Add support for persistent file access in apps.

apps/saved_files_service.h

+// Copyright 2013 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 APPS_SAVED_FILES_SERVICE_H_
+#define APPS_SAVED_FILES_SERVICE_H_
+
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "base/files/file_path.h"
+#include "base/gtest_prod_util.h"
+#include "base/stl_util.h"
+#include "components/browser_context_keyed_service/browser_context_keyed_service.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+class SavedFilesServiceUnitTest;
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, RetainTwoFilesTest);
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, EvictionTest);
+FORWARD_DECLARE_TEST(SavedFilesServiceUnitTest, SequenceNumberCompactionTest);
+
+namespace extensions {
+class Extension;
+}
+
+namespace apps {
+
+// Represents a file entry that a user has given an app permission to
+// access. Will be persisted to disk (in the Preferences file), so should remain
+// serializable.
+struct SavedFileEntry {
+  SavedFileEntry();
+
+  SavedFileEntry(const std::string& id,
+                 const base::FilePath& path,
+                 bool writable,
+                 int sequence_number);
+
+  // The opaque id of this file entry.
+  std::string id;
+
+  // The path to a file entry that the app had permission to access.
+  base::FilePath path;
+
+  // Whether or not the app had write access to a file entry.
+  bool writable;
+
+  // The sequence number in the LRU of the file entry. The value 0 indicates
+  // that the entry is not in the LRU.
+  int sequence_number;
+};
+
+// Tracks the files that apps have retained access to both while running and
+// when suspended.
+class SavedFilesService : public BrowserContextKeyedService,
+                          public content::NotificationObserver {
+ public:
+  explicit SavedFilesService(Profile* profile);
+  virtual ~SavedFilesService();
+
+  static SavedFilesService* Get(Profile* profile);
+
+  // Registers a file entry with the saved files service, making it eligible to
+  // be put into the queue. File entries that are in the retained files queue at
+  // object construction are automatically registered.
+  void RegisterFileEntry(const std::string& extension_id,
+                         const std::string& id,
+                         const base::FilePath& file_path,
+                         bool writable);
+
+  // If the file with |id| is not in the queue of files to be retained
+  // permanently, adds the file to the back of the queue, evicting the least
+  // recently used entry at the front of the queue if it is full. If it is
+  // already present, moves it to the back of the queue. The |id| must have been
+  // registered.
+  void EnqueueFileEntry(const std::string& extension_id, const std::string& id);
+
+  // Returns whether the file entry with the given |id| has been registered.
+  bool IsRegistered(const std::string& extension_id, const std::string& id);
+
+  // Gets a borrowed pointer to the file entry with the specified |id|. Returns
+  // NULL if the file entry has not been registered.
+  const SavedFileEntry* GetFileEntry(const std::string& extension_id,
+                                     const std::string& id);
+
+  // Returns all registered file entries.
+  std::vector<SavedFileEntry> GetAllFileEntries(
+      const std::string& extension_id);
+
+  // Clears all retained files if the app does not have the
+  // fileSystem.retainFiles permission.
+  void ClearQueueIfNoRetainPermission(const extensions::Extension* extension);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest, RetainTwoFilesTest);
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest, EvictionTest);
+  FRIEND_TEST_ALL_PREFIXES(::SavedFilesServiceUnitTest,
+                           SequenceNumberCompactionTest);
+  friend class ::SavedFilesServiceUnitTest;
+
+  // A container for the registered files for an app.
+  class SavedFiles;
+
+  // content::NotificationObserver.
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+  // Returns the SavedFiles for |extension_id|, creating it if necessary.
+  SavedFiles* GetOrInsert(const std::string& extension_id);
+
+  // Clears the SavedFiles for |extension_id|.
+  void Clear(const std::string& extension_id);
+
+  static void SetMaxSequenceNumberForTest(int max_value);
+  static void ClearMaxSequenceNumberForTest();
+  static void SetLruSizeForTest(int size);
+  static void ClearLruSizeForTest();
+
+  std::map<std::string, SavedFiles*> extension_id_to_saved_files_;
+  STLValueDeleter<std::map<std::string, SavedFiles*> >
+      extension_id_to_saved_files_deleter_;
+  content::NotificationRegistrar registrar_;
+  Profile* profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(SavedFilesService);
+};
+
+}  // namespace apps
+
+#endif  // APPS_SAVED_FILES_SERVICE_H_