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/*
* Copyright (C) 2013 Google, Inc. All Rights Reserved.
* Copyright (C) 2015, 2017 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/Noncopyable.h>
#include <wtf/Ref.h>
#include <wtf/ThreadSafeRefCounted.h>
#include <wtf/Threading.h>
namespace WTF {
template<typename> class WeakHashSet;
template<typename> class WeakPtr;
template<typename> class WeakPtrFactory;
// Note: WeakReference is an implementation detail, and should not be used directly.
template<typename T>
class WeakReference : public ThreadSafeRefCounted<WeakReference<T>> {
WTF_MAKE_NONCOPYABLE(WeakReference<T>);
WTF_MAKE_FAST_ALLOCATED;
public:
~WeakReference() { } // So that we can use a template specialization for testing purposes to detect leaks.
T* get() const { return m_ptr; }
void clear() { m_ptr = nullptr; }
private:
friend class WeakPtr<T>;
friend class WeakPtrFactory<T>;
static Ref<WeakReference<T>> create(T* ptr) { return adoptRef(*new WeakReference(ptr)); }
explicit WeakReference(T* ptr)
: m_ptr(ptr)
{
}
T* m_ptr;
};
template<typename T>
class WeakPtr {
WTF_MAKE_FAST_ALLOCATED;
public:
WeakPtr() { }
WeakPtr(std::nullptr_t) { }
WeakPtr(Ref<WeakReference<T>>&& ref) : m_ref(std::forward<Ref<WeakReference<T>>>(ref)) { }
template<typename U> WeakPtr(const WeakPtr<U>&);
template<typename U> WeakPtr(WeakPtr<U>&&);
T* get() const { return m_ref ? m_ref->get() : nullptr; }
explicit operator bool() const { return m_ref && m_ref->get(); }
WeakPtr& operator=(std::nullptr_t) { m_ref = nullptr; return *this; }
template<typename U> WeakPtr& operator=(const WeakPtr<U>&);
template<typename U> WeakPtr& operator=(WeakPtr<U>&&);
T* operator->() const { return m_ref->get(); }
T& operator*() const { return *m_ref->get(); }
void clear() { m_ref = nullptr; }
private:
template<typename> friend class WeakHashSet;
template<typename> friend class WeakPtr;
template<typename U> friend WeakPtr<U> makeWeakPtr(U&);
RefPtr<WeakReference<T>> m_ref;
};
// Note: you probably want to inherit from CanMakeWeakPtr rather than use this directly.
template<typename T>
class WeakPtrFactory {
WTF_MAKE_NONCOPYABLE(WeakPtrFactory<T>);
WTF_MAKE_FAST_ALLOCATED;
public:
WeakPtrFactory() = default;
~WeakPtrFactory()
{
if (!m_ref)
return;
m_ref->clear();
}
WeakPtr<T> createWeakPtr(T& ptr) const
{
if (!m_ref)
m_ref = WeakReference<T>::create(&ptr);
return { makeRef(*m_ref) };
}
WeakPtr<const T> createWeakPtr(const T& ptr) const
{
if (!m_ref)
m_ref = WeakReference<T>::create(const_cast<T*>(&ptr));
return { makeRef(reinterpret_cast<WeakReference<const T>&>(*m_ref)) };
}
void revokeAll()
{
if (!m_ref)
return;
m_ref->clear();
m_ref = nullptr;
}
private:
template<typename> friend class WeakHashSet;
mutable RefPtr<WeakReference<T>> m_ref;
};
template<typename T> class CanMakeWeakPtr {
public:
const WeakPtrFactory<T>& weakPtrFactory() const { return m_weakFactory; }
WeakPtrFactory<T>& weakPtrFactory() { return m_weakFactory; }
private:
WeakPtrFactory<T> m_weakFactory;
};
template<typename T, typename U> inline WeakReference<T>* weak_reference_upcast(WeakReference<U>* weakReference)
{
static_assert(std::is_convertible<U*, T*>::value, "U* must be convertible to T*");
return reinterpret_cast<WeakReference<T>*>(weakReference);
}
template<typename T, typename U> inline WeakReference<T>* weak_reference_downcast(WeakReference<U>* weakReference)
{
static_assert(std::is_convertible<T*, U*>::value, "T* must be convertible to U*");
return reinterpret_cast<WeakReference<T>*>(weakReference);
}
template<typename T> template<typename U> inline WeakPtr<T>::WeakPtr(const WeakPtr<U>& o)
: m_ref(weak_reference_upcast<T>(o.m_ref.get()))
{
}
template<typename T> template<typename U> inline WeakPtr<T>::WeakPtr(WeakPtr<U>&& o)
: m_ref(adoptRef(weak_reference_upcast<T>(o.m_ref.leakRef())))
{
}
template<typename T> template<typename U> inline WeakPtr<T>& WeakPtr<T>::operator=(const WeakPtr<U>& o)
{
m_ref = weak_reference_upcast<T>(o.m_ref.get());
return *this;
}
template<typename T> template<typename U> inline WeakPtr<T>& WeakPtr<T>::operator=(WeakPtr<U>&& o)
{
m_ref = adoptRef(weak_reference_upcast<T>(o.m_ref.leakRef()));
return *this;
}
template<typename T> inline WeakPtr<T> makeWeakPtr(T& ref)
{
return { adoptRef(*weak_reference_downcast<T>(ref.weakPtrFactory().createWeakPtr(ref).m_ref.leakRef())) };
}
template<typename T> inline WeakPtr<T> makeWeakPtr(T* ptr)
{
if (!ptr)
return { };
return makeWeakPtr(*ptr);
}
template<typename T, typename U> inline bool operator==(const WeakPtr<T>& a, const WeakPtr<U>& b)
{
return a.get() == b.get();
}
template<typename T, typename U> inline bool operator==(const WeakPtr<T>& a, U* b)
{
return a.get() == b;
}
template<typename T, typename U> inline bool operator==(T* a, const WeakPtr<U>& b)
{
return a == b.get();
}
template<typename T, typename U> inline bool operator!=(const WeakPtr<T>& a, const WeakPtr<U>& b)
{
return a.get() != b.get();
}
template<typename T, typename U> inline bool operator!=(const WeakPtr<T>& a, U* b)
{
return a.get() != b;
}
template<typename T, typename U> inline bool operator!=(T* a, const WeakPtr<U>& b)
{
return a != b.get();
}
} // namespace WTF
using WTF::CanMakeWeakPtr;
using WTF::WeakPtr;
using WTF::WeakPtrFactory;
using WTF::WeakReference;
using WTF::makeWeakPtr;