Use Observer to notify of WebDB load instead of callbacks

components/webdata/common/web_data_service_backend.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 COMPONENTS_WEBDATA_COMMON_WEB_DATA_SERVICE_BACKEND_H_
+#define COMPONENTS_WEBDATA_COMMON_WEB_DATA_SERVICE_BACKEND_H_
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "base/compiler_specific.h"
+#include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+#include "components/webdata/common/web_database_service.h"
+#include "content/public/browser/browser_thread.h"
+
+
+class WebDatabase;
+class WebDatabaseTable;
+class WebDataRequest;
+class WebDataRequestManager;
+
+namespace tracked_objects {
+class Location;
+}
+
+// WebDataServiceBackend handles all database tasks posted by
+// WebDatabaseService. It is refcounted to allow asynchronous destruction on the
+// DB thread.
+
+class WebDataServiceBackend
+    : public base::RefCountedThreadSafe<
+          WebDataServiceBackend,
+          content::BrowserThread::DeleteOnDBThread> {
+ public:
+  class Delegate {
+    public:
+    virtual ~Delegate() {}
+
+    // Invoked when the backend has finished loading the db.
+    virtual void DBLoaded(sql::InitStatus status) = 0;
+  };
+
+  explicit WebDataServiceBackend(const base::FilePath& path,
+                                 Delegate* delegate);
+
+  // Must call only before InitDatabaseWithCallback.
+  void AddTable(scoped_ptr<WebDatabaseTable> table);
+
+  // Initializes the database and notifies caller via callback when complete.
+  // Callback is called synchronously.
+  void InitDatabase();
+
+  // Opens the database file from the profile path if an init has not yet been
+  // attempted. Separated from the constructor to ease construction/destruction
+  // of this object on one thread but database access on the DB thread. Returns
+  // the status of the database.
+  sql::InitStatus LoadDatabaseIfNecessary();
+
+  // Shuts down database. |should_reinit| tells us whether or not it should be
+  // possible to re-initialize the DB after the shutdown.
+  void ShutdownDatabase(bool should_reinit);
+
+  // Task wrappers to run database tasks.
+  void DBWriteTaskWrapper(
+      const WebDatabaseService::WriteTask& task,
+      scoped_ptr<WebDataRequest> request);
+  void DBReadTaskWrapper(
+      const WebDatabaseService::ReadTask& task,
+      scoped_ptr<WebDataRequest> request);
+
+  const scoped_refptr<WebDataRequestManager>& request_manager() {
+    return request_manager_;
+  }
+
+  WebDatabase* database() { return db_.get(); }
+
+ private:
+  friend struct content::BrowserThread::DeleteOnThread<
+      content::BrowserThread::DB>;
+  friend class base::DeleteHelper<WebDataServiceBackend>;
+
+  virtual ~WebDataServiceBackend();
+
+  // Commit the current transaction.
+  void Commit();
+
+  // Path to database file.
+  base::FilePath db_path_;
+
+  // The tables that participate in managing the database. These are
+  // owned here but other than that this class does nothing with
+  // them. Their initialization is in whatever factory creates
+  // WebDatabaseService, and lookup by type is provided by the
+  // WebDatabase class. The tables need to be owned by this refcounted
+  // object, or they themselves would need to be refcounted. Owning
+  // them here rather than having WebDatabase own them makes for
+  // easier unit testing of WebDatabase.
+  ScopedVector<WebDatabaseTable> tables_;
+
+  scoped_ptr<WebDatabase> db_;
+
+  // Keeps track of all pending requests made to the db.
+  scoped_refptr<WebDataRequestManager> request_manager_;
+
+  // State of database initialization. Used to prevent the executing of tasks
+  // before the db is ready.
+  sql::InitStatus init_status_;
+
+  // True if an attempt has been made to load the database (even if the attempt
+  // fails), used to avoid continually trying to reinit if the db init fails.
+  bool init_complete_;
+
+  // Delegate. See the class definition above for more information.
+  scoped_ptr<Delegate> delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebDataServiceBackend);
+};
+
+#endif  // COMPONENTS_WEBDATA_COMMON_WEB_DATA_SERVICE_BACKEND_H_