The workaround added in 30f9f31 caused a regression where Dolphin
incorrectly replaced runs of one byte with runs of another byte
when writing WIA and RVZ files. ReuseID::operator< was always
returning false unless the ReuseIDs being compared had different
partition keys, which caused std::map<ReuseID, GroupEntry>
to treat all ReuseIDs with the same partition key as equal.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
The loop in WIARVZFileReader::Chunk::Read could terminate
prematurely if the size argument was smaller than the size
of an exception list which had only been partially loaded.
It's possible (but rare) for a WIA or RVZ file to support
this for some partitions but not all, and for the game and
the blob code to disagree on how large a partition is.
Gets rid of the need to seek to the end of the file
when opening a file.
The downside of this is that we waste a little space,
since we can't know in advance exactly how much
space the compressed parts of the headers will need.
This is useful for the way Dolphin scrubs Wii discs.
The encrypted data is what gets zeroed out, but this
zeroed out data then gets decrypted before being stored,
and the resulting data does not compress well.
However, each block of decrypted scrubbed data is
identical given the same encryption key, and there's
nothing stopping us from making multiple group entries
point to the same offset in the file, so we only have
to store one copy of this data per partition.
For reference, wit zeroes out the decrypted data,
but Dolphin's WIA writer can't do this because it currently
doesn't know which parts of the disc are scrubbed.
This is also useful for things such as storing Datel discs
full of 0x55 blocks (repesenting unreadable blocks)
without compression enabled.
