node-bindgen
Features
- Easy: Just write idiomatic Rust code, node-bindgen take care of generating Node.js FFI wrapper codes.
- Safe: Node.js arguments are checked automatically based on Rust types.
- Async: Support Async Rust. Async codes are translated into Node.js promises.
- Class: Rust struct can be accessed using Node.js classes.
- Stream: Implement Node.js stream using Rust
- N-API: Use Node.js N-API, which means you don't have to recompile your module.
Compatibility with Node.js version
This project uses the v7 of Node N-API. Please see following compatibility matrix.
Following OS are supported:
- Linux
- MacOs
- Windows
Why node-bindgen?
Writing native node-js requires lots of boilerplate code. Node-bindgen generates external "C" glue code from rust code, including native module registration. node-bindgen make it writing node-js module easy and fun.
Getting started
CLI Installation
Install nj-cli command line, which will be used to generate the native library.
cargo install nj-cli
This is a one time step.
Configuring Cargo.toml
Add two dependencies to your projects' Cargo.toml
.
Add node-bindgen
as a regular dependency (as below):
[dependencies]
node-bindgen = { version = "5.1" }
Then add node-bindgen
's procedure macro to your build-dependencies as below:
[build-dependencies]
node-bindgen = { version = "5.1", features = ["build"] }
Then update crate type to cdylib
to generate node.js compatible native module:
[lib]
crate-type = ["cdylib"]
Finally, add build.rs
at the top of the project with following content:
fn main() {
node_bindgen::build::configure();
}
Example
Here is a function that adds two numbers. Note that you don't need to worry about JS conversion.
use node_bindgen::derive::node_bindgen;
/// add two integer
#[node_bindgen]
fn sum(first: i32, second: i32) -> i32 {
first + second
}
Building native library
To build node.js library, using nj-cli
to build:
nj-cli build
This will generate Node.js module in "./dist" folder.
To build a release version:
nj-cli build --release
./src
for Changes
Watching While developing your native module, you may want to watch for file changes and run a command when a change occurs, for example cargo check
or cargo build
.
For this, we can use nj-cli watch
.
nj-cli watch
installs [if it does not exist] and passes arguments to cargo watch
. By default, nj-cli watch
will run cargo check
against your ./src
files.
To see all available methods for nj-cli watch
, run the following command:
nj-cli watch -- --help
Using in Node.js
Then in the Node.js, rust function can be invoked as normal node.js function:
$ node
Welcome to Node.js v14.0.0.
Type ".help" for more information.
> let addon = require('./dist');
undefined
> addon.sum(2,3)
5
>
Features
Function name or method can be renamed instead of default mapping
#[node_bindgen(name="multiply")]
fn mul(first: i32,second: i32) -> i32 {
first * second
}
Rust function mul is re-mapped as multiply
Optional argument
Argument can be skipped if it is marked as optional
#[node_bindgen]
fn sum(first: i32, second: Option<i32>) -> i32 {
first + second.unwrap_or(0)
}
Then sum can be invoked as
sum(10)
or sum(10,20)
Callback
JS callback are mapped as Rust closure.
#[node_bindgen]
fn hello<F: Fn(String)>(first: f64, second: F) {
let msg = format!("argument is: {}", first);
second(msg);
}
from node:
let addon = require('./dist');
addon.hello(2,function(msg){
assert.equal(msg,"argument is: 2");
console.log(msg); // print out argument is 2
});
Callback are supported in Async rust as well.
Support for Async Rust
Async rust function is mapped to Node.js promise.
use std::time::Duration;
use flv_future_aio::time::sleep;
use node_bindgen::derive::node_bindgen;
#[node_bindgen]
async fn hello(arg: f64) -> f64 {
println!("sleeping");
sleep(Duration::from_secs(1)).await;
println!("woke and adding 10.0");
arg + 10.0
}
let addon = require('./dist');
addon.hello(5).then((val) => {
console.log("future value is %s",val);
});
Struct serialization
Structs, including generic structs, can have have the to-JS conversion boilerplate autogenerated.
Just apply the node_bindgen
macro to your struct:
#[node_bindgen]
struct MyJson {
some_name: String,
a_number: i64
}
#[node_bindgen]
fn my_json() -> MyJson {
MyJson {
some_name: "John".to_owned(),
a_number: 1337
}
}
let addon = require('./dist');
assert.deepStrictEqual(addon.my_json(), {
someName: "John",
aNumber: 1337
});
Note that the fields must implement
node_bindgen::core::TryIntoJs
themselves.
Any references must also implement Clone
.
Field names will be converted to camelCase.
Enums
Enums will also have their JS representation autogenerated with the help of node_bindgen
:
#[node_bindgen]
enum ErrorType {
WithMessage(String, usize),
WithFields {
val: usize
},
UnitErrorType
}
#[node_bindgen]
fn with_message() -> ErrorType {
ErrorType::WithMessage("test".to_owned(), 321)
}
#[node_bindgen]
fn with_fields() -> ErrorType {
ErrorType::WithFields {
val: 123
}
}
#[node_bindgen]
fn with_unit() -> ErrorType {
ErrorType::UnitErrorType
}
assert.deepStrictEqual(addon.withMessage(), {
withMessage: ["test", 321n]
});
assert.deepStrictEqual(addon.withFields(), {
withFields: {
val: 123n
}
});
assert.deepStrictEqual(addon.withUnit(), "UnitErrorType")
Tuple variants will be converted into lists, struct variants converted to objects, and unit variants converted into strings matching the variant's name in PascalCase. Generics and references are supported, with the same caveats as for structs.
JavaScript class
JavaScript class is supported.
struct MyClass {
val: f64,
}
#[node_bindgen]
impl MyClass {
#[node_bindgen(constructor)]
fn new(val: f64) -> Self {
Self { val }
}
#[node_bindgen]
fn plus_one(&self) -> f64 {
self.val + 1.0
}
#[node_bindgen(getter)]
fn value(&self) -> f64 {
self.val
}
}
let addon = require('./dist');
const assert = require('assert');
let obj = new addon.MyObject(10);
assert.equal(obj.value,10,"verify value works");
assert.equal(obj.plusOne(),11);
There are more features in the examples folder.
Windows + Electron Support
When using node-bindgen with electron on Windows, nj-build
must
compile a C++ file, win_delay_load_hook.cc
, and therefore it is required that the development
environment has a valid C/C++ compiler.
If your machine does not have a valid C/C++ compiler, install Microsoft VSCode.
In the future, this file will be re-written in Rust, removing this dependency.
Just make sure that you are compiling the rust module using
$ npx electron-build-env nj-cli build --release
otherwise you will get dreaded A dynamic link library (DLL) initialization routine failed
when importing the rust module in electron
Contributing
If you'd like to contribute to the project, please read our Contributing guide.
License
This project is licensed under the Apache license.