fromPacket static method

TsPacket fromPacket(String raw)

fromPacket creates a TsPacket from a string packet in the format of Layrz Protocol v3.

Implementation

static TsPacket fromPacket(String raw) {
  if (!raw.startsWith('<Ts>') || !raw.endsWith('</Ts>')) {
    throw ParseException('Invalid identification packet, should be <Ts>...</Ts>');
  }

  final parts = raw.substring(4, raw.length - 5).split(';');
  if (parts.length != 3) {
    throw MalformedException('Invalid packet parts, should have 3 parts');
  }

  int? receivedCrc = int.tryParse(parts[2], radix: 16);
  int? calculatedCrc = calculateCrc("${parts.sublist(0, 2).join(';')};".codeUnits);

  if (receivedCrc != calculatedCrc) {
    throw CrcException('Invalid CRC, received: $receivedCrc, calculated: $calculatedCrc');
  }

  DateTime timestamp;
  try {
    timestamp = DateTime.fromMillisecondsSinceEpoch(int.parse(parts[0]) * 1000, isUtc: true);
  } catch (e) {
    throw MalformedException('Invalid timestamp');
  }

  return TsPacket(
    timestamp: timestamp,
    tripId: parts[1],
  );
}