javascript bitwise 64 bit implementation

Question

In javascript we can't able to evaluate larger than 32 bits in the bitwise operation. But In c# we can able to do this.

Here is the example If we try to run the below one browser console

4294967296 & 8589934591

Its returns 0 But in C# its returns the 4294967296

I googled and I have found that we can able to use this one goog.math.Long to implement larger than 32 bitwise implementation.

But my problem is, I am not able to find the sample to implement the logic in client side.

Can any one help me on this.

Thanks in advance

The documentation you link to clearly mentions an `and` method. What happens when you try it? — Jeremy J Starcher, Jun 18 '16 at 13:59
Do you mean the [view source](http://google.github.io/closure-library/api/source/closure/goog/math/long.js.src.html#l51)? ln. 130-139 and ln. 51-63 — Tim Vermaelen, Jun 18 '16 at 14:01
@shankar.siva Remember: you need to include any library that you use _before_ you use it. How did you include it? — Sebastian Simon, Jun 18 '16 at 14:20

score 1 · Answer 1 · edited May 23 '17 at 10:28

I got clue from this URL but not used the goog.math.Long.

How to do bitwise AND in javascript on variables that are longer than 32 bit?

Here's a fun function for arbitrarily large integers:

function BitwiseAndLarge(val1, val2) {
    var shift = 0, result = 0;
    var mask = ~((~0) << 30); // Gives us a bit mask like 01111..1 (30 ones)
    var divisor = 1 << 30; // To work with the bit mask, we need to clear bits at a time
    while( (val1 != 0) && (val2 != 0) ) {
        var rs = (mask & val1) & (mask & val2);
        val1 = Math.floor(val1 / divisor); // val1 >>> 30
        val2 = Math.floor(val2 / divisor); // val2 >>> 30
        for(var i = shift++; i--;) {
            rs *= divisor; // rs << 30
        }
        result += rs;
    }
    return result;
}

Assuming that the system handles at least 30-bit bitwise operations properly.

shankar.siva · Accepted Answer · 2016-07-01T09:51:58.013

javascript bitwise 64 bit implementation using goog.math.Long

Add Js library http://www.hobsonassoc.com/scripts/closure/goog/docs/closure_goog_math_long.js.source.html
Comment the // goog.provide('goog.math.Long') in js library
Add the var goog = {}; goog.math = {}; in js library
Call the function var val1 = goog.math.Long.fromString("4611686018427387904");

Here is the example:

<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8" />
    <title>Bitmask 64 Bit</title>
    <script type="text/javascript" src="goog.math.long.js"></script>
    <script type="text/javascript">
        var val1 = goog.math.Long.fromString("4611686018427387904"); // 2^62
        var val2 = goog.math.Long.fromString("6917529027641081856"); // 2^61 | 2^62
        var val3 = goog.math.Long.fromString("2305843009213693952"); // 2^61
        var val4 = goog.math.Long.fromString("4611686018427387904"); // 2^62
        document.writeln(val1.and(val2)); // 2^62 & (2^61 | 2^62)  
        document.writeln(val3.or(val4));  // 2^61 | 2^62
    </script>
</head>
<body>
</body>
</html>

Licenses were required to use this library.

score 0 · Answer 3 · answered Jun 18 '16 at 14:27

0

I think you don't really need goog.math.long ? Suffice it to convert into string, to split. Then proceed AND operation and recompose :

var a = 8589934592;
var str = a.toString()
var subNumber1 = parseInt(str.slice(0, str.length - 5));
var subNumber2 = parseInt(str.slice(str.length - 5));
var res1 = (subNumber1 & subNumber1).toString();
var res2 = (subNumber2 & subNumber2).toString();
var res = parseInt(res1.concat(res2));
console.log(res);

answered Jun 18 '16 at 14:27

kevin ternet

4,514
2
19
27

Why is that correct? (actually, *is* it correct?) AFAIK there's no simple way to relate bitwise operations to what happens to the decimal digits. – harold Jun 18 '16 at 14:39
I mean yea it works now, but that's because `x & x == x` is always true anyway, regardless of how meaningful the `x` is. If you had an `a` and a `b` though, there's no way this is going to work. – harold Jun 18 '16 at 14:42
You have Little misunderstood the question. Now I have updated different example. Can you check it. – shankar.siva Jun 18 '16 at 15:02

score 0 · Answer 4 · answered Jun 18 '16 at 16:59

0

I'm not sure if this what you're looking for but if you are using google/closure-library with npm. You can use Browserify or Webpack to bundle the module into client side.

answered Jun 18 '16 at 16:59

Narongdej Sarnsuwan

5,095
1
12
10

javascript bitwise 64 bit implementation

4 Answers4