Preon

Preon aims to provide a framework for dealing with binary encoded data; or more specifically, it aims to deal with situations in which bytes are considered to be overkill. The project is named after the "point-like" particles, conceived to be subcomponents of quarks and leptons. Let's just say very small particles that you don't see with the naked eye, but you probably rely on them without knowing.

Preon is to bitstream encoded content what JAXB is to XML, or Hibernate to relational databases. You define your in memory representation of the data structure in Java classes, and add annotations to 'tell' how it should be mapped onto a bitstream encoded representation. Preon takes care of the rest: it will give you a decoder, hyperlinked documentation on the encoding format, and - if you want - annotated hexdumps explaining you exactly what you're looking at.