feat(handler): add erofs filesystem & decompression handler

[rxpha3l]

feat(handler): add erofs filesystem & decompression handler

EROFS is a high-performance read-only filesystem originally developed by Huawei and now used extensively in AOSP. It offers features like compression (LZ4, LZMA), inline data, and reduced
storage overhead, making it ideal for read-only system images.

Create erofs file :

mkfs.erofs -z[compressor, level (optional)] foo.erofs.img foo/

Extract erofs file:

fsck.erofs --extract=foo_extracted/ foo.erofs.img

Key notes:

• First 1024 bytes are reserved for the boot loader
• Header starts at 0x400 with E0F5E1E2
• Header can be more than 128 bytes if extra slots provided
• File format in little endian
• There is no standarized file extension. The official documentation
  uses ".erofs.img"
• Checksum is differ form verion to version

Header format :

4 bytes : Magic
4 bytes : Checksum, crc32c
4 byets : feature compact
1 byte : Block size in bit shift
1 byte : Super block extra slots (128 + sb_extslots * 16)
2 bytes : Root ID number
8 bytes : Total valid inodes
8 bytes : Built time
4 bytes : Built time nsec
4 bytes : Block count
4 bytes : Start block addr of metadata area
4 bytes : Start block of shared xattr area
16 bytes : UUID
16 bytes : Volume name
4 bytes : Feature incompact
2 bytes : Union of Compresion algorithm & LZ4 max distance
2 bytes : Extra device
2 bytes : Devt slotoff
1 byte : Directory block size in bit shit
1 byte : Number of ling xattr prefixes
8 bytes : NID of special packed inode
1 byte : Reserved fir xattr name filter
23 bytes : Reserved (Most likely NULL bytes)
Unblob struct the header until the feature_incompact. The rest is labeled
as "reserved". Unblob parser the end offset by multiplying the block
size in bit shift with the block count. Since the checksum is not
consistent troughout the version, unblob matched on block count (at
least 1), printable volume name and if there is a build time.

[Sources]
https://elixir.bootlin.com/linux/v6.14-rc6/source/fs/erofs/erofs_fs.h
https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/erofs/erofs_fs.h?h=v6.6
https://erofs.docs.kernel.org/en/latest/core_ondisk.html
https://www.kernel.org/doc/html/latest/filesystems/erofs.html

[Copilot]

Copilot reviewed 3 out of 9 changed files in this pull request and generated 2 comments.

Files not reviewed (6)

• install-deps.sh: Language not supported
• overlay.nix: Language not supported
• package.nix: Language not supported
• shell.nix: Language not supported
• tests/integration/filesystem/android/erofs/input/foo.erofs.img: Language not supported
• tests/integration/filesystem/android/erofs/output/foo.erofs.img_extract/bar.txt: Language not supported

[qkaiser]

@rxpha3l make sure you pull from your remote with git pull origin erofs before doing anything else. I cleaned up your commits.

[qkaiser]

Code is clean. Nice catch on fsck.erofs being able to extract. Copilot's comments are relevant, you can take care of it.

[qkaiser]

@rxpha3l please make sure to also update the documentation with information about EROFS.