napi-rs

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A framework for building compiled Node.js add-ons in Rust via Node-API. Website: https://napi.rs

Platform Support

MSRV

Rust 1.57.0

	node12	node14	node16	node18
Windows x64	✓	✓	✓	✓
Windows x86	✓	✓	✓	✓
Windows arm64	✓	✓	✓	✓
macOS x64	✓	✓	✓	✓
macOS aarch64	✓	✓	✓	✓
Linux x64 gnu	✓	✓	✓	✓
Linux x64 musl	✓	✓	✓	✓
Linux aarch64 gnu	✓	✓	✓	✓
Linux aarch64 musl	✓	✓	✓	✓
Linux arm gnueabihf	✓	✓	✓	✓
Linux aarch64 android	✓	✓	✓	✓
Linux armv7 android	✓	✓	✓	✓
FreeBSD x64	✓	✓	✓	✓

This library depends on Node-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

/// import the preludes
use napi::bindgen_prelude::*;
use napi_derive::napi;

/// module registration is done by the runtime, no need to explicitly do it now.
#[napi]
fn fibonacci(n: u32) -> u32 {
  match n {
    1 | 2 => 1,
    _ => fibonacci(n - 1) + fibonacci(n - 2),
  }
}

/// use `Fn`, `FnMut` or `FnOnce` traits to defined JavaScript callbacks
/// the return type of callbacks can only be `Result`.
#[napi]
fn get_cwd<T: Fn(String) -> Result<()>>(callback: T) {
  callback(env::current_dir().unwrap().to_string_lossy().to_string()).unwrap();
}

/// or, define the callback signature in where clause
#[napi]
fn test_callback<T>(callback: T)
where T: Fn(String) -> Result<()>
{}

/// async fn, require `async` feature enabled.
/// [dependencies]
/// napi = {version="2", features=["async"]}
#[napi]
async fn read_file_async(path: String) -> Result<Buffer> {
  tokio::fs::read(path)
    .map(|r| match r {
      Ok(content) => Ok(content.into()),
      Err(e) => Err(Error::new(
        Status::GenericFailure,
        format!("failed to read file, {}", e),
      )),
    })
    .await
}

more examples at examples

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 = "2"
napi-derive = "2"

[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.

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

Related projects

• neon
• node-bindgen

Features table

Rust Type	Node Type	NAPI Version	Minimal Node version	Enable by napi feature
u32	Number	1	v8.0.0
i32/i64	Number	1	v8.0.0
f64	Number	1	v8.0.0
bool	Boolean	1	v8.0.0
String/&'a str	String	1	v8.0.0
Latin1String	String	1	v8.0.0	latin1
UTF16String	String	1	v8.0.0
Object	Object	1	v8.0.0
serde_json::Map	Object	1	v8.0.0	serde-json
serde_json::Value	any	1	v8.0.0	serde-json
Array	Array	1	v8.0.0
Vec	Array	1	v8.0.0
Buffer	Buffer	1	v8.0.0
External	External	1	v8.0.0
Null	null	1	v8.0.0
Undefined/()	undefined	1	v8.0.0
Result<()>	Error	1	v8.0.0
T: Fn(...) -> Result	Function	1	v8.0.0
Async/Future	Promise	4	v10.6.0	async
AsyncTask	Promise	1	v8.5.0
JsGlobal	global	1	v8.0.0
JsSymbol	Symbol	1	v8.0.0
Int8Array/Uint8Array ...	TypedArray	1	v8.0.0
JsFunction	threadsafe function	4	v10.6.0	napi4
BigInt	BigInt	6	v10.7.0	napi6