[C++-sig] Re: [Boost-python-cvs] CVS: boost/boost/python/object pickle_support.hpp,NONE,1.1

[David Abrahams]

More questions...

1. I don't see how your error message thing is going to cause a message to
appear under any circumstance (?)

2. Are users expected to call this "register_" function?
It would be nice to avoid that.

3. How about a "curiously recursive template" formulation,
roughly:

template <class Derived>
struct pickle_support
{
    typedef char undefined;
    undefined getintitargs;
    undefined getstate;
    undefined setstate;
    undefined getstate_manages_dict;

    // I'm not attached to using the constructor here.
    template <class Class_>
    pickle_support(Class_ c)
    {
        // Guarantees derivation of Derived.
        Derived* self = static_cast<Derived*>(this);
        register_(c,
            &Derived::getinitargs, &Derived::getstate,
            &Derived::setstate, &Derived::getstate_manages_dict);
    }
 private:
    // Definitions of appropriate register_ functions left as an exercise
};

Used as:

struct pickle_world : pickle_support<pickle_world>
{
    ...
};

???

----- Original Message -----
From: "Ralf W. Grosse-Kunstleve" <rwgk at users.sourceforge.net>
To: <boost-python-cvs at lists.sourceforge.net>
Sent: Sunday, July 21, 2002 3:49 AM
Subject: [Boost-python-cvs] CVS: boost/boost/python/object
pickle_support.hpp,NONE,1.1


> Update of /cvsroot/boost/boost/boost/python/object
> In directory usw-pr-cvs1:/tmp/cvs-serv31721/object
>
> Added Files:
> pickle_support.hpp
> Log Message:
> additional files for pickle support; no modification of any existing
files
>
> --- NEW FILE: pickle_support.hpp ---
> //  (C) Copyright R.W. Grosse-Kunstleve 2002.
> //  Permission to copy, use, modify, sell and distribute this software
> //  is granted provided this copyright notice appears in all copies. This
> //  software is provided "as is" without express or implied warranty, and
> //  with no claim as to its suitability for any purpose.
> #ifndef BOOST_PYTHON_OBJECT_PICKLE_SUPPORT_RWGK20020603_HPP
> #define BOOST_PYTHON_OBJECT_PICKLE_SUPPORT_RWGK20020603_HPP
>
> #include <boost/python/object/class.hpp>
> #include <boost/python/tuple.hpp>
>
> namespace boost { namespace python {
>
> handle<> make_instance_reduce_function();
>
> namespace error_messages {
>
>   template <class T>
>   struct missing_pickle_support_function_or_incorrect_signature {};
>
> }
>
> class pickle_support_base
> {
>   private:
>     struct dummy_return_type_ {};
>
>   public:
>     template <class Class_, class Tgetinitargs>
>     static
>     void
>     register_(
>       Class_& cl,
>       tuple (*getinitargs_fn)(Tgetinitargs),
>       dummy_return_type_* (*getstate_fn)(),
>       dummy_return_type_* (*setstate_fn)(),
>       bool)
>     {
>       cl.enable_pickle_support(false);
>       cl.def("__getinitargs__", getinitargs_fn);
>     }
>
>     template <class Class_, class Tgetstate, class Tsetstate>
>     static
>     void
>     register_(
>       Class_& cl,
>       dummy_return_type_* (*getinitargs_fn)(),
>       tuple (*getstate_fn)(Tgetstate),
>       void (*setstate_fn)(Tsetstate, object),
>       bool getstate_manages_dict)
>     {
>       cl.enable_pickle_support(getstate_manages_dict);
>       cl.def("__getstate__", getstate_fn);
>       cl.def("__setstate__", setstate_fn);
>     }
>
>     template <class Class_,
>               class Tgetinitargs, class Tgetstate, class Tsetstate>
>     static
>     void
>     register_(
>       Class_& cl,
>       tuple (*getinitargs_fn)(Tgetinitargs),
>       tuple (*getstate_fn)(Tgetstate),
>       void (*setstate_fn)(Tsetstate, object),
>       bool getstate_manages_dict)
>     {
>       cl.enable_pickle_support(getstate_manages_dict);
>       cl.def("__getinitargs__", getinitargs_fn);
>       cl.def("__getstate__", getstate_fn);
>       cl.def("__setstate__", setstate_fn);
>     }
>
>     template <class Class_>
>     static
>     void
>     register_(
>       Class_&,
>       ...)
>     {
>       typedef typename
>
error_messages::missing_pickle_support_function_or_incorrect_signature<
>           Class_>::error_type error_type;
>     }
>
>     static dummy_return_type_* getinitargs() { return 0; }
>     static dummy_return_type_* getstate() { return 0; }
>     static dummy_return_type_* setstate() { return 0; }
>
>     static bool getstate_manages_dict() { return false; }
> };
>
> }} // namespace boost::python
>
> #endif // BOOST_PYTHON_OBJECT_PICKLE_SUPPORT_RWGK20020603_HPP
>
>
>
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