payload property

@override Uint8List get payload

Implementation

@override
Uint8List get payload {
  List<int> languagePayload = utf8.encode(language!);
  late List<int> textPayload;
  late int encodingFlag;
  if (encoding == TextEncoding.UTF8) {
    textPayload = utf8.encode(text!);
    encodingFlag = 0;
  } else if (encoding == TextEncoding.UTF16) {
    // use UTF-16 LE only in encoding
    List<int> encodedChar = [0xFEFF];
    encodedChar.addAll(text!.codeUnits);
    textPayload = Uint16List.fromList(encodedChar).buffer.asUint8List();
    encodingFlag = 1;
  }
  int flag = (encodingFlag << 7) | languagePayload.length;
  return Uint8List.fromList([flag] + languagePayload + textPayload);
}

@override set payload (Uint8List? payload)

Implementation

@override
set payload(Uint8List? payload) {
  var stream = ByteStream(payload!);

  int flag = stream.readByte();
  int languagePayloadLength = flag & 0x3F;

  assert(languagePayloadLength != 0, "language code length can not be zero");

  if (flag >> 7 == 1) {
    encoding = TextEncoding.UTF16;
  } else {
    encoding = TextEncoding.UTF8;
  }

  var languagePayload = stream.readBytes(languagePayloadLength);
  var textPayload = stream.readAll();
  language = utf8.decode(languagePayload);

  if (encoding == TextEncoding.UTF8) {
    text = utf8.decode(textPayload);
  } else if (encoding == TextEncoding.UTF16) {
    // decode UTF-16 manually
    var bytes = textPayload;
    Endianness end;
    if (bytes[0] == 0xFF) {
      end = Endianness.Little;
    } else if (bytes[1] == 0xFE) {
      end = Endianness.Big;
    } else {
      throw ArgumentError("Unknown BOM in UTF-16 encoded string.");
    }
    StringBuffer buffer = StringBuffer();
    for (int i = 2; i < bytes.length;) {
      int firstWord = end == Endianness.Little
          ? (bytes[i + 1] << 8) + bytes[i]
          : (bytes[i] << 8) + bytes[i + 1];
      if (0xD800 <= firstWord && firstWord <= 0xDBFF) {
        int secondWord = end == Endianness.Little
            ? (bytes[i + 3] << 8) + bytes[i + 2]
            : (bytes[i + 2] << 8) + bytes[i + 3];
        int charCode =
            ((firstWord - 0xD800) << 10) + (secondWord - 0xDC00) + 0x10000;
        buffer.writeCharCode(charCode);
        i += 4;
      } else {
        buffer.writeCharCode(firstWord);
        i += 2;
      }
    }
    text = buffer.toString();
  }
}