otpauth/src/utils/encoding/uint.js

One Time Password (HOTP/TOTP) library for Node.js, Deno and browsers

/**
 * Converts an integer to an ArrayBuffer.
 * @param {number} num Integer.
 * @returns {ArrayBuffer} ArrayBuffer.
 */
const uintToBuf = (num) => {
	const buf = new ArrayBuffer(8);
	const arr = new Uint8Array(buf);
	let acc = num;

	for (let i = 7; i >= 0; i--) {
		if (acc === 0) break;
		arr[i] = acc & 255;
		acc -= arr[i];
		acc /= 256;
	}

	return buf;
};

/**
 * Converts an ArrayBuffer to an integer.
 * @param {ArrayBuffer} buf ArrayBuffer.
 * @returns {number} Integer.
 */
const uintFromBuf = (buf) => {
	const arr = new Uint8Array(buf);
	let num = 0;

	for (let i = 0; i < arr.length; i++) {
		if (arr[i] !== 0) {
			num *= 256;
			num += arr[i];
		}
	}

	return num;
};

export { uintToBuf, uintFromBuf };