// http://www.razorberry.com/blog/archives/2004/08/22/lzw-compression-methods-in-as2/
//
// A class for LZW compression modified from code posted at the following URL's
// http://www.shoe-box.org/blog/index.php/2004/05/05/13-CompressionLzw
// http://www.lalex.com/blog/comments/200405/164-compression-lzw-actionscript-2.html
// Use compress_fp6() instead of compress() if exporting to flash player 6
class LZW
{
	// Change this variable to output an xml safe string
	private static var xmlsafe:Boolean = false;
	private function LZW()
	{
	}
	public static function compress(str:String):String
	{
		var dico:Array = new Array();
		var skipnum:Number = xmlsafe?5:0;
		for (var i = 0; i < 256; i++)
		{
			dico[String.fromCharCode(i)] = i;
		}
		if (xmlsafe)
		{
			dico["<"] = 256;
			dico[">"] = 257;
			dico["&"] = 258;
			dico["\""] = 259;
			dico["'"] = 260;
		}
		var res:String = "";
		var txt2encode:String = str;
		var splitStr:Array = txt2encode.split("");
		var len:Number = splitStr.length;
		var nbChar:Number = 256+skipnum;
		var buffer:String = "";
		for (var i = 0; i <= len; i++)
		{
			var current = splitStr[i];
			if (dico[buffer + current] !== undefined)
			{
				buffer += current;
			}
			else
			{
				res += String.fromCharCode(dico[buffer]);
				dico[buffer + current] = nbChar;
				nbChar++;
				buffer = current;
			}
		}
		return res;
	}
	public static function decompress(str:String):String
	{
		var dico:Array = new Array();
		var skipnum:Number = xmlsafe?5:0;
		for (var i = 0; i < 256; i++)
		{
			var c:String = String.fromCharCode(i);
			dico[i] = c;
		}
		if (xmlsafe)
		{
			dico[256] = "<";
			dico[257] = ">";
			dico[258] = "&";
			dico[259] = "\"";
			dico[260] = "'";
		}
		var txt2encode:String = str;
		var splitStr:Array = txt2encode.split("");
		var length:Number = splitStr.length;
		var nbChar:Number = 256+skipnum;
		var buffer:String = "";
		var chaine:String = "";
		var result:String = "";
		for (var i = 0; i < length; i++)
		{
			var code:Number = txt2encode.charCodeAt(i);
			var current:String = dico[code];
			if (buffer == "")
			{
				buffer = current;
				result += current;
			}
			else
			{
				if (code <= 255+skipnum)
				{
					result += current;
					chaine = buffer + current;
					dico[nbChar] = chaine;
					nbChar++;
					buffer = current;
				}
				else
				{
					chaine = dico[code];
					if (chaine == undefined) chaine = buffer + buffer.slice(0,1);
					result += chaine;
					dico[nbChar] = buffer + chaine.slice(0, 1);
					nbChar++;
					buffer = chaine;
					
				}
			}
		}
		return result;
	}
	
	public static function compress_fp6(str:String):String
	{
		var dico:Array = new Array();
		var skipnum:Number = xmlsafe?5:0;
		for (var i = 0; i < 256; i++)
		{
			dico[String(i)] = i;
		}
		if (xmlsafe)
		{
			var let = String(new String("<").charCodeAt(0));
			var grt = String(new String(">").charCodeAt(0));
			var amp = String(new String("&").charCodeAt(0));
			var bsl = String(new String("\"").charCodeAt(0));
			var apo = String(new String("'").charCodeAt(0));
			dico[let] = 256;
			dico[grt] = 257;
			dico[amp] = 258;
			dico[bsl] = 259;
			dico[apo] = 260;
		}
		var res:String = "";
		var txt2encode:String = str;
		var splitStr:Array = txt2encode.split("");
		var len:Number = splitStr.length;
		var nbChar:Number = 256+skipnum;
		var buffer:Array = new Array();
		for (var i = 0; i <= len; i++)
		{
			var current = splitStr[i];
			if (buffer.length == 0)
			var xstr = String(current.charCodeAt(0));
			else
			var xstr = buffer.join("-") + "-" + String(current.charCodeAt(0));
			if (dico[xstr] !== undefined)
			{
				buffer.push(current.charCodeAt(0));
			}
			else
			{
				res += String.fromCharCode(dico[buffer.join("-")]);
				dico[xstr] = nbChar;
				nbChar++;
				delete buffer;
				buffer = new Array();
				buffer.push(current.charCodeAt(0));
			}
		}
		return res;
	}
}