feed method
Append chunk to the internal buffer and return any items that became
fully available. The returned list may be empty if the chunk only
completed part of a frame.
Throws FormatException if a frame declares an unknown tag.
Implementation
List<MultiResultItem> feed(Uint8List chunk) {
if (chunk.isEmpty) return const [];
_buffer.add(chunk);
return _drainCompleteFrames();
}