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c#binarybiginteger

Convert BigInteger binary to BigInteger number

Currently I am using the Long integer type. I used the following to convert from/to binary/number:

Convert.ToInt64(BinaryString, 2); // Convert binary string of base 2 to number
Convert.ToString(LongNumber, 2); // Convert long number to binary string of base 2

Now the numbers I am using have exceeded 64 bit, so it has started using BigInteger. I can't seem to find the equivalent of the code above.

How can I convert from a BinaryString that have over 64bits to a BigInteger number and vice versa?

The references in the answer contains the answer I want, but I am having some trouble in the conversion from Number to Binary.

I have used the following code which is available in the first reference:

    public static string ToBinaryString(this BigInteger bigint)
    {
        var bytes = bigint.ToByteArray();
        var idx = bytes.Length - 1;

        // Create a StringBuilder having appropriate capacity.
        var base2 = new StringBuilder(bytes.Length * 8);

        // Convert first byte to binary.
        var binary = Convert.ToString(bytes[idx], 2);

        // Ensure leading zero exists if value is positive.
        if (binary[0] != '0' && bigint.Sign == 1)
        {
            base2.Append('0');
        }

        // Append binary string to StringBuilder.
        base2.Append(binary);

        // Convert remaining bytes adding leading zeros.
        for (idx--; idx >= 0; idx--)
        {
            base2.Append(Convert.ToString(bytes[idx], 2).PadLeft(8, '0'));
        }

        return base2.ToString();
    }

The result I got was wrong:

100001000100000000000100000110000100010000000000000000000000000000000000 ===>  2439583056328331886592
2439583056328331886592 ===> 0100001000100000000000100000110000100010000000000000000000000000000000000

If you put the resulted binary string under each other, you will notice that the conversion is correct and that the problem is that there is a leading zero from the left:

100001000100000000000100000110000100010000000000000000000000000000000000
0100001000100000000000100000110000100010000000000000000000000000000000000

I tried reading the explanation provided in the code and changing it, but no luck.

I was later able to solve it by changing the following in the code:

        // Ensure leading zero exists if value is positive.
        if (binary[0] != '0' && bigint.Sign == 1)
        {
            base2.Append('0');

            // Append binary string to StringBuilder.
            base2.Append(binary);
        }
Solution

  • Unfortunately, there is nothing built-in in the .NET framework.

    Fortunately, the Stack Overflow community has already solved both problems: