COM관점에서 구현한 HelloWorld

/*************************************************************************
Written by Seunghwan
*************************************************************************/

#include<iostream>
#include<objbase.h>
using namespace std;

//////////////////////////////////////////////////////////////////////////
interface ISimpleHelloWorld : public IUnknown
{
 virtual void __stdcall PrintHello() = 0;
};

//////////////////////////////////////////////////////////////////////////
extern const IID IID_ISimpleHelloWorld;

//////////////////////////////////////////////////////////////////////////
class SimpleHelloWorld : public ISimpleHelloWorld
{
 virtual HRESULT __stdcall QueryInterface(const IID & iid , void **ppv);
 virtual ULONG   __stdcall AddRef()
 {
  return 0;
 };
 virtual ULONG   __stdcall Release()
 {
  return 0;
 };
public:
 virtual void __stdcall PrintHello()
 {
  cout << "Hello World" <<endl;
 }
};

//////////////////////////////////////////////////////////////////////////
HRESULT __stdcall SimpleHelloWorld :: QueryInterface(const IID & iid , void ** ppv)
{
 if(iid == IID_IUnknown)
 {
  cout<< "QueryInterface : Return pointer to IUnknown." <<endl;
  *ppv = static_cast<ISimpleHelloWorld*>(this);
 }
 else if(iid == IID_ISimpleHelloWorld)
 {
  cout<< "QueryInterface : Return pointer to ISimpleHelloWorld."<<endl;
  *ppv = static_cast<ISimpleHelloWorld*>(this);
 }
 else
 {
  cout<< "QueryInterface : Interface not supported."<<endl;
  *ppv = NULL;
  return E_NOINTERFACE;
 }
  static_cast<IUnknown*>(*ppv)->AddRef();
 return S_OK;
}

//////////////////////////////////////////////////////////////////////////
IUnknown* CreateInstance()
{
 IUnknown* pI = static_cast<ISimpleHelloWorld*>( new SimpleHelloWorld );
 pI->AddRef();
 return pI;
}

//////////////////////////////////////////////////////////////////////////
static const IID IID_ISimpleHelloWorld =
// {D035B70E-55A1-4869-808E-C395C4964C54}
{ 0xd035b70e, 0x55a1, 0x4869, { 0x80, 0x8e, 0xc3, 0x95, 0xc4, 0x96, 0x4c, 0x54 } };

//////////////////////////////////////////////////////////////////////////
void main()
{
 HRESULT hr;

 cout << "Client : Get and IUNknown pointer."<<endl;
 IUnknown * pIUnknown = CreateInstance();

 cout << "Client : Get interface ISimpleHelloWorld"<<endl;
 ISimpleHelloWorld * pISimpleHelloWorld = NULL;
 hr = pIUnknown->QueryInterface(IID_ISimpleHelloWorld , (void**)&pISimpleHelloWorld);

 if(SUCCEEDED(hr))
 {
  cout<<"Client : Succeeded getting ISimpleHelloWorld"<<endl;
  pISimpleHelloWorld->PrintHello();
 }

 delete pIUnknown;
}