[boost] Re: [serialize] xml archives and versioning

From: Robert Ramey (ramey_at_[hidden])
Date: 2004-10-21 10:40:06

There is a confusion here.  Check the manual section titled "Class
Versioning"

There should be something like:

BOOST_CLASS_VERSION(Test_c, 99)

in your code.  I don't remember what the maximum class version might be but
it could be small like 255 for binary archives.

Robert Ramey

"Russell Hind" <rh_gmane_at_[hidden]> wrote in message
news:cl7tra$jqe$1_at_sea.gmane.org...
> Robert Ramey wrote:
> >
> > It certainly should - send me a code snippet.  The package includes
tests of
> >
>
> If I change this to use text_i/o archive then it works fine, but with
> XML, m_Version is set to zero when writing, but set to 3 when reading
> (this is with latest trunk from just before branch for release yesterday
> morning).  Also, if I provide a version number for the class of anything
> but 0 then it works find (e.g. 1) but 0 or no version lead to the
> ambiguity (running under borland bcc32 5.6.4)
>
> #include <fstream>
> #include <iostream>
> #include <boost/archive/xml_iarchive.hpp>
> #include <boost/archive/xml_oarchive.hpp>
>
> class Test_c
> {
> public:
>      Test_c(void) : m_Version(99999999)
>      {
>      }
>
>      template <typename ArchiveT>
>      void serialize(ArchiveT& ar, const unsigned int version)
>      {
>          m_Version = version;
>      }
>
>      unsigned int m_Version;
> };
>
> int main(int argc, char** argv)
> {
> Test_c Test;
>
>      {
>      std::ofstream ofs("C:\\test.xml");
>      boost::archive::xml_oarchive toa(ofs);
>          toa & BOOST_SERIALIZATION_NVP(Test);
>      std::cout << "Test version = " << Test.m_Version << std::endl;
>      }
>
>      {
>      std::ifstream ifs("C:\\test.xml");
>      boost::archive::xml_iarchive tia(ifs);
>          tia & BOOST_SERIALIZATION_NVP(Test);
>      std::cout << "Test version = " << Test.m_Version << std::endl;
>      }
>
>      return 0;
> }
>
> >
> > serialization traits determine whether or not a class is versioned.
Default
> > is for non primititve types to be versioned and the default version
number
> > is 0.  The usage of version number when not necessary could be a
performance
> > issue so there is the option of setting serialization traits for any
type so
> > that versioning isn't done.  For example, this is not done for STL
> > collections.  Review the section of the documentation "serialization
traits"
> >
>
> Thanks, I will do.
>
> Cheers
>
> Russell
>
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