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

21 Oct 2004

      ...
Robert Ramey wrote:
...
It certainly should - send me a code snippet.  The package includes
tests of
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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
...
...
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
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@mac.com> wrote in message
news:cl7tra$jqe$1@sea.gmane.org...
performance
traits"
...
...
Thanks, I will do.
Cheers
Russell
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