How can I convert BitArray to single int?

Question

How can I convert BitArray to a single int?

BitArray to int Array or literally a BitArray to a single integer? — Brandon Boone, Mar 12 '11 at 14:49

Luca Fagioli · Accepted Answer · 2013-01-02T23:09:11.260

74

private int getIntFromBitArray(BitArray bitArray)
{

    if (bitArray.Length > 32)
        throw new ArgumentException("Argument length shall be at most 32 bits.");

    int[] array = new int[1];
    bitArray.CopyTo(array, 0);
    return array[0];

}

edited Jan 02 '13 at 23:09

answered Mar 12 '11 at 14:50

Luca Fagioli

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5
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1

Wow... I didn't think this would work to put all the bits into one integer value - but it does! – codekaizen Nov 19 '11 at 11:27
4

Refer this: http://codereview.stackexchange.com/questions/3796/converting-binary-value-from-bitarray-to-an-int-and-back-in-c/3797#3797 Need to check the length of bitArray – coder_bro Aug 02 '12 at 06:41
5

Nice trick, however it could have issues related to byte order (endianess) on various platforms. It would be better to use `byte` array as destination for bit array copy and use `BitConverter.ToInt32(array, 0)` method afterwards. – Jozef Benikovský Feb 08 '19 at 12:09

William Casarin · Answer 2 · 2018-07-20T16:53:13.293

10

This version:

works for up to 64 bits
doesn't rely on knowledge of BitArray implementation details
doesn't needlessly allocate memory
doesn't throw any exceptions (feel free to add a check if you expect more bits)
should be more than reasonably performant

Implementation:

public static ulong BitArrayToU64(BitArray ba)
{
    var len = Math.Min(64, ba.Count);
    ulong n = 0;
    for (int i = 0; i < len; i++) {
        if (ba.Get(i))
            n |= 1UL << i;
    }
    return n;
}

edited Jul 20 '18 at 16:53

answered Jul 19 '18 at 20:03

William Casarin

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Can you explain how this is better than the accepted solution from 7 years ago? Is it faster, more accurate, better at error handling, using less memory? – nvoigt Jul 20 '18 at 09:12

score 9 · Answer 3 · answered Aug 12 '12 at 08:22

9

private int getIntFromBitArray(BitArray bitArray)
{
    int value = 0;

    for (int i = 0; i < bitArray.Count; i++)
    {
        if (bitArray[i])
            value += Convert.ToInt16(Math.Pow(2, i));
    }

    return value;
}

answered Aug 12 '12 at 08:22

K4KNOWLEDGE

99
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3

Can you explain why the OP should use this over the other solution? – Austin Henley Sep 27 '12 at 04:47
1

@AustinHenley I wrote this solution for debug purposes. I can step through my code to see how the number is being converted. I'm not sure if you can do that with the first solution. – K4KNOWLEDGE Aug 01 '13 at 18:34
1

It's also interesting to know that the first solution is not available on WinRT (probably because of the way ARM processors save the numbers) – tec-goblin Sep 17 '13 at 10:19
1

I have to use this because its not available on ARM. – Mike Christiansen Aug 23 '14 at 21:32
5

The .NET Core stack may not have BitArray.CopyTo. That being said, why not `1 << i` rather than `Convert.ToInt16(Math.Pow(2, i))`? – ChristopheD Feb 11 '17 at 19:39

score 1 · Answer 4 · answered May 12 '17 at 11:00

Reffering to this post (#43935747). A value X is short tpe whic I set two bits (6 and 10) like below: short X=1;

        var result = X;
        var bitsToSet = new [ ] { 5,9 };
        foreach ( var bitToSet in bitsToSet )
            {
            result+=( short ) Math.Pow ( 2,bitToSet );
            }
        string binary = Convert.ToString ( result,2 );

Now I would like to read the specific all bits from Value X and put it in to an array or a bit type like bool Val1= bit1, bool Val2=bit2....

I am a newbie and I think it is pretty simple for you guyes..

OK but you should make it `|=` and `(short)(1 << bitToSet)` to make it more obvious at a glance. It's not like this code is incomprehensible, but it relies on the combination of some "carefully chosen coincidences" instead of just obviously doing the right thing. — harold, May 12 '17 at 13:43

How can I convert BitArray to single int?

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