Re: [Boost-users] DeSerialization to update content ofobjectinsteadof construct new object

From: Ng Pan (panng_wts_at_[hidden])
Date: 2007-05-16 04:30:48

Hi Matthias

It is so strange that all the derived objects are treated as base objects 
during serialization and deserialization. From the xml file, I found that 
all the class_id_reference are same within the vector.

        <m_vpBase class_id="3" tracking_level="0" version="0">
                <count>7</count>
                <loaditem class_id_reference="1" object_id="_2">
                        <ComponentID>4</ComponentID>
                        <BaseInt>11478</BaseInt>
                </loaditem>
                <loaditem class_id_reference="1" object_id="_3">
                        <ComponentID>3</ComponentID>
                        <BaseInt>19169</BaseInt>
                </loaditem>
                <loaditem class_id_reference="1" object_id="_4">
                        <ComponentID>6</ComponentID>
                        <BaseInt>5705</BaseInt>
                </loaditem>
                <loaditem class_id_reference="1" object_id="_5">
                        <ComponentID>7</ComponentID>
                        <BaseInt>23281</BaseInt>
                </loaditem>
                <loaditem class_id_reference="1" object_id="_6">
                        <ComponentID>5</ComponentID>
                        <BaseInt>26962</BaseInt>
                </loaditem>
                <loaditem class_id_reference="1" object_id="_7">
                        <ComponentID>0</ComponentID>
                        <BaseInt>41</BaseInt>
                </loaditem>
                <loaditem class_id_reference="1" object_id="_8">
                        <ComponentID>1</ComponentID>
                        <BaseInt>18467</BaseInt>
                </loaditem>
        </m_vpBase>

Is it correct? And It works properly when some of the pointers are pointing 
to class base objects.

One more question, I wonder could I add virtual to the function
"void serialize(Archive &ar, const unsigned int /* file_version */)" ?

