前言:為了介紹C#寫界面，C++寫算法的快捷交互開發方式，首先介紹c++，C#內部的DLL，COM調用。
一，COM
COM (Component Object Model),微軟為提高代碼的可從用性而開發的組件對象模型的軟件架構，在windows系統的開發中大量的使用了這種技術，使用這種技術我們盡可能的把我們的軟件劃分位許多組件，通過組件的組合調用最總實現軟件的目的，COM的使用不僅大大的提高了代碼的可從用性，而且減小了代碼間的耦合。更多的關于OLE，COM，COM+，DCOM，ActiveX的概念。
二，COM的創建
一般COM的創建有2中方法，使用ATL Wizard 和不使用ATL。
1）使用ATL Wizard創建COM非常的簡單，可以參考下面2個鏈接，分別使用ATL6.0和ATL7.0，最新的類似：
ATL7.0 COM: http://www.codeproject.com/atl/SimpleDlls.asp
ATL6.0 com: http://www.codeproject.com/atl/com_atl.asp
2）不使用ATL，當然更沒有Wizard，只有手動的一步一步的實現，不過這也是學習COM最好的方法和必經之路。可以參考：
http://www.codeproject.com/com/LocalCOMServerClient.asp
具體的步驟如下：
1）建立一個Win32的DLL。例如CarLocalServer。
2）首先加入IDL接口描述文件CarLocalServerTypeInfo.idl，編譯后會生成4個文件CarLocalServerTypeInfo_h.h，CarLocalServerTypeInfo_i.cpp，CarLocalServerTypeInfo_p.cpp， dlldata.cpp 。
import "oaidl.idl";
import "ocidl.idl";
// define IStats interface
[object, uuid(FE78387F-D150-4089-832C-BBF02402C872),
oleautomation, helpstring("Get the status information about this car")]
interface IStats : IUnknown
{
HRESULT DisplayStats();
HRESULT GetPetName([out,retval] BSTR* petName);
};
// define the IEngine interface
[object, uuid(E27972D8-717F-4516-A82D-B688DC70170C),
oleautomation, helpstring("Rev your car and slow it down")]
interface IEngine : IUnknown
{
HRESULT SpeedUp();
HRESULT GetMaxSpeed([out,retval] int* maxSpeed);
HRESULT GetCurSpeed([out,retval] int* curSpeed);
};
// define the ICreateMyCar interface
[object, uuid(5DD52389-B1A4-4fe7-B131-0F8EF73DD175),
oleautomation, helpstring("This lets you create a car object")]
interface ICreateMyCar : IUnknown
{
HRESULT SetPetName([in]BSTR petName);
HRESULT SetMaxSpeed([in] int maxSp);
};
// library statement
[uuid(957BF83F-EE5A-42eb-8CE5-6267011F0EF9), version(1.0),
helpstring("Car server with typeLib")]
library CarLocalServerLib
{
importlib("stdole32.tlb");
[uuid(1D66CBA8-CCE2-4439-8596-82B47AA44E43)]
coclass MyCar
{
[default] interface ICreateMyCar;
interface IStats;
interface IEngine;
};
};
3） 加入生命周期管理類managesycle.h，
#pragma once
class CManageSycle
{
public:
CManageSycle(void);
~CManageSycle(void);
static void InObject() {++m_nObject;}
static void DeObject() {--m_nObject;}
static bool IsZeroObject() { return m_nObject==0 ;}
static void InLock() {++m_nLock;}
static void DeLock() {--m_nLock;}
static bool IsZeroLock() { return m_nLock==0 ; }
private:
static ULONG m_nObject;
static ULONG m_nLock;
};
managesycle.cpp實現文件：
#include "StdAfx.h"
#include "managesycle.h"
ULONG CManageSycle::m_nObject=0;
ULONG CManageSycle::m_nLock=0;
CManageSycle::CManageSycle(void)
{
}
CManageSycle::~CManageSycle(void)
{
}
4）加入真正的com的接口的實現類，MyCar.h （除了實現COM的接口，還必須實現IUnKnown接口）
