Here's a post to the git mailing list from Martin Uecker describing the same from 2005: https://lore.kernel.org/git/20050416173702.GA12605@macavity/ . From the tone of the email it sounds like he didn't consider the idea new at that point:

> The chunk boundaries should be determined deterministically from local properties of the data. Use a rolling checksum over some small window and split the file it it hits a special value (0). This is what the rsyncable patch to zlib does.

He calls it a merkle hash tree.

Edit: here's one that's one day earlier from C. Scott Ananian: https://lore.kernel.org/git/Pine.LNX.4.61.0504151232160.2763...

> We already have the rsync algorithm which can scan through a file and efficiently tell which existing chunks match (portions of) it, using a rolling checksum. (Here's a refresher: http://samba.anu.edu.au/rsync/tech_report/node2.html ). Why not treat the 'chunk' as the fundamental unit, and compose files from chunks?

I am working on related things[r], using Merkle-fied LSM trees. Ink&Switch do things that very closely resemble Merklefied LSM[h], although they are not exactly LSM. I would not be surprised if someone else is doing something similar in parallel. The tricks are very similar to Prollies, but LSM instead of B-trees.

That reminds me my younger years when I "invented" the Causal Tree[c] data structure. It was later reinvented as RGA (Replicated Growable Array [a]), Timestamped Insertion Tree and, I believe, YATA. All seem to be variations of a very very old revision control data structure named "weave"[w].

Recently I improved CT to the degree that warranted a new algorithm name (DISCONT [d]). Fundamentally the same, but much cheaper. Probably, we should see all these "inventions" as improvements. All the Computer Science basics seem to have been invented in the 70s, 80s the latest.

[w]: https://docs.rs/weave/latest/weave/

[r]: https://github.com/gritzko/librdx

[d]: https://github.com/gritzko/go-rdx/blob/main/DISCOUNT.md

[h]: https://www.inkandswitch.com/keyhive/notebook/05/

[c]: https://dl.acm.org/doi/10.1145/1832772.1832777

[a]: https://pages.lip6.fr/Marc.Shapiro/papers/RR-7687.pdf links to the authors of RGA

I have a related cryptosystem that I came up with, but is so obvious I'm sure someone else has invented it first. The idea is to back up a file like so: first, do a rolling-hash based chunking, then encrypt each chunk where the key is the hash of that chunk. Then, upload the chunks to the server, along with a file (encrypted by your personal key) that contains the information needed to decrypt each chunk and reassemble them. If multiple users used this strategy, any files they have in common would result in the same chunks being uploaded. This would let the server provider deduplicate those files (saving space), without giving the server provider the ability to read the files. (Unless they already know exactly which file they're looking for, and just want to test whether you're storing it.)

Tangent: why is it that downloading a large file is such a bad experience on the internet? If you lose internet halfway through, the connection is closed and you're just screwed. I don't think it should be a requirement, but it would be nice if there was some protocol understood by browsers and web servers that would be able to break-up and re-assemble a download request into a prolly tree, so I could pick up downloading where I left off, or only download what changed since the last time I downloaded something.

I never went to high school or college or anything.

I can't tell you how many times I come up with something, only to discover years later that someone else came up with the same idea later (or sometimes earlier), branded it, and marketed it.

Is there a way to search for a structure by properties? E.g. O(1) lookups, O(log(n)) inserts or better, navigates like a tree (just making this up), etc?

It's almost a pity computers are as fast as they are and they are so rarely needed because having "arrays" and "maps/dicts/associative arrays/whatever" solves so many problems so much faster than we need anyhow. I don't get to pull out the bag of tricks very often. But then again, when I do, it's because it's a life saver and the difference between success and failure, so maybe it all balances out.

Googling "Prolly Trees", there's not much and this article is one of the top results.