Rotate right by n only using bitwise operators in C

Question

I'm trying to implement a rotateRight by n function in C by only using bitwise operators.

So far, I have settled on using this.

y = x >> n
z = x << (32 - n)

g = y | z

So take for instance the value 11010011

If I were to try and `rotateRight(5):

y becomes 11111110

z becomes 01100000

Then g becomes 111111110

However the correct answer should be 10011110

This almost works, but the problem is that the right-shift copies the sign bit when I need it to perform logical shift, and so some of my answers are the negative of what they should be. How can I fix this?

Note I am unable to use casting or unsigned types

Answer 1

You could shift unsigned values:

y = (int)((unsigned)x >> n);
z = x << (32 - n);
g = y | z;

Or, you could mask appropriately:

y = (x >> n) & ~(-1 << (32 - n));
z = x << (32 - n);
g = y | z;