[C++-sig] Serialization/pickle (original) (raw)

David Abrahams dave at boost-consulting.com
Tue Dec 6 20:21:59 CET 2005

The following message is a courtesy copy of an article that has been posted to gmane.comp.lib.boost.user as well.

"Drumheller, Michael" <michael.drumheller at boeing.com> writes:

From: David Abrahams <dave boost-consulting.com> Subject: Re: Boost.python serialization Newsgroups: gmane.comp.lib.boost.user Date: 2005-11-29 23:28:17 GMT (6 days, 17 hours and 9 minutes ago)

"Drumheller, Michael" <michael.drumheller boeing.com> writes: > Thank you for the help. I have seen that link (the one you supplied) > before, but I posted my question because that link in particular does > not mention the words "Boost.Serialization" or "Archive" at all. That's because the Boost Serialization library is unrelated. I understand that it is technically unrelated. I am asking for information about about patterns of actual usage.

I'm afraid I don't know that.

> I suppose what I was really getting at, and was probably not very > clear about (sorry :| ) was whether the specific approach (by > N. Becker) of using a stringstream wrapped with a > boost::archive::binaryoarchive is a standard idiom.

"Standard?" OK: "common," "popular," "preferred," "regarded-as-best-practice," "effective."

Ditto.

> (Basically, I would have thought that "python pickle boost::archive" > would be a million-hit Google query, but it's only about a dozen. I > find that weird. Do people just not serialize their C++ extensions > very often?)

Yes, they do it very often. There's usually no need to touch Boost.Serialization in order to do so, though. My extensions refer to one another, i.e., they form a significant object hierarchy in and of themselves. E.g., on the C++ side I might have an instance x of class X, which contains a vector of sharedptrs p1,...,pn to instances y1,...,yn of another C++ class Y. At pickle-time there may be Python object z with a member u bound to to x and members w1,...,wm bound to a subset of the y1,...,yn. Is it even feasible to expect to be able to simple pickle.dump z and have it all work?

Yes. Of course you have to do some work in your wrapping code to say how X gets pickled.

Please keep in mind: I am just getting started wading into serializing a pretty complicated set of strongly interdependent Python and C++ objects and I am just trying to get my bearings. If this is the wrong forum to be asking these questions, please tell me.

Well, the C++-sig might be more appropriate: http://www.boost.org/more/mailing_lists.htm#cplussig (cross-posted there)

We (Boost Consulting) are actually planning to do something like this with one of our clients, but we haven't gotten started with it yet. I think everything should "just work" as long as you take care not to try to serialize the same object both from the C++ side (using Boost.Serialization) and from the Python side (using pickle). Because each system implements its own object tracking, you could end up representing the same object twice.

HTH,

-- Dave Abrahams Boost Consulting www.boost-consulting.com

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