napi-rs

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Platform Support

Operating Systems

NodeJS

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

This library depends on N-API and requires Node 8.9 or later. It is still pretty raw and has not been tested in a production setting.

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

Taste

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

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

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.

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

[dependencies]
napi-rs = "0.1"

[build-dependencies]
napi-build = "0.1"

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 and Windows x64 MSVC.

See the included test_module for an example add-on.

Run cargo build to produce the Dynamic lib file. And install the napi-rs to help you copy Dynamic lib file to .node file in case you can require it in your program.

{
  "package": "your pkg",
  "dependencies": {
    "napi-rs": "^0.1"
  },
  "scripts": {
    "build": "cargo build && napi",
    "build-release": "cargo build --release && napi --release"
  }
}

Then you can require your native binding:

require('./target/debug|release/[module_name].node')

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

xxx => ./target/debug|release/xxx.node

xxx-yyy => ./target/debug|release/xxx_yyy.node

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

napi [--release] .
napi [--release] ./mylib
napi [--release] ./mylib.node

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:

cd test_module
npm run build
npm test

Features table

Create JavaScript values

Functions to convert from N-API to C types

Working with JavaScript Values and Abstract Operations