Move "CArchive" file pointer backward.

[C++ Programming]

Hi

I want to use CArchive to seek backward. I did following:

int CmyClass::Serialize(CArchive& ar)
{
...
ar >> bt;
ar >> bt;
...

----->>>> Move ar file pointer backward here.
}


How can I implement this? Or How can I stop CArchive moving forward while I read something from a file?

Thanks,