Može ovako
Code:
static int[] firstBitTable = {
63, 30, 3, 32, 25, 41, 22, 33, 15, 50, 42, 13, 11, 53, 19, 34, 61, 29, 2,
51, 21, 43, 45, 10, 18, 47, 1, 54, 9, 57, 0, 35, 62, 31, 40, 4, 49, 5, 52,
26, 60, 6, 23, 44, 46, 27, 56, 16, 7, 39, 48, 24, 59, 14, 12, 55, 38, 28,
58, 20, 37, 17, 36, 8
};
public static int GetIndexOfFirstBit(ulong p_number)
{
ulong b = p_number ^ (p_number - 1);
uint fold = (uint)((b & 0xffffffff) ^ (b >> 32));
return firstBitTable[(fold * 0x783a9b23) >> 26];
}
Ako nekom zatreba :)