Re: [boost] [serialization] Proposal for an extension API to the Archive concept

From: Joaquín Mª López Muñoz (joaquin_at_[hidden])
Date: 2007-09-27 02:07:19

Robert Ramey ha escrito:

> "JOAQUIN LOPEZ MU?Z" wrote:
> > cons: A naked archive implementation, while conforming
> > with the concept requirements, will fail to handle shared_ptr
> > and any type relying on the helper API.
>
> And will not force everyone who doesn't happen to be
> using shared_ptr to pay a penalty.  This is pro for me.

With the {get|set}_extension_obj proposal, those who are not
using shared_ptr do not pay a penalty -- the extension object is
never created.

> > So, how to make B.S provide shared_ptr and helper support
> > whitout polluting the archive concept with too specific
> > provisions? My proposal is to add a single "hook" to the
> > Archive concept which is as agnostic as possible and
> > can be leveraged in the future for unforeseen necessities
> > beyond shared_ptr and helper support.
> [...]
> This sounds to me exactly the 1.34 version.  Its just that the
> "hook" is undocumented as I considered it a hack required
> to overcome the problems associated with just one type -
> shared_ptr.

There are important differences with respect to Boost 1.34. Hooking
is done at run-time, whereas the Boost 1.34 solution was compile-time.
Extension is created lazily, which means you don't pay for it if you're
not using it. The extension class can grow in the future without
Archive classes needing to be redefined or recompiled.

> I proposed making this much simpler.
>
> make a helper api which is similar to that which 1.34 has.  The only
> difference is that it is not implemented in the base class but rather
> as a mix in - similar to the way shared_ptr_helper is now.
>
> So we would have
>
> naked_archive
> archive = naked_archive + helper api
>
> and the old shared_ptr serialization would be put back in.  The
> implemenation would be the same, its just taht the calles would
> be implemented in the mix-in rather than in the base.

Well, I think our respective positions are clear, and I don't want to beat
this to death, but please answer the following: under your proposed
scheme, does the type shared_ptr conform to the concept Serializable?
Note that the only reasonably acceptable answers are "yes" and "no" :)

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo