fdds/threadManager.js

   1 'use strict';
   2
   3 const MAX_BATCH_SIZE = 10;
   4 const TIMEOUT_MS = 80;
   5
   6 async function loadImagesInBatches(imageIndex=0, batchSize, imageInfos, worker) {
   7     let batchLimit = Math.min(imageIndex + batchSize, imageInfos.length - 1);
   8     for (imageIndex; imageIndex <= batchLimit; imageIndex++) {
   9         let imageInfo = imageInfos[imageIndex];
  10         worker.postMessage(imageInfo);
  11     }
  12     if (imageIndex < imageInfos.length) {
  13         setTimeout(loadImagesInBatches, TIMEOUT_MS, imageIndex, batchSize, imageInfos, worker);
  14     }
  15 }
  16
  17 export class ThreadManager {
  18     constructor(updateCallback) {
  19         this.updateCallback = updateCallback;
  20         this.N_WORKERS = 2;
  21         if(navigator.userAgent.indexOf("Firefox") != -1 ) {
  22             this.N_WORKERS = 1;
  23         }
  24         this.workers = [];
  25     }
  26
  27     loadImages(loadFirst, loadLater) {
  28         let firstSize = Math.ceil(loadFirst.length / this.N_WORKERS);
  29         let laterSize = Math.ceil(loadLater.length / this.N_WORKERS);
  30         this.cancelCurrentLoad();
  31         for (let i = 0; i < this.N_WORKERS; i++) {
  32             let iFirst = i * firstSize;
  33             let jFirst = Math.min((i+1) * firstSize, loadFirst.length);
  34             let firstBatch = loadFirst.slice(iFirst, jFirst);
  35
  36             let iLater = i * laterSize;
  37             let jLater = Math.min((i+1) * laterSize, loadLater.length);
  38             let laterBatch = loadLater.slice(iLater, jLater);
  39
  40             let worker = this.startThread(firstBatch, laterBatch);
  41             this.workers.push(worker);
  42         }
  43     }
  44
  45     startThread(loadFirst, loadLater) {
  46         let worker = new Worker('imageLoadingWorker.js');
  47         worker.addEventListener('message', async event => {
  48             const imageData = event.data;
  49             this.updateCallback(imageData);
  50         });
  51
  52         let batchSize = Math.min(Math.ceil(loadFirst.length / 20), MAX_BATCH_SIZE);
  53         loadImagesInBatches(0, batchSize, loadFirst, worker);
  54         loadImagesInBatches(0, batchSize, loadLater, worker);
  55
  56         return worker;
  57     }
  58
  59     cancelCurrentLoad() {
  60         for (let worker of this.workers) {
  61             worker.terminate();
  62         }
  63         this.workers = [];
  64     }
  65 }