/**
 * Repeatedly calls the given callback for a new Promise, until the provided `stop()` callback is called.
 * Waits to generate each Promise so that only a specified amount run concurrently.
 *
 * The entire Pool can be awaited, and will resolve once the feeder function calls `stop()`, and all pending promises finish.
 *
 * Note that if the feeder function is itself async, it may be called more than once after `stop` is triggered.
 *
 * @param feeder The function that should create and return new Promises. Call the provided `stop()` function to stop the pool.
 * @param concurrent Amount of Promises to run concurrently.
 * @param errHandler A callback to receive any otherwise uncaught errors. Defaults to logging.
 */
export default function promisePool(feeder: (stop: () => void, threadNumber: number) => Promise<any> | null, concurrent: number, errHandler?: (err: any) => void): Promise<number>;
/**
 * Returns the given function, but wrapped so that only one call may run concurrently.
 */
export declare function mutex<T, A extends any[]>(fn: (...args: A) => T): (...args: A) => Promise<T>;
/**
 * Simple sleep function, just to save the trouble of retyping it.
 */
export declare function sleep(ms: number): Promise<unknown>;