nsZip is an open source PC tool to lossless compress/decompress NSP files in order to save a lot of storage while all NCA files keep their exact same hash.
But it’s more than just a compression. A lot of data like NDV0 partitions or fragment NCA3 files will be removed while compressing and exactly recreated when decompressed which saves even more space especially on updates higher than v65536.
In addition, the NSZ format was designed with emulators in mind so adding NSZ support to Yuzu will be possible in the future and because NSZ contains decrypted NCAs no keys would be needed to only extract game files. As compression algorithm Zstandard is used to multithreaded compress 256 KB chunks while uncompressible chunks are stored uncompressed. That way NSPZ/XCIZ allows random read access. Zstandard has a 43MB/s compression and 7032MB/s decompression speed on an 8 threaded CPU at level 18 while having one of the best compression ratios compared to other compression algorithms.
How compressing works: NSP => extracted NSP => decrypted NCAs => trim fragments => compressing to NSZ => verify correctness => repacking NSPZ file
How decompressing works: NSPZ file => extracted NSPZ => decompress NSZ => untrim fragments => encrypt NCAs => verify correctness => repack as NSP
Check out my GitHub page to report bugs, follow this project, post your suggestions or contribute.
GitHub link: https://github.com/nicoboss/nsZip
Version 1.0.1 Changelog:
- Let the user continue when detecting a yet unimplemented multifile NDV0 fragment. I'll add proper support for that unimplemented multifile NDV0 fragment format in the following days.
- The compression level can now be changed (tradeoff between speed and compression ratio)
- The block size can now be changed (tradeoff between random access time and compression ratio)
- XCIZ to XCI recreation (Currently working on)
- Improve performance a lot by not saving every step to HDD
- Mono builds for cross platform support
- Yuzu integration
- Homebrew integration
Q: It prod.keys not found!
A: Dump them using Lockpick and copy them to %userprofile%/.switch/prod.keys
Q: How much storage does this save?
A: It depends on the game. The compressed size is usually around 40-80% of the original size.
Q: What about XCI?
A: Compression to XCIZ is supported, but XCIZ to XCI recreation is still in development.
Q: The program throws an error or seems to behaves not as intended!
A: Open an issue on my GitHub page where you give me exact steps how to reproduce.