[Zope] cataloging text files

[bak (kedai)]

hi
any body with ideas to index textfiles with ZCatalog?  i've read cataloging 
everything with zcatalog, and would like to do the same with text files.  i 
saw two steps
1-setup a ZSQL methods that returns what we want to index (return as 
PrincipiaSearchSource)
2-catalog the objects

what/how can i do #1 with text files?  how can i retrun 
PrincipiaSearchSource?  i know how to treturn text, but not how to return it 
to the script that does the cataloging.  i can't think of a way...

thanks