Re: [Boost-users] [serialization] conditional serialization of membersand base classes

From: Robert Ramey (ramey_at_[hidden])
Date: 2007-02-22 18:30:11

An interesting case.  But I don't see how this could be done without 
enhancing the library in some non-obvious way. .

Then general problem is that the seialization library writes a serial stream 
of bytes.  So you can't skip a piece without throwing things out of sync. 
But you don't know how long something is until it's serialized and then its 
too late.

 You might be able to do it for some special cases though

Robert Ramey

n.torrey.pines wrote:
> Hi
>
> The logic I want to implement is:
> * b contains a
> * when saving b, save a, followed by other data
> * when loading b, load a into a temporary, if it matches b.m_a, load
> other data
>
> Would you expect the following code to work?
>
> class b {
>     a m_a; // a is serializable
>     vector<int> m_v; // other data
>
>     template<class Archive>
>     void save(Archive& ar, const unsigned version) const {
>         ar & m_a;
>         ar & m_v;
>     }
>
>     template<class Archive>
>     void load(Archive& ar, const unsigned version) {
>         a tmp;
>         ar & tmp;
>         if(tmp == m_a) ar & m_v;
>     }
>
>     // ...
> };
>
> Now, what if b is derived from a instead of containing it? Would this
> work?
>
> class b : public a {
>     vector<int> m_v; // other data
>
>     template<class Archive>
>     void save(Archive& ar, const unsigned version) const {
>         ar & boost::serialization::base_object<a>(*this);
>         ar & m_v;
>     }
>
>     template<class Archive>
>     void load(Archive& ar, const unsigned version) {
>         a tmp;
>         ar & tmp;
>         if(tmp == static_cast< const a& >(*this)) ar & m_v;
>     }
>
>     // ...
> };
>
> Thanks!