ui/base/metadata/metadata_cache.h

// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_BASE_METADATA_METADATA_CACHE_H_
#define UI_BASE_METADATA_METADATA_CACHE_H_

#include <memory>
#include <utility>
#include <vector>

#include "base/component_export.h"
#include "base/macros.h"
#include "ui/base/metadata/metadata_types.h"

namespace ui {
namespace metadata {

class ClassMetaData;
// The MetaDataCache speeds up frequent traversals over the meta data for
// various classes by caching one instance of ClassMetaData for each class on
// which metadata is required.
// MetaDataCache is implemented as a singleton. This also implies that each
// instance of ClassMetaData registered into the cache represents one and only
// one class type.
class COMPONENT_EXPORT(UI_BASE_METADATA) MetaDataCache {
 public:
  MetaDataCache();

  static MetaDataCache* GetInstance();

  void AddClassMetaData(std::unique_ptr<ClassMetaData> class_data);
  std::vector<ClassMetaData*>& GetCachedTypes();

 private:
  ~MetaDataCache();

  std::vector<ClassMetaData*> class_data_cache_;

  DISALLOW_COPY_AND_ASSIGN(MetaDataCache);
};

// These functions are rarely called directly, rather they are called from
// within the macros used to declare the metadata for a class. See the macros in
// reflections_macros.h
//
// Registers the class metadata into the global cache. Will DCHECK if the
// metadata for a class is already registered.
COMPONENT_EXPORT(UI_BASE_METADATA)
void RegisterClassInfo(std::unique_ptr<ClassMetaData> meta_data);

// Help function for creating and registering the metadata container into the
// global cache for a given class. The metadata information is owned by the
// given class.
template <typename TMetaData>
ClassMetaData* MakeAndRegisterClassInfo() {
  std::unique_ptr<TMetaData> class_meta_data = std::make_unique<TMetaData>();
  TMetaData* const ret = class_meta_data.get();
  RegisterClassInfo(std::move(class_meta_data));
  return ret;
}

}  // namespace metadata
}  // namespace ui

#endif  // UI_BASE_METADATA_METADATA_CACHE_H_