typedef struct PosixFile {
  const char* filename;
  int fd;
} PosixFile;

static void Cleanup(TF_RandomAccessFile* file) {
  auto posix_file = static_cast<PosixFile*>(file->plugin_file);
  close(posix_file->fd);
  // This would be safe to free using `free` directly as it is only opaque.
  // However, it is better to be consistent everywhere.
  plugin_memory_free(const_cast<char*>(posix_file->filename));
  delete posix_file;
}

  std::vector<std::string> variable_list;
};

TF_CheckpointReader* TF_NewCheckpointReader(const char* filename,
                                            TF_Status* status) {
  TF_CheckpointReader* reader = new TF_CheckpointReader(filename, status);
  if (!status->status.ok()) {
    TF_DeleteCheckpointReader(reader);
    return nullptr;
  }

  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);

  // Third read. File signatures are different.
  EXPECT_FALSE(cache.ValidateAndUpdateFileSignature(filename, 321));

}

void RamFileBlockCache::RemoveFile(const std::string& filename) {
  absl::MutexLock lock(&mu_);
  RemoveFile_Locked(filename);
}

void RamFileBlockCache::RemoveFile_Locked(const std::string& filename) {
  Key begin = std::make_pair(filename, 0);
  auto it = block_map_.lower_bound(begin);
  while (it != block_map_.end() && it->first.first == filename) {
    auto next = std::next(it);
    RemoveBlock(it);

CheckpointReader::CheckpointReader(const string& filename, TF_Status* status)
    : reader_(nullptr),
      v2_reader_(nullptr),
      var_to_shape_map_(nullptr),
      var_to_data_type_map_(nullptr) {
  // Depending on whether this is a V2 ckpt, initializes "reader_" or
  // "v2_reader_".
  std::vector<string> v2_path;
  if (Env::Default()->GetMatchingPaths(MetaFilename(filename), &v2_path).ok() &&
      !v2_path.empty()) {

                c_outputs, target_oper_names, nullptr, status);
}

TF_Library* TF_LoadLibrary(const char* library_filename, TF_Status* status) {
  TF_Library* lib_handle = new TF_Library;
  status->status = tensorflow::LoadDynamicLibrary(
      library_filename, &lib_handle->lib_handle, &lib_handle->op_list.data,
      &lib_handle->op_list.length);
  if (!status->status.ok()) {
    delete lib_handle;

    if (!status.ok())
      GTEST_SKIP() << "NewWritableFile() not supported: " << status;
  }

  for (const auto& filename : other_filenames) {
    std::unique_ptr<WritableFile> file;
    Status status = env_->NewWritableFile(filename, &file);
    if (!status.ok())
      GTEST_SKIP() << "NewWritableFile() not supported: " << status;
  }

  std::vector<std::string> results;

  *undeleted_file_count = f;
  *undeleted_dir_count = d;
}

void TF_FileStat(const char* filename, TF_FileStatistics* stats,
                 TF_Status* status) {
  ::tensorflow::FileStatistics cc_stats;
  TF_SetStatus(status, TF_OK, "");
  ::tensorflow::Status s =
      ::tensorflow::Env::Default()->Stat(filename, &cc_stats);
  ::tensorflow::Set_TF_Status_from_Status(status, s);
  if (s.ok()) {

}

Status ModularRandomAccessFile::Name(StringPiece* result) const {
  *result = filename_;
  return OkStatus();
}

Status ModularWritableFile::Append(StringPiece data) {
  if (ops_->append == nullptr)
    return errors::Unimplemented(tensorflow::strings::StrCat(
        "Append() not implemented for ", filename_));

  UniquePtrTo_TF_Status plugin_status(TF_NewStatus(), TF_DeleteStatus);

  file_block_cache = std::make_unique<RamFileBlockCache>(
      block_size, max_bytes, max_staleness,
      [this](const std::string& filename, size_t offset, size_t buffer_size,
             char* buffer, TF_Status* status) {
        return LoadBufferFromGCS(filename, offset, buffer_size, buffer, this,
                                 status);
      });

  uint64_t stat_cache_max_age = kStatCacheDefaultMaxAge;