What's this?

ES2017 Atomics and SharedArrayBuffer based Semaphore for WebWorker.

Current works on Google Chrome Canary only.

If you don't know about SharedArrayBuffer and Atomics,
Following pages explain what, how, why.

• Shared Memory and Atomics.
• ECMAScript Shared Memory and Atomics

Install

npm install shared-semaphore

Usage

In main thred,

const MAX_WORKERS = 10;
const workers = [];
const semaphore = new Semaphore(2);

for (let i = 0; i < MAX_WORKERS; i++) {
  workers.push(new Worker('worker.js'));
}

workers.forEach(worker => worker.postMessage({shared: semaphore.shared}));

In worker thread.

importScripts('semaphore.js');

self.addEventListener('message', function(e) {
  const {shared} = e.data;
  const semaphore = Semaphore.fromShared(shared, 2);
  
  console.log('foo');
  console.log('foobar');
  console.log('foobarbaz');

  semaphore.signal();
}, false);

API

Semaphore

Semaphore(allowedSectionCount, opt_sharedArray): Semaphore

Instantiate Semaphore.
If opt_sharedArray is passed, this semaphore constructed from that SharedArrayBuffer.

args

• allowedSectionCount: The number which allowed to enter critical section,
• opt_sharedArray: Optional SharedArrayBuffer.

Semaphore.fromShared(sharedArray: SharedArrayBuffer, allowedSectionCount: number): Semaphore

Create Semaphore instance from existing SharedArrayBuffer.

args

• sharedArray: Constructed SharedArrayBuffer.
• allowedSectionCount: The number which allowed to enter critical section.

get Semaphore#shared(): SharedArrayBuffer

Return SharedArrayBuffer.
This method often used in main thread.

Semaphore#signal()

Release occupied section.

Mutex

inherit Semaphore

Mutex(opt_sharedArray): Mutex

Instantiate Mutex.
If opt_sharedArray is passed, this mutex constructed from that SharedArrayBuffer.

args

• opt_sharedArray: Optional SharedArrayBuffer.

Mutex.fromShared(sharedArray: SharedArrayBuffer): Mutex

Create Mutex instance from existing SharedArrayBuffer.