how to convert array of integers into hex string and vice versa in javascript

Question

I have array of 32 bit integers in javascript. How to convert it into the Hex string and again build the same 32 bit integer array from that Hex string when required?

hexString = yourNumber.toString(16); can be used to convert number to hex but when array of numbers is converted into Hex string (it will be continuous or separated by some character) then how do I get back array of numbers from that string?

Answer 1

If you want to do it without commas

[3546,-24,99999,3322] ==> "00000ddaffffffe80001869f00000cfa"

then you can build up the string using 8 hex-digits for each number. Of course, you'll have to zero-pad numbers that are shorter than 8 hex-digits. And you'll have to ensure that the numbers are encoded with twos-compliment to properly handle any negative values.

Here's how to do that:

var a = [3546,-24,99999,3322];
alert("Original is " + JSON.stringify(a));    // [3546,-24,99999,3322]


// convert to hex string...
//
var b = a.map(function (x) {
    x = x + 0xFFFFFFFF + 1;  // twos complement
    x = x.toString(16); // to hex
    x = ("00000000"+x).substr(-8); // zero-pad to 8-digits
    return x
}).join('');
alert("Hex string " + b);   // 00000ddaffffffe80001869f00000cfa


// convert from hex string back to array of ints
//
c = [];
while( b.length ) {
    var x = b.substr(0,8);
    x = parseInt(x,16);  // hex string to int
    x = (x + 0xFFFFFFFF + 1) & 0xFFFFFFFF;   // twos complement
    c.push(x);
    b = b.substr(8);
}
alert("Converted back: " + JSON.stringify(c));    // [3546,-24,99999,3322]

here's a jsFiddle that shows the above example.