1// Copyright (c) 2012 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 BASE_THREADING_WORKER_POOL_H_
6#define BASE_THREADING_WORKER_POOL_H_
7
8#include "base/base_export.h"
9#include "base/callback_forward.h"
10#include "base/memory/ref_counted.h"
11
12class Task;
13
14namespace tracked_objects {
15class Location;
16}  // namespace tracked_objects
17
18namespace base {
19
20class TaskRunner;
21
22// This is a facility that runs tasks that don't require a specific thread or
23// a message loop.
24//
25// WARNING: This shouldn't be used unless absolutely necessary. We don't wait
26// for the worker pool threads to finish on shutdown, so the tasks running
27// inside the pool must be extremely careful about other objects they access
28// (MessageLoops, Singletons, etc). During shutdown these object may no longer
29// exist.
30class BASE_EXPORT WorkerPool {
31 public:
32  // This function posts |task| to run on a worker thread.  |task_is_slow|
33  // should be used for tasks that will take a long time to execute.  Returns
34  // false if |task| could not be posted to a worker thread.  Regardless of
35  // return value, ownership of |task| is transferred to the worker pool.
36  static bool PostTask(const tracked_objects::Location& from_here,
37                       const base::Closure& task, bool task_is_slow);
38
39  // Just like MessageLoopProxy::PostTaskAndReply, except the destination
40  // for |task| is a worker thread and you can specify |task_is_slow| just
41  // like you can for PostTask above.
42  static bool PostTaskAndReply(const tracked_objects::Location& from_here,
43                               const Closure& task,
44                               const Closure& reply,
45                               bool task_is_slow);
46
47  // Return true if the current thread is one that this WorkerPool runs tasks
48  // on.  (Note that if the Windows worker pool is used without going through
49  // this WorkerPool interface, RunsTasksOnCurrentThread would return false on
50  // those threads.)
51  static bool RunsTasksOnCurrentThread();
52
53  // Get a TaskRunner wrapper which posts to the WorkerPool using the given
54  // |task_is_slow| behavior.
55  static const scoped_refptr<TaskRunner>& GetTaskRunner(bool task_is_slow);
56};
57
58}  // namespace base
59
60#endif  // BASE_THREADING_WORKER_POOL_H_
61