napi-rs

This project was initialized from xray

A minimal library for building compiled Node.js add-ons in Rust.

Platform Support

This library depends on N-API and requires [email protected] or later.

We already have some packages written by napi-rs: node-rs

One nice feature is that this crate allows you to build add-ons purely with the Rust/JavaScript toolchain and without involving node-gyp.

Taste

You can start from package-template to play with napi-rs

Define JavaScript functions

#[js_function(1)] // ------> arguments length
fn fibonacci(ctx: CallContext) -> Result<JsNumber> {
  let n = ctx.get::<JsNumber>(0)?.try_into()?;
  ctx.env.create_int64(fibonacci_native(n))
}

#[inline(always)]
fn fibonacci_native(n: i64) -> i64 {
  match n {
    1 | 2 => 1,
    _ => fibonacci_native(n - 1) + fibonacci_native(n - 2),
  }
}

Register module

#[macro_use]
extern crate napi_derive;

use napi::{JsObject, Result};

/// `exports` is `module.exports` object in NodeJS
#[module_exports]
fn init(mut exports: JsObject) -> Result<()> {
  exports.create_named_method("fibonacci", fibonacci)?;
  Ok(())
}

And you can also create JavaScript value while registering module:

#[macro_use]
extern crate napi_derive;

use napi::{JsObject, Result, Env};

#[module_exports]
fn init(mut exports: JsObject, env: Env) -> Result<()> {
  exports.create_named_method("fibonacci", fibonacci)?;
  exports.set_named_property("DEFAULT_VALUE", env.create_int64(100)?)?;
  Ok(())
}

Building

This repository is a Cargo crate. Any napi-based add-on should contain Cargo.toml to make it a Cargo crate.

In your Cargo.toml you need to set the crate-type to "cdylib" so that cargo builds a C-style shared library that can be dynamically loaded by the Node executable. You'll also need to add this crate as a dependency.

[package]
name = "awesome"

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

[dependencies]
napi = "1"
napi-derive = "1"

[build-dependencies]
napi-build = "1"

And create build.rs in your own project:

// build.rs
extern crate napi_build;

fn main() {
  napi_build::setup();
}

So far, the napi build script has only been tested on macOS Linux Windows x64 MSVC and FreeBSD.

See the included test_module for an example add-on.

Install the @napi-rs/cli to help you build your Rust codes and copy Dynamic lib file to .node file in case you can require it in your program.

{
  "package": "awesome-package",
  "devDependencies": {
    "@napi-rs/cli": "^1.0.0"
  },
  "napi": {
    "name": "jarvis" // <----------- Config the name of native addon, or the napi command will use the name of `Cargo.toml` for the binary file name.
  },
  "scripts": {
    "build": "napi build --release",
    "build:debug": "napi build"
  }
}

Then you can require your native binding:

require('./jarvis.node')

The module_name would be your package name in your Cargo.toml.

xxx => ./xxx.node

xxx-yyy => ./xxx_yyy.node

You can also copy Dynamic lib file to an appointed location:

napi build [--release] ./dll
napi build [--release] ./artifacts

There are documents which contains more details about the @napi-rs/cli usage.

Testing

Because libraries that depend on this crate must be loaded into a Node executable in order to resolve symbols, all tests are written in JavaScript in the test_module subdirectory.

To run tests:

yarn build:test
yarn test

Features table

Create JavaScript values

I have no plan to implement nape_type_tag and related API in napi-rs, because we have implemented a rust replacement in TaggedObject which is more convenient and more compatible.

Functions to convert from N-API to C types

Working with JavaScript Values and Abstract Operations