[crates] Add sworn-disk crate

[lucassong-mh]

This PR adds sworn-disk to NGO's crates

RFC issue: #328

[tatetian]

I like the overall code structure; it is clear and modular.

The following is some of my initial comments. Most of them is about the index. I will submit more comments for other modules later.

[tatetian]

More comments.

[tatetian]

What I am about to say does not mean I am encouraging the PR author to take the advice into action now. Because if it was to be done, it would mean a major overhaul. But I think it is beneficial to discuss the future direction of improvement now.

Personally, I think the current codebase suffers a structural problem. The problem is that the codebase looks modular, but the modules are in fact highly entangled.

One of the main symptom is that the index cannot be tested alone. The index directly depends on the checkpoint. Without the checkpoint initialized, it is impossible to do anything on the index. The checkpoint not only contains the metadata required by the index, but also the rest of SwornDisk. So it is safe to say that the index code is entangled with the rest of SwornDisk.

I think that the current codebase is under too much influence of the paper's design. The paper's design is mainly concerned with security and clarity, not software engineering practices. So making the codebase closely follow the paper's design is harmful to the codebase.

But no worry. We have the time to figure out a plan to refactor the code structure later.

[tatetian]

The new version looks promising. Good job on improving the code quality.

One major issue is that we need to rename SwornDisk to JinDisk. The crate name should be jindisk (Yes, no - between jin and disk) as JinDisk should be considered one name and word, not two. On the other hand, Jinzhao Disk is two words.

[tatetian]

Thanks for submitting the updated version. Here are my comments for the first commit. I will submit the comments for the second commit later.

[tatetian]

Well done! I really appreciate your persevere and patience in improving the code quality constantly. The code is now good enough for merge. Before we do, let's fix some trivial issues listed in the comments below. Then, you can re-submit this PR to the Occlum repo (not NGO). See you there!