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

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

const lookup = [];
const revLookup = [];
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) => {
	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) => {
	const lens = getLens(b64);
	const validLen = lens[0];
	const placeHoldersLen = lens[1];
	return (((validLen + placeHoldersLen) * 3) / 4) - placeHoldersLen;
};

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

export const toByteArray = (b64) => {
	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 => lookup[(num >> 18) & 0x3F]
	+ lookup[(num >> 12) & 0x3F]
	+ lookup[(num >> 6) & 0x3F]
	+ lookup[num & 0x3F];

const encodeChunk = (uint8, start, end) => {
	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) => {
	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('');
};