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Interoptopus

C#, Python, C, ... → 🐙 → 🦀

FFI from your favorite language to Rust. Escape hatchets included. 🪓

Overview

If you ...

• are about to write an extern "C" API in Rust,
• need C#, Python, C, ... bindings to your library,
• prefer having fine-grained-control over your API and interop generation,
• would like to use quality-of-life patterns on both sides (e.g., options, slices, 'classes') where feasible,
• might need to swiftly support a new language,
• think your FFI single source of truth should be living Rust code,

... then Interoptopus might be for you.

Known Limitations

• not yet used in production
• a bit verbose if you don't own your types (still possible, just more work)
• if you target only a single language and don't care about your FFI layer other solutions might be better

Rust Code You Write

This is code you would write:

```rust use interoptopus::{ffifunction, ffitype};

[ffi_type]

[repr(C)]

pub struct Vec3 { pub x: f32, pub y: f32, pub z: f32, }

[ffi_function]

[no_mangle]

pub extern "C" fn my_function(input: Vec3) -> Vec3 { Vec3 { x: 2.0, y: 4.0, z: input.z } }

interoptopus::inventoryfunction!(ffiinventory, [], [my_function], []); ```

Generated Code

Once you've written the code above you use one of these backends to generate interop code:

| Language | Crate | Sample Output | | --- | --- | --- | | C# (incl. Unity) | interoptopusbackendcsharp | Interop.cs | | C | interoptopusbackendc | myheader.h | | Python CFFI | interoptopusbackendcpythoncffi | reference.py | | Your language | Write your own backend! | - |

Features

See the reference project lists all supported constructs including: - functions (extern "C" functions and delegates) - types (primitives, composite, enums (numeric only), opaques, references, pointers, ...) - constants (primitive constants; results of const evaluation) - patterns (ASCII pointers, options, slices, classes, ...)

As a rule of thumb we recommend to be slightly conservative with your signatures and always "think C", since other languages don't track lifetimes well and it's is easy to accidentally pass an outlived pointer or doubly alias a &mut X on reentrant functions.

Current Status

• June 20, 2021 - Alpha. Has generated simple working<sup>TM</sup> bindings for a few projects for a week now, many things missing.
• June 13, 2021 - Pre-alpha. Has generated C#, C, Python-CFFI bindings at least once, many things missing, untested.

FAQ

• FAQ and Safety Guides.

Contributing

PRs are welcome.

• Bug fixes can be submitted directly. Major changes should be filed as issues first.

• Anything that would make previously working bindings change behavior or stop compiling is a major change; which doesn't mean we're opposed to breaking stuff before 1.0, just that we'd like to talk about it before it happens.

• New features or patterns must be materialized in the reference project and accompanied by an interop test (i.e., a backend test running C# / Python against a DLL invoking that code) in at least one included backend.