Racket to Rust

For a small project I was working on, I was looking at Racket to Rust FFI. There’s enough relevant documentation for both languages respective FFI interfaces, but when I first started googling, the only example post I saw was from 2013: Embedding Rust in Racket by John Clements.

Unsurprisingly the racket hasn’t changed, but the rust used in the article is no-longer valid.

If you wanted an example simpler example of FFI valid for current rust, you could use this:

#lang racket

(require ffi/unsafe
         ffi/cvector
         ffi/unsafe/define)


;; Define the C types we will use
(define rust-lib (ffi-lib (build-path (current-directory) "target/debug/librusty411.so")))
(define rust-print (get-ffi-obj "display_string" rust-lib (_fun _bytes _uint -> _void)))


;; Wrap ffi call
(define (call-rust-print str)
  (let* ([str_ptr (string->bytes/utf-8 str)]
        [len (bytes-length str_ptr)])
  (rust-print str_ptr len)))

(module+ main
  (call-rust-print "Hello, from Racket!"))

# Cargo.toml preamble ...
[lib]
crate-type=["cdylib"]

[dependencies]
libc = "0.2.169"
# ...

use libc::c_uint;
use std::slice;
use std::str;

#[no_mangle]
pub extern "C" fn display_string(data: *mut u8, len: c_uint) {
    let len = len as usize;
    let sl = unsafe { slice::from_raw_parts(data, len) };
    let st = str::from_utf8(sl).unwrap();
    println!("{:?}", st);
}

Sadly Racket’s FFI doesn’t make it easy to play with quazi-quoted lists for lots of obvious reasons…