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/*
* Copyright (C) 2013 Google, Inc. All rights reserved.
* Copyright (C) 2015-2020 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/Threading.h>
namespace WTF {
template<typename, typename> class WeakHashSet;
template<typename, typename> class WeakPtrFactory;
struct EmptyCounter {
static void increment() { }
static void decrement() { }
};
template<typename Counter = EmptyCounter> class WeakPtrImpl : public ThreadSafeRefCounted<WeakPtrImpl<Counter>> {
WTF_MAKE_NONCOPYABLE(WeakPtrImpl);
WTF_MAKE_FAST_ALLOCATED;
public:
template<typename T> static Ref<WeakPtrImpl> create(T* ptr)
{
return adoptRef(*new WeakPtrImpl(ptr));
}
~WeakPtrImpl()
{
Counter::decrement();
}
template<typename T> typename T::WeakValueType* get()
{
return static_cast<typename T::WeakValueType*>(m_ptr);
}
explicit operator bool() const { return m_ptr; }
void clear() { m_ptr = nullptr; }
#if ASSERT_ENABLED
bool wasConstructedOnMainThread() const { return m_wasConstructedOnMainThread; }
#endif
private:
template<typename T> explicit WeakPtrImpl(T* ptr)
: m_ptr(static_cast<typename T::WeakValueType*>(ptr))
#if ASSERT_ENABLED
, m_wasConstructedOnMainThread(isMainThread())
#endif
{
Counter::increment();
}
void* m_ptr;
#if ASSERT_ENABLED
bool m_wasConstructedOnMainThread;
#endif
};
template<typename T, typename Counter> class WeakPtr {
WTF_MAKE_FAST_ALLOCATED;
public:
WeakPtr() { }
WeakPtr(std::nullptr_t) { }
template<typename U> WeakPtr(const WeakPtr<U, Counter>&);
template<typename U> WeakPtr(WeakPtr<U, Counter>&&);
T* get() const
{
// FIXME: Our GC threads currently need to get opaque pointers from WeakPtrs and have to be special-cased.
ASSERT(!m_impl || Thread::mayBeGCThread() || m_impl->wasConstructedOnMainThread() == isMainThread());
return m_impl ? static_cast<T*>(m_impl->template get<T>()) : nullptr;
}
bool operator!() const { return !m_impl || !*m_impl; }
explicit operator bool() const { return m_impl && *m_impl; }
WeakPtr& operator=(std::nullptr_t) { m_impl = nullptr; return *this; }
template<typename U> WeakPtr& operator=(const WeakPtr<U, Counter>&);
template<typename U> WeakPtr& operator=(WeakPtr<U, Counter>&&);
T* operator->() const
{
ASSERT(!m_impl || m_impl->wasConstructedOnMainThread() == isMainThread());
return get();
}
T& operator*() const
{
ASSERT(!m_impl || m_impl->wasConstructedOnMainThread() == isMainThread());
return *get();
}
void clear() { m_impl = nullptr; }
private:
template<typename, typename> friend class WeakHashSet;
template<typename, typename> friend class WeakPtr;
template<typename, typename> friend class WeakPtrFactory;
explicit WeakPtr(Ref<WeakPtrImpl<Counter>>&& ref)
: m_impl(WTFMove(ref))
{
}
RefPtr<WeakPtrImpl<Counter>> m_impl;
};
// Note: you probably want to inherit from CanMakeWeakPtr rather than use this directly.
template<typename T, typename Counter = EmptyCounter> class WeakPtrFactory {
WTF_MAKE_NONCOPYABLE(WeakPtrFactory);
WTF_MAKE_FAST_ALLOCATED;
public:
using CounterType = Counter;
WeakPtrFactory()
#if ASSERT_ENABLED
: m_wasConstructedOnMainThread(isMainThread())
#endif
{
}
~WeakPtrFactory()
{
if (!m_impl)
return;
m_impl->clear();
}
void initializeIfNeeded(const T& object) const
{
if (m_impl)
return;
ASSERT(m_wasConstructedOnMainThread == isMainThread());
m_impl = WeakPtrImpl<Counter>::create(const_cast<T*>(&object));
}
template<typename U> WeakPtr<U, Counter> createWeakPtr(U& object) const
{
initializeIfNeeded(object);
ASSERT(&object == m_impl->template get<T>());
return WeakPtr<U, Counter>(makeRef(*m_impl));
}
void revokeAll()
{
if (!m_impl)
return;
m_impl->clear();
m_impl = nullptr;
}
private:
template<typename, typename> friend class WeakHashSet;
mutable RefPtr<WeakPtrImpl<Counter>> m_impl;
#if ASSERT_ENABLED
bool m_wasConstructedOnMainThread;
#endif
};
// We use lazy initialization of the WeakPtrFactory by default to avoid unnecessary initialization. Eager
// initialization is however useful if you plan to call makeWeakPtr() from other threads.
