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

user_341574 0
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I have 2 numbers in javascript that I want to bit and. They both are 33bit long

in C#:

 ((4294967296 & 4294967296 )==0) is false

but in javascript: 

 ((4294967296 & 4294967296 )==0) is true

4294967296 is ((long)1) << 32

As I understand it, it is due to the fact that javascript converts values to int32 when performing bit wise operations.

How do I work around this? Any suggestions on how to replace bit and with a set of other math operations so that bits are not lost?

bit-manipulation 64-bit javascript
5 Answers

Ran into this problem today and this is what I came up with:

function bitwiseAnd(firstNumber, secondNumber) {
    let // convert the numbers to binary strings
        firstBitArray = (firstNumber).toString(2),
        secondBitArray = (secondNumber).toString(2),
        resultedBitArray = [],
        // get the length of the largest number
        maxLength = Math.max(firstBitArray.length, secondBitArray.length);

        //add zero fill ahead in case the binary strings have different lengths
        //so we can have strings equal in length and compare bit by bit
        firstBitArray = firstBitArray.padStart(maxLength,'0');
        secondBitArray = secondBitArray.padStart(maxLength,'0');

        // bit by bit comparison
        for(let i = 0; i < maxLength; i++) {
            resultedBitArray.push(parseInt(firstBitArray[i]) && secondBitArray[i]);
        }

        //concat  the result array back to a string and parse the binary string back to an integer
        return parseInt(resultedBitArray.join(''),2);
}

Hope this helps anyone else who runs into this problem.

user_18792970
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