1// Copyright (C) 2019 The Android Open Source Project 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14 15import {publishLoading} from '../frontend/publish'; 16import {LoadingTracker} from '../trace_processor/engine'; 17 18// Used to keep track of whether the engine is currently querying. 19export class LoadingManager implements LoadingTracker { 20 private static _instance: LoadingManager; 21 private numQueuedQueries = 0; 22 private numLastUpdate = 0; 23 24 static get getInstance(): LoadingManager { 25 // eslint-disable-next-line @typescript-eslint/strict-boolean-expressions 26 return this._instance || (this._instance = new this()); 27 } 28 29 beginLoading() { 30 this.update(1); 31 } 32 33 endLoading() { 34 this.update(-1); 35 } 36 37 private update(change: number) { 38 this.numQueuedQueries += change; 39 if ( 40 this.numQueuedQueries === 0 || 41 Math.abs(this.numLastUpdate - this.numQueuedQueries) > 2 42 ) { 43 this.numLastUpdate = this.numQueuedQueries; 44 publishLoading(this.numQueuedQueries); 45 } 46 } 47} 48