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WeakRef.h
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143 lines (107 loc) · 2.88 KB
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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT license.
#pragma once
//-----------------------------------------------------------------------------
// forward declarations
//-----------------------------------------------------------------------------
template <typename T>
class WeakRefTarget;
template <typename T>
class WeakRefImpl;
//-----------------------------------------------------------------------------
// WeakRef
//-----------------------------------------------------------------------------
template <typename T>
class WeakRef final
{
friend class WeakRefTarget<T>;
public:
WeakRef<T>(const WeakRef<T>& that):
m_spImpl(that.m_spImpl)
{
}
WeakRef<T>(WeakRef<T>&& that) noexcept:
m_spImpl(std::move(that.m_spImpl))
{
}
const WeakRef<T>& operator=(const WeakRef<T>& that)
{
m_spImpl = that.m_spImpl;
return *this;
}
const WeakRef<T>& operator=(WeakRef<T>&& that) noexcept
{
m_spImpl = std::move(that.m_spImpl);
return *this;
}
SharedPtr<T> GetTarget() const
{
return m_spImpl->GetTarget();
}
private:
explicit WeakRef(const SharedPtr<WeakRefImpl<T>>& spImpl):
m_spImpl(spImpl)
{
}
SharedPtr<WeakRefImpl<T>> m_spImpl;
};
//-----------------------------------------------------------------------------
// WeakRefTarget
//-----------------------------------------------------------------------------
template <typename T>
class WeakRefTarget: public SharedPtrTarget
{
public:
WeakRefTarget<T>():
m_spWeakRefImpl(new WeakRefImpl<T>(static_cast<T*>(this)))
{
}
WeakRef<T> CreateWeakRef() const
{
return WeakRef<T>(m_spWeakRefImpl);
}
protected:
~WeakRefTarget()
{
m_spWeakRefImpl->OnTargetDeleted();
}
private:
SharedPtr<WeakRefImpl<T>> m_spWeakRefImpl;
};
//-----------------------------------------------------------------------------
// WeakRefImpl
//-----------------------------------------------------------------------------
template <typename T>
class WeakRefImpl final: public SharedPtrTarget
{
friend class WeakRef<T>;
friend class WeakRefTarget<T>;
private:
explicit WeakRefImpl(T* pTarget):
m_pTarget(pTarget)
{
}
SharedPtr<T> GetTarget()
{
SharedPtr<T> spTarget;
BEGIN_MUTEX_SCOPE(m_Mutex)
if (m_pTarget != nullptr)
{
AddRefScope addRefScope(m_pTarget->GetRefCount());
if (addRefScope.GetRefCountValue() > 1)
{
spTarget = m_pTarget;
}
}
END_MUTEX_SCOPE
return spTarget;
}
void OnTargetDeleted()
{
BEGIN_MUTEX_SCOPE(m_Mutex)
m_pTarget = nullptr;
END_MUTEX_SCOPE
}
SimpleMutex m_Mutex;
T* m_pTarget;
};