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;

// This function is used to initialize a filesystem without the need of setting
// manually environement variables.
void InitTest(TF_Filesystem* filesystem, bool compose, uint64_t block_size,
              size_t max_bytes, uint64_t max_staleness,

  /// that there is no limit on the number of entries in the cache (however, if
  /// `max_age` is also 0, the cache will not be populated).
  ExpiringLRUCache(uint64_t max_age, size_t max_entries,
                   std::function<uint64_t()> timer_seconds = TF_NowSeconds)
      : max_age_(max_age),
        max_entries_(max_entries),
        timer_seconds_(timer_seconds) {}

namespace tf_random_access_file {
using ReadFn =
    std::function<int64_t(const std::string& path, uint64_t offset, size_t n,
                          char* buffer, TF_Status* status)>;
typedef struct GCSFile {
  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);

                                TF_Status* status)>
      BlockFetcher;

  RamFileBlockCache(size_t block_size, size_t max_bytes, uint64_t max_staleness,
                    BlockFetcher block_fetcher,
                    std::function<uint64_t()> timer_seconds = TF_NowSeconds)
      : block_size_(block_size),
        max_bytes_(max_bytes),
        max_staleness_(max_staleness),

  // However, it is better to be consistent everywhere.
  plugin_memory_free(const_cast<char*>(posix_file->filename));
  delete posix_file;
}

static int64_t Read(const TF_RandomAccessFile* file, uint64_t offset, size_t n,
                    char* buffer, TF_Status* status) {
  auto posix_file = static_cast<PosixFile*>(file->plugin_file);
  char* dst = buffer;
  int64_t read = 0;

  while (n > 0) {

}

TF_CAPI_EXPORT extern uint64_t TF_NowNanos(void) {
  return ::tensorflow::Env::Default()->NowNanos();
}

// Returns the number of microseconds since the Unix epoch.
TF_CAPI_EXPORT extern uint64_t TF_NowMicros(void) {
  return ::tensorflow::Env::Default()->NowMicros();
}

// Returns the number of seconds since the Unix epoch.
TF_CAPI_EXPORT extern uint64_t TF_NowSeconds(void) {

// Returns the number of nanoseconds since the Unix epoch.
TF_CAPI_EXPORT extern uint64_t TF_NowNanos(void);

// Returns the number of microseconds since the Unix epoch.
TF_CAPI_EXPORT extern uint64_t TF_NowMicros(void);

// Returns the number of seconds since the Unix epoch.
TF_CAPI_EXPORT extern uint64_t TF_NowSeconds(void);

// Populates a TF_ThreadOptions struct with system-default values.

  off_t offset = 0;
  int bytes_transferred = 0;
  int rc = 1;
  // When `sendfile` returns 0 we stop copying and let callers handle this.
  while (offset < size && rc > 0) {
    // Use uint64 for safe compare SSIZE_MAX
    uint64_t chunk = size - offset;
    if (chunk > SSIZE_MAX) chunk = SSIZE_MAX;

    rc = sendfile(dst_fd, src_fd, &offset, static_cast<size_t>(chunk));
    if (rc < 0) return -1;
    bytes_transferred += rc;

  return cache_size_;
}

void RamFileBlockCache::Prune() {
  while (!stop_pruning_thread_.WaitForNotificationWithTimeout(
      absl::Microseconds(1000000))) {
    absl::MutexLock lock(&mu_);
    uint64_t now = timer_seconds_();
    while (!lra_list_.empty()) {
      auto it = block_map_.find(lra_list_.back());
      if (now - it->second->timestamp <= max_staleness_) {

  /// `is_directory`, `delete_file`, and `delete_dir`.
  void (*delete_recursively)(const TF_Filesystem* filesystem, const char* path,
                             uint64_t* undeleted_files,
                             uint64_t* undeleted_dirs, TF_Status* status);

  /// Renames the file given by `src` to that in `dst`.
  ///
  /// Replaces `dst` if it exists. In case of error, both `src` and `dst` keep