This is a starting point for parsing and navigating ext2 file systems. cargo run will start a session that looks like a shell. All you can do for now are the ls, and cd commands. It's left as an exercise to implement cat to view the contents of files, and removing other limitations.

Here's an example session:

% cargo run
   <building and intro stuff>
:> ls
.	..	lost+found	test_directory	hello.txt	
:> cat hello.txt
cat not yet implemented
:> cd test_directory
:> ls
.	..	file_in_folder.txt	
:> cd file_in_folder.txt    # <- whoops
:> ls
'm a file inside a folder.  # <- whoops^2
	
:> 

Limitations (also possible exercises):

• see "TODO" in cd command - you can currently cd into a text file - whoops!
• implement cat command to view text files
• currently it only parses small directories, remove this limitation
• implement mkdir
• implement link <source name> <destination path> to create hard links
• write tests
• write more tests
• implement rm (aka unlink) for plain files
• make link robust against ... (what should link be robust against?)
• once modifications can be made, implement unmount which cleanly writes modifications back to the "device" (file)
• implement import to get a file from the "host" filesystem into ours
• implement a mount <host-file> <dirname> command to mount a local file as an ext2 filesystem over an empty directory.

Big projects:

• make it #[no_std] compatible
• instead of reading from a big byte-buffer, read from a device into manually managed page-sized buffers
• implement a buffer cache
• implement fsck - identify different inconsistencies and find them
• implement a simple line editor (ed?) to create text files in the filesystem

Bigger projects:

• ext4 support?
• integrate with reedos kernel memory allocation
• integrate caching with kernel VM

Credits: Reed College CS393 students, @tzlil on the Rust #osdev discord