| // Copyright 2023 The Dawn Authors |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #ifndef SRC_DAWN_COMMON_WEAKREF_H_ |
| #define SRC_DAWN_COMMON_WEAKREF_H_ |
| |
| #include <utility> |
| |
| #include "dawn/common/Ref.h" |
| #include "dawn/common/WeakRefSupport.h" |
| |
| namespace dawn { |
| |
| template <typename T> |
| class WeakRef { |
| public: |
| WeakRef() {} |
| |
| // Constructors from nullptr. |
| // NOLINTNEXTLINE(runtime/explicit) |
| constexpr WeakRef(std::nullptr_t) : WeakRef() {} |
| |
| // Constructors from a WeakRef<U>, where U can also equal T. |
| template <typename U, typename = typename std::enable_if<std::is_base_of_v<T, U>>::type> |
| WeakRef(const WeakRef<U>& other) : mData(other.mData) {} |
| template <typename U, typename = typename std::enable_if<std::is_base_of_v<T, U>>::type> |
| WeakRef<T>& operator=(const WeakRef<U>& other) { |
| mData = other.mData; |
| return *this; |
| } |
| template <typename U, typename = typename std::enable_if<std::is_base_of_v<T, U>>::type> |
| WeakRef(WeakRef<U>&& other) : mData(std::move(other.mData)) {} |
| template <typename U, typename = typename std::enable_if<std::is_base_of_v<T, U>>::type> |
| WeakRef<T>& operator=(WeakRef<U>&& other) { |
| if (&other != this) { |
| mData = std::move(other.mData); |
| } |
| return *this; |
| } |
| |
| // Promotes a WeakRef to a Ref. Access to the raw pointer is not allowed because a raw pointer |
| // could become invalid after being retrieved. |
| Ref<T> Promote() { |
| if (mData != nullptr) { |
| return AcquireRef(static_cast<T*>(mData->TryGetRef().Detach())); |
| } |
| return nullptr; |
| } |
| |
| private: |
| // Friend is needed so that we can access the data ref in conversions. |
| template <typename U> |
| friend class WeakRef; |
| // Friend is needed to access the private constructor. |
| template <typename U> |
| friend class Ref; |
| |
| // Constructor from data should only be allowed via the GetWeakRef function. |
| explicit WeakRef(detail::WeakRefSupportBase* data) : mData(data->mData) {} |
| |
| Ref<detail::WeakRefData> mData = nullptr; |
| }; |
| |
| } // namespace dawn |
| |
| #endif // SRC_DAWN_COMMON_WEAKREFCOUNTED_H_ |