#pragma once
#include "unknwn.h"
#include "CarLocalServerTypeInfo_h.h"
const int MAX_SPEED = 500;
const int MAX_NAME_LENGTH = 20;
class MyCar :
public IEngine,
public ICreateMyCar,
public IStats
{
public:
MyCar();
virtual ~MyCar();
// IUnknown
STDMETHODIMP QueryInterface(REFIID riid, void** pIFace);
STDMETHODIMP_(DWORD)AddRef();
STDMETHODIMP_(DWORD)Release();
// IEngine
STDMETHODIMP SpeedUp();
STDMETHODIMP GetMaxSpeed(int* maxSpeed);
STDMETHODIMP GetCurSpeed(int* curSpeed);
// IStats
STDMETHODIMP DisplayStats();
STDMETHODIMP GetPetName(BSTR* petName);
// ICreateMyCar
STDMETHODIMP SetPetName(BSTR petName);
STDMETHODIMP SetMaxSpeed(int maxSp);
private:
DWORD m_refCount;
BSTR m_petName;
int m_maxSpeed;
int m_currSpeed;
};
MyCar.cpp
#include "stdafx.h"
#include <stdio.h>
#include "CarLocalServerTypeInfo_i.c"
#include "MyCar.h"
#include "ManageSycle.h"
//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////
MyCar::MyCar() : m_refCount(0), m_currSpeed(0), m_maxSpeed(0)
{
m_refCount=0;
CManageSycle::InObject();
m_petName = SysAllocString(L"Default Pet Name");
}
MyCar::~MyCar()
{
CManageSycle::DeObject();
if(m_petName) SysFreeString(m_petName);
MessageBox(NULL,
L"MyCar is being distructed. Make sure you see this message, if not, you might have memory leak!",
L"Destructor",MB_OK | MB_SETFOREGROUND);
}
// IUnknown
STDMETHODIMP MyCar::QueryInterface(REFIID riid, void** pIFace)
{
// Which aspect of me do they want?
if(riid == IID_IUnknown)
{
*pIFace = (IUnknown*)(IEngine*)this;
// MessageBox(NULL, "Handed out IUnknown","QI",MB_OK | MB_SETFOREGROUND);
}
else if(riid == IID_IEngine)
{
*pIFace = (IEngine*)this;
// MessageBox(NULL, "Handed out IEngine","QI",MB_OK | MB_SETFOREGROUND);
}
else if(riid == IID_IStats)
{
*pIFace = (IStats*)this;
// MessageBox(NULL, "Handed out IStats","QI",MB_OK | MB_SETFOREGROUND);
}
else if(riid == IID_ICreateMyCar)
{
*pIFace = (ICreateMyCar*)this;
// MessageBox(NULL, "Handed out ICreateMyCar","QI",MB_OK | MB_SETFOREGROUND);
}
else
{
*pIFace = NULL;
return E_NOINTERFACE;
}
((IUnknown*)(*pIFace))->AddRef();
return S_OK;
}
STDMETHODIMP_(DWORD) MyCar::AddRef()
{
++m_refCount;
return m_refCount;
}
STDMETHODIMP_(DWORD) MyCar::Release()
{
if(--m_refCount == 0)
{
delete this;
return 0;
}
else
return m_refCount;
}
// IEngine
STDMETHODIMP MyCar::SpeedUp()
{
m_currSpeed += 10;
return S_OK;
}
STDMETHODIMP MyCar::GetMaxSpeed(int* maxSpeed)
{
*maxSpeed = m_maxSpeed;
return S_OK;
}
STDMETHODIMP MyCar::GetCurSpeed(int* curSpeed)
{
*curSpeed = m_currSpeed;
return S_OK;
}
// IStats
STDMETHODIMP MyCar::DisplayStats()
{
// Need to transfer a BSTR to a char array.
