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// Copyright (C) 2023 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QCOMOBJECT_P_H
#define QCOMOBJECT_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include <QtCore/private/qglobal_p.h>
#if defined(Q_OS_WIN) || defined(Q_QDOC)
# include <QtCore/qt_windows.h>
QT_BEGIN_NAMESPACE
namespace QtPrivate {
template <typename... TInterfaces>
struct QComObjectTraits
{
static constexpr bool isGuidOf(REFIID riid) noexcept
{
return ((riid == __uuidof(TInterfaces)) || ...);
}
};
} // namespace QtPrivate
// NOTE: In order to be able to query the intermediate interface, i.e. the one you do not specify in
// QComObject interface list (TFirstInterface, TInterfaces) but that is a base for any of them
// (except IUnknown) you need to provide an explicit specialization of function
// QComObjectTraits<...>::isGuidOf for that type. For example, if you want to inherit interface
// IMFSampleGrabberSinkCallback which inherits IMFClockStateSink and you want to be able to query
// the latter one you need to provide this explicit specialization:
//
// class SinkCallback : public QComObject<IMFSampleGrabberSinkCallback>
// {
// ...
// };
//
// namespace QtPrivate {
//
// template <>
// struct QComObjectTraits<IMFSampleGrabberSinkCallback>
// {
// static constexpr bool isGuidOf(REFIID riid) noexcept
// {
// return QComObjectTraits<IMFSampleGrabberSinkCallback, IMFClockStateSink>::isGuidOf(riid);
// }
// };
//
// }
template <typename TFirstInterface, typename... TAdditionalInterfaces>
class QComObject : public TFirstInterface, public TAdditionalInterfaces...
{
public:
STDMETHODIMP QueryInterface(REFIID riid, void **ppvObject) override
{
if (!ppvObject)
return E_POINTER;
if (riid == __uuidof(IUnknown)) {
*ppvObject = static_cast<IUnknown *>(static_cast<TFirstInterface *>(this));
AddRef();
return S_OK;
}
return tryQueryInterface<TFirstInterface, TAdditionalInterfaces...>(riid, ppvObject);
}
STDMETHODIMP_(ULONG) AddRef() override { return ++m_referenceCount; }
STDMETHODIMP_(ULONG) Release() override
{
const LONG referenceCount = --m_referenceCount;
if (referenceCount == 0)
delete this;
return referenceCount;
}
protected:
QComObject() = default;
// Destructor is not public. Caller should call Release.
// Derived class should make its destructor private to force this behavior.
virtual ~QComObject() = default;
private:
template <typename TInterface, typename... TRest>
HRESULT tryQueryInterface(REFIID riid, void **ppvObject)
{
if (QtPrivate::QComObjectTraits<TInterface>::isGuidOf(riid)) {
*ppvObject = static_cast<TInterface *>(this);
AddRef();
return S_OK;
}
if constexpr (sizeof...(TRest) > 0)
return tryQueryInterface<TRest...>(riid, ppvObject);
*ppvObject = nullptr;
return E_NOINTERFACE;
}
std::atomic<LONG> m_referenceCount = 1;
};
QT_END_NAMESPACE
#endif // Q_OS_WIN
#endif // QCOMOBJECT_P_H
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