rust-fs-squashfs

Pure-Rust, read-only SquashFS driver. A clean-room SquashFS 4.0 reader over the shared am-fs-core block-device trait, exposing a stable C ABI (fs_squashfs_*) for FFI from Swift/FSKit, C, or Go.

SquashFS is a compressed, read-only filesystem — a peer format to ext4/ntfs/erofs, not built on top of any of them. It cannot be modified in place (you regenerate the whole image with mksquashfs), so this crate has no write path: the C ABI is the read subset of its sister drivers' surface — no mkfs / create / write.

Every standard compressor mksquashfs can emit is decoded. gzip/xz/zstd use their container stream formats (zlib / .xz / zstd frames); lz4 uses the raw LZ4 block format with the uncompressed size taken from the block geometry; lzo is a clean-room LZO1X decoder.

• superblock — 96-byte superblock parse + validate
• decompress — codec dispatch (gzip / xz / lz4 / zstd / lzo, all pure-Rust)
• lzo1x — clean-room LZO1X decompressor (no liblzo2-derived code)
• metablock — 8 KiB metadata-block reader + cross-block cursor
• table — indirect lookup tables (id, fragment)
• inode — all SquashFS inode shapes
• dir — directory-listing parser
• fs — top-level handle: path lookup, dir listing, file/symlink read
• capi — C ABI exports matching include/fs_squashfs.h

cargo run --release --bin lssquashfs -- <image> info
cargo run --release --bin lssquashfs -- <image> tree /
cargo run --release --bin lssquashfs -- <image> cat /path/to/file

use std::sync::Arc;
use fs_core::{BlockRead, FileDevice};
use fs_squashfs::Filesystem;
let dev = Arc::new(FileDevice::open("image.sqfs")?) as Arc<dyn BlockRead>;
let fs = Filesystem::open(dev)?;
let inode = fs.lookup_path("/etc/hostname")?;
let mut buf = vec![0u8; inode.file_size as usize];
fs.read_file(&inode, 0, &mut buf)?;

cargo test # unit + in-crate tests (no external tools)
cargo test --release -- --ignored # oracle tests: need `squashfs-tools` on PATH
cargo clippy --all-targets -- -D warnings

The oracle tests (tests/oracle_compat.rs) build a fixture tree with mksquashfs -comp {gzip,xz,lz4,zstd,lzo} and read every path back through the driver, asserting exact bytes. They are #[ignore]-gated so cargo test stays green on a host without squashfs-tools; run them with -- --ignored.

MIT — see LICENSE.