code: @Override
    public int putByteArray(int rowId, byte[] value, int offset, int length) {
      int result = arrayData().appendBytes(length, value, offset);
      Platform.putInt(null, lengthData + 4L * rowId, length);
      Platform.putInt(null, offsetData + 4L * rowId, result);
      return result;
    }
docs: APIs dealing with ByteArrays