Rust + Wasm + Threads

A Field Report

1

Rust + Wasm + Threads

A Field Report

Our Quirky Wasm + Threads
use case

2

Hello, I’m Roberto

I work at StackBlitz

Been doing Rust and Wasm for a while

Somewhat involved, pandemic permitting

@_rvidal

jrvidal

3

StackBlitz

"Online IDE"

take #1: thin clients
- 👩‍💻 🪟 . . . . . . .
take #2: playgrounds
- 👩‍💻 🪟 . . . . . . 🪟
take #3: ???
- 👩‍💻 🪟 . . . . . . 🙃

4

it is possible, however unlikely, that
they might find a weakness and exploit it.
xxxxx

5

it is possible, however unlikely, that
they might find a weakness and exploit it.
build a full development runtime in the browser.

6

it is possible, however unlikely, that
they might find a weakness and exploit it.
build a full development runtime in the browser.

7

Possible

Web Workers

SharedArrayBuffer

ServiceWorkers

8

Practical

Restricted to JS code (for now)

9

Practical

Restricted to JS code (for now)
And, yes… uses WebAssembly

10

Field Report

11

Field Report: boring!

thread_local! {
  static CWD: RefCell<Cwd> = RefCell::new(Cwd { path: PathBuf::from("/") });

  static CONTROLLING_TTY: RefCell<Option<Dirent>> = RefCell::new(None);
}

use parking_lot::Mutex;
use once_cell::sync::Lazy;

static TTY_OUTPUT: Lazy<Mutex<TTYOutputMap>> = Lazy::new(Default::default);

12

Field Report: boring!

use wasm_bindgen_futures::spawn_local;

pub fn create_tty(output_callback: js_sys::Function) -> Result<JsValue, JsValue> {
  // ...

  let output_listener = TTYOutputListener(output_callback);

  spawn_local(async move {
    output_receiver.receiver
      .for_each(|data| {
        output_listener.on_message(data);

        async {}
      })
      .await
  });

  // ...
}