CComPtr

Hello everyone,


In the book ATL Internals, it is mentioned, the properties of CComPtr is,

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Release the encapsulated interface pointer when the class destructor executes;
Automatically releases its interface pointer during exception handling, ...
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They both means invoking the Relase method (inherited from IUnknown) of the interface?


thanks in advance,
George

Yes, that's what it does! It calls Release when appropriate, and AddRef when you assign a new handle to it.

Yes in both cases the destructor is called which calls Release.

I find CComPtr to be fairly good. The only downsides I find are the lack of an operator < for use in sets etc. (Note that to use a CComPtr in a std container etc you sometimes need to wrap it in a CAdapt as well anyway)
It's IsEqualObject function is a little sub-optimal too, but there is a site on the net somewhere showing the optimisation for it. The VS2008 implementation doesn't offer any improvement here from what I've seen. Still, on the whole they're rather good.

Other alternatives like IUnknownPtr lack a lot of const-correctness, making things like their operator < a bit useless.

Thanks Elysia,


Clear reply.

Quote:

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Originally Posted by Elysia

Yes, that's what it does! It calls Release when appropriate, and AddRef when you assign a new handle to it.

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Thanks iMalc,


Two more comments,

1.

Quote:

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Originally Posted by iMalc

Yes in both cases the destructor is called which calls Release.

I find CComPtr to be fairly good. The only downsides I find are the lack of an operator < for use in sets etc. (Note that to use a CComPtr in a std container etc you sometimes need to wrap it in a CAdapt as well anyway)

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Confused. CAdapt is used for rewrite the address of operator -- &. How could you use it to re-write operator <?

Here is what MSDN said,

(http://msdn2.microsoft.com/en-us/library/bs6acf5x.aspx)

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This template is used to wrap classes that redefine the address-of operator to return something other than the address of the object.
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2.

Quote:

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Originally Posted by iMalc

It's IsEqualObject function is a little sub-optimal too, but there is a site on the net somewhere showing the optimisation for it. The VS2008 implementation doesn't offer any improvement here from what I've seen. Still, on the whole they're rather good.

Other alternatives like IUnknownPtr lack a lot of const-correctness, making things like their operator < a bit useless.

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Interested in it. Could you refer some links about what you mean what is the performance degration and how to optimize IsEqualObject please?


regards,
George

Quote:

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Originally Posted by iMalc

The VS2008 implementation doesn't offer any improvement here from what I've seen. Still, on the whole they're rather good.

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On what?

Thanks Elysia,


I mean I want to learn from iMalc about how other people optimize IsEqualObject function, this is what he said before "It's IsEqualObject function is a little sub-optimal too"

Quote:

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Originally Posted by Elysia

On what?

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regards,
George

On what was aimed at iMalc since I quoted the part of the text I was curious about.

Me too, Elysia.


Let us wait for his reply. :-)

Quote:

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Originally Posted by Elysia

On what was aimed at iMalc since I quoted the part of the text I was curious about.

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regards,
George

Hi guys, this is the article I was talking about:
http://www.codeproject.com/KB/bugs/w...s.aspx#CComPtr

Basically with the original code it calls QueryInterface on both objects even when the pointer values are identical. QI need only be used when the pointer are from different interfaces of the same object.

Thanks iMalc,


I looked through the code you posted, and the optimization method looks good. :-)

BTW: What is the relationship between the article and code you referred below and my original question?

Quote:

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Originally Posted by iMalc

Hi guys, this is the article I was talking about:
http://www.codeproject.com/KB/bugs/w...s.aspx#CComPtr

Basically with the original code it calls QueryInterface on both objects even when the pointer values are identical. QI need only be used when the pointer are from different interfaces of the same object.

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regards,
George

Quote:

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Originally Posted by George2

I looked through the code you posted, and the optimization method looks good. :-)

BTW: What is the relationship between the article and code you referred below and my original question?

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Oh, I was just mentioning some of the good and bad things I've found about that class, since you were interested in it.

Cool, iMalc!


Thanks for clarifying that. :-)

Quote:

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Originally Posted by iMalc

Oh, I was just mentioning some of the good and bad things I've found about that class, since you were interested in it.

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have a good day,
George