shared-semaphore

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.