anchor.diff:  
          Future parse(_) {
   
  +         _cancel.check();
            PackedObject object = _matchObjectAtOffset(_offset);
            object.crc = getCrc32(data.sublist(object.offset, _offset));
   
  
positive.code:   int _offset = 0;
    ObjectStore _store;
    List<PackedObject> objects = [];
  
    Pack(this.data, [this._store]);
  
    Uint8List _peek(int length) => data.sublist(_offset, _offset + length);
  
  
negative.code:        }
  
         Future expandDeltified(PackedObject obj) {
           _cancel.check();
           return expandDeltifiedObject(obj).then((PackedObject deltifiedObj) {
             deltifiedObj.data = null;
             // TODO(grv) : add progress.
  