/**
 * base64 string len
 * @param b64
 * @description base64 is 4/3 + up to two characters of the original data
 * @return {number} len
 */
export declare function b64ByteLength(b64: string): number;
/**
 * base64 转换成 Uint8Array
 * @param b64
 * @return {Uint8Array | string[]}
 */
export declare function b64ToByteArray(b64: string): Uint8Array | string[];
/**
 * Uint8Array to base64
 * @param uint8
 * @return {string} base64 string
 */
export declare function byteArrayToB64(uint8: number[]): string;