[HELP] how do you know whats stored in the blockData section in the cache?

I'm trying to understand how the cache works.

so far i have figured out that the main_file_cache.dat contains blocks of 520 bytes formatted as such:

Code:

short nextFileId short currentFilePartId tribyte nextDataBlockId byte nextFileTypeId byte[512] blockData

and the .idx files contain blocks of 6 bytes formatted as such:

Code:

tribyte fileSize tribyte blockId

and i understand how i would go about finding the files stored in the main_file_cache.dat
so for example if i wanted to read file 5 in the cache
i would open an idx file and move 30(5*6) bytes and read the next 6 bytes to get the size and block id,
and i would then go read the main_file_cache.dat and move (blockId * 520) bytes to find the block that i was looking for and then reading the last 512 bytes of that block to get the blockData.

but what i dont understand is:
what kinds of things are even stored in the cache?
i know model files are, but, then, how exactly are they being stored? like, are they using a custom format, or are they stored as something like .obj files?
and have they been compressed before packed in the cache? and how would i know?

from using toms cache editor, i can see that there are things like item configurations stored in the cache as wel, but again, how can you know if the blockData is containing 3d model data, or item configuration data?
and again, how is the data formatted? just as plain ascii text, orr?

i will seriously appreciate it if someone can explain it to me, i really want to learn this.
i will thanks and rep u!

edit: please....someone ;_;