Lonami
commented
4 years ago how to determine the window size ahead of time
It should be "agreed" beforehand between the party who provides the compressed file and the party interested in decompressing it. That is, you can't determine it ahead of time (unless you're the one compressing it, then you decide, but this library can't compress LZXD yet).
The library was designed for XNB files in mind and I haven't had the chance to test it anywhere else (surprisingly most LZXD implementations out there don't implement compression either :P), so it might need some adjustments to get it to work in other files. PRs or sample files are more than welcome!
The WindowSize talks about reference and subject data because it's pretty much extracted from the official documentation, 2.1.2 Window Size:
The sliding window size MUST be a power of 2, from 2^17 (128 kilobytes (KB)) up to 2^25 (32 megabytes (MB)). The window size is not stored in the compressed data stream and MUST be specified to the decoder before decoding begins. The window size SHOULD be the smallest power of two between 2^17 and 2^25 that is greater than or equal to the sum of the size of the reference data rounded up to a multiple of 32,768 and the size of the subject data.
To be completely honest, I'm not exactly sure what those refer to since most of the document talks about compression but the library used the reference decompression which is just a section in the entire document.
jdm
https://docs.rs/lzxd/0.1.0/lzxd/enum.WindowSize.html refers to the reference data and the subject data, but I'm having trouble figuring out what that means, and how to determine the window size ahead of time. The context here is that I'm trying to integrate lzxd into this code where I have the size of the compressed data and the decompressed size.