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import { Deferred, deferred } from "./deps.ts";
/** * An event object. Not thread-safe. * * An event can be used to notify multiple tasks that some event has happend. */export class Event {  #waiter: Deferred<void> | null;
  constructor() {    this.#waiter = deferred();  }
  /**   * Wait until the event is set.   *   * If the event is set, return `true` immediately.   * Otherwise block until another task calls `set()`.   */  async wait(): Promise<true> {    if (this.#waiter) {      await this.#waiter;    }    return true;  }
  /**   * Set the event.   *   * All tasks waiting for event to be set will be immediately awakened.   */  set(): void {    if (this.#waiter) {      this.#waiter.resolve();      this.#waiter = null;    }  }
  /**   * Clear (unset) the event.   *   * Tasks awaiting on `wait()` will now block until the `set()` method is called again.   */  clear(): void {    if (!this.#waiter) {      this.#waiter = deferred();    }  }
  /**   * Return `true` if the event is set.   */  is_set(): boolean {    return !this.#waiter;  }}