These disc images are only used on dev units and not retail units.
There are two important differences compared to normal Wii disc images:
- The data starts 0x8000 bytes into each partition instead of 0x20000
- The data of a partition is stored unencrypted and contains no hashes
Our old implementation was just guesswork and doesn't work at all.
According to testing by GerbilSoft, this commit's implementation
is able to read and extract files in the filesystem correctly,
but the tested game still isn't able to boot. (It's thanks to their
info about unencrypted disc images that I was able to make this commit.)
There were two problems with this:
1. If the starting offset was beyond the end of the disc,
we would dereference an invalid iterator.
2. The data beyond the end of the disc was non-deterministic.
Having DiscContents with size 0 would mean that some DiscContents
might not get added to the std::set because of them comparing
identically to another DiscContent.
This replaces an older piece of code in WriteDirectory that ensures
that no two files have the same starting offset. (We now care about
the ending offset, not the starting offset. The new solution both
ensures that no two files have the same ending offset and that no
two files have the same starting offset.)
For instance, we don't want to show TGC files that might be
inside the /files/ directory of a GameCube DirectoryBlob,
and we don't want to show the /sys/main.dol files for extra
partitions of Wii DirectoryBlobs.
Now it's clearer that SetDOL depends on SetApploader
and BuildFST depends on SetDOL.
As a side note, we now load the DOL even if there's
no apploader. (I don't think it matters whether we
do it, but it was easier to implement this way.)
This lets VolumeDirectory/DirectoryBlob skip implementing
various volume functions like GetGameID, GetBanner, etc.
It also lets us view extracted discs in the game list.
This ends up breaking the boot process for Wii
DirectoryBlobs due to workarounds being removed from the
boot process, but that will be fixed later by adding
proper DirectoryBlob support for things like TMDs.
We now expect the directories to be laid out in a certain
format (based on the format that WIT uses) instead of requiring
the user to set the DVD root and apploader path settings.
Techjar