char buff[MAX_NAME_LENGTH];
WideCharToMultiByte(CP_ACP, NULL, m_petName, -1, buff,
MAX_NAME_LENGTH, NULL, NULL);
//MessageBox(NULL, buff, L"Pet Name",MB_OK | MB_SETFOREGROUND);
memset(buff, 0, sizeof(buff));
sprintf(buff, "%d", m_maxSpeed);
//MessageBox(NULL, buff,L"Max Speed", MB_OK| MB_SETFOREGROUND);
return S_OK;
}
STDMETHODIMP MyCar::GetPetName(BSTR* petName)
{
*petName = SysAllocString(m_petName);
return S_OK;
}
// ICreateMyCar
STDMETHODIMP MyCar::SetPetName(BSTR petName)
{
SysReAllocString(&m_petName, petName);
return S_OK;
}
STDMETHODIMP MyCar::SetMaxSpeed(int maxSp)
{
if(maxSp < MAX_SPEED)
m_maxSpeed = maxSp;
return S_OK;
}
5）加入工廠類MyCarClassFactory.h，（實現IUnKnown接口和IClassFactory接口）
// the class object (class factory) for CoMyCar class
#pragma once
class MyCarClassFactory : public IClassFactory
{
public:
MyCarClassFactory();
virtual ~MyCarClassFactory();
// IUnknown
STDMETHODIMP QueryInterface(REFIID riid,void** pIFace);
STDMETHODIMP_(ULONG)AddRef();
STDMETHODIMP_(ULONG)Release();
// IClassFactory
STDMETHODIMP LockServer(BOOL fLock);
STDMETHODIMP CreateInstance(LPUNKNOWN pUnkOuter,REFIID riid,void** ppv);
private:
ULONG m_refCount;
};
MyCarClassFactory.cpp
#include "stdafx.h"
#include "MyCar.h"
#include "MyCarClassFactory.h"
#include "locks.h"
#include "ManageSycle.h"
MyCarClassFactory::MyCarClassFactory()
{
m_refCount = 0;
}
MyCarClassFactory::~MyCarClassFactory()
{
MessageBox(NULL,
L"MyCarClassFactory is being distructed. Make sure you see this message, if not, you might have memory leak!",
L"Destructor",MB_OK | MB_SETFOREGROUND);
}
STDMETHODIMP_(ULONG) MyCarClassFactory::AddRef()
{
//return ++m_refCount;
return 10;
}
STDMETHODIMP_(ULONG) MyCarClassFactory::Release()
{
/*
if ( --m_refCount == 0 )
{
delete this;
return 0;
}
return m_refCount;
*/
return 20;
}
STDMETHODIMP MyCarClassFactory::QueryInterface(REFIID riid,void** pIFace)
{
if ( riid == IID_IUnknown )
*pIFace = (IUnknown*)this;
else if ( riid == IID_IClassFactory )
*pIFace = (IClassFactory*)this;
else
{
*pIFace = NULL;
return E_NOINTERFACE;
}
((IUnknown*)(*pIFace))->AddRef();
return S_OK;
}
STDMETHODIMP MyCarClassFactory::LockServer(BOOL fLock)
{
(VARIANT_TRUE == fLock) ? CManageSycle::InLock() : CManageSycle::DeLock();
return S_OK;
}
STDMETHODIMP MyCarClassFactory::CreateInstance(LPUNKNOWN pUnkOuter,REFIID riid,void** ppv)
{
if ( pUnkOuter != NULL ) return CLASS_E_NOAGGREGATION;
MyCar* pMyCarObj = NULL;
HRESULT hr;
pMyCarObj = new MyCar();
hr = pMyCarObj->QueryInterface(riid,ppv);
if ( FAILED(hr) ) delete pMyCarObj;
return hr;
}
6）實現COM入口和自注冊函數CarLocalServer.cpp，
// CarLocalServer.cpp : Defines the entry point for the DLL application.
