writeMessage method

void writeMessage(int channelId, Message message, { MessageProperties? properties, Object? payloadContent, })

Implementation

void writeMessage(int channelId, Message message,
    {MessageProperties? properties, Object? payloadContent}) {
  // Make sure our buffer contains no stale data from previous messages
  _outputEncoder.writer.clear();

  // Buffer message so we can measure its length
  message.serialize(_outputEncoder);

  // Now that we know the message length, create the header and prepend it to the encoder
  _frameHeader
    ..channel = channelId
    ..type = FrameType.METHOD
    ..size = _outputEncoder.writer.lengthInBytes
    ..serialize(_bufferEncoder);

  _outputEncoder.writer
    ..addFirst(_bufferEncoder.writer.joinChunks())
    ..addLast(FRAME_TERMINATOR_SEQUENCE);

  _bufferEncoder.writer.clear();

  // if a data payload is specified, encode it and append it before flushing the buffer
  if (payloadContent != null) {
    // Serialize content
    Uint8List serializedContent;
    if (payloadContent is Uint8List) {
      serializedContent = payloadContent;
    } else if (payloadContent is Map || payloadContent is Iterable) {
      serializedContent =
          Uint8List.fromList(utf8.encode(json.encode(payloadContent)));
      properties = (properties == null ? MessageProperties() : properties)
        ..contentType = "application/json"
        ..contentEncoding = "UTF-8";
    } else if (payloadContent is String) {
      serializedContent = Uint8List.fromList(utf8.encode(payloadContent));
    } else {
      throw ArgumentError(
          "Message payload should be either a Map, an Iterable, a String or an UInt8List instance");
    }

    // Build the content header
    _contentHeader
      ..classId = message.msgClassId
      ..bodySize = serializedContent.lengthInBytes
      ..properties = properties
      ..serialize(_bufferEncoder);

    Uint8List serializedContentHeader = _bufferEncoder.writer.joinChunks();
    _contentHeader.properties = null;
    _bufferEncoder.writer.clear();

    // Fill in the frame header for the content header frame
    _frameHeader
      ..type = FrameType.HEADER
      ..size = serializedContentHeader.lengthInBytes
      ..serialize(_bufferEncoder);

    // Append after the method frame
    _outputEncoder.writer
      ..addLast(_bufferEncoder.writer.joinChunks())
      ..addLast(serializedContentHeader)
      ..addLast(FRAME_TERMINATOR_SEQUENCE);
    _bufferEncoder.writer.clear();

    // Emit the payload data split in ceil( length / maxFrameLength ) chunks
    int contentLen = serializedContent.lengthInBytes;
    for (int offset = 0;
        offset < contentLen;
        offset += _tuningSettings.maxFrameSize) {
      // Setup  and encode the frame header
      _frameHeader
        ..type = FrameType.BODY
        ..size = math.min(_tuningSettings.maxFrameSize, contentLen - offset)
        ..serialize(_outputEncoder);

      // Encode the payload for the frame
      _outputEncoder.writer
        ..addLast(Uint8List.view(
            serializedContent.buffer, offset, _frameHeader.size))
        ..addLast(FRAME_TERMINATOR_SEQUENCE);
    }
  }
}