I need help implement based64 decoding in javascript: a function to
return a script that has been base64 encoded into a string (decoding in
client side). For encode, online base64 encoder tool was used.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>JavaScript Base64 Decoder</title>
<script type="text/javascript">
<!--
/*
//here is base64-encoded string:
PHNjcmlwdCB0eXBlPSJ0ZXh0L3Zic2NyaXB0Ij4gDQpGdW5jdG lvbiBlbmRlY3J5cHRfdmJzKGJvb2wpIA0KICAgIENvbnN0IGRp ZmYgPSAxIA0KICAgIERpbSBjaGFyLCBjb2RlLCBpLCB0ZW1wLC B0ZXh0IA0KICAgICAgICB0ZW1wID0gIiIgDQogICAgICAgIHRl eHQgPSBkb2N1bWVudC5nZXRFbGVtZW50QnlJZCgidGV4dCIpLn ZhbHVlIA0KICAgIEZvciBpID0gMSBUbyBMZW4odGV4dCkgDQog ICAgICAgIGNoYXIgPSBBc2MoTWlkKHRleHQsaSwxKSkgDQogIC AgICAgIElmIGJvb2wgVGhlbiANCiAgICAgICAgICAgIGNvZGUg PSBjaGFyICsgZGlmZiANCiAgICAgICAgRWxzZSANCiAgICAgIC AgICAgIGNvZGUgPSBjaGFyIC0gZGlmZiANCiAgICAgICAgRW5k IElmIA0KICAgICAgICB0ZW1wID0gdGVtcCAmIENocihjb2RlKS ANCiAgICBOZXh0IA0KICAgIGRvY3VtZW50LmdldEVsZW1lbnRC eUlkKCJ0ZXh0IikudmFsdWUgPSB0ZW1wIA0KRW5kIEZ1bmN0aW 9uIA0KPC9zY3JpcHQ+IA==
//Heres the decode function
function decode64(inp)
{
var out = ""; //This is the output
var chr1, chr2, chr3 = ""; //These are the 3 decoded bytes
var enc1, enc2, enc3, enc4 = ""; //These are the 4 bytes to be decoded
var i = 0; //Position counter
// remove all characters that are not A-Z, a-z, 0-9, +, /, or =
var base64test = /[^A-Za-z0-9\+\/\=]/g;
}
inp = inp.replace(/[^A-Za-z0-9\+\/\=]/g, "");
do { //Here.s the decode loop.
//Grab 4 bytes of encoded content.
enc1 = keyStr.indexOf(inp.charAt(i++));
enc2 = keyStr.indexOf(inp.charAt(i++));
enc3 = keyStr.indexOf(inp.charAt(i++));
enc4 = keyStr.indexOf(inp.charAt(i++));
//Heres the decode part. There.s really only one way to do it.
chr1 = (enc1 << 2) | (enc2 >4);
chr2 = ((enc2 & 15) << 4) | (enc3 >2);
chr3 = ((enc3 & 3) << 6) | enc4;
//Start to output decoded content
out = out + String.fromCharCode(chr1);
if (enc3 != 64) {
out = out + String.fromCharCode(chr2);
}
if (enc4 != 64) {
out = out + String.fromCharCode(chr3);
}
//now clean out the variables used
chr1 = chr2 = chr3 = "";
enc1 = enc2 = enc3 = enc4 = "";
} while (i < inp.length); //finish off the loop
//Now return the decoded values.
return out;
}
//-->
</script>
</head>
<body>
</body>
</html>
I'm not expert in javascript, so i dont know the correct method to
decode, the above decoder script is that i just found.
Another version:
this.decode = function()
{
var binary = new String();
var result = new String();
for(i = 0; i < this.string.length; i++)
{
for(j = 0; j < this.base64.length; j++)
{
if(this.string.charAt(i) == this.base64[j])
{
binary += String("000000" +
j.toString(2)).substring(j.toString(2).length);
}
}
}
for(i = 0; i < binary.length; i+=8)
{
var number = new Number();
var counter = new Number();
for(j = 0; j < binary.substring(i, i+8).length; j++)
{
for(k = 128; k >= 1; k-=(k/2))
{
if(binary.substring(i, i+8).charAt(counter++) ==
"1")
{
number += k;
}
}
}
result += String.fromCharCode(number);
}
return result;
}
}
thank you.
mistral
