329 lines
11 KiB
C++
329 lines
11 KiB
C++
/*
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* Copyright (C) 2013 Google, Inc. All rights reserved.
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* Copyright (C) 2015-2020 Apple Inc. 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
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (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 <wtf/HashTraits.h>
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#include <wtf/Threading.h>
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namespace WTF {
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template<typename, typename> class WeakHashSet;
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template<typename, typename> class WeakPtrFactory;
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struct EmptyCounter {
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static void increment() { }
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static void decrement() { }
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};
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enum class EnableWeakPtrThreadingAssertions : bool { No, Yes };
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template<typename Counter = EmptyCounter> class WeakPtrImpl : public ThreadSafeRefCounted<WeakPtrImpl<Counter>> {
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WTF_MAKE_NONCOPYABLE(WeakPtrImpl);
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WTF_MAKE_FAST_ALLOCATED;
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public:
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template<typename T> static Ref<WeakPtrImpl> create(T* ptr)
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{
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return adoptRef(*new WeakPtrImpl(ptr));
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}
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~WeakPtrImpl()
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{
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Counter::decrement();
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}
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template<typename T> typename T::WeakValueType* get()
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{
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return static_cast<typename T::WeakValueType*>(m_ptr);
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}
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explicit operator bool() const { return m_ptr; }
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void clear() { m_ptr = nullptr; }
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#if ASSERT_ENABLED
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bool wasConstructedOnMainThread() const { return m_wasConstructedOnMainThread; }
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#endif
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private:
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template<typename T> explicit WeakPtrImpl(T* ptr)
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: m_ptr(static_cast<typename T::WeakValueType*>(ptr))
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#if ASSERT_ENABLED
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, m_wasConstructedOnMainThread(isMainThread())
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#endif
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{
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Counter::increment();
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}
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void* m_ptr;
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#if ASSERT_ENABLED
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bool m_wasConstructedOnMainThread;
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#endif
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};
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template<typename Counter> struct HashTraits<Ref<WeakPtrImpl<Counter>>> : RefHashTraits<WeakPtrImpl<Counter>> {
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static constexpr bool hasIsReleasedWeakValueFunction = true;
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static bool isReleasedWeakValue(const Ref<WeakPtrImpl<Counter>>& value)
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{
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return !value.isHashTableDeletedValue() && !value.isHashTableEmptyValue() && !value.get();
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}
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};
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template<typename T, typename Counter> class WeakPtr {
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WTF_MAKE_FAST_ALLOCATED;
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public:
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WeakPtr() { }
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WeakPtr(std::nullptr_t) { }
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template<typename U> WeakPtr(const WeakPtr<U, Counter>&);
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template<typename U> WeakPtr(WeakPtr<U, Counter>&&);
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T* get() const
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{
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// FIXME: Our GC threads currently need to get opaque pointers from WeakPtrs and have to be special-cased.
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ASSERT(!m_impl || !m_shouldEnableAssertions || Thread::mayBeGCThread() || m_impl->wasConstructedOnMainThread() == isMainThread());
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return m_impl ? static_cast<T*>(m_impl->template get<T>()) : nullptr;
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}
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bool operator!() const { return !m_impl || !*m_impl; }
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explicit operator bool() const { return m_impl && *m_impl; }
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WeakPtr& operator=(std::nullptr_t) { m_impl = nullptr; return *this; }
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template<typename U> WeakPtr& operator=(const WeakPtr<U, Counter>&);
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template<typename U> WeakPtr& operator=(WeakPtr<U, Counter>&&);
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T* operator->() const
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{
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ASSERT(!m_impl || !m_shouldEnableAssertions || m_impl->wasConstructedOnMainThread() == isMainThread());
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return get();
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}
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T& operator*() const
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{
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ASSERT(!m_impl || !m_shouldEnableAssertions || m_impl->wasConstructedOnMainThread() == isMainThread());
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return *get();
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}
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void clear() { m_impl = nullptr; }
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private:
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template<typename, typename, typename> friend class WeakHashMap;
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template<typename, typename> friend class WeakHashSet;
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template<typename, typename> friend class WeakPtr;
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template<typename, typename> friend class WeakPtrFactory;
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explicit WeakPtr(Ref<WeakPtrImpl<Counter>>&& ref, EnableWeakPtrThreadingAssertions shouldEnableAssertions)
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: m_impl(WTFMove(ref))
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#if ASSERT_ENABLED
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, m_shouldEnableAssertions(shouldEnableAssertions == EnableWeakPtrThreadingAssertions::Yes)
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#endif
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{
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UNUSED_PARAM(shouldEnableAssertions);
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}
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RefPtr<WeakPtrImpl<Counter>> m_impl;
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#if ASSERT_ENABLED
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bool m_shouldEnableAssertions { true };
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#endif
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};
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// Note: you probably want to inherit from CanMakeWeakPtr rather than use this directly.
