export declare function formatBytes(bytes: number): string;
export declare function validateFileSize(file: File, maxSize: number): void;
export declare function getFileExtension(filename: string): string;
export declare function isAllowedFileType(file: File, allowedTypes: string[]): boolean;
export declare function sanitizeFilename(filename: string): string;
export declare function getUniqueFilename(filename: string, existingFilenames?: Set<string>): string;