three
Version:
JavaScript 3D library
166 lines (120 loc) • 3.03 kB
JavaScript
/**
* A simple pool for managing Web Workers.
*/
export class WorkerPool {
/**
* Constructs a new Worker pool.
*
* @param {number} [pool=4] - The size of the pool.
*/
constructor( pool = 4 ) {
/**
* The size of the pool.
*
* @type {number}
* @default 4
*/
this.pool = pool;
/**
* A message queue.
*
* @type {Array<Object>}
*/
this.queue = [];
/**
* An array of Workers.
*
* @type {Array<Worker>}
*/
this.workers = [];
/**
* An array with resolve functions for messages.
*
* @type {Array<Function>}
*/
this.workersResolve = [];
/**
* The current worker status.
*
* @type {number}
*/
this.workerStatus = 0;
/**
* A factory function for creating workers.
*
* @type {?Function}
*/
this.workerCreator = null;
}
_initWorker( workerId ) {
if ( ! this.workers[ workerId ] ) {
const worker = this.workerCreator();
worker.addEventListener( 'message', this._onMessage.bind( this, workerId ) );
this.workers[ workerId ] = worker;
}
}
_getIdleWorker() {
for ( let i = 0; i < this.pool; i ++ )
if ( ! ( this.workerStatus & ( 1 << i ) ) ) return i;
return - 1;
}
_onMessage( workerId, msg ) {
const resolve = this.workersResolve[ workerId ];
resolve && resolve( msg );
if ( this.queue.length ) {
const { resolve, msg, transfer } = this.queue.shift();
this.workersResolve[ workerId ] = resolve;
this.workers[ workerId ].postMessage( msg, transfer );
} else {
this.workerStatus ^= 1 << workerId;
}
}
/**
* Sets a function that is responsible for creating Workers.
*
* @param {Function} workerCreator - The worker creator function.
*/
setWorkerCreator( workerCreator ) {
this.workerCreator = workerCreator;
}
/**
* Sets the Worker limit
*
* @param {number} pool - The size of the pool.
*/
setWorkerLimit( pool ) {
this.pool = pool;
}
/**
* Post a message to an idle Worker. If no Worker is available,
* the message is pushed into a message queue for later processing.
*
* @param {Object} msg - The message.
* @param {Array<ArrayBuffer>} transfer - An array with array buffers for data transfer.
* @return {Promise} A Promise that resolves when the message has been processed.
*/
postMessage( msg, transfer ) {
return new Promise( ( resolve ) => {
const workerId = this._getIdleWorker();
if ( workerId !== - 1 ) {
this._initWorker( workerId );
this.workerStatus |= 1 << workerId;
this.workersResolve[ workerId ] = resolve;
this.workers[ workerId ].postMessage( msg, transfer );
} else {
this.queue.push( { resolve, msg, transfer } );
}
} );
}
/**
* Terminates all Workers of this pool. Call this method whenever this
* Worker pool is no longer used in your app.
*/
dispose() {
this.workers.forEach( ( worker ) => worker.terminate() );
this.workersResolve.length = 0;
this.workers.length = 0;
this.queue.length = 0;
this.workerStatus = 0;
}
}