base/sequence_checker_impl.h

   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/memory/ref_counted.h"
  11 #include "base/synchronization/lock.h"
  12 #include "base/threading/thread_checker_impl.h"
  13
  14 namespace base {
  15
  16 class SequencedTaskRunner;
  17
  18 // SequenceCheckerImpl is used to help verify that some methods of a
  19 // class are called in sequence -- that is, called from the same
  20 // SequencedTaskRunner. It is a generalization of ThreadChecker; in
  21 // particular, it behaves exactly like ThreadChecker if its passed a
  22 // NULL SequencedTaskRunner.
  23 class BASE_EXPORT SequenceCheckerImpl {
  24  public:
  25   // |sequenced_task_runner| can be NULL.  In that case, this object
  26   // behaves exactly like a ThreadChecker bound to the current thread,
  27   // i.e.  CalledOnValidSequence() behaves like CalledOnValidThread().
  28   explicit SequenceCheckerImpl(
  29       const scoped_refptr<SequencedTaskRunner>& sequenced_task_runner);
  30   ~SequenceCheckerImpl();
  31
  32   // Returns whether the we are being called on the underyling
  33   // SequencedTaskRunner.  If we're not bound to a
  34   // |sequenced_task_runner|, returns whether we are being called on
  35   // the underlying ThreadChecker's thread.
  36   bool CalledOnValidSequence() const;
  37
  38   // Changes the underyling SequencedTaskRunner.
  39   // |sequenced_task_runner| can be NULL.  In that case, this object
  40   // behaves exactly like a ThreadChecker that has been detached from
  41   // its thread, i.e. we will be bound to the thread on which we next
  42   // call CalledOnValidSequence().
  43   void ChangeSequence(
  44       const scoped_refptr<SequencedTaskRunner>& sequenced_task_runner);
  45
  46  private:
  47   // Guards all variables below.
  48   mutable Lock lock_;
  49   scoped_refptr<SequencedTaskRunner> sequenced_task_runner_;
  50   // Used if |sequenced_task_runner_| is NULL.
  51   ThreadCheckerImpl thread_checker_;
  52
  53   DISALLOW_COPY_AND_ASSIGN(SequenceCheckerImpl);
  54 };
  55
  56 }  // namespace base
  57
  58 #endif  // BASE_SEQUENCE_CHECKER_IMPL_H_