The chrome.lockScreen.data API implementation

extensions/browser/api/lock_screen_data/item_storage.h

+// Copyright 2017 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 EXTENSIONS_BROWSER_API_LOCK_SCREEN_DATA_ITEM_STORAGE_H_
+#define EXTENSIONS_BROWSER_API_LOCK_SCREEN_DATA_ITEM_STORAGE_H_
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/scoped_observer.h"
+#include "base/sequenced_task_runner.h"
+#include "extensions/browser/api/lock_screen_data/data_item.h"
+#include "extensions/browser/extension_registry_observer.h"
+
+class PrefRegistrySimple;
+class PrefService;
+
+namespace base {
+class Value;
+}
+
+namespace content {
+class BrowserContext;
+}
+
+namespace extensions {
+
+class Extension;
+class ExtensionRegistry;
+
+namespace lock_screen_data {
+
+class DataItem;
+enum class OperationResult;
+
+// Keeps track of lock screen data items created by extensions.
+// Note only single instance is allowed per process - once created, the instance
+// can be retrieved using ItemStorage::Get().
+class ItemStorage : public ExtensionRegistryObserver {
+ public:
+  using WriteCallback = DataItem::WriteCallback;
+  using ReadCallback = DataItem::ReadCallback;
+
+  static void RegisterLocalState(PrefRegistrySimple* registry);
+
+  // Gets the global ItemStorage instance.
+  // |context| - Context from which the item storage is needed, if the context
+  // is not allowed to use ItemStorage, this will return null.
+  // ItemStorage can be only used from:
+  //   * lock screen browser context while session state is set to locked
+  //   * from the browser process passed to the ItemStorage ctor when the

[rkc, 2017/06/22 18:35:48]

Should ItemStorage be context keyed? What happens if multiple profiles are
loaded in one user session?

[tbarzic, 2017/06/26 22:21:42]

It will be supported only for the primary user.

+  //     session state is set to unlocked.
+  static ItemStorage* Get(content::BrowserContext* context);
+
+  // Creates a ItemStorage instance. Note that only one ItemStorage can be
+  // present at a time - the constructor will set a global reference to the
+  // created object that can be retrieved using ItemStorage::Get (the reference
+  // will be reset when the instance goes out of scoped, i.e. in ~ItemStorage).
+  //
+  // |context| - primary user context, only apps from that context should be
+  //     able to use the storage.
+  // |local_state| - Local state preference - used to persist set of created
+  //     item metadata.
+  // |crypto_key| - Symmetric key that should be used to encrypt data content
+  //     when it's persisted on the disk.
+  // |storage_root| - Directory on the disk to which data item content should be
+  //     persisted.
+  ItemStorage(content::BrowserContext* context,
+              PrefService* local_state,
+              const std::string& crypto_key,
+              const base::FilePath& storage_root);
+  ~ItemStorage() override;
+
+  using ItemFactoryCallback =
+      base::Callback<std::unique_ptr<DataItem>(const std::string& id)>;
+  static void SetItemFactoryForTesting(ItemFactoryCallback* callback);
+
+  // Updates the ItemStorage's view of whether the user session is locked.
+  void SetSessionLocked(bool session_locked);
+
+  // Creates a new data item for the extension.
+  const DataItem* CreateItem(const std::string& extension_id);
+
+  // Returns all existing data items associated with the extension.
+  std::vector<const DataItem*> GetAllForExtension(
+      const std::string& extension_id);
+
+  // Updates the content of the item identified by |item_id| that is associated
+  // with the provided extension.
+  OperationResult SetItemContent(const std::string& extension_id,

[rkc, 2017/06/22 18:35:48]

Same comment as on the DataItem class. Can we avoid having two separate return
value mechanisms?

[tbarzic, 2017/06/26 22:21:42]

Done.

+                                 const std::string& item_id,
+                                 const std::vector<char>& data,
+                                 const WriteCallback& callback);
+
+  // Retrieves the content of the item identified by |item_id| that is
+  // associated with the provided extension.
+  OperationResult GetItemContent(const std::string& extension_id,
+                                 const std::string& item_id,
+                                 const ReadCallback& callback);
+
+  // Deletes the data item associated with the extension.
+  OperationResult DeleteItem(const std::string& extension_id,
+                             const std::string& item_id);
+
+  // extensions::ExtensionRegistryObserver:
+  void OnExtensionUninstalled(content::BrowserContext* browser_context,
+                              const Extension* extension,
+                              UninstallReason reason) override;
+
+  // Exposed so test code can ensure that all tasks on the task runner are run
+  // before testing an expectation.
+  scoped_refptr<base::SequencedTaskRunner> task_runner_for_testing() {
+    return task_runner_;
+  }
+
+ private:
+  // Maps a data item ID to the data item instance.
+  using DataItemMap = std::map<std::string, std::unique_ptr<DataItem>>;

[rkc, 2017/06/22 18:35:48]

would using unordered_map here and below be better?

[tbarzic, 2017/06/26 22:21:42]

hm, I'm not sure. it might.

+  // Maps an extension ID to data items associated with the extension.
+  using ExtensionDataItemMap = std::map<std::string, DataItemMap>;
+
+  // The session state as seen by the ItemStorage.
+  enum class SessionLockedState { kUnknown, kLocked, kNotLocked };
+
+  // Gets the key in lock screen data preferences for the item.
+  std::string GetDataItemPrefKey(const std::string& extension_id,
+                                 const std::string& item_id);
+
+  // Whether the context is allowed to use ItemStorage.
+  // Result depends on the current ItemStorage state - see ItemStorage::Get.
+  bool IsContextAllowed(content::BrowserContext* context);
+
+  // Finds a data item associated with the extension.
+  DataItem* FindItem(const std::string& extension_id,
+                     const std::string& item_id);
+
+  // Clears all data items associated with the extension.
+  void ClearDataForExtension(const std::string& extension_id);
+
+  // Used on startup to load extension -> data item mapping from local state
+  // prefs.
+  void ReloadDataItems();
+  bool LoadDataItemsForExtension(const std::string& extension_id,
+                                 const base::Value& extension_pref);
+
+  content::BrowserContext* context_;
+
+  // The user associated with the primary profile.
+  const std::string user_id_;
+  const std::string crypto_key_;
+  PrefService* local_state_;
+  const base::FilePath storage_root_;
+
+  SessionLockedState session_locked_state_ = SessionLockedState::kUnknown;
+
+  ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
+      extension_registry_observer_;
+
+  // Mapping containing all known data items for extensions.
+  ExtensionDataItemMap data_items_;
+
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ItemStorage);
+};
+
+}  // namespace lock_screen_data
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_API_LOCK_SCREEN_DATA_ITEM_STORAGE_H_