/// fetched from the underlying block store.
  std::list<Key> lra_list_ ABSL_GUARDED_BY(mu_);

  /// The combined number of bytes in all of the cached blocks.
  size_t cache_size_ ABSL_GUARDED_BY(mu_) = 0;

  // A filename->file_signature map.
  std::map<std::string, int64_t> file_signature_map_ ABSL_GUARDED_BY(mu_);
};

}  // namespace tf_gcs_filesystem

  const std::string path;
  const bool is_cache_enable;
  const uint64_t buffer_size;
  ReadFn read_fn;
  absl::Mutex buffer_mutex;
  uint64_t buffer_start ABSL_GUARDED_BY(buffer_mutex);
  bool buffer_end_is_past_eof ABSL_GUARDED_BY(buffer_mutex);
  std::string buffer ABSL_GUARDED_BY(buffer_mutex);

  GCSFile(std::string path, bool is_cache_enable, uint64_t buffer_size,
          ReadFn read_fn)
      : path(path),