How to read the structure of a binary file?

Question

hex

Hello. Need help understanding localization file structure from one unity project.

There is a file lc_error.dat which is a zip archive. Inside error.idx and several files like this:

error_en.bin
error_ru.bin
// и т.д

Here are the files - link .

I'm assuming the .idx is an index file that may contain "keys" and an offset to translate. Something like "offset - key - delimiter" or "offset - limit - key - delimiter". And the rest of the content can be in one of the .bin files in the desired language.
In addition, the .idx file at the very end contains a piece of a human-readable string. And the first 4 bytes in all files are repeated - 87 ff ed ff, except for the third (ed) - it may differ. Could this be some kind of "separator"? There are some repeating sequences along the file, but I can't test this theory.

Is there a hex editor that could highlight repetitions or with a template function?
- I would like to hear any advice or hypotheses - how to understand the structure and read these files?

Answer 1

Find developers or fans of the game from which this file is copied and communicate with them. It will be much easier - it is possible that the file format has long been disassembled there and there are ready-made editors.
Hex editors are zillion, I use Hex Editor Neo but don't know if it has what you need :)

Answer 2

It looks like it's protobuf so the issue can be considered solved ^^
Thanks for the replies.