base64-js/lib/b64.js

(function (exports) {
	'use strict';

	var lookup = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

	function b64ToByteArray(b64) {
		var i, j, l, tmp, placeHolders, arr;
	
		if (b64.length % 4 > 0) {
			throw 'Invalid string. Length must be a multiple of 4';
		}

		// the number of equal signs (place holders)
		// if there are two placeholders, than the two characters before it
		// represent one byte
		// if there is only one, then the three characters before it represent 2 bytes
		// this is just a cheap hack to not do indexOf twice
		placeHolders = indexOf(b64, '=');
		placeHolders = placeHolders > 0 ? b64.length - placeHolders : 0;

		// base64 is 4/3 + up to two characters of the original data
		arr = [];//new Uint8Array(b64.length * 3 / 4 - placeHolders);

		// if there are placeholders, only get up to the last complete 4 chars
		l = placeHolders > 0 ? b64.length - 4 : b64.length;

		for (i = 0, j = 0; i < l; i += 4, j += 3) {
			tmp = (indexOf(lookup, b64.charAt(i)) << 18) | (indexOf(lookup, b64.charAt(i + 1)) << 12) | (indexOf(lookup, b64.charAt(i + 2)) << 6) | indexOf(lookup, b64.charAt(i + 3));
			arr.push((tmp & 0xFF0000) >> 16);
			arr.push((tmp & 0xFF00) >> 8);
			arr.push(tmp & 0xFF);
		}

		if (placeHolders === 2) {
			tmp = (indexOf(lookup, b64.charAt(i)) << 2) | (indexOf(lookup, b64.charAt(i + 1)) >> 4);
			arr.push(tmp & 0xFF);
		} else if (placeHolders === 1) {
			tmp = (indexOf(lookup, b64.charAt(i)) << 10) | (indexOf(lookup, b64.charAt(i + 1)) << 4) | (indexOf(lookup, b64.charAt(i + 2)) >> 2);
			arr.push((tmp >> 8) & 0xFF);
			arr.push(tmp & 0xFF);
		}

		return arr;
	}

	function uint8ToBase64(uint8) {
		var i,
			extraBytes = uint8.length % 3, // if we have 1 byte left, pad 2 bytes
			output = "",
			temp, length;

		function tripletToBase64 (num) {
			return lookup.charAt(num >> 18 & 0x3F) + lookup.charAt(num >> 12 & 0x3F) + lookup.charAt(num >> 6 & 0x3F) + lookup.charAt(num & 0x3F);
		};

		// go through the array every three bytes, we'll deal with trailing stuff later
		for (i = 0, length = uint8.length - extraBytes; i < length; i += 3) {
			temp = (uint8[i] << 16) + (uint8[i + 1] << 8) + (uint8[i + 2]);
			output += tripletToBase64(temp);
		}

		// pad the end with zeros, but make sure to not forget the extra bytes
		switch (extraBytes) {
			case 1:
				temp = uint8[uint8.length - 1];
				output += lookup.charAt(temp >> 2);
				output += lookup.charAt((temp << 4) & 0x3F);
				output += '==';
				break;
			case 2:
				temp = (uint8[uint8.length - 2] << 8) + (uint8[uint8.length - 1]);
				output += lookup.charAt(temp >> 10);
				output += lookup.charAt((temp >> 4) & 0x3F);
				output += lookup.charAt((temp << 2) & 0x3F);
				output += '=';
				break;
		}

		return output;
	}

	module.exports.toByteArray = b64ToByteArray;
	module.exports.fromByteArray = uint8ToBase64;
}());

function indexOf (arr, elt /*, from*/) {
	var len = arr.length;

	var from = Number(arguments[1]) || 0;
	from = (from < 0)
		? Math.ceil(from)
		: Math.floor(from);
	if (from < 0)
		from += len;

	for (; from < len; from++) {
		if ((typeof arr === 'string' && arr.charAt(from) === elt) ||
				(typeof arr !== 'string' && arr[from] === elt)) {
			return from;
		}
	}
	return -1;
}