Bitwise XOR on Byte Array

Posted by patrick on August 31, 2011 0 comments

Spent the past few hours scrambling for a generic XOR solution on two byte arrays. I needed a solution that would add the match value to a specific result value if it did not already exist (assuming the most significant byte starts at the beginning of the array). You’d think this would be somewhere in the C# libraries by now. After an hour of searching, I decided to write my own. Ended up with the solution below.

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static byte[] BitwiseXOR(byte[] result, byte[] matchValue)
{
    if (result.Length == 0)
    {
        return matchValue;
    }

    byte[] newResult = new byte[matchValue.Length > result.Length ? matchValue.Length : result.Length];
           
    for (int i = 1; i < newResult.Length+1; i++)
    {
        //Use XOR on the LSBs until we run out
        if(i > result.Length)
        {
            newResult[newResult.Length - i] = matchValue[matchValue.Length - i];
        }
        else if (i > matchValue.Length)
        {
            newResult[newResult.Length - i] = result[result.Length - i];
        }
        else
        {
            newResult[newResult.Length -i] =
                (byte)(matchValue[matchValue.Length - i] ^ result[result.Length - i]);
        }
    }
    return newResult;
}