Warframe's game files are located in the directory ...SteamLibrary/steamapps/common/Warframe/Cache.Windows/
Each archive comes with two files: a .cache file containing the data and a .toc that provides a table of contents for the former - letting us know where to find all the individual files in the cache.
The .toc file begins with the 8-byte magic number 4E C6 67 18 14 00 00 00.
It is then followed by arbitrarily many blocks (entries) of the following format.
| Size | Description |
|---|---|
| 28 bytes | all set to 0xFF |
| 4 bytes | folder depth; 0 for the top level folder, 1 for its containing folders, etc. |
| 64 bytes | folder name (zero-terminated string) |
If the folder has any files directly inside it, they will appear immediately after the folder block in the following format.
| Size | Description |
|---|---|
| 8 bytes | offset; location of this file in the .cache file |
| 4 bytes | ??? |
| 4 bytes | ??? (seems to be a few discrete values ending with D9 01) |
| 4 bytes | compressed size in .cache |
| 4 bytes | uncompressed size |
| 4 bytes | file depth; i.e. one more than its containing folder |
| 64 bytes | file name (zero-terminated string) |
The .cache files contain all the actual game data.
The files are compressed with a mixture of Oodle and custom LZ algorithms.
The Oodle files can be decompressed with the oo2core_X_win64.dll found in ...SteamLibrary/steamapps/common/Warframe\Tools\Oodle\x64\final\.
See game file extractors (you can find them on GitHub) for the LZ algorithm.