//
#include "stdafx.h"
#include <iostream>
#include <string.h>
#include "CarLocalServerTypeInfo_h.h"
//#include "CarLocalServerTypeInfo_i.c"
#include "MyCarClassFactory.h"
#include "ManageSycle.h"
using namespace std;
#ifdef _MANAGED
#pragma managed(push, off)
#endif
HMODULE g_hmodule;
BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
g_hmodule = static_cast<HMODULE>(hModule);
return TRUE;
}
STDAPI DllCanUnloadNow()
{
bool bDllCanUnloadNow = CManageSycle::IsZeroObject() && CManageSycle::IsZeroLock();
return bDllCanUnloadNow ? S_OK : S_FALSE;
}
STDAPI DllGetClassObject(REFCLSID rclsid,REFIID riid,LPVOID* ppv)
{
*ppv = NULL;
if(__uuidof(MyCar) != rclsid)
{
return E_NOINTERFACE;
}
MyCarClassFactory* pBirdFactory = new MyCarClassFactory();
if(NULL == pBirdFactory)
{
return E_OUTOFMEMORY;
}
HRESULT hr = pBirdFactory->QueryInterface(riid,ppv);
if(FAILED(hr))
{
delete pBirdFactory;
}
return hr;
}
STDAPI DllRegisterServer()
{
HKEY hRoot, hNew;
::RegOpenKey(HKEY_CLASSES_ROOT,L"CLSID",&hRoot);
::RegCreateKey(hRoot,L"{1F0A9759-FCBE-4870-8336-971BD19A7452}\\InprocServer32",&hNew);
wchar_t strFile[MAX_PATH];
::GetModuleFileName(g_hmodule,strFile,MAX_PATH);
::RegSetValue(hNew,NULL,REG_SZ,strFile,MAX_PATH);
::RegCloseKey(hRoot);
return S_OK;
}
STDAPI DllUnregisterServer()
{
HKEY hRoot;
::RegOpenKey(HKEY_CLASSES_ROOT,L"CLSID",&hRoot);
::RegDeleteKey(hRoot,L"{1F0A9759-FCBE-4870-8336-971BD19A7452}");
::RegDeleteKey(hRoot,L"{1F0A9759-FCBE-4870-8336-971BD19A7452}\\InprocServer32");
::RegCloseKey(hRoot);
return S_OK;
}
#ifdef _MANAGED
#pragma managed(pop)
#endif
7）增加def到處文件CarLocalServer.def，
LIBRARY "CarLocalServer"
EXPORTS
DllCanUnloadNow PRIVATE
DllGetClassObject PRIVATE
DllRegisterServer PRIVATE
DllUnregisterServer PRIVATE
三，COM的調用過程
通過一個創建COM組件的最小框架結構，然后看一看其內部處理流程是怎樣的
|
IUnknown *pUnk=NULL;
IObject *pObject=NULL;
CoInitialize(NULL);
CoCreateInstance(CLSID_Object, CLSCTX_INPROC_SERVER, NULL, IID_IUnknown, (void**)&pUnk);
pUnk->QueryInterface(IID_IOjbect, (void**)&pObject);
pUnk->Release();
pObject->Func();
pObject->Release();
CoUninitialize();
|
這就是一個典型的創建COM組件的框架，不過我的興趣在CoCreateInstance身上，讓我們來看看它內部做了一些什么事情。
以下是它內部實現的一個偽代碼:
|
CoCreateInstance(....)
{
.......
IClassFactory *pClassFactory=NULL;
CoGetClassObject(CLSID_Object, CLSCTX_INPROC_SERVER, NULL, IID_IClassFactory, (void **)&pClassFactory);
pClassFactory->CreateInstance(NULL, IID_IUnknown, (void**)&pUnk);
pClassFactory->Release();
........
}
|
這段話的意思就是先得到類廠對象，再通過類廠創建組件從而得到IUnknown指針。繼續深入一步，看看CoGetClassObject的內部偽碼：
|
CoGetClassObject(.....)
{
//通過查注冊表CLSID_Object，得知組件DLL的位置、文件名
//裝入DLL庫
//使用函數GetProcAddress(...)得到DLL庫中函數DllGetClassObject的函數指針。
//調用DllGetClassObject
}
DllGetClassObject是干什么的，它是用來獲得類廠對象的。只有先得到類廠才能去創建組件.
下面是DllGetClassObject的偽碼：
DllGetClassObject(...)
{
......
CFactory* pFactory= new CFactory; //類廠對象
pFactory->QueryInterface(IID_IClassFactory, (void**)&pClassFactory);
//查詢IClassFactory指針
pFactory->Release();
......
