Rust FFI Example for Java & Python

Example project for sharing logic between Python & Java using rust FFI.

Why?

Python and Java are two popular languages, sometimes we need them to share a common logic, for example calculating some formula or running domain specific algorithm.

FFI has been around for a while but writing C/C++ code considered unsafe, which most of the time is unacceptable on memory managed languages like Python & Java.

Rust comes to the picture with a safe(r) memory management model, with comparable speed to C/C++ that compiles to native shared libraries so we can enjoy both worlds and make Python & Java friends again (not really :).

Getting Started

Dependencies

rustc & cargo nightly (nightly for PyO3)
Python3
Java (1.8+ preferred)
make (for automating commands)

tested on ubuntu-18.04 x64

run these commands:

$ make build
$ make test

now you can just copy the shared libraries from dist/ directory

Project Structure

we got 3 packages on our Cargo workspace:

rs-divider - shared library implementation in rust
rs-divider-java - java bindings for rs-divider
rs-divider-py - python bindings for rs-divider

Project Structure:

.
├── Cargo.lock
├── Cargo.toml          # our workspace, definition of the 3 packages
├── dist/               # contains java & python shared libraries (.so files)
├── Makefile            # for automating build and test tasks
├── rs-divider          # our shared rust lib
│   ├── Cargo.toml
│   └── src
│       └── lib.rs      # our shared rust lib source code
├── rs-divider-java     # java binding to rs-divider
│   ├── Cargo.toml
│   ├── RsDivider.h     # auto generated jni header file. contains the function signature for our lib
│   ├── RsDivider.java  # example main for using our rsdivider lib from java
│   └── src
│       └── lib.rs      # src of the wrapper between java and rust using the `jni` crate
└── rs-divider-py       # python binding to rs-divider
    ├── Cargo.toml
    ├── rsdivider.py    # example main for using rsdivider lib from python
    └── src
        └── lib.rs      # code using `pyo3` crate for wrapping rs-divider as python shared lib

License

MIT & APACHE dual license