Bitwise Operations Tips/Tricks

How do you negate a number, ignoring leading zeroes?

Let's say you have unsigned, 8 bit integer: 5. How can we get the inverse of this? (~5)

5 in binary is 101, so the inverse would be 010 or 2.

If we were to do the bitwise operation inverse, we would get something different. Since it is a 8 bit integer, 5 is actually 00000101 and the inverse would be 11111010.

So how do we do this? ~5 & ((1 << 3) - 1)

We take 1, shift it over by however many digits we want to inverse and subtract 1. This gives us leadings zeroes with a specific number of tailing ones. We then intersect this with the inverse. This essentially get's rid of the leading ones that result from the inverse.

How do you do a bitwise equals operation?

Let's say we have 101110 and 101001. How can we get a binary value that shows which digits are equal? In this case, 111000?

You can do a XOR and negate!