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// **************************************************************************
// * This file is part of the FreeFileSync project. It is distributed under *
// * GNU General Public License: http://www.gnu.org/licenses/gpl.html *
// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved *
// **************************************************************************
#ifndef SMART_COM_PTR_H
#define SMART_COM_PTR_H
#include <algorithm>
#include "win.h" //includes "windows.h" -> always include before other headers that also might include "windows.h"!
#include <Objbase.h>
namespace zen
{
/*
ComPtr: RAII class handling COM objects
Example:
--------
ComPtr<IUPnPDeviceFinder> devFinder;
if (FAILED(::CoCreateInstance(CLSID_UPnPDeviceFinder,
nullptr,
CLSCTX_ALL,
IID_PPV_ARGS(devFinder.init()))))
return -1;
ComPtr<IEnumUnknown> devEnum = com_dynamic_cast<IEnumUnknown>(devColl);
if (!devEnum)
return -1;
*/
template <class T>
class ComPtr
{
public:
ComPtr() : ptr(nullptr) {} //
ComPtr(const ComPtr& other) : ptr(other.ptr) { if (ptr) ptr->AddRef(); } //noexcept in C++11
ComPtr( ComPtr&& tmp ) : ptr(tmp.release()) {} //
~ComPtr() { if (ptr) ptr->Release(); } //has exception spec of compiler-generated destructor by default
ComPtr& operator=(const ComPtr& other) { ComPtr(other).swap(*this); return *this; } //noexcept in C++11
ComPtr& operator=(ComPtr&& tmp) { swap(tmp); return *this; } //
//don't use unifying assignment but save one move-construction in the r-value case instead!
void swap(ComPtr& rhs) { std::swap(ptr, rhs.ptr); } //noexcept in C++11
T** init() //get pointer for use with ::CoCreateInstance()
{
ComPtr<T>().swap(*this);
return &ptr;
}
T* get() const { return ptr; }
T* operator->() const { return ptr; }
T& operator* () const { return *ptr; }
T* release() //noexcept in C++11
{
T* tmp = ptr;
ptr = nullptr;
return tmp;
}
private:
T* ptr;
struct ConversionToBool { int dummy; };
public:
//use member pointer as implicit conversion to bool (C++ Templates - Vandevoorde/Josuttis; chapter 20)
operator int ConversionToBool::* () const { return ptr != nullptr ? &ConversionToBool::dummy : nullptr; }
};
template <class S, class T>
ComPtr<S> com_dynamic_cast(const ComPtr<T>& other); //noexcept in C++11
//################# implementation #############################
//we cannot partially specialize std::swap() for a class template and are not allowed to overload it => offer swap in own namespace
template <class T> inline
void swap(zen::ComPtr<T>& lhs, zen::ComPtr<T>& rhs)
{
lhs.swap(rhs);
}
template <class S, class T> inline
ComPtr<S> com_dynamic_cast(const ComPtr<T>& other) //noexcept in C++11
{
ComPtr<S> outPtr;
if (other)
other->QueryInterface(IID_PPV_ARGS(outPtr.init()));
return outPtr;
}
}
#endif //SMART_COM_PTR_H
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