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https://github.com/SerenityOS/serenity
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![Sam Atkins](/assets/img/avatar_default.png)
This makes it an error to not do something with a returned smart pointer, which should help prevent mistakes. In cases where you do need to ignore the value, casting to void will placate the compiler. I did have to add comments to disable clang-format on a couple of lines, where it wanted to format the code like this: ```c++ private : NonnullRefPtr() = delete; ```
213 lines
5.9 KiB
C++
213 lines
5.9 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#ifdef KERNEL
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# include <Kernel/Library/ThreadSafeWeakPtr.h>
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#else
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# include <AK/Weakable.h>
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namespace AK {
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template<typename T>
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class [[nodiscard]] WeakPtr {
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template<typename U>
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friend class Weakable;
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public:
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WeakPtr() = default;
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr(const WeakPtr<U>& other)
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: m_link(other.m_link)
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{
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr(WeakPtr<U>&& other)
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: m_link(other.take_link())
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{
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr& operator=(WeakPtr<U>&& other)
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{
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m_link = other.take_link();
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return *this;
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr& operator=(const WeakPtr<U>& other)
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{
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if ((const void*)this != (const void*)&other)
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m_link = other.m_link;
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return *this;
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}
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WeakPtr& operator=(std::nullptr_t)
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{
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clear();
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return *this;
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr(const U& object)
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: m_link(object.template make_weak_ptr<U>().take_link())
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{
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr(const U* object)
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{
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if (object)
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m_link = object->template make_weak_ptr<U>().take_link();
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr(RefPtr<U> const& object)
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{
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if (object)
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m_link = object->template make_weak_ptr<U>().take_link();
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr(NonnullRefPtr<U> const& object)
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{
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m_link = object->template make_weak_ptr<U>().take_link();
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr& operator=(const U& object)
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{
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m_link = object.template make_weak_ptr<U>().take_link();
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return *this;
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr& operator=(const U* object)
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{
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if (object)
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m_link = object->template make_weak_ptr<U>().take_link();
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else
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m_link = nullptr;
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return *this;
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr& operator=(const RefPtr<U>& object)
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{
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if (object)
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m_link = object->template make_weak_ptr<U>().take_link();
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else
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m_link = nullptr;
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return *this;
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>>::Type* = nullptr>
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WeakPtr& operator=(const NonnullRefPtr<U>& object)
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{
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m_link = object->template make_weak_ptr<U>().take_link();
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return *this;
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}
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[[nodiscard]] RefPtr<T> strong_ref() const
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{
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return RefPtr<T> { ptr() };
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}
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T* ptr() const { return unsafe_ptr(); }
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T* operator->() { return unsafe_ptr(); }
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const T* operator->() const { return unsafe_ptr(); }
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operator const T*() const { return unsafe_ptr(); }
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operator T*() { return unsafe_ptr(); }
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[[nodiscard]] T* unsafe_ptr() const
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{
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if (m_link)
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return m_link->template unsafe_ptr<T>();
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return nullptr;
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}
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operator bool() const { return m_link ? !m_link->is_null() : false; }
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[[nodiscard]] bool is_null() const { return !m_link || m_link->is_null(); }
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void clear() { m_link = nullptr; }
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[[nodiscard]] RefPtr<WeakLink> take_link() { return move(m_link); }
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private:
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WeakPtr(const RefPtr<WeakLink>& link)
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: m_link(link)
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{
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}
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RefPtr<WeakLink> m_link;
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};
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template<typename T>
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template<typename U>
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inline WeakPtr<U> Weakable<T>::make_weak_ptr() const
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{
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if constexpr (IsBaseOf<RefCountedBase, T>) {
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// Checking m_being_destroyed isn't sufficient when dealing with
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// a RefCounted type.The reference count will drop to 0 before the
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// destructor is invoked and revoke_weak_ptrs is called. So, try
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// to add a ref (which should fail if the ref count is at 0) so
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// that we prevent the destructor and revoke_weak_ptrs from being
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// triggered until we're done.
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if (!static_cast<const T*>(this)->try_ref())
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return {};
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} else {
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// For non-RefCounted types this means a weak reference can be
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// obtained until the ~Weakable destructor is invoked!
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if (m_being_destroyed.load(AK::MemoryOrder::memory_order_acquire))
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return {};
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}
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if (!m_link) {
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// There is a small chance that we create a new WeakLink and throw
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// it away because another thread beat us to it. But the window is
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// pretty small and the overhead isn't terrible.
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m_link.assign_if_null(adopt_ref(*new WeakLink(const_cast<T&>(static_cast<const T&>(*this)))));
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}
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WeakPtr<U> weak_ptr(m_link);
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if constexpr (IsBaseOf<RefCountedBase, T>) {
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// Now drop the reference we temporarily added
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if (static_cast<const T*>(this)->unref()) {
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// We just dropped the last reference, which should have called
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// revoke_weak_ptrs, which should have invalidated our weak_ptr
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VERIFY(!weak_ptr.strong_ref());
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return {};
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}
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}
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return weak_ptr;
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}
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template<typename T>
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struct Formatter<WeakPtr<T>> : Formatter<const T*> {
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ErrorOr<void> format(FormatBuilder& builder, WeakPtr<T> const& value)
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{
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return Formatter<const T*>::format(builder, value.ptr());
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}
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};
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template<typename T>
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WeakPtr<T> try_make_weak_ptr(const T* ptr)
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{
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if (ptr) {
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return ptr->template make_weak_ptr<T>();
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}
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return {};
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}
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}
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using AK::WeakPtr;
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#endif
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