bitwise operations

bits.h

/* 
http://graphics.stanford.edu/~seander/bithacks.html
*/

int is_power_of_two(unsigned int x)
{
  return ((x != 0) && !(x & (x - 1)));
}

int count_bits(unsigned int v)
{
  unsigned int c; // c accumulates the total bits set in v
  for (c = 0; v; c++)
    v &= v - 1; // clear the least significant bit set
}