }
        }

        obs.write_bytes("; "sv);
        obs.write_bytes(f.name);
        obs.write_bytes("\r\n"sv);
      });