Introduction
CComPtr
wraps any interface pointer and will call AddRef()
and Release()
properly. That is, you don't need to worry about controlling the lifetime of your interface pointer.
Details
- ATL does provide a Smart Pointer class named
CComQIPtr
. But it uses some ATL related funtion so that it can be used only in an ATL environment.
- VC does provide
_com_ptr_t
& _bstr_ptr_t
keywords to provide some kind of a wrapper. But it depends on the MS VC compiler, without which you can benefit.
- My
CComPtr
provides compiler unrelated features to wrap any interface pointer except IUnknown
. Later I will explain why this limitation comes.
Illustration
Note: INTERFACE
and piid
are passed into the class CComPtr
through template parameters.
CComPtr
has four constructors to meet different requirement.
Simply constructor, do nothing.
Construct a new CComPtr
object with an existing interface pointer. After that this new CComPtr
object can be used as interface pointer itself.
CComPtr(IUnknown* pIUnknown, IID iid)
Construct a new CComPtr
object with an IUnknown
pointer and an IID, which represents the interface you are interested in. Internally constructor will call pIUnknown->QueryInterface
to fetch interface pointer according to the IID.
CComPtr(const CComPtr<INTERFACE, piid>& RefComPtr)
This contsructor takes another existing CComPtr
object as parameter. After that, clone the old CComPtr
object.
CComPtr
has one destructor, which will release interface pointer.
~CComPtr(){ if (m_Ptr) { m_Ptr->Release(); m_Ptr = NULL; } }
CComPtr
has five operators.
- (a) Operator
INTERFACE*
: Returns interface pointer wrapped by class CComPtr
.
Example:
CComPtr<IWavePciStream> m_wavePciStreamPtr;
IWavePciStream* pWavePciStream = (IWavePciStream*)m_wavePciStreamPtr;
- (b) Operator
*
: Used to fetch interface object wrapped by class CComPtr
.
Example:
CComPtr<IWavePciStream> m_wavePciStreamPtr;
IWavePciStream wavePciStream = *m_wavePciStreamPtr;
- (c) Operator
&
: Used to fetch the pointer to interface pointer wrapped by class CComPtr
.
Example:
CComPtr<IWavePciStream> m_wavePciStreamPtr;
IWavePciStream** ppWavePciStream = &m_wavePciStreamPtr;
- (d) Operator
->
: Used to make CComPtr
object act as a TRUE
interface pointer.
Example
CComPtr<IWavePciStream> m_wavePciStreamPtr;
m_wavePciStreamPtr->AnyPciStreamMethods();
- (e) Operator
=
: Used to transfer an exsiting interface pointer information to a new CComPtr
object. This operator has three different parameter list.
- In parameter is
INTERFACE*
- In parameter is another
CComPtr
object.
- In parameter is an interface pointer to
IUnknown
, which will be used to query other interface pointer defined by piid.
CComPtr
has another three methods.
Attach
: Used to attach an existing interface pointer to a CComPtr
object.
Detach
: Used to detach interface pointer from a CComPtr
object.
Release
: Used to release wrapped interface pointer explicitly.
CComPtr
is implemented in pure C++. That is, it does not depend on any specific C/C++ compiler and can be compiled under any ANSI C/C++ compliant compiler. I have tested in VC++ 6.0. I do believe it works in GNU C/C++ and MAC CodeWarrior.
Graduated from Shanghai Tongji university in 1997 with bachelor degree in computer science, Wenbin got his first job as a system engineer at Bell Alcatel Mobile Shanghai office responsible for telcom-class mobile system development and deployment. Since then, Wenbin has in turn worked for Intel and Microsoft both inside and outside China, first as senior engineer, later project manager and then senior product manager.
With 15-year experience working with the world top IT companies, Wenbin has developed solid skill in C/C++, C#, Java, software engineering, agile development, etc, and multiple talents in product management, public presentation and speech, etc. He has always been an active member at PMI (Project Management Institution) and a regular lecture at Intel Developer Forum, Microsoft TechED conference as well as many other world-class industrial conferences. His wide-ranged industrial practice and high-level personal maturity have made him one of the best in public speech and professional training.
Over the years, Wenbin has cultivated his very own style in public speech, which is considered informative, engaging and refined. Since last year, Wenbin has also taken new adventure in project and product management consulting business and has proven high capacity through his work with many local emergent IT firms. Wenbin’s specialty in management consulting is on project management methodologies and processes, project management tools (e.g. MS Project), and team recruitment, build, and motivation.
In addition, Wenbin has received many professional qualifications including MCSE (Microsoft Certified System Engineer), MCSD (Microsoft Certified System Developer), MCDBA (Microsoft Certified Database Administrator), SCJP 2 (Sun Certified Java Programmer 2), and PMP (PMI Certified Project Management Professional). On top of that, Wenbin has got several on-duty inventions and one of them was successfully patented by United States Patent and Trademark Office.