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/synchronization/lock.h"
  11 #include "base/threading/sequenced_worker_pool.h"
  12 #include "base/threading/thread_checker_impl.h"
  13
  14 namespace 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.
  21 class 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_