COM编程入门
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COM技术初探
http://www.vckbase.com/document/viewdoc/?id=915
COM编程入门
http://www.vckbase.com/document/viewdoc/?id=212
1、 COM基本知识
1.1 返回值HRESULT
COM要求所有的方法都会返回一个HRESULT类型的错误号。HRESULT 其实就一个类型定义:
typedef LONG HRESULT;
1.2 COM接口用到的宏
COM接口用到的宏主要有六个:
STDMETHOD,STDMETHODIMP,STDMETHOD_,STDMETHODIMP_,SUCCEEDED,FAILED
STDMETHODIMP:
#define STDMETHODIMP HRESULT STDMETHODCALLTYPE
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
由定义我们可以看出两点:
1)STDMETHOD和STDMETHODIMP,STDMETHOD_和STDMETHODIMP_分别为一对,SUCCEEDED和FAILED为相反.
2)STDMETHOD只是STDMETHOD_的简化版.
比如这两个语句互为等价关系:
STDMETHOD (QueryInterface) (REFIID riid, LPVOID * ppv);
STDMETHOD_ (HRESULT,QueryInterface) (REFIID riid, LPVOID *ppv);
既然有STDMETHOD,也有STDMETHODIMP,那么应该在什么情况下使用其中一个呢?
如果继承的函数的声明和定义都在类内定义,则只需使用STDMETHOD即可,如:
//////////////////////////////////////////////
//Browser.h
//////////////////////////////////////////////
classCBrowser:public IOleContainer
{
...
STDMETHOD(LockContainer)(BOOL){returnOK;}
}
如果函数的定义在外部,那么声明采用STDMETHOD,定义时使用STDMETHODIMP
//////////////////////////////////////////////
//Browser.h
//////////////////////////////////////////////
classCBrowser:public IOleContainer
{
...
STDMETHOD(LockContainer)(BOOL);
}
//////////////////////////////////////////////
//Browser.cpp
//////////////////////////////////////////////
STDMETHODIMPCBrowser::LockContainer(BOOL)
{
return S_OK;
}
这六个宏的定义:
STDMETHOD:
#define STDMETHOD(method) virtual HRESULT STDMETHODCALLTYPEmethod
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
#define STDMETHOD(method) virtual HRESULT STDMETHODCALLTYPEmethod
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
#define STDMETHODIMP HRESULT STDMETHODCALLTYPE
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
STDMETHOD_:
#define STDMETHOD_(type,method) virtual type STDMETHODCALLTYPEmethod
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
#define STDMETHOD_(type,method) virtual type STDMETHODCALLTYPEmethod
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
STDMETHODIMP_:
#define STDMETHODIMP_(type) type STDMETHODCALLTYPE
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
#define STDMETHODIMP_(type) type STDMETHODCALLTYPE
#ifdef _WIN32 // Win32 doesn't support __export
#define STDMETHODCALLTYPE __stdcall
#else
#define STDMETHODCALLTYPE __export __stdcall
#endif
SUCCEEDED:
#define SUCCEEDED(Status) ((HRESULT)(Status) >=0)
#define SUCCEEDED(Status) ((HRESULT)(Status) >=0)
FAILED:
#define FAILED(Status) ((HRESULT)(Status)<0)
#define FAILED(Status) ((HRESULT)(Status)<0)
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