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_SEQUENCE_CHECKER_IMPL_H_
6#define BASE_SEQUENCE_CHECKER_IMPL_H_
7
8#include "base/base_export.h"
9#include "base/basictypes.h"
10#include "base/synchronization/lock.h"
11#include "base/threading/sequenced_worker_pool.h"
12#include "base/threading/thread_checker_impl.h"
13
14namespace base {
15
16// SequenceCheckerImpl is used to help verify that some methods of a
17// class are called in sequence -- that is, called from the same
18// SequencedTaskRunner. It is a generalization of ThreadChecker; in
19// particular, it behaves exactly like ThreadChecker if constructed
20// on a thread that is not part of a SequencedWorkerPool.
21class BASE_EXPORT SequenceCheckerImpl {
22 public:
23  SequenceCheckerImpl();
24  ~SequenceCheckerImpl();
25
26  // Returns whether the we are being called on the same sequence token
27  // as previous calls. If there is no associated sequence, then returns
28  // whether we are being called on the underlying ThreadChecker's thread.
29  bool CalledOnValidSequencedThread() const;
30
31  // Unbinds the checker from the currently associated sequence. The
32  // checker will be re-bound on the next call to CalledOnValidSequence().
33  void DetachFromSequence();
34
35 private:
36  void EnsureSequenceTokenAssigned() const;
37
38  // Guards all variables below.
39  mutable Lock lock_;
40
41  // Used if |sequence_token_| is not valid.
42  ThreadCheckerImpl thread_checker_;
43  mutable bool sequence_token_assigned_;
44
45  mutable SequencedWorkerPool::SequenceToken sequence_token_;
46
47  DISALLOW_COPY_AND_ASSIGN(SequenceCheckerImpl);
48};
49
50}  // namespace base
51
52#endif  // BASE_SEQUENCE_CHECKER_IMPL_H_
53