/* How many 1 bits are there in the Uint32. Low performance, do not call often.  */
static int number_of_bits_set(Uint32 a)
/* How many 1 bits are there in the Uint32. Low performance, do not call often.  */
static int number_of_bits_set(Uint32 a)
{
    if(!a) return 0;
    if(a & 1) return 1 + number_of_bits_set(a >> 1);
    return(number_of_bits_set(a >> 1));
}