If you are interested in the research aspect of this, Kathleen Fisher  
did interesting work on parsing ad-hoc data (mostly ascii):

http://www.research.att.com/~kfisher/hancock/release.php
http://www.research.att.com/~kfisher/hancock/release.php

I remember to have seen something like this for OCaml in the recent  
proceedings of ICFP or POPL but can't remember right now.

My own work in the context of calling conventions proposes an algebra  
to describe structures in memory. This could be a starting point for  
a DSL; it is also implemented in the Quick C-- compiler (in OCaml) in  
module block.nw.

http://www.st.cs.uni-sb.de/~lindig/papers/blocks/next.pdf
http://www.cminusminus.org/rsync/qc--/src/block.nw

-- Christian