private ReaderImpl(GcsFilename file) {
Marshaller<ByteBuffer> identity = Marshallers.getByteBufferMarshaller();
Marshaller<KeyValue<ByteBuffer, ByteBuffer>> marshaller =
new KeyValueMarshaller<>(identity, identity);
GoogleCloudStorageLevelDbInputReader in =
new GoogleCloudStorageLevelDbInputReader(file, DEFAULT_IO_BUFFER_SIZE);
reader = new UnmarshallingInputReader<>(in, marshaller);
}