| // Copyright 2020 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_REFBASE_H_ |
| #define SRC_DAWN_COMMON_REFBASE_H_ |
| |
| #include <type_traits> |
| #include <utility> |
| |
| #include "dawn/common/Assert.h" |
| #include "dawn/common/Compiler.h" |
| |
| namespace dawn { |
| |
| // A common class for various smart-pointers acting on referenceable/releasable pointer-like |
| // objects. Logic for each specialization can be customized using a Traits type that looks |
| // like the following: |
| // |
| // struct { |
| // static constexpr T kNullValue = ...; |
| // static void Reference(T value) { ... } |
| // static void Release(T value) { ... } |
| // }; |
| // |
| // RefBase supports |
| template <typename T, typename Traits> |
| class RefBase { |
| public: |
| // Default constructor and destructor. |
| RefBase() : mValue(Traits::kNullValue) {} |
| |
| ~RefBase() { Release(mValue); } |
| |
| // Constructors from nullptr. |
| // NOLINTNEXTLINE(runtime/explicit) |
| constexpr RefBase(std::nullptr_t) : RefBase() {} |
| |
| RefBase<T, Traits>& operator=(std::nullptr_t) { |
| Set(Traits::kNullValue); |
| return *this; |
| } |
| |
| // Constructors from a value T. |
| // NOLINTNEXTLINE(runtime/explicit) |
| RefBase(T value) : mValue(value) { Reference(value); } |
| |
| RefBase<T, Traits>& operator=(const T& value) { |
| Set(value); |
| return *this; |
| } |
| |
| // Constructors from a RefBase<T> |
| RefBase(const RefBase<T, Traits>& other) : mValue(other.mValue) { Reference(other.mValue); } |
| |
| RefBase<T, Traits>& operator=(const RefBase<T, Traits>& other) { |
| Set(other.mValue); |
| return *this; |
| } |
| |
| RefBase(RefBase<T, Traits>&& other) { mValue = other.Detach(); } |
| |
| RefBase<T, Traits>& operator=(RefBase<T, Traits>&& other) { |
| if (&other != this) { |
| Release(mValue); |
| mValue = other.Detach(); |
| } |
| return *this; |
| } |
| |
| // Constructors from a RefBase<U>. Note that in the *-assignment operators this cannot be the |
| // same as `other` because overload resolution rules would have chosen the *-assignement |
| // operators defined with `other` == RefBase<T, Traits>. |
| template <typename U, typename UTraits, typename = typename std::is_convertible<U, T>::type> |
| RefBase(const RefBase<U, UTraits>& other) : mValue(other.mValue) { |
| Reference(other.mValue); |
| } |
| |
| template <typename U, typename UTraits, typename = typename std::is_convertible<U, T>::type> |
| RefBase<T, Traits>& operator=(const RefBase<U, UTraits>& other) { |
| Set(other.mValue); |
| return *this; |
| } |
| |
| template <typename U, typename UTraits, typename = typename std::is_convertible<U, T>::type> |
| RefBase(RefBase<U, UTraits>&& other) { |
| mValue = other.Detach(); |
| } |
| |
| template <typename U, typename UTraits, typename = typename std::is_convertible<U, T>::type> |
| RefBase<T, Traits>& operator=(RefBase<U, UTraits>&& other) { |
| Release(mValue); |
| mValue = other.Detach(); |
| return *this; |
| } |
| |
| // Comparison operators. |
| bool operator==(const T& other) const { return mValue == other; } |
| |
| bool operator!=(const T& other) const { return mValue != other; } |
| |
| const T operator->() const { return mValue; } |
| T operator->() { return mValue; } |
| |
| bool operator<(const RefBase<T, Traits>& other) const { return mValue < other.mValue; } |
| |
| // Smart pointer methods. |
| const T& Get() const { return mValue; } |
| T& Get() { return mValue; } |
| |
| [[nodiscard]] T Detach() { |
| T value{std::move(mValue)}; |
| mValue = Traits::kNullValue; |
| return value; |
| } |
| |
| void Acquire(T value) { |
| Release(mValue); |
| mValue = value; |
| } |
| |
| [[nodiscard]] T* InitializeInto() { |
| ASSERT(mValue == Traits::kNullValue); |
| return &mValue; |
| } |
| |
| private: |
| // Friend is needed so that instances of RefBase<U> can call Reference and Release on |
| // RefBase<T>. |
| template <typename U, typename UTraits> |
| friend class RefBase; |
| |
| static void Reference(T value) { |
| if (value != Traits::kNullValue) { |
| Traits::Reference(value); |
| } |
| } |
| static void Release(T value) { |
| if (value != Traits::kNullValue) { |
| Traits::Release(value); |
| } |
| } |
| |
| void Set(T value) { |
| if (mValue != value) { |
| // Ensure that the new value is referenced before the old is released to prevent any |
| // transitive frees that may affect the new value. |
| Reference(value); |
| Release(mValue); |
| mValue = value; |
| } |
| } |
| |
| T mValue; |
| }; |
| |
| } // namespace dawn |
| |
| #endif // SRC_DAWN_COMMON_REFBASE_H_ |