private static unsafe void MaskArrayAsLongs(int mask, int[] ints)
{
    var longMask = ((long)mask << 32) + mask;

    fixed (int* pt = ints)
    {
        var end = (long*)pt + ints.Length / 2;

        if (ints.Length % 2 == 1)
        {
            ints[ints.Length - 1] ^= mask;
        }

        for (var curr = (long*)pt; curr < end; curr++)
        {
            *curr ^= longMask;
        }
    }
}