denoland / deno_bindgen

deno_bindgen

This tool aims to simplify glue code generation for Deno FFI libraries written in Rust.

QuickStart

Annotate on top of Rust fn, struct and enum to make them avaiable to Deno.

// add.rs
use deno_bindgen::deno_bindgen;

#[deno_bindgen]
pub struct Input {
  a: i32,
  b: i32,
}

#[deno_bindgen]
fn add(input: Input) -> i32 {
  input.a + input.b
}

Invoke the CLI to compile and generate bindings:

$ deno_bindgen

And finally import the generated bindings in your JS

// add.ts
import { add } from "./bindings/bindings.ts";

add({ a: 1, b: 2 }); // 3

Installation

• Install the deno_bindgen CLI with Deno.

deno install -Afq -n deno_bindgen https://deno.land/x/deno_bindgen/cli.ts

Add the following dependencies to your crate.

# Cargo.toml
[dependencies]
deno_bindgen = "0.7.0"
serde = { version = "1", features = ["derive"] }

Change your crate-type to cdylib and set your package name as well.

[lib]
name = "___"
crate-type = ["cdylib"]

Bindings

Put #[deno_bindgen] on top of a "serde-deriavable" struct, enum or fn.

struct (named fields)

These transform into Typescript types.

// lib.rs
#[deno_bindgen]
pub struct A {
  b: Vec<Vec<String>>,
}

becomes:

// bindings/bindings.ts
export type A = {
  b: Array<Array<string>>;
};

enum

Enums become type unions in Typescript.

#[deno_bindgen]
pub enum Event {
  Quit,
  MouseMove {
    x: i32,
    y: i32,
  }
}

becomes:

export type Enum =
  | "quit"
  | {
    mouse_move: {
      x: number;
      y: number;
    };
  };

fn

Functions are exposed through the FFI boundaries.

#[deno_bindgen]
fn greet(name: &str) {
  println!("Hello, {}!", name);
}

becomes:

export function greet(name: string) {
  // ... glue code for calling the
  // symbol.
}

Notes

• Use #[deno_bindgen(non_blocking)] attribute to call symbol without blocking JS event loop. Exposed as an async funtion from bindings.

• Rust doc comments transform to JS docs.

  #[deno_bindgen]
  pub struct Me {
    /// My name...
    /// ...it is
    name: String,
  }

  becomes:

  export type Me = {
    /**
     * My name...
     * ...it is
     */
    name: string;
  };

• If the argument type of Rust is f32, the calculation result may be different.
  Number in Java Script is float64, when data is passed to Rust, it becomes float32, so the number may change.
  e.g: 1.3 + 1.5 will be 2.799999952316284

CLI

The deno_bindgen CLI tool provides the following flags:

• Pass --release to create a release build.

• --release=URL will load library artifacts from a remote location. This is useful for updating bindings for end users after a release:

  deno_bindgen --release=https://github.com/littledivy/deno_sdl2/releases/download/0.2-alpha.1

  Under the hood this uses x/plug to fetch and cache the artifact.

  Artifacts must be following the remote asset naming scheme, as follows:

  OS	Arch	Naming
  Windows	x86_64	name.dll
  Linux	x86_64	libname.so
  MacOS	x86_64	libname.dylib
  MacOS	arm64	libname_arm64.dylib

• Flags after -- will be passed to cargo build. Example:

  deno_bindgen -- --features "cool_stuff"