What is the fastest way to calculate the number of bits needed to store a number

Question

I\'m trying to optimize some bit packing and unpacking routines. In order to do the packing I need to calculate the number of bits needed to store integer values. Here is th

Answer 1

You would have to check the execution time to figure the granularity, but my guess is that doing 4 bits at a time, and then reverting to one bit at a time would make it faster. Log operations would probably be slower than logical/bit operations.

if (n < 0) return 32;
int r = 0;
while (n && 0x7FFFFFF0) {
  r+=4;
  n >>= 4; }
while (n) {
  r++;
  n >>= 1; }
return r;