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template<typename T, typename Counter = EmptyCounter> class WeakPtrFactory {
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WTF_MAKE_NONCOPYABLE(WeakPtrFactory);
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WTF_MAKE_FAST_ALLOCATED;
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public:
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using CounterType = Counter;
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WeakPtrFactory()
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#if ASSERT_ENABLED
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: m_wasConstructedOnMainThread(isMainThread())
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#endif
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{
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}
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~WeakPtrFactory()
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{
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if (!m_impl)
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return;
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m_impl->clear();
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}
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void initializeIfNeeded(const T& object) const
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{
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if (m_impl)
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return;
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ASSERT(m_wasConstructedOnMainThread == isMainThread());
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m_impl = WeakPtrImpl<Counter>::create(const_cast<T*>(&object));
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}
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template<typename U> WeakPtr<U, Counter> createWeakPtr(U& object, EnableWeakPtrThreadingAssertions enableWeakPtrThreadingAssertions = EnableWeakPtrThreadingAssertions::Yes) const
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{
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initializeIfNeeded(object);
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ASSERT(&object == m_impl->template get<T>());
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return WeakPtr<U, Counter>(makeRef(*m_impl), enableWeakPtrThreadingAssertions);
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}
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void revokeAll()
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{
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if (!m_impl)
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return;
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m_impl->clear();
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m_impl = nullptr;
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}
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unsigned weakPtrCount() const { return m_impl ? m_impl->refCount() - 1 : 0; }
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#if ASSERT_ENABLED
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bool isInitialized() const { return m_impl; }
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#endif
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private:
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template<typename, typename> friend class WeakHashSet;
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template<typename, typename, typename> friend class WeakHashMap;
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mutable RefPtr<WeakPtrImpl<Counter>> m_impl;
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#if ASSERT_ENABLED
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bool m_wasConstructedOnMainThread;
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#endif
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};
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// We use lazy initialization of the WeakPtrFactory by default to avoid unnecessary initialization. Eager
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// initialization is however useful if you plan to call makeWeakPtr() from other threads.
