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/** @ignore */export interface Deferred<T> {  promise: Promise<T>;  resolve: (t?: T) => void;  reject: (e?: any) => void;}
/** @ignore */export interface DeferredStackItemCreator<T> {  (): Promise<T>;}
/** @ignore */export function defer<T>(): Deferred<T> {  let reject, resolve;  const promise = new Promise<T>((res, rej) => {    resolve = res;    reject = rej;  });  return {    promise,    reject,    resolve  };}
/** @ignore */export class DeferredStack<T> {  private _queue: Deferred<T>[] = [];  private _size = 0;  constructor(    readonly max: number,    private _array: T[] = [],    private readonly create: DeferredStackItemCreator<T>  ) {    this._size = _array.length;  }
  get size(): number {    return this._size;  }
  get length(): number {    return this._array.length;  }
  async pop(): Promise<T> {    if (this._array.length) {      return this._array.pop();    } else if (this._size < this.max) {      this._size++;      const item = await this.create();      return item;    }    const d = defer<T>();    this._queue.push(d);    await d.promise;    return this._array.pop();  }
  async push(item: T) {    this._array.push(item);    if (this._queue.length) {      this._queue.shift().resolve();    }  }
  reduceSize() {    this._size--;  }}