/// <reference types="node" />
import { PassThrough } from 'stream';
export declare class MessageStreamError extends Error {
}
/** A class that extends PassThrough stream, supports async message fetching */
export declare class MessageStream<T> extends PassThrough {
    /** Deleter is a function that'll called by free() */
    private readonly deleter;
    constructor(deleter: () => void);
    /**
     * get an object asynchronously.
     * if there is an object in the stream, it'll be directly resolved;
     * else it'll be resolved when a new object is pushed into the stream.
     */
    get(condition?: (ctx: T) => Promise<boolean> | boolean): Promise<T>;
    /** Alias of this.resume() */
    waste(): void;
    /** Alias of this.pause() */
    keep(): void;
    /** End the stream and free related resources */
    free(): void;
}