Add support for 7zip compressed ROMs

[ashishekka97]

Apparently, the apache commons compress' 7zip implementation does not support streams.
This PR uses the SevenZFile API rather than the stream implementation.

[Swordfish90]

Hi @ashishekka97 . Thank you very much for this contribution. I'm sorry, but I was not aware apache compress did not support compressed input streams and you're definitely right there is no straightforward way to do so.

This is implementation looks good from a code standpoint, but I do have a couple of concerns:

1. Wouldn't this copy each 7z file into the cache directory every time a scan is performed?
2. What are the performances of this approach? Have you tried scanning thousands of 7zip roms?

[ashishekka97]

Hi @Swordfish90.

Yes, your concerns regarding the performance during scanning are valid.

1. It will copy each 7z file into the cache directory for each scan.
2. I haven't checked by scanning a large number of 7z files, but the operation indeed would be too slow. I'll check on this one.

Meanwhile, I'm still looking for another viable approach, i.e to use android's Uri to get the file directly (perhaps extracting the actual filePath??).
Let me know if you have any ideas regarding this.

[Swordfish90]

Hi @ashishekka97 ,

With the latest Android versions, it's no longer possible to retrieve a standard file path from content providers so the only option would be to pass from the ContentResolver.

The only option I can think of is this to retrieve a file descriptor and pass it down to some C++ code which can open 7z files with a native library which extract the info Lemuroid requires (hash, filename and size). This is probably required only during the scanning phase, afterwards, we can probably live with the double copy.

Needless to say, this is a lot more involved than I originally thought this issue would be...