text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef BASE_SEQUENCE_CHECKER_IMPL_H_
  #define BASE_SEQUENCE_CHECKER_IMPL_H_
  
  #include <memory>
  
  #include "base/base_export.h"
  #include "base/compiler_specific.h"
  #include "base/macros.h"
  #include "base/synchronization/lock.h"
  #include "base/thread_annotations.h"
  
  namespace base {
  
  // Real implementation of SequenceChecker for use in debug mode or for temporary
  // use in release mode (e.g. to CHECK on a threading issue seen only in the
  // wild).
  //
  // Note: You should almost always use the SequenceChecker class to get the right
  // version for your build configuration.
  class BASE_EXPORT SequenceCheckerImpl {
   public:
    SequenceCheckerImpl();
    ~SequenceCheckerImpl();
  
    // Allow move construct/assign. This must be called on |other|'s associated
    // sequence and assignment can only be made into a SequenceCheckerImpl which
    // is detached or already associated with the current sequence. This isn't
    // thread-safe (|this| and |other| shouldn't be in use while this move is
    // performed). If the assignment was legal, the resulting SequenceCheckerImpl
    // will be bound to the current sequence and |other| will be detached.
    SequenceCheckerImpl(SequenceCheckerImpl&& other);
    SequenceCheckerImpl& operator=(SequenceCheckerImpl&& other);
  
    // Returns true if called in sequence with previous calls to this method and
    // the constructor.
    bool CalledOnValidSequence() const WARN_UNUSED_RESULT;
  
    // Unbinds the checker from the currently associated sequence. The checker
    // will be re-bound on the next call to CalledOnValidSequence().
    void DetachFromSequence();
  
   private:
    class Core;
  
    // Calls straight to ThreadLocalStorage::HasBeenDestroyed(). Exposed purely
    // for 'friend' to work.
    static bool HasThreadLocalStorageBeenDestroyed();
  
    mutable Lock lock_;
    mutable std::unique_ptr<Core> core_ GUARDED_BY(lock_);
  
    DISALLOW_COPY_AND_ASSIGN(SequenceCheckerImpl);
  };
  
  }  // namespace base
  
  #endif  // BASE_SEQUENCE_CHECKER_IMPL_H_
  