TF_Status* status);

// Flush local buffers to the filesystem. If the process terminates after a
// successful flush, the contents may still be persisted, since the underlying
// filesystem may eventually flush the contents.  If the OS or machine crashes
// after a successful flush, the contents may or may not be persisted, depending
// on the implementation.

  ASSERT_TF_OK(status_);
  tf_writable_file::Flush(file, status_);
  ASSERT_TF_OK(status_);
  ASSERT_TRUE(
      CompareWithServer(filepath, 0, 4, &gcs_file->gcs_client, status_));

  tf_writable_file::Append(file, content + 4, 4, status_);
  ASSERT_TF_OK(status_);
  length = tf_writable_file::Tell(file, status_);
  ASSERT_EQ(length, 8);
  ASSERT_TF_OK(status_);
  tf_writable_file::Flush(file, status_);
  ASSERT_TF_OK(status_);

namespace tf_writable_file {
void Cleanup(TF_WritableFile* file);
void Append(const TF_WritableFile* file, const char* buffer, size_t n,
            TF_Status* status);
int64_t Tell(const TF_WritableFile* file, TF_Status* status);
void Flush(const TF_WritableFile* file, TF_Status* status);
void Sync(const TF_WritableFile* file, TF_Status* status);
void Close(const TF_WritableFile* file, TF_Status* status);
}  // namespace tf_writable_file

}

Status ModularWritableFile::Flush() {
  if (ops_->flush == nullptr) return OkStatus();

  UniquePtrTo_TF_Status plugin_status(TF_NewStatus(), TF_DeleteStatus);
  ops_->flush(file_.get(), plugin_status.get());
  return StatusFromTF_Status(plugin_status.get());
}

Status ModularWritableFile::Sync() {
  if (ops_->sync == nullptr) return Flush();

  const std::string test_data("asdf");
  status = new_file->Append(test_data);
  if (!status.ok()) GTEST_SKIP() << "Append() not supported: " << status;
  status = new_file->Flush();
  if (!status.ok()) GTEST_SKIP() << "Flush() not supported: " << status;
  status = new_file->Close();
  if (!status.ok()) GTEST_SKIP() << "Close() not supported: " << status;

  std::unique_ptr<ReadOnlyMemoryRegion> region;

  std::vector<char> out;
  TF_EXPECT_OK(ReadCache(&cache, "", block_size / 2, block_size / 2, &out));
  EXPECT_EQ(out.size(), block_size / 2);

  EXPECT_EQ(1, num_requests);
}

TEST(RamFileBlockCacheTest, Flush) {
  int calls = 0;
  auto fetcher = [&calls](const string& filename, size_t offset, size_t n,
                          char* buffer, TF_Status* status) -> int64_t {
    calls++;
    memset(buffer, 'x', n);

      // be used within RemoveFile_Locked after `it` is deleted.
      RemoveFile_Locked(std::string(it->first.first));
    }
  }
}

void RamFileBlockCache::Flush() {
  absl::MutexLock lock(&mu_);
  block_map_.clear();
  lru_list_.clear();
  lra_list_.clear();
  cache_size_ = 0;
}

void RamFileBlockCache::RemoveFile(const std::string& filename) {

  // For historical reasons, this does the same as `Flush` at the moment.
  // TODO(b/144055243): This should use `fsync`/`sync`.
  Flush(file, status);
}

static void Close(const TF_WritableFile* file, TF_Status* status) {
  auto posix_file = static_cast<PosixFile*>(file->plugin_file);

  if (fclose(posix_file->handle) != 0)
    TF_SetStatusFromIOError(status, errno, posix_file->filename);
  else

  return position == -1
             ? -1
             : position + (gcs_file->offset == -1 ? 0 : gcs_file->offset);
}

void Flush(const TF_WritableFile* file, TF_Status* status) {
  auto gcs_file = static_cast<GCSFile*>(file->plugin_file);
  if (gcs_file->sync_need) {
    TF_VLog(3, "Flush started: gs://%s/%s", gcs_file->bucket.c_str(),
            gcs_file->object.c_str());
    if (!gcs_file->outfile) {

  auto* cc_file = reinterpret_cast<::tensorflow::WritableFile*>(handle);
  TF_SetStatus(status, TF_OK, "");
  ::tensorflow::Set_TF_Status_from_Status(status, cc_file->Flush());
}

void TF_AppendWritableFile(TF_WritableFileHandle* handle, const char* data,
                           size_t length, TF_Status* status) {
  auto* cc_file = reinterpret_cast<::tensorflow::WritableFile*>(handle);