std::unique_ptr<ExpiringLRUCache<GcsFileStat>> stat_cache;
  GCSFile(google::cloud::storage::Client&& gcs_client);
  // This constructor is used for testing purpose only.
  GCSFile(google::cloud::storage::Client&& gcs_client, bool compose,
          uint64_t block_size, size_t max_bytes, uint64_t max_staleness,
          uint64_t stat_cache_max_age, size_t stat_cache_max_entries);
} GCSFile;

==============================================================================*/
#ifndef TENSORFLOW_C_EXPERIMENTAL_FILESYSTEM_PLUGINS_POSIX_COPY_FILE_H_
#define TENSORFLOW_C_EXPERIMENTAL_FILESYSTEM_PLUGINS_POSIX_COPY_FILE_H_

#include <sys/stat.h>

namespace tf_posix_filesystem {

// Transfers up to `size` bytes from `dst_fd` to `src_fd`.
//
// This method uses `sendfile` if available (i.e., linux 2.6.33 or later) or an
// intermediate buffer if not.
//

    if (max_age_ == 0) {
      return compute_func(key, value, status);
    }

    // Note: we hold onto mu_ for the rest of this function. In practice, this
    // is okay, as stat requests are typically fast, and concurrent requests are
    // often for the same file. Future work can split this up into one lock per
    // key if this proves to be a significant performance bottleneck.

#ifndef TENSORFLOW_C_EXPERIMENTAL_FILESYSTEM_PLUGINS_POSIX_POSIX_FILESYSTEM_HELPER_H_
#define TENSORFLOW_C_EXPERIMENTAL_FILESYSTEM_PLUGINS_POSIX_POSIX_FILESYSTEM_HELPER_H_

#include <dirent.h>
#include <sys/stat.h>

namespace tf_posix_filesystem {

// Copies up to `size` of `src` to `dst`, creating destination if needed.
//
// Callers should pass size of `src` in `size` and the permissions of `src` in

                              TransactionToken* token) override;
  Status CreateDir(const std::string& dirname,
                   TransactionToken* token) override;
  Status Stat(const std::string& fname, TransactionToken* token,
              FileStatistics* stat) override;
  Status IsDirectory(const std::string& fname,
                     TransactionToken* token) override;
  Status GetFileSize(const std::string& fname, TransactionToken* token,

  ///     filesystem entry.
  ///   * Must set `status` to `TF_FAILED_PRECONDITION` if `path` is invalid.
  ///   * Might use any other error value for `status` to signal other errors.
  void (*stat)(const TF_Filesystem* filesystem, const char* path,
               TF_FileStatistics* stats, TF_Status* status);

  /// Checks whether the given `path` is a directory or not.
  ///