Regards
Barr Ng

>From: Matthias Troyer <troyer_at_[hidden]>
>Reply-To: boost-users_at_[hidden]
>To: boost-users_at_[hidden]
>Subject: Re: [Boost-users] DeSerialization to update content 
>ofobjectinsteadof construct new object
>Date: Wed, 16 May 2007 16:16:39 +1000
>
>Be careful that this will not work if your base* is a pointer to a
>base class, and you actually want to (de)serialize the derived object.
>
>Matthias
>
>On 16 May 2007, at 13:44, Ng Pan wrote:
>
> > Thank you very much.
> > I have successfully overloaded the serialization function. Here is
> > the code
> > as the reference for other ppl doing the similar modification.
> >
> > base.h
> >     #ifndef BASE_H
> >     #define BASE_H
> >     ...
> >     #include<boost\serialization\vector.hpp>
> >     ...
> >     class base
> >     {
> >        friend class boost::serialization::access;
> >        template<class Archive>
> >        void serialize(Archive &ar, const unsigned int /*
> > file_version */){
> >            ar & BOOST_SERIALIZATION_NVP(m_nID);
> >         }
> >         .....
> >     }
> >     ...
> >
> >      #if defined(__SGI_STL_PORT) || defined(_STLPORT_VERSION)
> >      #define STD _STLP_STD
> >      #else
> >      #define STD std
> >     #endif
> >
> >     namespace boost {
> >     namespace serialization {
> >
> >      //vector<Base *>
> >     template<class Archive, class Allocator>
> >     inline void save(
> >         Archive & ar,
> >         const STD::vector<base *, Allocator> &t,
> >         const unsigned int /* file_version */
> >     ){
> >          // record number of elements
> >         unsigned int count = t.size();
> >         ar << BOOST_SERIALIZATION_NVP(count);
> >        for(unsigned int i=0; i< count; i++)
> >           ar<<boost::serialization::make_nvp("loaditem", t.at(i));
> >      }
> >
> >      template<class Archive, class Allocator>
> >      inline void load(
> >          Archive & ar,
> >          STD::vector<base *, Allocator> &t,
> >           const unsigned int  /*file_version*/
> >      ){
> >       //   // retrieve number of elements
> >           unsigned int count;
> >          ar >> BOOST_SERIALIZATION_NVP(count);
> >          for(unsigned int i=0; i<count; i++)
> > 	ar >> boost::serialization::make_nvp("loaditem", *t.at(i));
> >           }
> >      }
> >      }
> >     ...
> >    #endif
> >
> >
> > Barr Ng
> >
> >
> >> From: Matthias Troyer <troyer_at_[hidden]>
> >> Reply-To: boost-users_at_[hidden]
> >> To: boost-users_at_[hidden]
> >> Subject: Re: [Boost-users] DeSerialization to update content of
> >> objectinsteadof construct new object
> >> Date: Wed, 16 May 2007 07:22:28 +1000
> >>
> >> Another, maybe easier option, could be to  overload the serialization
> >> functions for std::vector<base *> .
> >>
> >> Matthias Troyer
> >>
> >> On 16 May 2007, at 01:02, Robert Ramey wrote:
> >>
> >>> The code for serialization of a vector is found in serialization/
> >>> vector.hpp.
> >>>
> >>> I implemented this code to reconstuct the vector items rather than
> >>> just reload them.  I did this for a number of reasons - which for
> >>> this discussion are not important.
> >>>
> >>> If this doesn't suit your needs, I would suggest you make your own
> >>> version of serialization.hpp which operates differently.  Starting
> >>> with the current version it wouldn't be at all hard to do.
> >>>
> >>> If you want to use both current ("standard") method in some
> >>> places in addition to your "custom" method, you might consider
> >>> making some sort of wrapper which tags your special
> >>> vectors with a type which can be distinguished for special
> >>> serialization treatment.
> >>>
> >>> Robert Ramey
> >>>
> >>> Ng Pan wrote:
> >>>> Hi
> >>>>
> >>>> I am using boost serialization to synchronise objects between
> >>>> different computers (network). The objects would be serializated
> >>>> as a
> >>>> string instead of a file by using the class stringstream(instead of
> >>>> fstream). The string would be transferred via TCP/IP layer.
> >>>>
> >>>> Let simpify the situation as only two computers (Master and Slave)
> >>>> ,both of two computers have N objects and I wanna synchronise their
> >>>> content. I create a vector of pointer ( std::vector<base *>
> >>>> m_vpBase
> >>>> ) which points to the dirty objects. Both of two computers have
> >>>> this
> >>>> vector. Let assume the vectors are already pointing to the
> >>>> corresponding objects. For Tx side, it would serialize the
> >>>> objects as
> >>>> a string. For Rx side, I want to update the content of the objects
> >>>> that its vector is pointing to.
> >>>>
> >>>> Tx side:
> >>>> oa << BOOST_SERIALIZATION_NVP(m_vpBase);
> >>>>
> >>>> Rx side:
> >>>> oa >> BOOST_SERIALIZATION_NVP(m_vpBase );
> >>>>
> >>>> However, the above code would construct new objects.
> >>>>
> >>>> What i want is just update the content of the objects , not
> >>>> construct
> >>>> new objects.
> >>>>
> >>>> I know how to update the content for one object by using pointer (
> >>>> base * m_pBase).
> >>>> Tx side:
> >>>> oa << BOOST_SERIALIZATION_NVP(m_pBase);
> >>>>
> >>>> Rx side:
> >>>> oa >> BOOST_SERIALIZATION_NVP(*m_pBase);
> >>>>
> >>>>
> >>>> But, I don't know how to do for a vector of pointer. If you know,
> >>>> please give me some hints. Thank you very much.
> >>>>
> >>>> Regards
> >>>> Barr Ng
> >>>> [I found Boost serialization is useful and easy to use. ]
> >>>>
> >>>> _________________________________________________________________
> >>>> No masks required! Use MSN Messenger to chat with friends and
> >>>> family.
> >>>> http://go.msnserver.com/HK/25382.asp
> >>>
> >>>
> >>>
> >>> _______________________________________________
> >>> Boost-users mailing list
> >>> Boost-users_at_[hidden]
> >>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
> >>
> >> _______________________________________________
> >> Boost-users mailing list
> >> Boost-users_at_[hidden]
> >> http://lists.boost.org/mailman/listinfo.cgi/boost-users
> >
> > _________________________________________________________________
> > Get 10Mb extra storage for MSN Hotmail. Subscribe Now!
> > http://join.msn.com/?pgmarket=en-hk
> >
> > _______________________________________________
> > Boost-users mailing list
> > Boost-users_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/boost-users
>
>_______________________________________________
>Boost-users mailing list
>Boost-users_at_[hidden]
>http://lists.boost.org/mailman/listinfo.cgi/boost-users

_________________________________________________________________
Learn English via Shopping Game, FREE! 
http://www.linguaphonenet.com/BannerTrack.asp?EMSCode=MSN06-03ETFJ-0211E