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1 // Copyright 2015 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_SEQUENCED_TASK_RUNNER_HANDLE_H_
6 #define BASE_THREADING_SEQUENCED_TASK_RUNNER_HANDLE_H_
7 
8 #include "base/compiler_specific.h"
9 #include "base/macros.h"
10 #include "base/memory/ref_counted.h"
11 #include "base/sequenced_task_runner.h"
12 
13 namespace base {
14 
15 class BASE_EXPORT SequencedTaskRunnerHandle {
16  public:
17   // Returns a SequencedTaskRunner which guarantees that posted tasks will only
18   // run after the current task is finished and will satisfy a SequenceChecker.
19   // It should only be called if IsSet() returns true (see the comment there for
20   // the requirements).
21   static scoped_refptr<SequencedTaskRunner> Get();
22 
23   // Returns true if one of the following conditions is fulfilled:
24   // a) A SequencedTaskRunner has been assigned to the current thread by
25   //    instantiating a SequencedTaskRunnerHandle.
26   // b) The current thread has a ThreadTaskRunnerHandle (which includes any
27   //    thread that has a MessageLoop associated with it).
28   static bool IsSet();
29 
30   // Binds |task_runner| to the current thread.
31   explicit SequencedTaskRunnerHandle(
32       scoped_refptr<SequencedTaskRunner> task_runner);
33   ~SequencedTaskRunnerHandle();
34 
35  private:
36   scoped_refptr<SequencedTaskRunner> task_runner_;
37 
38   DISALLOW_COPY_AND_ASSIGN(SequencedTaskRunnerHandle);
39 };
40 
41 }  // namespace base
42 
43 #endif  // BASE_THREADING_SEQUENCED_TASK_RUNNER_HANDLE_H_
44