Crate wasi_worker

This crate provides rust library to easily compose WASM/WASI browser service worker.

General overview

ServiceWorker is a singleton which holds input and output file handles and owns worker via Handler trait. Worker is supposedly reactive, usually operating on incoming events (on_message) and posting messages to main browser application via ServiceWorker::post_message().

Example usage:

use wasi_worker::*;
 
struct MyWorker {}
impl Handler for MyWorker {
  fn on_message(&self, msg: &[u8]) -> std::io::Result<()> {
    // Process incoming message
    println!("My Worker got message: {:?}", msg);
    Ok(())
  }
}
 
fn main() {
  // In usual WASI setup with JS glue all output will be posted to /output.bin
  // Though in user filesystem to be able to run from shell we operate under current dir
  #[cfg(target_os="wasi")]
  let opt = ServiceOptions::default();
  #[cfg(not(target_os="wasi"))]
  let opt = ServiceOptions { output: FileOptions::File("./testdata/output.bin".to_string()) };
  let output_file = match &opt.output { FileOptions::File(path) => path.clone() };
  ServiceWorker::initialize(opt)
    .expect("ServiceWorker::initialize");
 
  // Attach Agent to ServiceWorker as message handler singleton
  ServiceWorker::set_message_handler(Box::new(MyWorker {}));
 
  // Send binary message to main browser application
  ServiceWorker::post_message(b"message")
    .expect("ServiceWorker.post_message");
  // It still requires cleanup (TODO impl Drop)
  std::fs::remove_file(output_file)
    .expect("Remove ./testdata/output.bin");
}
 
// this function will be called from worker.js when it receives message
// In the future it will be substituted by poll_oneoff or thread::yield, 
// though currently poll_oneoff does not return control to browser
pub extern "C" fn message_ready() -> usize {
  ServiceWorker::on_message()
    .expect("ServiceWorker.on_message")
}

Structs

ServiceOptions	Options for ServiceWorker
ServiceWorker	Connects Rust Handler with browser service worker via WASI filesystem.

Enums

FileOptions

Instructs on file descriptor configuration for ServiceWorker

Traits

Handler

Handler for incoming messages via ServiceWorker