COM from scratch - PART TWO

//
// Component.cpp

#include <iostream.h>
#include <objbase.h>
#include "Interface.h"

void TRACE(const char* msg) { cout << "Component:\t" << msg << endl ;}

//
// Component
//
class CComponent : public IComponent
{
	// IUnknown implementation
	virtual HRESULT __stdcall QueryInterface(const IID& iid, void** ppv) ;			
	virtual ULONG __stdcall AddRef() ;
	virtual ULONG __stdcall Release() ;

	// Interface IComponent implementation
	virtual void __stdcall Print(const char* msg);

public:
	CComponent() ;
	~CComponent();

private:
	long m_cRef ;
       
} ;

/////////////////////
CComponent::CComponent()
{
	m_cRef=0;
}
//////////////////////
CComponent::~CComponent()
{
	TRACE("Destructing the component...") ;
}


///////////////////////////////////////////////////////////////////////////
HRESULT __stdcall CComponent::QueryInterface(const IID& iid, void** ppv)
{ 	
	if (iid == IID_IUnknown)
	{
		TRACE("Returning pointer to IUnknown...") ;
		*ppv = static_cast<IComponent*>(this) ;
	} 
	else if (iid == IID_IComponent)
	{
		TRACE("Returning pointer to IComponent interface...") ;
		*ppv = static_cast<IComponent*>(this) ;
	}
	else
	{  	   
		TRACE("Interface is not supported!.") ;
		*ppv = NULL ;
		return E_NOINTERFACE ;
	}

	//The reinterpret_cast operator allows any pointer to be converted into 
	//any other pointer type.
	reinterpret_cast<IUnknown*>(*ppv)->AddRef() ; 
	return S_OK ;
}

//////////////////////////////////////
ULONG __stdcall CComponent::AddRef()
{
	return InterlockedIncrement(&m_cRef) ;
}

//////////////////////////////////////
ULONG __stdcall CComponent::Release() 
{
	if (InterlockedDecrement(&m_cRef) == 0)
	{
		delete this ;
		return 0 ;
	}
	return m_cRef ;
}


//-------------
//Print method
//------------
//////////////////////////////////////////////////
void __stdcall CComponent:: Print(const char* msg)
{
	cout<<"-----------------------"<<endl;
	cout<<msg<<endl;
    cout<<"-----------------------"<<endl;
}

//
// Creation function
//
extern "C" IUnknown* CreateInstance()
{
	IUnknown* pIUnknown = static_cast<IComponent*>(new CComponent) ;
	pIUnknown->AddRef() ;
	return pIUnknown ;
}