/**
 * Base64 encoding
 * http://www.ietf.org/rfc/rfc2045.txt
 */

var Base64 = function() {
	this.initialize();
};

Base64.prototype.initialize = function() {
	this.symbols = [];
	var startChar = "A".charCodeAt(0);
	for(var i = 0; i < 26; i++) {
		this.symbols.push(String.fromCharCode(startChar + i));
	}
	var startChar = "a".charCodeAt(0);
	for(var i = 0; i < 26; i++) {
		this.symbols.push(String.fromCharCode(startChar + i));
	}
	var startChar = "0".charCodeAt(0);
	for(var i = 0; i < 10; i++) {
		this.symbols.push(String.fromCharCode(startChar + i));
	}
	this.symbols.push("+", "/");
	
	this.encodeMap = [];
	for(var i = 0; i < this.symbols.length; i++) {
		this.encodeMap[i] = this.symbols[i];
	}
	
	this.decodeMap = [];
	for(var i = 0; i < this.symbols.length; i++) {
		this.decodeMap[this.symbols[i]] = i;
	}
	this.decodeMap["="] = null;
};

Base64.prototype.encode = function(octets) {
	var i;
	var map = this.encodeMap;
	var encoded = [];
	for (i = 0, len = Math.floor(octets.length / 3) * 3;
		i < len; i += 3) {
		var b0 = octets[i];
		var b1 = octets[i + 1];
		var b2 = octets[i + 2];
		var qs = map[(b0 >> 2) & 0x3f] 
	  				+ map[((b0 << 4) + (b1 >> 4)) & 0x3f]
	  				+ map[((b1 << 2) + (b2 >> 6)) & 0x3f]
	  				+ map[b2 & 0x3f];
		encoded.push(qs);
	}

	switch(octets.length % 3) {
		case 1:
			var b0 = octets[i];
			var qs = map[(b0 >> 2) & 0x3f] 
			       + map[(b0 << 4) & 0x3f]
						 + "=="; 
			encoded.push(qs);
			break;
		case 2:
			var b0 = octets[i];
		  var b1 = octets[i + 1];			
			var qs = map[(b0 >> 2) & 0x3f] 
						 + map[((b0 << 4) + (b1 >> 4)) & 0x3f] 
						 + map[(b1 << 2) & 0x3f] 
						 + "=";
			encoded.push(qs);
		  break;
	}
	
	return encoded.join("");
};

Base64.prototype.decode = function(encoded) {
	if(encoded.length % 4 != 0) {
		throw "encoded.length must be a multiple of 4.";
	}
	
	var decoded = [];
	var map = this.decodeMap;

	for (var i = 0, len = encoded.length; i < len; i += 4) {
		var b0 = map[encoded.charAt(i)];
		var b1 = map[encoded.charAt(i + 1)];
		var b2 = map[encoded.charAt(i + 2)];
		var b3 = map[encoded.charAt(i + 3)];

		var d0 = ((b0 << 2) + (b1 >> 4)) & 0xff;
		decoded.push(d0);

		
		if(b2 == null) break; // encoded[i + 1] == "="

		var d1 = ((b1 << 4) + (b2 >> 2)) & 0xff;
		decoded.push(d1);
		
		if(b3 == null) break; // encoded[i + 2] == "="
		
	  var d2 = ((b2 << 6) + b3) & 0xff;
		decoded.push(d2);
		
	}

	return decoded;
};

Base64.prototype.uriEncodedToOctets = function(uriEncoded) {
	var octets = [];
	for(var i = 0, len = uriEncoded.length; i < len; i++) {
		// Note that IE6 doesn't allow an expression like "uriEncoded[i]";
		var c = uriEncoded.charAt(i);
		var b;
		if (c == "%") {
			var hex = uriEncoded.charAt(++i) + uriEncoded.charAt(++i);
			b = parseInt(hex, 16);
		} else {
			b = c.charCodeAt(0);
		}
		octets.push(b);
  }
	return octets;
};

Base64.prototype.encodeStringAsUTF8 = function(utf8str) {
	var uriEncoded = encodeURIComponent(utf8str);
	var octets = this.uriEncodedToOctets(uriEncoded);
	return this.encode(octets);
};

Base64.prototype.octetsToUriEncoded = function(octets) {
	var uriEncoded = [];
	
	for(var i = 0, len = octets.length; i < len; i++) {
		var hex = octets[i].toString(16);
		hex = ("0" + hex).substr(hex.length - 1, 2);
		uriEncoded.push("%" + hex);
  }
	return uriEncoded.join("");
};

Base64.prototype.decodeStringAsUTF8 = function(encoded) {
	var octets = this.decode(encoded);
	var uriEncoded = this.octetsToUriEncoded(octets);
	return 	decodeURIComponent(uriEncoded);
};

var base64 = new Base64();