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0bin/zerobin/static/js/lzw.js

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2012-04-26 13:38:55 +04:00
// Author: Anthony McKale
//
// Note: modifed to javascript from orginal as2 found below
// basically identical actual to as2
//
// 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
//
var lzw = {
// Change this variable to output an xml safe string
xmlsafe : false,
compress : function(str){
var dico = new Array();
var skipnum = lzw.xmlsafe?5:0;
for (var i = 0; i < 256; i++)
{
dico[String.fromCharCode(i)] = i;
}
if (lzw.xmlsafe)
{
dico["<"] = 256;
dico[">"] = 257;
dico["&"] = 258;
dico["\""] = 259;
dico["'"] = 260;
}
var res = "";
var txt2encode = str;
var splitStr = txt2encode.split("");
var len = splitStr.length;
var nbChar = 256+skipnum;
var buffer = "";
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;
},
decompress : function (str)
{
var dico = new Array();
var skipnum = lzw.xmlsafe?5:0;
for (var i = 0; i < 256; i++)
{
var c = String.fromCharCode(i);
dico[i] = c;
}
if (lzw.xmlsafe)
{
dico[256] = "<";
dico[257] = ">";
dico[258] = "&";
dico[259] = "\"";
dico[260] = "'";
}
var txt2encode = str;
var splitStr = txt2encode.split("");
var length = splitStr.length;
var nbChar = 256+skipnum;
var buffer = "";
var chaine = "";
var result = "";
for (var i = 0; i < length; i++)
{
var code = txt2encode.charCodeAt(i);
var current = 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;
}
}