Rocket.Chat.ReactNative/app/utils/base64-js/index.ts

/* eslint-disable no-bitwise */
// https://github.com/beatgammit/base64-js/blob/master/index.js

const lookup: string[] = [];
const revLookup: number[] = [];
const Arr = typeof Uint8Array !== 'undefined' ? Uint8Array : Array;

const code = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
for (let i = 0, len = code.length; i < len; i += 1) {
	lookup[i] = code[i];
	revLookup[code.charCodeAt(i)] = i;
}

// Support decoding URL-safe base64 strings, as Node.js does.
// See: https://en.wikipedia.org/wiki/Base64#URL_applications
revLookup['-'.charCodeAt(0)] = 62;
revLookup['_'.charCodeAt(0)] = 63;

const getLens = (b64: string) => {
	const len = b64.length;

	// We're encoding some strings not multiple of 4, so, disable this check
	// if (len % 4 > 0) {
	// 	throw new Error('Invalid string. Length must be a multiple of 4');
	// }

	// Trim off extra bytes after placeholder bytes are found
	// See: https://github.com/beatgammit/base64-js/issues/42
	let validLen = b64.indexOf('=');
	if (validLen === -1) {
		validLen = len;
	}

	const placeHoldersLen = validLen === len ? 0 : 4 - (validLen % 4);

	return [validLen, placeHoldersLen];
};

// base64 is 4/3 + up to two characters of the original data
export const byteLength = (b64: string) => {
	const lens = getLens(b64);
	const validLen = lens[0];
	const placeHoldersLen = lens[1];
	return ((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;
};

const _byteLength = (b64: string, validLen: number, placeHoldersLen: number) =>
	((validLen + placeHoldersLen) * 3) / 4 - placeHoldersLen;

export const toByteArray = (b64: string) => {
	let tmp;
	const lens = getLens(b64);
	const validLen = lens[0];
	const placeHoldersLen = lens[1];

	const arr = new Arr(_byteLength(b64, validLen, placeHoldersLen));

	let curByte = 0;

	// if there are placeholders, only get up to the last complete 4 chars
	const len = placeHoldersLen > 0 ? validLen - 4 : validLen;

	let i;
	for (i = 0; i < len; i += 4) {
		tmp =
			(revLookup[b64.charCodeAt(i)] << 18) |
			(revLookup[b64.charCodeAt(i + 1)] << 12) |
			(revLookup[b64.charCodeAt(i + 2)] << 6) |
			revLookup[b64.charCodeAt(i + 3)];
		arr[curByte] = (tmp >> 16) & 0xff;
		curByte += 1;
		arr[curByte] = (tmp >> 8) & 0xff;
		curByte += 1;
		arr[curByte] = tmp & 0xff;
		curByte += 1;
	}

	if (placeHoldersLen === 2) {
		tmp = (revLookup[b64.charCodeAt(i)] << 2) | (revLookup[b64.charCodeAt(i + 1)] >> 4);
		arr[curByte] = tmp & 0xff;
		curByte += 1;
	}

	if (placeHoldersLen === 1) {
		tmp =
			(revLookup[b64.charCodeAt(i)] << 10) | (revLookup[b64.charCodeAt(i + 1)] << 4) | (revLookup[b64.charCodeAt(i + 2)] >> 2);
		arr[curByte] = (tmp >> 8) & 0xff;
		curByte += 1;
		arr[curByte] = tmp & 0xff;
		curByte += 1;
	}

	return arr;
};

const tripletToBase64 = (num: number) =>
	lookup[(num >> 18) & 0x3f] + lookup[(num >> 12) & 0x3f] + lookup[(num >> 6) & 0x3f] + lookup[num & 0x3f];

const encodeChunk = (uint8: number[] | Uint8Array, start: number, end: number) => {
	let tmp;
	const output = [];
	for (let i = start; i < end; i += 3) {
		tmp = ((uint8[i] << 16) & 0xff0000) + ((uint8[i + 1] << 8) & 0xff00) + (uint8[i + 2] & 0xff);
		output.push(tripletToBase64(tmp));
	}
	return output.join('');
};

export const fromByteArray = (uint8: number[] | Uint8Array) => {
	let tmp;
	const len = uint8.length;
	const extraBytes = len % 3; // if we have 1 byte left, pad 2 bytes
	const parts = [];
	const maxChunkLength = 16383; // must be multiple of 3

	// go through the array every three bytes, we'll deal with trailing stuff later
	for (let i = 0, len2 = len - extraBytes; i < len2; i += maxChunkLength) {
		parts.push(encodeChunk(uint8, i, i + maxChunkLength > len2 ? len2 : i + maxChunkLength));
	}

	// pad the end with zeros, but make sure to not forget the extra bytes
	if (extraBytes === 1) {
		tmp = uint8[len - 1];
		parts.push(`${lookup[tmp >> 2] + lookup[(tmp << 4) & 0x3f]}==`);
	} else if (extraBytes === 2) {
		tmp = (uint8[len - 2] << 8) + uint8[len - 1];
		parts.push(`${lookup[tmp >> 10] + lookup[(tmp >> 4) & 0x3f] + lookup[(tmp << 2) & 0x3f]}=`);
	}

	return parts.join('');
};