How do I implement hex2bin()?

Question

I need to communicate between Javascript and PHP (I use jQuery for AJAX), but the output of the PHP script may contain binary data. That\'s why I use bin2hex()

Answer 1

With reference to node.js ( not in browser ).

Basically it's all over-engineered and does not work well.

responses are out of alignment and though text-wise they are the same bit wise everything is all over the place :

curl http://phpimpl.domain.com/testhex.php | xxd

00000000: de56 a735 4739 c01d f2dc e14b ba30 8af0  .Q.%G9.....;.0..

curl http://nodejs.domain.com/ | xxd

00000000: c39e 56c2 a725 4739 c380 c3ad c3b1 c39c  ..Q..%G9........
00000010: c3a1 37c2 6b30 c28f c3b0                 ..;..0....

The proper way to implement this in node is :

function hex2bin(hex){
   return new Buffer(hex,"hex");
}


curl http://nodejs.domain.com/ | xxd

00000000: de56 a735 4739 c01d f2dc e14b ba30 8af0  .Q.%G9.....;.0..

Hope this helps.

Answer 2

JavaScript doesn't have support for binary data. Nevertheless you can emulate this with regular strings.

var hex = "375771", // ASCII HEX: 37="7", 57="W", 71="q"
    bytes = [],
    str;

for(var i=0; i< hex.length-1; i+=2){
    bytes.push(parseInt(hex.substr(i, 2), 16));
}

str = String.fromCharCode.apply(String, bytes);

alert(str); // 7Wq

Answer 3

If someone needs the other direction (bin to hex), here is it:

function bin2hex(bin) {
    return new Buffer(bin).toString("hex");
}

Answer 4

function hex2bin(hex)
{
    var bytes = [], str;

    for(var i=0; i< hex.length-1; i+=2)
        bytes.push(parseInt(hex.substr(i, 2), 16));

    return String.fromCharCode.apply(String, bytes);    
}

thanks to Andris!

---

Other useful information about this topic (dex2bin,bin2dec) can be found here. According to that, here is a bin2hex solution:

parseInt(1100,2).toString(16); //--> c

Answer 5

JavaScript does actually contain support for binary data. See Uint8Array.

Just read each byte from the array and convert it into hexadecimal.

Answer 6

All proposed solutions use String.fromCharCode, why not simply using unescape?

String.prototype.hex2bin = function()
{ 
   var i = 0, len = this.length, result = "";

   //Converting the hex string into an escaped string, so if the hex string is "a2b320", it will become "%a2%b3%20"
   for(; i < len; i+=2)
      result += '%' + this.substr(i, 2);      

   return unescape(result);
}

and then:

alert( "68656c6c6f".hex2bin() ); //shows "hello"