/// 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

  absl::Mutex mu_;

  /// The cache (a map from string key to Entry).
  std::map<std::string, Entry> cache_ ABSL_GUARDED_BY(mu_);

  /// The LRU list of entries. The front of the list identifies the most
  /// recently accessed entry.
  std::list<std::string> lru_list_ ABSL_GUARDED_BY(mu_);
};

}  // namespace tf_gcs_filesystem

} GcsFileStat;

typedef struct GCSFile {
  google::cloud::storage::Client gcs_client;  // owned
  bool compose;
  absl::Mutex block_cache_lock;
  std::shared_ptr<RamFileBlockCache> file_block_cache
      ABSL_GUARDED_BY(block_cache_lock);
  uint64_t block_size;  // Reads smaller than block_size will trigger a read
                        // of block_size.
  std::unique_ptr<ExpiringLRUCache<GcsFileStat>> stat_cache;

  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),