capture method Null safety

Implementation

List<RawSample> capture(Uint8List encodedImage) {
  final cap = _dll_handle.lookupFunction<_CapturerCapBytes_c, _CapturerCapBytes_dart>(_c_namespace + 'Capturer_capture_encoded_image');

  final Pointer<Uint8> frameData = malloc.allocate<Uint8>(encodedImage.length);
  final pointerList = frameData.asTypedList(encodedImage.length);
  Pointer<Pointer<Void>> _emptyPointerList = malloc.allocate(sizeOf<Pointer<Pointer<Void>>>() * 100);
  Pointer<Pointer<Void>> exception = _getException();
  List<int> addressBefore = new List<int>.generate(100, (i) => _emptyPointerList[i].address);

  pointerList.setAll(0, encodedImage);
  cap(_impl, frameData.cast(), encodedImage.length, _emptyPointerList.cast(), Pointer.fromFunction(_assign_pointers_vector_func), exception);
  checkException(exception, _dll_handle);

  List<RawSample> rss = [];

  for (var i = 0; i < 100; i++) {
    if (addressBefore[i] != _emptyPointerList[i].address)
      rss.add(RawSample(_dll_handle, _emptyPointerList[i]));
    else
      break;
  }

  malloc.free(_emptyPointerList);
  malloc.free(frameData);
  return rss;
}