/**
 * return an UTF-8 encoded string as URL Safe Base64
 *
 * Note: This function encodes to the RFC 4648 Spec where '+' is encoded
 *       as '-' and '/' is encoded as '_'. The padding character '=' is
 *       removed.
 */
export declare function encodeBase64UrlSafe(str: string): string;
/**
 * encode an UTF-8 encoded string as Base64
 */
export declare function encodeBase64(str: string): string;
/**
 * return an decoded URL Safe Base64 as UTF-8 encoded string
 */
export declare function decodeBase64UrlSafe(base64: string): string;
/**
 * Encode an array into Base64 url safe - Used for PKCE random/hash functions.
 */
export declare function encodeToBase64(array: ArrayBuffer | Uint8Array): string;
/**
 * decode Base64 as UTF-8 encoded string
 */
export declare function decodeBase64(str: string): string;