/**
 * Computes the SHA-256 hash of the given buffer and returns it as a hex string.
 * SHA-256 is cryptographically modern and collision-resistant.
 */
export declare function computeHash(buffer: Buffer): string;
/**
 * Detect MIME type and extension from a buffer using magic bytes.
 * Returns `{ mime, ext }` or `undefined` if unrecognized.
 */
export declare function detectFileType(buffer: Buffer): Promise<{
    mime: string;
    ext: string;
} | undefined>;
export declare function randomFileName(fileName: string): string;