Add Callback::IsCancelled

base/callback_internal.h

 // 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.
 
 // This file contains utility functions and classes that help the
 // implementation, and management of the Callback objects.
 
 #ifndef BASE_CALLBACK_INTERNAL_H_
 #define BASE_CALLBACK_INTERNAL_H_
 
@@ skipping 18 matching lines @@
 // RefCountedThreadSafe since it requires the destructor to be a virtual method.
 // Creating a vtable for every BindState template instantiation results in a lot
 // of bloat. Its only task is to call the destructor which can be done with a
 // function pointer.
 class BASE_EXPORT BindStateBase {
  public:
   using InvokeFuncStorage = void(*)();
 
  protected:
   BindStateBase(InvokeFuncStorage polymorphic_invoke,
-                void (*destructor)(BindStateBase*));
+                void (*destructor)(BindStateBase*),
+                bool (*is_cancelled)(const BindStateBase*));
   ~BindStateBase() = default;
 
  private:
   friend class scoped_refptr<BindStateBase>;
   template <CopyMode copy_mode>
   friend class CallbackBase;
 
+  bool IsCancelled() const {
+    return is_cancelled_(this);
+  }
+
   void AddRef();
   void Release();
 
   // In C++, it is safe to cast function pointers to function pointers of
   // another type. It is not okay to use void*. We create a InvokeFuncStorage
   // that that can store our function pointer, and then cast it back to
   // the original type on usage.
   InvokeFuncStorage polymorphic_invoke_;
 
   AtomicRefCount ref_count_;
 
   // Pointer to a function that will properly destroy |this|.
   void (*destructor_)(BindStateBase*);
+  bool (*is_cancelled_)(const BindStateBase*);
 
   DISALLOW_COPY_AND_ASSIGN(BindStateBase);
 };
 
 // Holds the Callback methods that don't require specialization to reduce
 // template bloat.
 // CallbackBase<MoveOnly> is a direct base class of MoveOnly callbacks, and
 // CallbackBase<Copyable> uses CallbackBase<MoveOnly> for its implementation.
 template <>
 class BASE_EXPORT CallbackBase<CopyMode::MoveOnly> {
  public:
   CallbackBase(CallbackBase&& c);
   CallbackBase& operator=(CallbackBase&& c);
 
   // Returns true if Callback is null (doesn't refer to anything).
   bool is_null() const { return bind_state_.get() == NULL; }
   explicit operator bool() const { return !is_null(); }
 
+  // Returns true if the callback invocation will be nop due to an cancellation.
+  // It's invalid to call this on uninitialized callback.
+  bool IsCancelled() const;
+
   // Returns the Callback into an uninitialized state.
   void Reset();
 
  protected:
   using InvokeFuncStorage = BindStateBase::InvokeFuncStorage;
 
   // Returns true if this callback equals |other|. |other| may be null.
   bool EqualsInternal(const CallbackBase& other) const;
 
   // Allow initializing of |bind_state_| via the constructor to avoid default
@@ skipping 27 matching lines @@
   ~CallbackBase() {}
 };
 
 extern template class CallbackBase<CopyMode::MoveOnly>;
 extern template class CallbackBase<CopyMode::Copyable>;
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_CALLBACK_INTERNAL_H_