Hex Fiend does data structures and file formats now too, using parsers written in TCL. I’d probably rate Hex Fiend as being in the middle too, especially if you

Hex Fiend does data structures and file formats now too, using parsers written in TCL. I’d probably rate Hex Fiend as being in the middle too, especially if you’re going to put xxd at the low end :) Personally, for file format parsing I like to use Hachoir (specifically Hachoir-wx for GUI file structure browsing), which is a somewhat obscure bit of software that I’ve made some contributions to.