Semaphore

A semaphore designed for multi-threaded browser environments.

npm install @mogoe1/semaphore (we are not on npm yet)

npm install --save git+https://github.com/mogoe1/semaphore.git

• The implementation relies on SharedArrayBuffers. Make sure your site meets the security requirements.
• The implementation relies on Atomics.waitAsync which is implemented by v8 but not documented at mdn yet. You might want to proivide a polyfill.

The following example shows how a samaphore can be used to make sure only one thrad at a time has access to a shared ressource.

// file: main.js
import { Semaphore } from "@mogoe1/semaphore";

const sem = Semaphore.createWithCapacity(1);
const worker = new Worker("worker.js", {type: "module"});

worker.postMessage(sem.buffer);

sem.acquireAsync(1).then(_=>{
    // exclusive access to resource
    sem.release(1);
});

// file: worker.js
import { Semaphore } from "@mogoe1/semaphore";

self.addEventListener("message", message => {
    const buffer = message.data;
    const sem = new Semaphore(new Int32Array(buffer));
    sem.acquire(1); // this blocks the worker thread untill one permit is acquired!
    // exclusive access to resource
    sem.release(1);
});

Docs are availabe at https://mogoe1.github.io/semaphore/index.html.