https://github.com/travisbrown/rust-jvm-demo
Rust on the JVM
https://github.com/travisbrown/rust-jvm-demo
Last synced: 10 months ago
JSON representation
Rust on the JVM
- Host: GitHub
- URL: https://github.com/travisbrown/rust-jvm-demo
- Owner: travisbrown
- Created: 2021-05-12T12:13:29.000Z (about 5 years ago)
- Default Branch: main
- Last Pushed: 2021-05-16T14:34:44.000Z (about 5 years ago)
- Last Synced: 2025-08-10T19:15:54.626Z (12 months ago)
- Language: Scala
- Size: 83 KB
- Stars: 6
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Rust on the JVM
[](https://github.com/travisbrown/rust-jvm-demo/actions)
## Motivation
This repository is a quick self-contained experiment I put together to check the feasibility of
publishing build tools written in Rust for use in pure JVM contexts.
I'm working on a parser generator that can output (among other things) Java and Scala code
(specifically a parser for the provided grammar implemented in Java, and a safe wrapper, ScalaCheck
instances, etc. in Scala). The parser generator is implemented in Rust, but ideally I'd want to be
able to publish it as a pure JVM library and sbt plugin that wouldn't require the user to have any
Rust tooling installed or to have to worry about platform-specific issues.
## This demo
This project includes implementations of two simple operations in Rust and Scala:
* Parse an arbitrary JSON document and return all strings that look like URLs as a JSON array.
* Parse an arbitrary JSON document and count all scalar values.
The Rust implementation uses [Serde](https://docs.serde.rs/serde_json/) and the Scala implementation uses [Circe](https://github.com/circe/circe).
I've [compiled the Rust implementations into WASM](https://rustwasm.github.io/docs/book/)
and then the WASM into JVM bytecode with a modified version of [Asmble](https://github.com/cretz/asmble)
(which unfortunately isn't currently maintained). The resulting jar is available in the `lib/` directory, and is currently only 36K.
There are tests and [JMH](https://openjdk.java.net/projects/code-tools/jmh/) benchmarks for the two implementations on the JVM.
These operations don't exactly match my actual use case, but they're close:
in both cases I'm parsing small documents in Rust, using "real" Rust libraries, doing some work, and generating new documents as output.
## Results
There's currently some unpleasant code on both the Rust and Scala sides that's needed to get strings back and forth,
but it's fairly generic and could probably mostly be moved into the WASM-to-JVM tooling.
Performance doesn't matter much for my actual use case, but I wanted to be sure it wasn't excessively bad,
and it looks okay (definitely better than I expected):
```
Benchmark Mode Cnt Score Error Units
ExtractUrlsBench.circe thrpt 20 51351.757 ± 749.093 ops/s
ExtractUrlsBench.serde thrpt 20 14380.148 ± 30.884 ops/s
CountScalarValuesBench.circe thrpt 20 57325.181 ± 2662.133 ops/s
CountScalarValuesBench.serde thrpt 20 16471.974 ± 345.556 ops/s
```
Warning: this code is terrible and this approach might not end up working at all.