Re: [boost] An attempt to generalize the Pimpl idom withproperly separated interface and implementation

From: Vladimir Batov (batov_at_[hidden])
Date: 2007-10-12 20:15:21

Phil, thank you for your encouragement and
Peter, thank you for the pointers. Much and truly appreciated.

I'll definitely have a look at both Alan's and Peter's implementations if I
can make use of those. It's Saturday -- my family-duties day -- and I am
just running out the door. After a rrrreally quick look the grip_ptr seems
to provide a deep-copy semantics without exposing private implementation. It
that is the case, then Alan and Peter (who implemented a similar thing) are
definitely smarter than I am as I was not able to figure out how to achieve
that (without exposing implementation details). Then I'll steal :-) their
idea (with proper acknowledments :-)).

That will have to be done in addition to my currently proposed
shared_ptr-based implementation as, for example, my current usage pattern is
such that I use one data repository/implementation and share/pass many
smart-pointer type instances pointing to that sole implementation.

Will let you know how it all fired soon.

Best,
Vladimir.

"Phil Endecott" <spam_from_boost_dev_at_[hidden]> wrote in message
news:1192106650916_at_dmwebmail.japan.chezphil.org...
> Peter Dimov wrote:
>> Phil Endecott:
>>
>>> Vladimir Batov wrote:
>>>> Given I've been using this Pimpl idiom quite extensively lately I've
>>>> noticed
>>>> writing the same scaffolding over and over again.
>>>
>>> Maybe we need something with a mixture of features from scoped_ptr and
>>> shared_ptr.  scoped_ptr does everything that I need for a pimpl, except
>>> that it can't delete the incomplete implementation type.  shared_ptr
>>> can delete the incomplete implementation, but it has the unneeded
>>> overhead of reference counting and thread safety issues.  So, can the
>>> incomplete deletion feature of shared_ptr be extracted and added to
>>> scoped_ptr?  I have just had a quick look at the shared_ptr
>>> implementation to see how deletion works, but it's too clever for me to
>>> understand....
>>
>> Alan Griffiths has written a similar smart pointer, arg::grin_ptr:
>>
>> http://www.octopull.demon.co.uk/arglib/TheGrin.html
>
> Thanks Peter, that's exactly what's needed.  And very well described by
> Alan on that page.
>
> It seems that the trick needed to allow incomplete types to be deleted
> is the same one that allows a shared_ptr to be given a custom deleter,
> e.g. so that I can free() things that have been malloc()ed by C code.
> A smart pointer with these features would be great for Boost.
>
> Vladimir, would you like to revise your pimpl template to use this?
>
>
> Regards,  Phil.