// function. Otherwise return nullptr in result and error Status from the
// function.
//
// If `library_filename` has already been loaded, we return a cached handle.
// Device and Kernels/Ops are registered as globals when a library is loaded
// for the first time.
TF_Library* TF_LoadPluggableDeviceLibrary(const char* library_filename,

  TFE_TensorHandle* var_value_unpacked =
      UnpackTensorHandle(var_value, status.get());
  ASSERT_TRUE(TF_GetCode(status.get()) == TF_OK) << TF_Message(status.get());
  std::unique_ptr<TF_Tensor, decltype(&TF_DeleteTensor)> resolved_value(
      TFE_TensorHandleResolve(var_value_unpacked, status.get()),
      TF_DeleteTensor);

        status, TF_UNIMPLEMENTED,
        absl::StrCat(
            "Trying to copy a tensor out of a parallel device. Since there "
            "are multiple components to parallel tensors, they must be "
            "unpacked explicitly.\n",
            tensorflow::unwrap(tensor)->DebugString())
            .c_str());
    return nullptr;
  }
}

// For TFE_CustomDevice::execute in the parallel device registration.
//

constexpr char kMaxCacheSize[] = "GCS_READ_CACHE_MAX_SIZE_MB";
constexpr size_t kDefaultMaxCacheSize = 0;
// The environment variable that overrides the maximum staleness of cached file
// contents. Once any block of a file reaches this staleness, all cached blocks
// will be evicted on the next read.
constexpr char kMaxStaleness[] = "GCS_READ_CACHE_MAX_STALENESS";
constexpr uint64_t kDefaultMaxStaleness = 0;

  // ...but is no longer valid 2 seconds after the insertion.
  env->SetNowSeconds(6);
  EXPECT_FALSE(cache.Lookup(key, &value));
}

TEST(ExpiringLRUCacheTest, MaxEntries) {
  // max_age of 0 means nothing will be cached.
  tf_gcs_filesystem::ExpiringLRUCache<int> cache1(0, 4);
  cache1.Insert("a", 1);
  int value = 0;
  EXPECT_FALSE(cache1.Lookup("a", &value));
  // Now set max_age = 1 and verify the LRU eviction logic.

  TF_EXPECT_OK(ReadCache(&cache, "", block_size, block_size, &out));
  EXPECT_EQ(out.size(), 1);
  // Now read the first block; this should yield an INTERNAL error because we
  // had already cached a partial block at a later position.
  Status status = ReadCache(&cache, "", 0, block_size, &out);
  EXPECT_EQ(status.code(), error::INTERNAL);
}

TEST(RamFileBlockCacheTest, LRU) {
  const size_t block_size = 16;