}
CoGetClassObject的流程已經到此為止，現在返回CoCreateInstance，看看CreateInstance的偽碼：
CFactory::CreateInstance(.....)
{
...........
CObject *pObject = new CObject; //組件對象
pObject->QueryInterface(IID_IUnknown, (void**)&pUnk);
pObject->Release();
...........
}
|
四，COM的調用方法
對上面手動創建的COM的調用實例：
int main()
{
// initialize the COM runtime
cout << "Initialize the COM runtime
";
CoInitialize(NULL);
cout << "success." << endl;
// declare variables
HRESULT hr;
IClassFactory* pICF = NULL;
ICreateMyCar* pICreateMyCar = NULL;
IEngine* pIEngine = NULL;
IStats* pIStats = NULL;
cout << endl << "Get the class factory interface for the Car class";
hr = CoGetClassObject(CLSID_MyCar,CLSCTX_LOCAL_SERVER,NULL,IID_IClassFactory,(void**)&pICF);
if ( FAILED(hr) )
{
cout<<"fail";
exit(1);
}
else cout << "success." << endl;
cout << "Create the Car object and get back the ICreateMyCar interface";
hr = pICF->CreateInstance(NULL,IID_ICreateMyCar,(void**)&pICreateMyCar);
if ( FAILED(hr) )
{
//ShowErrorMessage("CoGetClassObject()",hr);
exit(1);
}
else cout << "success." << endl;
// set parameters on the car
cout << endl << "Set different parameters on the car";
pICreateMyCar->SetMaxSpeed(30);
BSTR carName = SysAllocString(OLESTR("COMCar?!"));
pICreateMyCar->SetPetName(carName);
SysFreeString(carName);
cout << "success." << endl;
cout << endl << "Query the IStats interface";
pICreateMyCar->QueryInterface(IID_IStats,(void**)&pIStats);
cout << "success." << endl;
cout << endl << "Use the IStats interface to display the status of the car:" << endl;
pIStats->DisplayStats();
cout << endl << "Query the IEngine interface";
pICreateMyCar->QueryInterface(IID_IEngine,(void**)&pIEngine);
cout << "success." << endl;
cout << endl << "Start to use the engine" << endl;
int curSp = 0;
int maxSp = 0;
pIEngine->GetMaxSpeed(&maxSp);
do
{
pIEngine->SpeedUp();
pIEngine->GetCurSpeed(&curSp);
cout << "current speed is: " << curSp << endl;
} while (curSp <= maxSp);
cout << endl << "Report status again: " << endl;
pIStats->DisplayStats();
if ( pICF ) pICF->Release();
if ( pICreateMyCar) pICreateMyCar->Release();
if ( pIStats ) pIStats->Release();
if ( pIEngine ) pIEngine->Release();
cout << endl << "Close the COM runtime";
CoUninitialize();
cout << "success." << endl;
return 0;
}
方法一：向上面的調用，通過包含#include "../CarLocalServer/CarLocalServerTypeInfo_h.h"和#include "../CarLocalServer/CarLocalServerTypeInfo_i.c"
方法二：使用#import導入tlb
可以使用： CComBSTR ，CComPtr<> 和 CComQIPtr<> 等來簡化調用。
五，總結
COM比一般的DLL有很多的優點，COM沒有重名問題，因為根本不是通過函數名來調用函數，而是通過虛函數表，自然也不會有函數名修飾的問題。路徑問題也不復存在，因為是通過查注冊表來找組件的，放在什么地方都可以，即使在別的機器上也可以。也不用考慮和EXE的依賴關系了，它們二者之間是松散的結合在一起，可以輕松的換上組件的一個新版本，而應用程序混然不覺。
但是COM仍然是有問題的，比如說版本控制的問題，.NET將逐步代替COM的使用。
六，參考
1）OLE/COM/COM+/DCOM/ActiveX/ActiveX contorl ( 概念)
2）用VC進行COM編程所必須掌握的理論知識
3）COM編程入門(1)
4）COM編程入門(2)
5）c++中使用com的方法