export declare function toBytes(src: Response | Blob): Promise<Uint8Array<ArrayBuffer>>;
/** Reports bytes downloaded for a single fetch; `total` from Content-Length. */
export type ProgressCallback = (bytesReceived: number, total?: number) => void;
/**
 * Read a Response body to bytes while reporting download progress.
 *
 * When Content-Length is known the body is streamed directly into one pre-sized
 * buffer (no per-chunk array, no second copy), ticking `onProgress` as chunks
 * arrive. Without a known length there is no fraction to show, so it falls back
 * to a single one-shot read and one completion tick rather than buffering
 * chunks. Only used when a caller opts in via `onProgress`; the plain {@link
 * toBytes} fast path is unaffected.
 */
export declare function toBytesWithProgress(res: Response, onProgress: ProgressCallback): Promise<Uint8Array<ArrayBuffer>>;