Thread: Bits and bytes- Please help.

Originally Posted by quzah

Yeah, I can do it in 1 with a lookup table.

But your lookup table will waste memory, as it will have 256 entries.

Here's a proof-of-concept code that does (not quite) exactly what the OP wanted to achieve:

Code:

int ffc(char c)
{
	c = ~c;

	static const char debruijn[8] = {0, 1, 2, 4, 7, 3, 6, 5};
	return debruijn[((c & -c) * 23) >> 5];
}

It is full of magic numbers and without reading the HOWTO, it will be very hard to understand what the code is doing.

Greets,
Philip