erofs-rs

A pure Rust library for reading and building EROFS (Enhanced Read-Only File System) images.

Note: This library aims to provide essential parsing and building capabilities for common use cases, not a full reimplementation of erofs-utils.

Features

• no_std support with alloc for embedded systems
• Zero-copy parsing via mmap (std) or byte slices (no_std)
• Directory traversal and file reading
• Multiple data layouts: flat plain, flat inline, chunk-based

Usage

Standard (with std)

use std::io::Read;
use erofs_rs::{EroFS, backend::MmapImage};

fn main() -> erofs_rs::Result<()> {
    let image = MmapImage::new_from_path("system.erofs")?;
    let fs = EroFS::new(image)?;

    // Read file
    let mut file = fs.open("/etc/os-release")?;
    let mut buf = Vec::new();
    file.read_to_end(&mut buf)?;

    // List directory
    for entry in fs.read_dir("/usr/bin")? {
        println!("{}", entry?.dir_entry.file_name());
    }

    Ok(())
}

no_std (with alloc)

#![no_std]

extern crate alloc;
use erofs_rs::{EroFS, backend::SliceImage};

fn main() -> erofs_rs::Result<()> {
    // Assuming you have the EROFS image data in memory
    let image_data: &'static [u8] = include_bytes!("system.erofs");
    let fs = EroFS::new(SliceImage::new(image_data))?;

    // List directory entries
    for entry in fs.read_dir("/etc")? {
        let entry = entry?;
        // Process directory entry...
    }

    // Walk directory tree
    for entry in fs.walk_dir("/")? {
        let entry = entry?;
        // Process each file/directory...
    }

    Ok(())
}

Feature Flags

• std (default): Enables standard library support, including mmap backend
• opendal: Enables async I/O via Apache OpenDAL, supporting remote backends (HTTP, S3, etc.)
• Without std: Operates in no_std mode with alloc

# Standard usage (default)
[dependencies]
erofs-rs = "0.1"

# Async with OpenDAL
[dependencies]
erofs-rs = { version = "0.1", features = ["opendal"] }

# no_std with alloc
[dependencies]
erofs-rs = { version = "0.1", default-features = false }

CLI

# Dump superblock info
erofs-cli dump image.erofs

# List directory
erofs-cli inspect -i image.erofs ls /

# Read file content
erofs-cli inspect -i image.erofs cat /etc/passwd

# Convert to tar
erofs-cli convert image.erofs -o out.tar

# Remote images via HTTP (async OpenDAL backend)
erofs-cli dump http://example.com/images/system.erofs
erofs-cli inspect -i http://example.com/images/system.erofs ls /
erofs-cli inspect -i http://example.com/images/system.erofs cat /etc/os-release

Status

Implemented

• Superblock / inode / dirent parsing
• Flat plain layout
• Flat inline layout
• Chunk-based layout (without chunk indexes)
• Directory walk (walk_dir)
• Convert to tar archive

TODO

• Extended attributes
• Compressed data (lz4, lzma, deflate)
• Image building (mkfs.erofs equivalent)

License

MIT OR Apache-2.0