Implement feed.audit() about hypercore HOT 5 OPEN

Good morning. I've implemented feed.audit() over here.

However thanks to Rust's borrow checker I'm having trouble writing a test for the "bad data" scenario: it wisely prevents me from altering storage while the Feed has ownership of it.

Any idea of how to insert bad data here?

from hypercore.

@chronoslynx oh that's awesome! -- a PR would be super welcome, even if there isn't any test data included yet! Apologies for not replying sooner; I was on vacation for the past few weeks.

I'm not quite sure how to edit the bad data yet, haha. Perhaps if we re-initialize the feed from disk we can get it into a bad state? Perhaps we can workshop this a bit in the PR?

Thanks so much for putting in the work; that's amazing! :D

from hypercore.

Hey, no need to apologize. Vacation is important!

Inserting bad data will be... weird. Does it write the data immediately to disk (if you're using disk-backed storage)? If so (and we can get the filename), we can open a second handle to it and stomp the data.
I'll need to read into your storage implementation to see

from hypercore.

Inserting bad data will be... weird. Does it write the data immediately to disk (if you're using disk-backed storage)? If so (and we can get the filename), we can open a second handle to it and stomp the data.

Yeah, that's what I was thinking! -- It's very possible that might surface some other fun issues, but that'll be good to verify!

We implement fsync() on Drop in random-access-storage, so that should probably work!

from hypercore.

fsync is also called after every write, and the disk is consulted on every read which leads to this being simpler than I expected.

It's brittle, however. If the disk implementation every changes the name of the data file, then this test will break

from hypercore.