Re: [boost] asio formal review - demuxer

From: Rene Rivera (grafik.list_at_[hidden])
Date: 2005-12-27 16:13:36

Andrew Schweitzer wrote:
>>Andrew Schweitzer wrote:
>>
>>>5) demuxer_service creates a platform-implementation demuxer_service 
>>>(right?)
>>
> Rene Rivera wrote:
> 
>>Not as far as I know. This is one of the points that some people have 
>>contention with. The real relation between demuxer_service and the 
>>implementation is closer to a PIMPL idiom, but without the pointer. In 
>>other words it's equivalent to:
>>
>>     demuxer_service *is-a*
>>         detail::win_iocp_demuxer_service
> 
> [snip]
> 
> I think I'm confused. As far as I can tell, there's no inheritance 
> relationship between demuxer_service and win_iocp_demuxer_service, but 
> as you said, it's a PIMPL relation, or perhaps an RIMPL relation since 
> it's a reference not a pointer.

We can consider the reference as just a different kind of pointer in 
this case. After all it could just as easily be a pointer and the 
forwarding functions would deref the pointer, instead of the compiler 
doing the deref for you.

> Is PIMPL considered is-a or has-a?

I've always considered it an is-a. A very special case, but equivalent.

> I think the library design or naming might be a bit confused on this 
> point (or quite possibly it's me).

The fact that it's confusing, even when looking at the code, is a point 
against the design ;-) OK, I'm rereading the code, instead of relying on 
memory...

> As far as I can tell two things are true:
>    1) the demuxer ends up with two actual services in its list after it
>       is constructed:
>        a) demuxer_service
>        b) win_iocp_demuxer_service (or the selected
>           platform-implemenation of demuxer_service)

OK, AFAICT it only ends up with (b) in the service_registry.

>    2) the demuxer also has a PIMPL relation with demuxer_service,
>       and demuxer_service has a PIMPL relation with
>       win_iocp_demuxer_service

Yes. I guess the key point here is that there's only 1 (singleton) of 
win_iocp_demuxer_service for all demuxer_service instances in the same 
basic_demuxer instance? (again AFAICT)

> Are you reading the code differently? I might have gotten lost.

I guess, I'm reading it differently :-)

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