A pure javascript shim for WASI

Implementation status: A subset of wasi_snapshot_preview1 is implemented. The rest either throws an exception, returns an error or is incorrectly implemented.

Usage

npm install @bjorn3/browser_wasi_shim --save

import { WASI, File, OpenFile, PreopenDirectory } from "@bjorn3/browser_wasi_shim";

let args = ["bin", "arg1", "arg2"];
let env = ["FOO=bar"];
let fds = [
    new OpenFile(new File([])), // stdin
    new OpenFile(new File([])), // stdout
    new OpenFile(new File([])), // stderr
    new PreopenDirectory(".", {
        "example.c": new File(new TextEncoder("utf-8").encode(`#include "a"`)),
        "hello.rs": new File(new TextEncoder("utf-8").encode(`fn main() { println!("Hello World!"); }`)),
    }),
];
let wasi = new WASI(args, env, fds);

let wasm = await WebAssembly.compileStreaming(fetch("bin.wasm"));
let inst = await WebAssembly.instantiate(wasm, {
    "wasi_snapshot_preview1": wasi.wasiImport,
});
wasi.start(inst);

Building

$ npm install
$ npm run build

Running tests

This project uses playwright to run tests in a browser using WebAssembly built from the Wasmtime project.

To clone wasmtime and build the test WebAssembly, run:

$ npm test:build

Once the WebAssembly is built, you can run the tests with:

$ npm test

Running the demo

The demo requires the wasm rustc artifacts and the xterm js package. To get them run:

$ git submodule update --init
$ cd examples && npm install

Run the demo with a static web server from the root of this project:

$ npx http-server

And visit http://127.0.0.1:8080/examples/rustc.html in your browser.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be dual licensed as above, without any additional terms or conditions.