takeFramedBytes method
Copies the accumulated payload into a fresh framed byte list:
[4-byte payload length][payload bytes].
Implementation
Uint8List takeFramedBytes() {
final total = 4 + _length;
final framed = Uint8List(total);
ByteData.sublistView(framed).setInt32(0, _length, Endian.little);
framed.setRange(4, total, _buffer);
return framed;
}