| // 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_H_ |
| #define BASE_SEQUENCE_CHECKER_H_ |
| |
| #include "base/compiler_specific.h" |
| #include "base/logging.h" |
| #include "base/sequence_checker_impl.h" |
| #include "build/build_config.h" |
| |
| // SequenceChecker is a helper class used to help verify that some methods of a |
| // class are called sequentially (for thread-safety). |
| // |
| // Use the macros below instead of the SequenceChecker directly so that the |
| // unused member doesn't result in an extra byte (four when padded) per |
| // instance in production. |
| // |
| // This class is much prefered to ThreadChecker for thread-safety checks. |
| // ThreadChecker should only be used for classes that are truly thread-affine |
| // (use thread-local-storage or a third-party API that does). |
| // |
| // Usage: |
| // class MyClass { |
| // public: |
| // MyClass() { |
| // // It's sometimes useful to detach on construction for objects that are |
| // // constructed in one place and forever after used from another |
| // // sequence. |
| // DETACH_FROM_SEQUENCE(my_sequence_checker_); |
| // } |
| // |
| // ~MyClass() { |
| // // SequenceChecker doesn't automatically check it's destroyed on origin |
| // // sequence for the same reason it's sometimes detached in the |
| // // constructor. It's okay to destroy off sequence if the owner |
| // // otherwise knows usage on the associated sequence is done. If you're |
| // // not detaching in the constructor, you probably want to explicitly |
| // // check in the destructor. |
| // DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_); |
| // } |
| // void MyMethod() { |
| // DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_); |
| // ... (do stuff) ... |
| // } |
| // |
| // private: |
| // SEQUENCE_CHECKER(my_sequence_checker_); |
| // } |
| |
| #if DCHECK_IS_ON() |
| #define SEQUENCE_CHECKER(name) base::SequenceChecker name |
| #define DCHECK_CALLED_ON_VALID_SEQUENCE(name) \ |
| DCHECK((name).CalledOnValidSequence()) |
| #define DETACH_FROM_SEQUENCE(name) (name).DetachFromSequence() |
| #else // DCHECK_IS_ON() |
| #if __OBJC__ && defined(OS_IOS) && !HAS_FEATURE(objc_cxx_static_assert) |
| // TODO(thakis): Remove this branch once Xcode's clang has clang r356148. |
| #define SEQUENCE_CHECKER(name) |
| #else |
| #define SEQUENCE_CHECKER(name) static_assert(true, "") |
| #endif |
| #define DCHECK_CALLED_ON_VALID_SEQUENCE(name) EAT_STREAM_PARAMETERS |
| #define DETACH_FROM_SEQUENCE(name) |
| #endif // DCHECK_IS_ON() |
| |
| namespace base { |
| |
| // Do nothing implementation, for use in release mode. |
| // |
| // Note: You should almost always use the SequenceChecker class (through the |
| // above macros) to get the right version for your build configuration. |
| class SequenceCheckerDoNothing { |
| public: |
| SequenceCheckerDoNothing() = default; |
| |
| // Moving between matching sequences is allowed to help classes with |
| // SequenceCheckers that want a default move-construct/assign. |
| SequenceCheckerDoNothing(SequenceCheckerDoNothing&& other) = default; |
| SequenceCheckerDoNothing& operator=(SequenceCheckerDoNothing&& other) = |
| default; |
| |
| bool CalledOnValidSequence() const WARN_UNUSED_RESULT { return true; } |
| void DetachFromSequence() {} |
| |
| private: |
| DISALLOW_COPY_AND_ASSIGN(SequenceCheckerDoNothing); |
| }; |
| |
| #if DCHECK_IS_ON() |
| class SequenceChecker : public SequenceCheckerImpl { |
| }; |
| #else |
| class SequenceChecker : public SequenceCheckerDoNothing { |
| }; |
| #endif // DCHECK_IS_ON() |
| |
| } // namespace base |
| |
| #endif // BASE_SEQUENCE_CHECKER_H_ |