Decoding NovaPack (NPK) binary format

I am trying to extract & replace some of the assets in the Mac game "Luxor 3" with my own. Inside the Contents/Resources folder there is a big file called data.npk.

Opening it up in a hex editor, I see "NovaPack" in the header, and a number of strings referring to the filetypes I am looking to extract (in this case, ogg, for audio).

I have found several pieces of software on the internet claiming to unpack NPK files from other games, but all of them run on Windows and do not succeed in unpacking the data from this game.

I am a reasonabl开发者_StackOverflow中文版y competent C programmer and could build a command line utility to extract the files I am looking for if I knew what the exact data format of the NPK file is. Presumably the header contains the "file name" of each packed file, and the offset and size of its contents. No doubt a piece of code inside the Luxor game reassembles the assets in memory based on this information.

Does anyone have any experience with this format specifically, or general advice on what the next steps would be towards decoding the structure of any proprietary data format?

I think you might be interested in the NPK project. It's primarily in C so I believe it'll suit your purpose.

They even state this on the project's page:

If you're finding a platform independent, easy-to-use and secure packaging system, choose npk. It works on most modern operating systems and also supports powerful tools for manipulating your package.