Question

i have this line of code:

 base_num = (arr[j]/base)%256;

This line runs in a loop and the operations “/” and “%” take a lot of resources and time to perform. I would like to change this line and apply bit operations in order to maximize the program performance. How can i do that?

Thanks.

Answer 1

If base is the nth power of two, you can replace division by it with a bitshift of n to the right. Then, since taking the mod 256 of an integer is equivalent to taking its last 8 bits, you can AND it with 0xFF. Alternately, you can reverse the operations if you AND it with 256*base and then bitshift n to the right.

base_num = arr[j] >> n;
base_num &= 0xFF;

Of course, any half-decent compiler should be able to do this for you.