[Zope] Appending to a file via manage_edit?

[Jeff Gentry]

I've been looking around for this, but can't seem to find anything.  I'm
assuming that it is just not possible, but thought I'd ask just in case.

For File objects, I see that manage_edit() has the parameters: title,
content_type, precondition, filedata & REQUEST.  Setting something in the
filedata parameter will replace the file's current data with that.

This implies (to me at least) that the only way one can edit a file is a
complete rewrite.  Does there exist a way to simply append data to the end
of the file?  For instance, if one wanted to write to a file line by line,
is that possible in Zope?

Thanks