Multi-game discs larger than 4 GB don't work properly

[GerbilSoft]

[filing this here for reference; I'm working on fixing this in my branch]

The disc read functions (ISO, RealDI, and FST) as well as ISOShift all use 32-bit offsets. This makes it impossible to use a GCOS Multi-Game disc with more than 4 GB.

Here's what currently happens:

• DVD-R5: Selecting a game that starts prior to the 4 GB boundary but ends after, it works initially, but will eventually crash.
• DVD-R9: If the disc contains any games that start after the 4 GB boundary, the Nintendont loader will crash with a DSI exception.

In my widescreen/CISO/menu branch, https://github.com/GerbilSoft/Nintendont/commits/widescreen-hax.r422, I've currently fixed the Nintendont loader crash when selecting a DVD-R9 image on an exFAT partition, and disabled selection of games that start after 4 GB.

What else needs to be done:

• Use 64-bit offsets for ISO and RealDI. This does add slight overhead for other uses, but it shouldn't be noticeable in practice.
• The ISOShift variable should be interpreted as a 34-bit shifted value, similar to Wii offsets. (GCOSDVD9 uses this already.) This may break on older discs if a game isn't aligned to a 4-byte boundary, but AFAIK the previous formats were all 32 KB aligned, while GCOSDVD9 is 128 KB aligned.

If I can find my old GCOSDVD9 discs tonight, I'll do some more fixes for RealDI.

[GerbilSoft]

https://github.com/GerbilSoft/Nintendont/raw/v4.422-CISO-test4/loader/loader.dol

The latest test build from my widescreen/CISO branch has full support for DVD-9 multi-game images on an exFAT partition. When using an actual DVD-R5, it still gets stuck on some games (Super Mario Sunshine freezes after the progressive scan prompt), and all games report that the disc cover is open on my DVD-R9. I'm not sure if it's a problem with RealDI or if my discs are broken.

I'll try ripping the discs to a file and test them again as disc images.