VideoCommon: add custom asset implementation and asset library that can load an asset

Source/Core/VideoCommon/Assets/CustomAsset.h

@@ -0,0 +1,81 @@
+// Copyright 2023 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "Common/CommonTypes.h"
+#include "VideoCommon/Assets/CustomAssetLibrary.h"
+
+#include <memory>
+#include <mutex>
+#include <optional>
+
+namespace VideoCommon
+{
+// An abstract class that provides operations for loading
+// data from a 'CustomAssetLibrary'
+class CustomAsset
+{
+public:
+  CustomAsset(std::shared_ptr<CustomAssetLibrary> library,
+              const CustomAssetLibrary::AssetID& asset_id);
+  virtual ~CustomAsset() = default;
+  CustomAsset(const CustomAsset&) = default;
+  CustomAsset(CustomAsset&&) = default;
+  CustomAsset& operator=(const CustomAsset&) = default;
+  CustomAsset& operator=(CustomAsset&&) = default;
+
+  // Loads the asset from the library returning a pass/fail result
+  bool Load();
+
+  // Queries the last time the asset was modified or standard epoch time
+  // if the asset hasn't been modified yet
+  CustomAssetLibrary::TimeType GetLastWriteTime() const;
+
+  // Returns the time that the data was last loaded
+  const CustomAssetLibrary::TimeType& GetLastLoadedTime() const;
+
+  // Returns an id that uniquely identifies this asset
+  const CustomAssetLibrary::AssetID& GetAssetId() const;
+
+  // A rough estimate of how much space this asset
+  // will take in memroy
+  std::size_t GetByteSizeInMemory() const;
+
+protected:
+  const std::shared_ptr<CustomAssetLibrary> m_owning_library;
+
+private:
+  virtual CustomAssetLibrary::LoadInfo LoadImpl(const CustomAssetLibrary::AssetID& asset_id) = 0;
+  CustomAssetLibrary::AssetID m_asset_id;
+  std::size_t m_bytes_loaded = 0;
+  CustomAssetLibrary::TimeType m_last_loaded_time;
+};
+
+// An abstract class that is expected to
+// be the base class for all assets
+// It provides a simple interface for
+// verifying that an asset data of type
+// 'UnderlyingType' is loaded by
+// checking against 'GetData()'
+template <typename UnderlyingType>
+class CustomLoadableAsset : public CustomAsset
+{
+public:
+  using CustomAsset::CustomAsset;
+
+  const UnderlyingType* GetData() const
+  {
+    std::lock_guard lk(m_lock);
+    if (m_loaded)
+      return &m_data;
+    return nullptr;
+  }
+
+protected:
+  bool m_loaded = false;
+  mutable std::mutex m_lock;
+  UnderlyingType m_data;
+};
+
+}  // namespace VideoCommon