base/sequence_checker.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_H_
   6 #define BASE_SEQUENCE_CHECKER_H_
   7
   8 // See comments for the similar block in thread_checker.h.
   9 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
  10 #define ENABLE_SEQUENCE_CHECKER 1
  11 #else
  12 #define ENABLE_SEQUENCE_CHECKER 0
  13 #endif
  14
  15 #include "base/sequence_checker_impl.h"
  16
  17 namespace base {
  18
  19 // Do nothing implementation, for use in release mode.
  20 //
  21 // Note: You should almost always use the SequenceChecker class to get
  22 // the right version for your build configuration.
  23 class SequenceCheckerDoNothing {
  24  public:
  25   bool CalledOnValidSequencedThread() const {
  26     return true;
  27   }
  28
  29   void DetachFromSequence() {}
  30 };
  31
  32 // SequenceChecker is a helper class used to help verify that some
  33 // methods of a class are called in sequence -- that is, called from
  34 // the same SequencedTaskRunner. It is a generalization of
  35 // ThreadChecker; see comments in sequence_checker_impl.h for details.
  36 //
  37 // Example:
  38 // class MyClass {
  39 //  public:
  40 //   void Foo() {
  41 //     DCHECK(sequence_checker_.CalledOnValidSequencedThread());
  42 //     ... (do stuff) ...
  43 //   }
  44 //
  45 //  private:
  46 //   SequenceChecker sequence_checker_;
  47 // }
  48 //
  49 // In Release mode, CalledOnValidSequencedThread() will always return true.
  50 #if ENABLE_SEQUENCE_CHECKER
  51 class SequenceChecker : public SequenceCheckerImpl {
  52 };
  53 #else
  54 class SequenceChecker : public SequenceCheckerDoNothing {
  55 };
  56 #endif  // ENABLE_SEQUENCE_CHECKER
  57
  58 #undef ENABLE_SEQUENCE_CHECKER
  59
  60 }  // namespace base
  61
  62 #endif  // BASE_SEQUENCE_CHECKER_H_