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#1362 in WebAssembly

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241,433 downloads per month
Used in 32 crates (via wasm-bindgen-cli-support)

MIT/Apache

24KB
321 lines

wasm-bindgen

Facilitating high-level interactions between Wasm modules and JavaScript.

Build Status Crates.io version Download docs.rs docs

Guide (main branch) | API Docs | Contributing | Chat

Built with 🦀🕸 by The Rust and WebAssembly Working Group

Install wasm-bindgen-cli

You can install it using cargo install:

cargo install wasm-bindgen-cli

Or, you can download it from the release page.

If you have cargo-binstall installed, then you can install the pre-built artifacts by running:

cargo binstall wasm-bindgen-cli

Example

Import JavaScript things into Rust and export Rust things to JavaScript.

use wasm_bindgen::prelude::*;

// Import the `window.alert` function from the Web.
#[wasm_bindgen]
extern "C" {
    fn alert(s: &str);
}

// Export a `greet` function from Rust to JavaScript, that alerts a
// hello message.
#[wasm_bindgen]
pub fn greet(name: &str) {
    alert(&format!("Hello, {}!", name));
}

Use exported Rust things from JavaScript with ECMAScript modules!

import { greet } from "./hello_world";

greet("World!");

Features

  • Lightweight. Only pay for what you use. wasm-bindgen only generates bindings and glue for the JavaScript imports you actually use and Rust functionality that you export. For example, importing and using the document.querySelector method doesn't cause Node.prototype.appendChild or window.alert to be included in the bindings as well.

  • ECMAScript modules. Just import WebAssembly modules the same way you would import JavaScript modules. Future compatible with WebAssembly modules and ECMAScript modules integration.

  • Designed with the "Web IDL bindings" proposal in mind. Eventually, there won't be any JavaScript shims between Rust-generated wasm functions and native DOM methods. Because the wasm functions are statically type checked, some of those native methods' dynamic type checks should become unnecessary, promising to unlock even-faster-than-JavaScript DOM access.

Guide

📚 Read the wasm-bindgen guide here! 📚

You can find general documentation about using Rust and WebAssembly together here.

API Docs

License

This project is licensed under either of

at your option.

Contribution

See the "Contributing" section of the guide for information on hacking on wasm-bindgen!

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


lib.rs:

A tiny and incomplete wasm interpreter

This module contains a tiny and incomplete wasm interpreter built on top of walrus's module structure. Each Interpreter contains some state about the execution of a wasm instance. The "incomplete" part here is related to the fact that this is only used to execute the various descriptor functions for wasm-bindgen.

As a recap, the wasm-bindgen macro generate "descriptor functions" which basically as a mapping of rustc's trait resolution in executable code. This allows us to detect, after the macro is invoke, what trait selection did and what types of functions look like. By executing descriptor functions they'll each invoke a known import (with only one argument) some number of times, which gives us a list of u32 values to then decode.

The interpreter here is only geared towards this one exact use case, so it's quite small and likely not extra-efficient.

Dependencies

~5.5MB
~121K SLoC