JavaScript Base64 encoder/decoder

base64.js

var base64 = {
	table: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/',
	decode: function(str, urlSafe, autoPad) {
		if(!(str = ('' + str)).length) {
			throw 'invalid string length in base64.decode';
		}
		
		var b10, i, arr = [], len = str.length, padding = 0, table = (urlSafe ? this.table.substr(0, 62) + '-_' : this.table);
		
		function charByte(c) {
			if((c = table.indexOf(c.charAt(0))) == -1) {
				throw 'invalid characater detected in base64.decode';
			}
			return c;
		}
		
		if(len == 0 || (len % 4 && !autoPad)) {
			throw 'invalid base64 string detected in base64.decode';
		} else if(len % 4 && autoPad) {
			padding = 4 - (len % 4);
			len -= 4;
		} else if(str.charAt(len - 1) == '=') {
			padding = (str.charAt(len - 2) == '=' ? 2 : 1);
			len -= 4;
		}
		
		for(i = 0; i < len; ) {
			b10 = ((charByte(str[i++]) << 18) | (charByte(str[i++]) << 12) | (charByte(str[i++]) << 6) | charByte(str[i++]));
			arr.push(String.fromCharCode(b10 >> 16, (b10 >> 8) & 0xFF, b10 & 0xFF));
		}
		
		switch(padding) {
			case 1:
				b10 = ((charByte(str[i++]) << 18) | (charByte(str[i++]) << 12) | (charByte(str[i++]) << 6));
				arr.push(String.fromCharCode(b10 >> 16, (b10 >> 8) & 0xFF));
				break;
				
			case 2:
				b10 = ((charByte(str[i++]) << 18) | (charByte(str[i++]) << 12));
				arr.push(String.fromCharCode(b10 >> 16));
				break;
		}
		
		return arr.join('');
	},
	encode: function(str, urlSafe, stripPad) {
		if(!(str = ('' + str)).length) {
			throw 'invalid string length in base64.encode';
		}
		
		var b10, i, arr = [], len = (str.length - str.length % 3), table = (urlSafe ? this.table.substr(0, 62) + '-_' : this.table);
		
		function charCode(c) {
			if((c = c.charCodeAt(0)) > 255) {
				throw 'invalid character detected in base64.encode';
			}
			return c;
		}
		
		for(i = 0; i < len; ) {
			b10 = ((charCode(str[i++]) << 16) | (charCode(str[i++]) << 8) | charCode(str[i++]));
			arr.push(table.charAt(b10 >> 18));
			arr.push(table.charAt((b10 >> 12) & 0x3F));
			arr.push(table.charAt((b10 >> 6) & 0x3F));
			arr.push(table.charAt(b10 & 0x3F));
		}
		
		switch(str.length - len) {
			case 1:
				b10 = charCode(str[i]) << 16;
				arr.push(table.charAt(b10 >> 18) + table.charAt((b10 >> 12) & 0x3F) + (stripPad ? '' : '=='));
				break;
				
			case 2:
				b10 = ((charCode(str[i]) << 16) | (charCode(str[++i]) << 8));
				arr.push(table.charAt(b10 >> 18) + table.charAt((b10 >> 12) & 0x3F) + table.charAt((b10 >> 6) & 0x3F) + (stripPad ? '' : '='));
				break;
		}
		
		return arr.join('');
	}
}