1// Copyright 2013 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef CHROME_BROWSER_HISTORY_HISTORY_DB_TASK_H_
6#define CHROME_BROWSER_HISTORY_HISTORY_DB_TASK_H_
7
8namespace history {
9
10class HistoryBackend;
11class HistoryDatabase;
12
13// HistoryDBTask can be used to process arbitrary work on the history backend
14// thread. HistoryDBTask is scheduled using HistoryService::ScheduleDBTask.
15// When HistoryBackend processes the task it invokes RunOnDBThread. Once the
16// task completes and has not been canceled, DoneRunOnMainThread is invoked back
17// on the main thread, after which this object is destroyed, also on the
18// main thread.
19class HistoryDBTask {
20 public:
21  virtual ~HistoryDBTask() {}
22
23  // Invoked on the database thread. The return value indicates whether the
24  // task is done. A return value of true signals the task is done and
25  // RunOnDBThread should NOT be invoked again. A return value of false
26  // indicates the task is not done, and should be run again after other
27  // tasks are given a chance to be processed.
28  virtual bool RunOnDBThread(HistoryBackend* backend, HistoryDatabase* db) = 0;
29
30  // Invoked on the main thread once RunOnDBThread has returned true. This is
31  // only invoked if the request was not canceled and returned true from
32  // RunOnDBThread.
33  virtual void DoneRunOnMainThread() = 0;
34};
35
36}  // namespace history
37
38#endif  // CHROME_BROWSER_HISTORY_HISTORY_DB_TASK_H_
39