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export type Deferred<T = any, R = Error> = {  promise: Promise<T>;  resolve: (t?: T) => void;  reject: (r?: R) => void;  readonly handled: boolean;};
/** Create deferred promise that can be resolved and rejected by outside */export function defer<T>(): Deferred<T> {  let handled = false,    resolve,    reject;
  const promise = new Promise<T>((res, rej) => {    resolve = r => {      handled = true;      res(r);    };    reject = r => {      handled = true;      rej(r);    };  });
  return {    promise,    resolve,    reject,
    get handled() {      return handled;    }  };}
export class DeferredStack<T> {  private _array: Array<T>;  private _queue: Array<Deferred>;
  constructor(ls?: Iterable<T>) {    this._array = ls ? [...ls] : [];    this._queue = [];  }
  async pop(): Promise<T> {    if (this._array.length > 0) {      return this._array.pop();    }    const d = defer();    this._queue.push(d);    await d.promise;    return this._array.pop();  }
  push(value: T): void {    this._array.push(value);    if (this._queue.length > 0) {      const d = this._queue.shift();      d.resolve();    }  }
  get size(): number {    return this._array.length;  }}