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enum class WeakPtrFactoryInitialization { Lazy, Eager };
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template<typename T, WeakPtrFactoryInitialization initializationMode = WeakPtrFactoryInitialization::Lazy, typename Counter = EmptyCounter> class CanMakeWeakPtr {
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public:
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using WeakValueType = T;
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const WeakPtrFactory<T, Counter>& weakPtrFactory() const { return m_weakPtrFactory; }
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WeakPtrFactory<T, Counter>& weakPtrFactory() { return m_weakPtrFactory; }
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protected:
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CanMakeWeakPtr()
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{
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if (initializationMode == WeakPtrFactoryInitialization::Eager)
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initializeWeakPtrFactory();
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}
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void initializeWeakPtrFactory()
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{
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m_weakPtrFactory.initializeIfNeeded(static_cast<T&>(*this));
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}
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private:
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WeakPtrFactory<T, Counter> m_weakPtrFactory;
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};
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template<typename T, typename U, typename Counter> inline WeakPtrImpl<Counter>* weak_ptr_impl_cast(WeakPtrImpl<Counter>* impl)
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{
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static_assert(std::is_same_v<typename T::WeakValueType, typename U::WeakValueType>, "Invalid weak pointer cast");
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return impl;
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}
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template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>::WeakPtr(const WeakPtr<U, Counter>& o)
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: m_impl(weak_ptr_impl_cast<T, U>(o.m_impl.get()))
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{
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}
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template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>::WeakPtr(WeakPtr<U, Counter>&& o)
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: m_impl(adoptRef(weak_ptr_impl_cast<T, U>(o.m_impl.leakRef())))
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{
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}
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template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>& WeakPtr<T, Counter>::operator=(const WeakPtr<U, Counter>& o)
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{
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m_impl = weak_ptr_impl_cast<T, U>(o.m_impl.get());
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return *this;
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}
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template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>& WeakPtr<T, Counter>::operator=(WeakPtr<U, Counter>&& o)
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{
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m_impl = adoptRef(weak_ptr_impl_cast<T, U>(o.m_impl.leakRef()));
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return *this;
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}
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template<typename T, typename = std::enable_if_t<!IsSmartPtr<T>::value>> inline auto makeWeakPtr(T& object, EnableWeakPtrThreadingAssertions enableWeakPtrThreadingAssertions = EnableWeakPtrThreadingAssertions::Yes)
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{
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return object.weakPtrFactory().template createWeakPtr<T>(object, enableWeakPtrThreadingAssertions);
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}
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template<typename T, typename = std::enable_if_t<!IsSmartPtr<T>::value>> inline auto makeWeakPtr(T* ptr, EnableWeakPtrThreadingAssertions enableWeakPtrThreadingAssertions = EnableWeakPtrThreadingAssertions::Yes) -> decltype(makeWeakPtr(*ptr))
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{
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if (!ptr)
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return { };
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return makeWeakPtr(*ptr, enableWeakPtrThreadingAssertions);
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}
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template<typename T, typename = std::enable_if_t<!IsSmartPtr<T>::value>> inline auto makeWeakPtr(const Ref<T>& object, EnableWeakPtrThreadingAssertions enableWeakPtrThreadingAssertions = EnableWeakPtrThreadingAssertions::Yes)
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{
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return makeWeakPtr(object.get(), enableWeakPtrThreadingAssertions);
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}
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template<typename T, typename = std::enable_if_t<!IsSmartPtr<T>::value>> inline auto makeWeakPtr(const RefPtr<T>& object, EnableWeakPtrThreadingAssertions enableWeakPtrThreadingAssertions = EnableWeakPtrThreadingAssertions::Yes)
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{
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return makeWeakPtr(object.get(), enableWeakPtrThreadingAssertions);
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}
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template<typename T, typename U, typename Counter> inline bool operator==(const WeakPtr<T, Counter>& a, const WeakPtr<U, Counter>& b)
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{
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return a.get() == b.get();
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}
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template<typename T, typename U, typename Counter> inline bool operator==(const WeakPtr<T, Counter>& a, U* b)
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{
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return a.get() == b;
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}
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template<typename T, typename U, typename Counter> inline bool operator==(T* a, const WeakPtr<U, Counter>& b)
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{
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return a == b.get();
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}
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template<typename T, typename U, typename Counter> inline bool operator!=(const WeakPtr<T, Counter>& a, const WeakPtr<U, Counter>& b)
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{
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return a.get() != b.get();
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}
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template<typename T, typename U, typename Counter> inline bool operator!=(const WeakPtr<T, Counter>& a, U* b)
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{
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return a.get() != b;
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}
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template<typename T, typename U, typename Counter> inline bool operator!=(T* a, const WeakPtr<U, Counter>& b)
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{
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return a != b.get();
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}
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} // namespace WTF
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using WTF::CanMakeWeakPtr;
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using WTF::EnableWeakPtrThreadingAssertions;
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using WTF::WeakPtr;
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using WTF::WeakPtrFactory;
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using WTF::WeakPtrFactoryInitialization;
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using WTF::makeWeakPtr;
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