code: public static UnsafeRow createFromByteArray(int numBytes, int numFields) {
      final UnsafeRow row = new UnsafeRow(numFields);
      row.pointTo(new byte[numBytes], numBytes);
      return row;
    }
docs: Creates an empty UnsafeRow from a byte array with specified numBytes and numFields.
  The returned row is invalid until we call copyFrom on it.