Libgist was designed to be a simple, low-overhead library that can be easily incorporated into applications that need fast access to the data they manage. It uses regular files for storage purposes and supports single-user access without transactional behavior. If you need multiuser access and/or recovery, wait for the upcoming SHORE release of libgist, which will provide the libgist functionality embedded in the SHORE object server.
This document should help you get the code installed, and get you writing your own index code quickly.
Comments, questions and suggestions may be directed to gist@postgres.berkeley.edu