std::vector<char> out;

  // First read.
  EXPECT_TRUE(cache.ValidateAndUpdateFileSignature(filename, 123));
  TF_EXPECT_OK(ReadCache(&cache, filename, 0, 16, &out));
  EXPECT_EQ(calls, 1);

  // Second read. Hit cache.
  EXPECT_TRUE(cache.ValidateAndUpdateFileSignature(filename, 123));
  TF_EXPECT_OK(ReadCache(&cache, filename, 0, 16, &out));
  EXPECT_EQ(calls, 1);

      break;
    }
  }
  TF_SetStatus(status, TF_OK, "");
  return total_bytes_transferred;
}

bool RamFileBlockCache::ValidateAndUpdateFileSignature(
    const std::string& filename, int64_t file_signature) {
  absl::MutexLock lock(&mu_);
  auto it = file_signature_map_.find(filename);
  if (it != file_signature_map_.end()) {

  // cache. Returns true if the signature doesn't change or the file doesn't
  // exist before. If the signature changes, update the existing signature with
  // the new one and remove the file from cache.
  bool ValidateAndUpdateFileSignature(const std::string& filename,
                                      int64_t file_signature)
      ABSL_LOCKS_EXCLUDED(mu_);

  /// Remove all cached blocks for `filename`.

                                  status);
          },
          status);
      if (TF_GetCode(status) != TF_OK) return -1;
      if (!gcs_file->file_block_cache->ValidateAndUpdateFileSignature(
              path, stat.generation_number)) {
        TF_VLog(
            1,
            "File signature has been changed. Refreshing the cache. Path: %s",
            path.c_str());
      }