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102 lines
3.5 KiB
C++
102 lines
3.5 KiB
C++
// Copyright 2018 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_OBSERVER_LIST_INTERNAL_H_
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#define BASE_OBSERVER_LIST_INTERNAL_H_
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#include "base/base_export.h"
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#include "base/logging.h"
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#include "base/macros.h"
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#include "base/memory/weak_ptr.h"
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#include "base/observer_list_types.h"
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namespace base {
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namespace internal {
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// Adapter for putting raw pointers into an ObserverList<Foo>::Unchecked.
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class BASE_EXPORT UncheckedObserverAdapter {
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public:
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explicit UncheckedObserverAdapter(const void* observer)
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: ptr_(const_cast<void*>(observer)) {}
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UncheckedObserverAdapter(UncheckedObserverAdapter&& other) = default;
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UncheckedObserverAdapter& operator=(UncheckedObserverAdapter&& other) =
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default;
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void MarkForRemoval() { ptr_ = nullptr; }
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bool IsMarkedForRemoval() const { return !ptr_; }
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bool IsEqual(const void* rhs) const { return ptr_ == rhs; }
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template <class ObserverType>
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static ObserverType* Get(const UncheckedObserverAdapter& adapter) {
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static_assert(
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!std::is_base_of<CheckedObserver, ObserverType>::value,
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"CheckedObserver classes must not use ObserverList<T>::Unchecked.");
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return static_cast<ObserverType*>(adapter.ptr_);
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}
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private:
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void* ptr_;
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DISALLOW_COPY_AND_ASSIGN(UncheckedObserverAdapter);
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};
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// Adapter for CheckedObserver types so that they can use the same syntax as a
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// raw pointer when stored in the std::vector of observers in an ObserverList.
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// It wraps a WeakPtr<CheckedObserver> and allows a "null" pointer via
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// destruction to be distinguished from an observer marked for deferred removal
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// whilst an iteration is in progress.
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class BASE_EXPORT CheckedObserverAdapter {
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public:
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explicit CheckedObserverAdapter(const CheckedObserver* observer);
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// Move-only construction and assignment is required to store this in STL
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// types.
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CheckedObserverAdapter(CheckedObserverAdapter&& other);
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CheckedObserverAdapter& operator=(CheckedObserverAdapter&& other);
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~CheckedObserverAdapter();
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void MarkForRemoval() {
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DCHECK(weak_ptr_);
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weak_ptr_ = nullptr;
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}
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bool IsMarkedForRemoval() const {
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// If |weak_ptr_| was invalidated then this attempt to iterate over the
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// pointer is a UAF. Tip: If it's unclear where the `delete` occurred, try
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// adding CHECK(!IsInObserverList()) to the ~CheckedObserver() (destructor)
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// override. However, note that this is not always a bug: a destroyed
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// observer can exist in an ObserverList so long as nothing iterates over
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// the ObserverList before the list itself is destroyed.
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CHECK(!weak_ptr_.WasInvalidated());
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return weak_ptr_ == nullptr;
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}
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bool IsEqual(const CheckedObserver* rhs) const {
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// Note that inside an iteration, ObserverList::HasObserver() may call this
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// and |weak_ptr_| may be null due to a deferred removal, which is fine.
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return weak_ptr_.get() == rhs;
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}
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template <class ObserverType>
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static ObserverType* Get(const CheckedObserverAdapter& adapter) {
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static_assert(
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std::is_base_of<CheckedObserver, ObserverType>::value,
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"Observers should inherit from base::CheckedObserver. "
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"Use ObserverList<T>::Unchecked to observe with raw pointers.");
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DCHECK(adapter.weak_ptr_);
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return static_cast<ObserverType*>(adapter.weak_ptr_.get());
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}
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private:
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WeakPtr<CheckedObserver> weak_ptr_;
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DISALLOW_COPY_AND_ASSIGN(CheckedObserverAdapter);
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};
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} // namespace internal
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} // namespace base
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#endif // BASE_OBSERVER_LIST_INTERNAL_H_
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