/**
 * @file Utility for encoding strings to byte sequences.
 */
export interface TextEncoderPolyfillResult {
    readonly written: number;
    readonly read: number;
}
/**
 * Encodes an UTF-8 string into a byte sequence according to the WHATWG spec.
 *
 * @param str String to encode.
 * @param buffer Buffer to write the encoded bytes to.
 * @returns Number of bytes written to the buffer.
 * @see {@link https://encoding.spec.whatwg.org/#utf-8-encoder}
 * @note Bytes written maybe larger than the string length, but never smaller.
 * For example, the string '你好' has a length of 2, but its byte representation has a length of 6.
 */
export declare const encodeIntoPolyfill: (str: string, buffer: Uint8Array) => TextEncoderPolyfillResult;