# napi-rs
> This project was initialized from [xray](https://github.com/atom/xray)
A framework for building compiled `Node.js` add-ons in `Rust` via Node-API. Website: https://napi.rs
<p>
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<a href="https://docs.rs/crate/napi"><img src="https://docs.rs/napi/badge.svg"></img></a>
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## Sponsors
## Platform Support
[](https://github.com/napi-rs/napi-rs/actions/workflows/test-release.yaml)
[](https://github.com/napi-rs/napi-rs/actions/workflows/asan.yml)
[](https://github.com/napi-rs/napi-rs/actions/workflows/memory-test.yml)
## MSRV
**Rust** `1.88.0`
| 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 arm muslebihf | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Linux powerpc64le gnu | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Linux s390x gnu | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Linux loong64 gnu | N/A | N/A | N/A | ✓ | ✓ | ✓ |
| Linux riscv64 gnu | N/A | N/A | ✓ | ✓ | ✓ | ✓ |
| Linux aarch64 android | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Linux armv7 android | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| FreeBSD x64 | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
This library depends on Node-API and requires `Node@10.0.0` or later.
We already have some packages written by `napi-rs`: [node-rs](https://github.com/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](https://github.com/napi-rs/package-template) to play with `napi-rs`
### Define JavaScript functions
```rust
use napi::bindgen_prelude::*;
use napi_derive::napi;
/// module registration is done by the runtime, no need to explicitly do it now.
#[napi]
pub 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]
pub fn get_cwd<T: Fn(String) -> Result<()>>(callback: T) {
callback(
std::env::current_dir()
.unwrap()
.to_string_lossy()
.to_string(),
)
.unwrap();
}
/// or, define the callback signature in where clause
#[napi]
pub fn test_callback<T>(callback: T) -> Result<()>
where
T: Fn(String) -> Result<()>,
{
callback(std::env::current_dir()?.to_string_lossy().to_string())
}
/// async fn, require `async` feature enabled.
/// [dependencies]
/// napi = {version="2", features=["async"]}
#[napi]
pub async fn read_file_async(path: String) -> Result<Buffer> {
Ok(tokio::fs::read(path).await?.into())
}
```
### Custom async runtimes
Enable `async-runtime` to route generated async exports through an addon-provided scheduler without
requiring Tokio:
```toml
[dependencies]
napi = { version = "4", default-features = false, features = ["napi4", "async-runtime"] }
```
Implement the unsafe `AsyncRuntime` contract and register one dormant backend from module
initialization:
```rust
use napi::bindgen_prelude::{register_async_runtime, AsyncRuntime};
use napi_derive::module_init;
#[module_init]
fn init() {
register_async_runtime(MyRuntime::new_dormant());
}
```
Create threads and active scheduler resources in `AsyncRuntime::start`, not in the constructor, and
fully quiesce them in `AsyncRuntime::shutdown`. The backend is reused across worker and renderer
reloads, and its `Drop` implementation is not guaranteed to run. The trait documentation defines
the task ownership, cancellation, guard, panic, and native-image unload-safety requirements.
Submission hooks return `AsyncRuntimeRejection::new(work, error)` when they decline ownership, and
the fallible `block_on` / `enter` hooks return backend-specific errors directly.
napi automatically starts the backend for the first live Node environment and shuts it down after
the last environment exits. Embedders and tests can use `try_start_async_runtime` and
`try_shutdown_async_runtime` for explicit lifecycle control; an explicit shutdown remains in
effect until an explicit start. See the
[complete custom-runtime example](https://github.com/napi-rs/napi-rs/tree/main/examples/custom-async-runtime)
for a scheduler implementation, blocking work, cancellation, reloads, and feature-unified builds.
For the coordinated v4 release, upgrade `napi` before `napi-derive`. Derive v3 remains compatible
with runtime v4 during migration, but does not gain v4 borrow and construction guarantees.
Specifically, napi-derive 3.5.9 synchronous `#[napi(async_runtime)]` guards use the established
Tokio compatibility entry point when `async-runtime` and `tokio_rt` are both enabled, even if a
custom backend was selected; legacy generated async exports still use that selected backend. Use a
pure `async-runtime` build or upgrade to derive v4 when synchronous custom-runtime entry is
required. Derive v4 intentionally requires runtime v4 and uses the versioned selected-runtime
codegen contract.
more examples at [examples](./examples/napi)
## 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.
```toml
[package]
name = "awesome"
[lib]
crate-type = ["cdylib"]
[dependencies]
napi = "4"
napi-derive = "4"
[build-dependencies]
napi-build = "1"
```
And create `build.rs` in your own project:
```rust
// 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 `@napi-rs/cli` as a local development dependency to build the Rust crate and copy its dynamic library to a loadable `.node` file.
```js
{
"name": "awesome-package",
"devDependencies": {
"@napi-rs/cli": "^3.0.0"
},
"napi": {
"binaryName": "jarvis"
},
"scripts": {
"build": "napi build --release",
"build:debug": "napi build"
}
}
```
Then you can require your native binding:
```js
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:
```bash
napi build [--release] ./dll
napi build [--release] ./artifacts
```
There are [documents](./cli) 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:
```sh
yarn build:test
yarn test
```
## Related projects
- [neon](https://www.neon-bindings.com)
- [node-bindgen](https://github.com/infinyon/node-bindgen)
## Features table
| 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 |
| OsString/&'a OsStr | String | 1 | v8.0.0 |
| PathBuf/&'a Path | 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<any> | 1 | v8.0.0 |
| Vec<T> | Array<T> | 1 | v8.0.0 |
| Buffer | Buffer | 1 | v8.0.0 |
| External<T> | External<T> | 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<T> | Function | 1 | v8.0.0 |
| Async/Future | Promise<T> | 4 | v10.6.0 | async or async-runtime |
| AsyncTask | Promise<T> | 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 |