lwext4-rs

A crate for interfacing with lwext4 from Rust.

Details

You can find the details of the interface in interface.md.

Usage

fn main(){
    let file = OpenOptions::new()
        .read(true)
        .write(true)
        .open("ext_images/ext_image")
        .unwrap();
    let mut config = BlockDeviceConfig::default();

    let bs: u64 = 512;
    config.block_size = bs as u32;
    config.part_size = file.metadata().unwrap().len();
    config.part_offset = 0;
    config.block_count = config.part_size / bs;

    println!("config: {:#x?}", config);

    set_debug_mask(DebugFlags::ALL);
    let blk = DefaultInterface::new_device(file, config);
    let register_handler = RegisterHandle::register(blk, "ext4fs".to_string()).unwrap();
    let mount_handler =
        MountHandle::mount(register_handler, "/mp/".to_string(), true, false).unwrap();
    let fs = FileSystem::new(mount_handler).unwrap();

    let stats = fs.mount_handle().stats().unwrap();
    println!("stats: {:#x?}", stats);

    let read_dir = fs.readdir("/mp/").unwrap();
    for entry in read_dir {
        println!("{:?}", entry);
    }
}

Examples

RUST_LOG=info cargo run --example usage/tests/mkfs

no_std

This crate is no_std compatible. You can disable the default features to use it in a no_std environment.

[dependencies]
lwext4-rs = { version = "0.1.0", default-features = false }

In the lwext4 configuration, debug output is enabled, so it relies on printf/fflush/stdout for output. In addition, it also relies on several functions:

1. malloc / free / calloc / realloc

2. strcmp / strcpy / strncmp

3. qsort

To handle these dependencies, you can define these functions manually or rely on some existing implementation.

The tinyrlibc library provides implementations of 1 and 2. In order to implement printf, you can refer to prinf_compat. c-ward provides the implementation of qsort, you can copy it directly from here. In the end, all we need to implement are fflush and stdout. Usually, we only need to implement these two as empty functions.

#[no_mangle]
static stdout: usize = 0;

#[no_mangle]
extern "C" fn fflush(file: *mut c_void) -> c_int{
    assert!(file.is_null());
    0
}

mkfs

cargo run -p lwext4-mkfs -- --help

Reference

lwext4 (C)

lwext4 (rust)