export type UnlockFn = () => void;
/**
 * An asynchronous semaphore implementation with associated items per lease.
 *
 * @internal This class is meant to be used in PowerSync SDKs only, and is not part of the public API.
 */
export declare class Semaphore<T> {
    private readonly available;
    readonly size: number;
    private firstWaiter?;
    private lastWaiter?;
    constructor(elements: Iterable<T>);
    private addWaiter;
    private deactivateWaiter;
    private requestPermits;
    /**
     * Requests a single item from the pool.
     *
     * The returned `release` callback must be invoked to return the item into the pool.
     */
    requestOne(abort?: AbortSignal): Promise<{
        item: T;
        release: UnlockFn;
    }>;
    /**
     * Requests access to all items from the pool.
     *
     * The returned `release` callback must be invoked to return items into the pool.
     */
    requestAll(abort?: AbortSignal): Promise<{
        items: T[];
        release: UnlockFn;
    }>;
}
/**
 * An asynchronous mutex implementation.
 *
 * @internal This class is meant to be used in PowerSync SDKs only, and is not part of the public API.
 */
export declare class Mutex {
    private inner;
    acquire(abort?: AbortSignal): Promise<UnlockFn>;
    runExclusive<T>(fn: () => PromiseLike<T> | T, abort?: AbortSignal): Promise<T>;
}
/**
 * Creates a signal aborting after the set timeout.
 */
export declare function timeoutSignal(timeout: number): AbortSignal;
export declare function timeoutSignal(timeout?: number): AbortSignal | undefined;