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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_mscom_Aggregation_h
#define mozilla_mscom_Aggregation_h
#include "mozilla/Attributes.h"
#include <stddef.h>
#include <unknwn.h>
namespace mozilla {
namespace mscom {
/**
* This is used for stabilizing a COM object's reference count during
* construction when that object aggregates other objects. Since the aggregated
* object(s) may AddRef() or Release(), we need to artifically boost the
* refcount to prevent premature destruction. Note that we increment/decrement
* instead of AddRef()/Release() in this class because we want to adjust the
* refcount without causing any other side effects (like object destruction).
*/
template <typename RefCntT>
class MOZ_RAII StabilizedRefCount {
public:
explicit StabilizedRefCount(RefCntT& aRefCnt) : mRefCnt(aRefCnt) {
++aRefCnt;
}
~StabilizedRefCount() { --mRefCnt; }
StabilizedRefCount(const StabilizedRefCount&) = delete;
StabilizedRefCount(StabilizedRefCount&&) = delete;
StabilizedRefCount& operator=(const StabilizedRefCount&) = delete;
StabilizedRefCount& operator=(StabilizedRefCount&&) = delete;
private:
RefCntT& mRefCnt;
};
namespace detail {
template <typename T>
class InternalUnknown : public IUnknown {
public:
STDMETHODIMP QueryInterface(REFIID aIid, void** aOutInterface) override {
return This()->InternalQueryInterface(aIid, aOutInterface);
}
STDMETHODIMP_(ULONG) AddRef() override { return This()->InternalAddRef(); }
STDMETHODIMP_(ULONG) Release() override { return This()->InternalRelease(); }
private:
T* This() {
return reinterpret_cast<T*>(reinterpret_cast<char*>(this) -
offsetof(T, mInternalUnknown));
}
};
} // namespace detail
} // namespace mscom
} // namespace mozilla
#define DECLARE_AGGREGATABLE(Type) \
public: \
STDMETHODIMP QueryInterface(REFIID riid, void** ppv) override { \
return mOuter->QueryInterface(riid, ppv); \
} \
STDMETHODIMP_(ULONG) AddRef() override { return mOuter->AddRef(); } \
STDMETHODIMP_(ULONG) Release() override { return mOuter->Release(); } \
\
protected: \
STDMETHODIMP InternalQueryInterface(REFIID riid, void** ppv); \
STDMETHODIMP_(ULONG) InternalAddRef(); \
STDMETHODIMP_(ULONG) InternalRelease(); \
friend class mozilla::mscom::detail::InternalUnknown<Type>; \
mozilla::mscom::detail::InternalUnknown<Type> mInternalUnknown
#endif // mozilla_mscom_Aggregation_h
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