Packing and unpacking integer lists into a single integer list

code.dart

/// Unpack an integer list into a list of integer lists.
List<List<int>> _unpackIntLists(List<int> input) {
  final output = new List<List<int>>();
  for (var i = 0; i < input.length;) {
    final length = input[i++];
    output.add(input.sublist(i, i + length));
    i += length;
  }
  return output;
}

/// Pack list of integer lists into a single integer list.
List<int> _packIntLists(List<List<int>> input) {
  final output = new List<int>();
  for (final list in input) {
    output.add(list.length);
    output.addAll(list);
  }
  return output;
}