[Feature Req] Zstandard support for CHDs

[LodanZark]

MAME added Zstandard support for CHDs, is it possible to implement the same feature into Genesis Plus GX?
source: mamedev/mame@05e69b4

[ekeeke]

It is surely possible to update libchdr to add support for ztsd codec but since I'm not really familiar with this library (it was submitted by an external contributor), I'm afraid I won't do it myself. I leave this as an open isue though in case anyone interested in it (and having zstd-compressed CHDS to test with) want to submit a pull request. It seems zstd is superior to lzma in regard to both compression ratio and decompression performance so it could be interesting to check how it performs vs increased memory footprint due to addition of another 3rd party library.

[rtissera]

As I wrote and maintain libchdr, I can give it a try...
@ekeeke libchdr is now really more light, you should expect lower memory footprint than the 7-years old version in current GPGX codebase.

[rtissera]

Started and did a good chunk of work on this inside the following PR : #586
Still needs to go through the following targets :

• Wii
• Android
• Standalone Windows

SDL1, SDL2, and libretro targets (both MSVC x64/x86 and Makefile based) are already building okay.

[ekeeke]

Thank you for taking the time to do this, Romain. I will take the time to quickly review the PR and merge it.

[ekeeke]

Fixed following 2986c1a

I tested a few chd files made use using latest chdman version (with default compression settings then compression set to zstd+cdfl) on sdl port to confirm it was working fine.