Repo created

TMessagesProj/jni/voip/webrtc/base/sequence_checker.h

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+// 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 "base/strings/string_piece.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). It supports thread safety
+// annotations (see base/thread_annotations.h).
+//
+// 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) ...
+//       MyOtherMethod();
+//     }
+//
+//     void MyOtherMethod()
+//         VALID_CONTEXT_REQUIRED(my_sequence_checker_) {
+//       foo_ = 42;
+//     }
+//
+//    private:
+//      // GUARDED_BY_CONTEXT() enforces that this member is only
+//      // accessed from a scope that invokes DCHECK_CALLED_ON_VALID_SEQUENCE()
+//      // or from a function annotated with VALID_CONTEXT_REQUIRED(). A
+//      // DCHECK build will not compile if the member is accessed and these
+//      // conditions are not met.
+//     int foo_ GUARDED_BY_CONTEXT(my_sequence_checker_);
+//
+//     SEQUENCE_CHECKER(my_sequence_checker_);
+//   }
+
+#define SEQUENCE_CHECKER_INTERNAL_CONCAT2(a, b) a##b
+#define SEQUENCE_CHECKER_INTERNAL_CONCAT(a, b) \
+  SEQUENCE_CHECKER_INTERNAL_CONCAT2(a, b)
+#define SEQUENCE_CHECKER_INTERNAL_UID(prefix) \
+  SEQUENCE_CHECKER_INTERNAL_CONCAT(prefix, __LINE__)
+
+#if DCHECK_IS_ON()
+#define SEQUENCE_CHECKER(name) base::SequenceChecker name
+#define DCHECK_CALLED_ON_VALID_SEQUENCE(name, ...)                   \
+  base::ScopedValidateSequenceChecker SEQUENCE_CHECKER_INTERNAL_UID( \
+      scoped_validate_sequence_checker_)(name, ##__VA_ARGS__);
+#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.
+// Note: This is only a check, not a "lock". It is marked "LOCKABLE" only in
+// order to support thread_annotations.h.
+class LOCKABLE 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()
+
+class SCOPED_LOCKABLE ScopedValidateSequenceChecker {
+ public:
+  explicit ScopedValidateSequenceChecker(const SequenceChecker& checker)
+      EXCLUSIVE_LOCK_FUNCTION(checker) {
+    DCHECK(checker.CalledOnValidSequence());
+  }
+
+  explicit ScopedValidateSequenceChecker(const SequenceChecker& checker,
+                                         const StringPiece& msg)
+      EXCLUSIVE_LOCK_FUNCTION(checker) {
+    DCHECK(checker.CalledOnValidSequence()) << msg;
+  }
+
+  ~ScopedValidateSequenceChecker() UNLOCK_FUNCTION() {}
+
+ private:
+};
+
+}  // namespace base
+
+#endif  // BASE_SEQUENCE_CHECKER_H_