pygccxml-development

[pygccxml-development] serialization support?

[Neal B. <ndb...@gm...>]

Has any work been done on adding boost::serialization support?

Re: [pygccxml-development] serialization support?

[Roman Y. <rom...@gm...>]

On 9/13/06, Neal Becker <ndb...@gm...> wrote:
> Has any work been done on adding boost::serialization support?

What do you mean?

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/

Re: [pygccxml-development] serialization support?

[Neal B. <ndb...@gm...>]

On Wednesday 13 September 2006 12:58 am, Roman Yakovenko wrote:
> On 9/13/06, Neal Becker <ndb...@gm...> wrote:
> > Has any work been done on adding boost::serialization support?
>
> What do you mean?

Automatic generation of pickle support.  Probably using boost::serialization.

Re: [pygccxml-development] serialization support?

[Roman Y. <rom...@gm...>]

On 9/13/06, Neal Becker <ndb...@gm...> wrote:
> On Wednesday 13 September 2006 12:58 am, Roman Yakovenko wrote:
> > On 9/13/06, Neal Becker <ndb...@gm...> wrote:
> > > Has any work been done on adding boost::serialization support?
> >
> > What do you mean?
>
> Automatic generation of pickle support.  Probably using boost::serialization.

That what I thought. No we don't work on this functionality. Moreover
I think, that Py++
can not implement it. The primary reason is that Py++ deals with class
interface
and not with its state. Py++ can provide some convinience API that
will make the task
to be easier to implement. Tell me what you need and I will check how
I can integrate
your ideas.


-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/

Re: [pygccxml-development] serialization support?

[Neal B. <ndb...@gm...>]

On Wednesday 13 September 2006 6:52 am, Roman Yakovenko wrote:
> On 9/13/06, Neal Becker <ndb...@gm...> wrote:
> > On Wednesday 13 September 2006 12:58 am, Roman Yakovenko wrote:
> > > On 9/13/06, Neal Becker <ndb...@gm...> wrote:
> > > > Has any work been done on adding boost::serialization support?
> > >
> > > What do you mean?
> >
> > Automatic generation of pickle support.  Probably using
> > boost::serialization.
>
> That what I thought. No we don't work on this functionality. Moreover
> I think, that Py++
> can not implement it. The primary reason is that Py++ deals with class
> interface
> and not with its state. Py++ can provide some convinience API that
> will make the task
> to be easier to implement. Tell me what you need and I will check how
> I can integrate
> your ideas.

The technique I have used is not really elegant, but works.  First serialize 
with boost::serializatoin into a string, then pickle the string:

struct mt_pickle_suite : python::pickle_suite {
    
  static python::object getstate (const rng_t& rng) {
    std::ostringstream os;
    boost::archive::binary_oarchive oa(os);
    oa << rng;
    return python::str (os.str());
  }

  static void
  setstate(rng_t& rng, python::object entries) {
    python::str s = python::extract<python::str> (entries)();
    std::string st = python::extract<std::string> (s)();
    std::istringstream is (st);
    
    boost::archive::binary_iarchive ia (is);
    ia >> rng;
  }
};

[...]
class_<rng_t> ("rng", "Mersenne Twister", python::init<rng_t::result_type>(
									     (python::arg ("seed")=4357),
									     "__init__(seed=4357)\n"
									     "Construct with optional seed\n"
									     "@param seed: initial seed\n"
									     ))
    .def_pickle(mt_pickle_suite())
    .def ("getstate", &mt_pickle_suite::getstate)
    .def ("setstate", &mt_pickle_suite::setstate)
[...]

Re: [pygccxml-development] serialization support?

[Roman Y. <rom...@gm...>]

On 9/13/06, Neal Becker <ndb...@gm...> wrote:
> The technique I have used is not really elegant, but works.  First serialize
> with boost::serializatoin into a string, then pickle the string:
>
> struct mt_pickle_suite : python::pickle_suite {
>
>   static python::object getstate (const rng_t& rng) {
>     std::ostringstream os;
>     boost::archive::binary_oarchive oa(os);
>     oa << rng;
>     return python::str (os.str());
>   }
>
>   static void
>   setstate(rng_t& rng, python::object entries) {
>     python::str s = python::extract<python::str> (entries)();
>     std::string st = python::extract<std::string> (s)();
>     std::istringstream is (st);
>
>     boost::archive::binary_iarchive ia (is);
>     ia >> rng;
>   }
> };
>
> [...]
> class_<rng_t> ("rng", "Mersenne Twister", python::init<rng_t::result_type>(
>                                                                              (python::arg ("seed")=4357),
>                                                                              "__init__(seed=4357)\n"
>                                                                              "Construct with optional seed\n"
>                                                                              "@param seed: initial seed\n"
>                                                                              ))
>     .def_pickle(mt_pickle_suite())
>     .def ("getstate", &mt_pickle_suite::getstate)
>     .def ("setstate", &mt_pickle_suite::setstate)
> [...]
>

Few comments:

1. This implementation will surprize any Python user. You don't
preserve references
    between objects.

2. I think you can make this code to be template on Pickled class.

3. I think this code belongs to goodies. Do you want to work a little
bit on it and contribute?
   ( test, few lines of documentation)

   from goodies import pickle
   pickle( module builder, list of classes )

   Something like this.

-- 
Roman Yakovenko
C++ Python language binding
http://www.language-binding.net/