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https://github.com/SerenityOS/serenity
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5d180d1f99
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED) Since all of these checks are done in release builds as well, let's rename them to VERIFY to prevent confusion, as everyone is used to assertions being compiled out in release. We can introduce a new ASSERT macro that is specifically for debug checks, but I'm doing this wholesale conversion first since we've accumulated thousands of these already, and it's not immediately obvious which ones are suitable for ASSERT.
275 lines
8.6 KiB
C++
275 lines
8.6 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/LogStream.h>
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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 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>::value>::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>::value>::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>::value>::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>::value>::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>::value>::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>::value>::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>::value>::Type* = nullptr>
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WeakPtr(const RefPtr<U>& object)
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{
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object.do_while_locked([&](U* obj) {
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if (obj)
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m_link = obj->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>::value>::Type* = nullptr>
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WeakPtr(const NonnullRefPtr<U>& object)
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{
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object.do_while_locked([&](U* obj) {
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if (obj)
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m_link = obj->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>::value>::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>::value>::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>::value>::Type* = nullptr>
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WeakPtr& operator=(const RefPtr<U>& object)
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{
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object.do_while_locked([&](U* obj) {
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if (obj)
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m_link = obj->template make_weak_ptr<U>().take_link();
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else
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m_link = nullptr;
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});
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return *this;
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}
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template<typename U, typename EnableIf<IsBaseOf<T, U>::value>::Type* = nullptr>
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WeakPtr& operator=(const NonnullRefPtr<U>& object)
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{
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object.do_while_locked([&](U* obj) {
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if (obj)
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m_link = obj->template make_weak_ptr<U>().take_link();
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else
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m_link = nullptr;
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});
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return *this;
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}
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RefPtr<T> strong_ref() const
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{
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// This only works with RefCounted objects, but it is the only
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// safe way to get a strong reference from a WeakPtr. Any code
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// that uses objects not derived from RefCounted will have to
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// use unsafe_ptr(), but as the name suggests, it is not safe...
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RefPtr<T> ref;
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// Using do_while_locked protects against a race with clear()!
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m_link.do_while_locked([&](WeakLink* link) {
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if (link)
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ref = link->template strong_ref<T>();
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});
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return ref;
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}
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#ifndef KERNEL
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// A lot of user mode code is single-threaded. But for kernel mode code
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// this is generally not true as everything is multi-threaded. So make
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// these shortcuts and aliases only available to non-kernel code.
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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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#endif
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T* unsafe_ptr() const
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{
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T* ptr = nullptr;
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m_link.do_while_locked([&](WeakLink* link) {
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if (link)
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ptr = link->unsafe_ptr<T>();
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});
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return ptr;
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}
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operator bool() const { return m_link ? !m_link->is_null() : false; }
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bool is_null() const { return !m_link || m_link->is_null(); }
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void clear() { m_link = nullptr; }
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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>::value) {
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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(*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>::value) {
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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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inline const LogStream& operator<<(const LogStream& stream, const WeakPtr<T>& value)
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{
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#ifdef KERNEL
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auto ref = value.strong_ref();
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return stream << ref.ptr();
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#else
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return stream << value.ptr();
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#endif
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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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void format(FormatBuilder& builder, const WeakPtr<T>& value)
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{
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#ifdef KERNEL
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auto ref = value.strong_ref();
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Formatter<const T*>::format(builder, ref.ptr());
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#else
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Formatter<const T*>::format(builder, value.ptr());
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#endif
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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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