/**
 * Calculates for some prefix of the given text, how many bytes the UTF-8
 * representation would be. Undefined behavior if the number of code units
 * doesn't correspond to a valid UTF-8 sequence.
 * @param text - Text to examine.
 * @param numCodeUnits The number of code units to look at.
 * @returns The number of bytes.
 */
export declare function numCodeUnitsToNumUtf8Bytes(text: string, numCodeUnits?: number): number;
export declare function numUtf8BytesToNumCodeUnits(text: string, numUtf8Bytes?: number): number;