generalizedTimeToDate static method

DateTime? generalizedTimeToDate({ required List<int> contentData, })

Converts a GeneralizedTime value to a date.

contentData the GeneralizedTime value to convert.

Implementation

static DateTime? generalizedTimeToDate({required List<int> contentData}) {
  /* The following formats can be used:
    YYYYMMDDHHMMSS
    YYYYMMDDHHMMSS.fff
    YYYYMMDDHHMMSSZ
    YYYYMMDDHHMMSS.fffZ
    YYYYMMDDHHMMSS+hh'mm'
    YYYYMMDDHHMMSS.fff+hh'mm'
    YYYYMMDDHHMMSS-hh'mm'
    YYYYMMDDHHMMSS.fff-hh'mm'
    Where:
    YYYY is the year
    MM is the month (01 to 12)
    DD is the day (01 to 31)
    hh is the hour (00 to 23)
    mm are the minutes (00 to 59)
    ss are the seconds (00 to 59)
    .fff is the second fraction, accurate to three decimal places
    Z indicates that local time is GMT, + indicates that local time is
    later than GMT, and - indicates that local time is earlier than GMT
    hh' is the absolute value of the offset from GMT in hours
    mm' is the absolute value of the offset from GMT in minutes */

  String? gentime;
  try {
    gentime = utf8.decode(contentData);
  } catch (e) {}
  if (gentime == null) {
    return null;
  }

  // if YY >= 50 use 19xx, if YY < 50 use 20xx
  // ignore: non_constant_identifier_names
  var YYYY = int.parse(gentime.substring(0, 4), radix: 10);
  // ignore: non_constant_identifier_names
  var MM = int.parse(gentime.substring(4, 6), radix: 10);
  // ignore: non_constant_identifier_names
  var DD = int.parse(gentime.substring(6, 8), radix: 10);
  var hh = int.parse(gentime.substring(8, 10), radix: 10);
  var mm = int.parse(gentime.substring(10, 12), radix: 10);
  var ss = int.parse(gentime.substring(12, 14), radix: 10);

  double fff = 0.0;
  var offset = 0;
  var isUTC = false;

  if (gentime[gentime.length - 1] == 'Z') {
    isUTC = true;
  }

  var end = gentime.length - 5;
  var c = gentime[end];
  if (c == '+' || c == '-') {
    // get hours+minutes offset
    var hhoffset =
        int.parse(gentime.substring(end + 1, end + 1 + 2), radix: 10);
    var mmoffset =
        int.parse(gentime.substring(end + 4, end + 4 + 2), radix: 10);

    // calculate offset in milliseconds
    offset = hhoffset * 60 + mmoffset;
    offset *= 60000;

    // apply offset
    if (c == '+') {
      offset *= -1;
    }

    isUTC = true;
  }

  // check for second fraction
  if (gentime[14] == '.') {
    fff = double.parse(gentime.substring(14)) * 1000;
  }

  var date = DateTime.utc(YYYY, MM, DD, hh, mm, ss, fff.toInt());

  if (isUTC) {
    var offsetDuration = Duration(milliseconds: offset);
    date.add(offsetDuration);
  }

  return date;
}