今天的研究课题：COM！！！

初步看了一下《COM技术内幕》，真是看得头晕眼花，如果现在要对COM有什么评价的话，那么感觉就是：光怪陆离，夷非所思！接口，组件，虚拟函数，多重继承，个个知识点扑面而来，完全是与以前程式设计不同的思路，看这本书唯一的办法就是一点一点啃，细嚼慢咽，生怕出半点差错。（个人觉得比看汇编还要复杂，汇编只是烦，而它却是完全思路的不同）

按照书上的例子写了一个简单的COM组件，并且在主函数中用到了它，程序首先是接口的设计，有IX,IY,IZ三个接口，派生自IUnknown,然后在CA类中实现了接口，CA即代表了一个组件。组件中必须设计好QueryInterface函数，该函数是根据相应的接口IID值设置相应接口的指针，并且返回值指明设置有没有成功。

CreateInstance函数是得到一个指向IUnknown类型的指针，客户需用此函数来创建指向类CA所代表的组件并指向其IUnknown接口的指针。

其中还是有好多的知识点弄不懂，跳过去，等看到后面再跳回来看看。

#include <iostream>
#include <unknwn.h>
#include <objbase.h>

using namespace std;

void trace(char *pmsg)
{
    cout<<pmsg<<endl;
}    

//Interfaces
interface IX:IUnknown
{
    virtual void __stdcall Fx()=0;
};

interface IY:IUnknown
{
    virtual void __stdcall Fy()=0;
};

interface IZ:IUnknown
{
    virtual void __stdcall Fz()=0;
};

//Forward references for GUIDS
extern const IID IID_IX;
extern const IID IID_IY;
extern const IID IID_IZ;


//Component
class CA:public IX,public IY
{
    //IUnknown implementation
    virtual HRESULT __stdcall QueryInterface(const IID& iid,void** ppv);
    virtual ULONG __stdcall AddRef(){return 0;}
    virtual ULONG __stdcall Release() {return 0;}
        
    //Interface IX implementation
    virtual void __stdcall Fx(){cout<<"Fx"<<endl;}
    
    //Interface IY implementation
    virtual void __stdcall Fy(){cout<<"Fy"<<endl;}
};  

HRESULT CA::QueryInterface(const IID& iid,void** ppv)
{
    if(iid==IID_IUnknown)
    {
        *ppv=static_cast<IX*>(this);
    }
    else if(iid==IID_IX)
    {
        *ppv=static_cast<IX*>(this);
    }        
    else if(iid==IID_IY)
    {
        *ppv=static_cast<IY*>(this);
    }    
    else
    {
        *ppv=NULL;
        return E_NOINTERFACE;
    }    
    static_cast<IUnknown*>(*ppv)->AddRef();
    return S_OK;
}              

IUnknown* CreateInstance()
{
    IUnknown* PI = static_cast<IX*>(new CA);
    PI->AddRef();
    return PI;
}
    
//
//IIDS
//
//{32bb8320-b41b-11cf-a6bb-0080c7b2d682}
static const IID IID_IX=
{0x32bb8320,0xb41b,0x11cf,
{0xa6,0xbb,0x0,0x80,0xc7,0xb2,0xd6,0x82}};

//{32bb8321-b41b-11cf-a6bb-0080c7b2d682}
static const IID IID_IY=
{0x32bb8321,0xb41b,0x11cf,
{0xa6,0xbb,0x0,0x80,0xc7,0xb2,0xd6,0x82}};

//{32bb8322-b41b-11cf-a6bb-0080c7b2d682}
static const IID IID_IZ=
{0x32bb8322,0xb41b,0x11cf,
{0xa6,0xbb,0x0,0x80,0xc7,0xb2,0xd6,0x82}};


//
//Client
//
int main()
{
    HRESULT hr;
    trace("Client: Get and IUnknown pointer");
    IUnknown* pIUnknown=CreateInstance();
    
    trace("Client:Get Interface IX.");
    IX* pIX=NULL;
    hr=pIUnknown->QueryInterface(IID_IX,(void**)&pIX);
    if(SUCCEEDED(hr))
    {
        trace("Client:Succeeded getting IX");
        pIX->Fx();
    }    
    
    trace("Client: Get Interface IY");
    IY* pIY=NULL;
    hr=pIUnknown->QueryInterface(IID_IY,(void**)&pIY);
    if(SUCCEEDED(hr))
    {
        trace("Client:Succeeded getting IY");
        pIY->Fy();
    }  
    
    trace("Client: Ask for an unsupported interface");
    IZ* pIZ=NULL;
    hr=pIUnknown->QueryInterface(IID_IZ,(void**)&pIZ);
    if(SUCCEEDED(hr))
    {
        trace("Client:Succeeded in getting interface IZ");
        pIZ->Fz();
    }
    else
    {
        trace("Client:Could not get interface IZ.");
    }    
    
    trace("Client Get Interface IY from interface IX.");
    IY* pIYfromIX=NULL;
    hr=pIX->QueryInterface(IID_IY,(void**)&pIYfromIX);
    if(SUCCEEDED(hr))
    {
        trace("Client:Succeeded Getting IY.");
        pIYfromIX->Fy();
    }
    
    trace("Client Get Interface IUnknown from IY.");
    IUnknown* pIUnknownFromIY=NULL;
    hr=pIY->QueryInterface(IID_IUnknown,(void**)&pIUnknownFromIY);
    if(SUCCEEDED(hr))
    {
        cout<<"Are the IUnknow pointers equal?";
        if(pIUnknownFromIY==pIUnknown)
        {
            cout<<"Yes PIUnknownFromIY==PIUnknown."<<endl;
        }  
        else  
        {
             cout<<"Yes PIUnknownFromIY!=PIUnknown."<<endl;
        }    
    }
    delete pIUnknown;
    return 0;
    
}