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DiscIO: Expand WIA/RVZ header size heuristic comments

This commit is contained in:
JosJuice 2020-08-31 14:46:13 +02:00
parent f7f0fa2d85
commit bdd28c0edf
1 changed files with 9 additions and 4 deletions
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13
Source/Core/DiscIO/WIABlob.cpp
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@ -1743,19 +1743,24 @@ WIARVZFileReader<RVZ>::Convert(BlobReader* infile, const VolumeDisc* infile_volu
const size_t raw_data_entries_size = raw_data_entries.size() * sizeof(RawDataEntry); const size_t raw_data_entries_size = raw_data_entries.size() * sizeof(RawDataEntry);
const size_t group_entries_size = group_entries.size() * sizeof(GroupEntry); const size_t group_entries_size = group_entries.size() * sizeof(GroupEntry);
// Conservative estimate for how much space will be taken up by headers. // An estimate for how much space will be taken up by headers.
// The compression methods None and Purge have very predictable overhead, // We will reserve this much space at the beginning of the file, and if the headers don't
// and the other methods are able to compress group entries well // fit on that space, we will need to write them at the end of the file instead.
const u64 headers_size_upper_bound = [&] { const u64 headers_size_upper_bound = [&] {
// 0x100 is added to account for compression overhead (in particular for Purge).
u64 upper_bound = sizeof(WIAHeader1) + sizeof(WIAHeader2) + partition_entries_size + u64 upper_bound = sizeof(WIAHeader1) + sizeof(WIAHeader2) + partition_entries_size +
raw_data_entries_size + 0x100; raw_data_entries_size + 0x100;
// RVZ's added data in GroupEntry usually compresses well // RVZ's added data in GroupEntry usually compresses well, so we'll assume the compression ratio
// for RVZ GroupEntries is 9 / 16 or better. This constant is somehwat arbitrarily chosen, but
// no games were found that get a worse compression ratio than that. There are some games that
// get a worse ratio than 1 / 2, such as Metroid: Other M (PAL) with the default settings.
if (RVZ && compression_type > WIARVZCompressionType::Purge) if (RVZ && compression_type > WIARVZCompressionType::Purge)
upper_bound += static_cast<u64>(group_entries_size) * 9 / 16; upper_bound += static_cast<u64>(group_entries_size) * 9 / 16;
else else
upper_bound += group_entries_size; upper_bound += group_entries_size;
// This alignment is also somewhat arbitrary.
return Common::AlignUp(upper_bound, VolumeWii::BLOCK_TOTAL_SIZE); return Common::AlignUp(upper_bound, VolumeWii::BLOCK_TOTAL_SIZE);
}(); }();