enum class WeakPtrFactoryInitialization { Lazy, Eager };
template<typename T, WeakPtrFactoryInitialization initializationMode = WeakPtrFactoryInitialization::Lazy, typename Counter = EmptyCounter> class CanMakeWeakPtr {
public:
using WeakValueType = T;
const WeakPtrFactory<T, Counter>& weakPtrFactory() const { return m_weakPtrFactory; }
WeakPtrFactory<T, Counter>& weakPtrFactory() { return m_weakPtrFactory; }
protected:
CanMakeWeakPtr()
{
if (initializationMode == WeakPtrFactoryInitialization::Eager)
m_weakPtrFactory.initializeIfNeeded(static_cast<T&>(*this));
}
private:
WeakPtrFactory<T, Counter> m_weakPtrFactory;
};
template<typename T, typename U, typename Counter> inline WeakPtrImpl<Counter>* weak_ptr_impl_cast(WeakPtrImpl<Counter>* impl)
{
static_assert(std::is_same_v<typename T::WeakValueType, typename U::WeakValueType>, "Invalid weak pointer cast");
return impl;
}
template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>::WeakPtr(const WeakPtr<U, Counter>& o)
: m_impl(weak_ptr_impl_cast<T, U>(o.m_impl.get()))
{
}
template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>::WeakPtr(WeakPtr<U, Counter>&& o)
: m_impl(adoptRef(weak_ptr_impl_cast<T, U>(o.m_impl.leakRef())))
{
}
template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>& WeakPtr<T, Counter>::operator=(const WeakPtr<U, Counter>& o)
{
m_impl = weak_ptr_impl_cast<T, U>(o.m_impl.get());
return *this;
}
template<typename T, typename Counter> template<typename U> inline WeakPtr<T, Counter>& WeakPtr<T, Counter>::operator=(WeakPtr<U, Counter>&& o)
{
m_impl = adoptRef(weak_ptr_impl_cast<T, U>(o.m_impl.leakRef()));
return *this;
}
template<typename T> inline auto makeWeakPtr(T& object)
{
return object.weakPtrFactory().template createWeakPtr<T>(object);
}
template<typename T> inline auto makeWeakPtr(T* ptr) -> decltype(makeWeakPtr(*ptr))
{
if (!ptr)
return { };
return makeWeakPtr(*ptr);
}
template<typename T, typename U, typename Counter> inline bool operator==(const WeakPtr<T, Counter>& a, const WeakPtr<U, Counter>& b)
{
return a.get() == b.get();
}
template<typename T, typename U, typename Counter> inline bool operator==(const WeakPtr<T, Counter>& a, U* b)
{
return a.get() == b;
}
template<typename T, typename U, typename Counter> inline bool operator==(T* a, const WeakPtr<U, Counter>& b)
{
return a == b.get();
}
template<typename T, typename U, typename Counter> inline bool operator!=(const WeakPtr<T, Counter>& a, const WeakPtr<U, Counter>& b)
{
return a.get() != b.get();
}
template<typename T, typename U, typename Counter> inline bool operator!=(const WeakPtr<T, Counter>& a, U* b)
{
return a.get() != b;
}
template<typename T, typename U, typename Counter> inline bool operator!=(T* a, const WeakPtr<U, Counter>& b)
{
return a != b.get();
}
} // namespace WTF
using WTF::CanMakeWeakPtr;
using WTF::WeakPtr;
using WTF::WeakPtrFactory;
using WTF::WeakPtrFactoryInitialization;
using WTF::makeWeakPtr;