Rust Snapshot Generator

[tisonkun]

This issue supersedes #10 to squash the historical discussion.

Currently, the C++/Go/Java implementations of DataSketches provide snapshot generators for sketches' serialization data.

You can check the following scripts for how their snapshots get generated:

• https://github.com/apache/datasketches-tck/blob/d363b12d/serialization/cpp/generator.py
• https://github.com/apache/datasketches-tck/blob/d363b12d/serialization/go/generator.py
• https://github.com/apache/datasketches-tck/blob/d363b12d/serialization/java/generator.py

We may provide a binary in datasketches-rust as well to generate snapshots for supported sketches' serialization data.

I can imagine it as a local workspace member depending on datasketches and we will have a cargo x task to invoke the generator for automation. Or else, being part of the serde_tests but write the Rust sketch's serialization data to a specific location.

[tomatotomata]

I was thinking of keeping this as a small workspace member under xtask that depends on datasketches, writes deterministic per-sketch snapshots into a dedicated output directory, and exposes one cargo x entry point for the existing serialization workflow. I would mirror the TCK generators only for the sketches currently covered by serde_tests, add a focused CLI test, and keep generated files out of Git as the contributor guide describes. Does that scope fit the intended first step for #176?

[tisonkun]

@tomatotomata Please go ahead. While I don't think it would be a "small workspace member under xtask", but a workspace member at the same level to datasketches, depending on datasketches and being called by xtask via cargo comands, you can submit a PR so that our discussion would be more concrete.