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 #include "base/memory/ref_counted.h"
   9
  10 // See comments for the similar block in thread_checker.h.
  11 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
  12 #define ENABLE_SEQUENCE_CHECKER 1
  13 #else
  14 #define ENABLE_SEQUENCE_CHECKER 0
  15 #endif
  16
  17 #if ENABLE_SEQUENCE_CHECKER
  18 #include "base/sequence_checker_impl.h"
  19 #endif
  20
  21 namespace base {
  22
  23 class SequencedTaskRunner;
  24
  25 // Do nothing implementation, for use in release mode.
  26 //
  27 // Note: You should almost always use the SequenceChecker class to get
  28 // the right version for your build configuration.
  29 class SequenceCheckerDoNothing {
  30  public:
  31   bool CalledOnValidSequencedThread() const {
  32     return true;
  33   }
  34
  35   void DetachFromSequence() {}
  36 };
  37
  38 // SequenceChecker is a helper class used to help verify that some
  39 // methods of a class are called in sequence -- that is, called from
  40 // the same SequencedTaskRunner. It is a generalization of
  41 // ThreadChecker; see comments in sequence_checker_impl.h for details.
  42 //
  43 // Example:
  44 // class MyClass {
  45 //  public:
  46 //   void Foo() {
  47 //     DCHECK(sequence_checker_.CalledOnValidSequencedThread());
  48 //     ... (do stuff) ...
  49 //   }
  50 //
  51 //  private:
  52 //   SequenceChecker sequence_checker_;
  53 // }
  54 //
  55 // In Release mode, CalledOnValidSequence will always return true.
  56 #if ENABLE_SEQUENCE_CHECKER
  57 class SequenceChecker : public SequenceCheckerImpl {
  58 };
  59 #else
  60 class SequenceChecker : public SequenceCheckerDoNothing {
  61 };
  62 #endif  // ENABLE_SEQUENCE_CHECKER
  63
  64 #undef ENABLE_SEQUENCE_CHECKER
  65
  66 }  // namespace base
  67
  68 #endif  // BASE_SEQUENCE_CHECKER_H_