[boost][serialization] Adding State to Archives

From: martin.ecker_at_[hidden]
Date: 2004-05-13 05:55:29

Hello,

I was wondering what the best way would be to extend the serialization 
library to allow storing state in e.g. the archive objects during the 
serialization process. We could use such a facility in our project for 
various purposes. For example, it would be possible to influence the 
serialization of certain classes, i.e. make them write out only their 
internal state but not any pointers or references to other objects, or 
something like that.

Another use case for having state variables in archives: We're using 
another library in our project that has its own serialization system. 
So instead of writing boost::serialization code for the classes of 
this library we want to use its serialization system. This is 
straightforward enough by having the library serialize into a memory 
buffer which is then written out using boost::serialization's 
binary_object. However, we also need to do proper tracking of pointers 
for that library, so we can't just create a new memory buffer every 
time we encounter a pointer to one of its objects during 
serialization. Therefore it would be convenient to store an "archive" 
object of the library's serialization system (which calls an archive a 
"stream") in the boost::serialization archive and simply write all 
objects of the library we encounter to it. The library's serialization 
system will track all these objects for us in a similar way 
boost::serialization does. Then at the end of the serialization 
process we write the additional serialization data out to the archive 
using a binary_object.

In general, there are a lot of use cases I can think of where having 
state variables in an archive is useful (setting flags to influence 
the serialization process, deserializing smart pointers, registering 
objects upon deserialization in some kind of object registry, etc.).

One way of achieving all this would, of course, be to derive from one of 
the existing archive classes and add the required functionality. 
However, we don't want to lose the flexibility of being able to write 
out data to a binary, text, XML, or any other archive with some other 
kind of representation. So basically we're looking for a good way of 
inserting an additional layer in between the archives and the actual 
serialize functions that can store state variables.

Thanks for any comments.

Best Regards,
Martin Ecker

TAB Austria
Industrie- und Unterhaltungselektronik GmbH & CoKG
http://www.tab.at