LISTING 1 - BITLOG FUNCTION IMPLEMENTATION

/* Bitlog function
 * Invented by Tom Lehman at Invivo Research, Inc.,
 * ca. 1990
 *
 * Gives an integer analog of the log function
 * For large x,
 *
 * B(x) = 8*(log(base 2)(x) - 1)
 */

short bitlog(unsigned long n)
{
   short b;
    
   // shorten computation for small numbers
   if(n <= 8)
      return (short)(2 * n);
	
   // find the highest non-zero bit
   b=31;
   while((b > 2) && ((long)n > 0))
   {
      --b;
      n <<= 1;
   }
   n &= 0x70000000;
   n >>= 28;
   cout << b << ' ' << n << endl;
   return (short)n + 8 * (b - 1);
}

listing 2 - integer exponential

/* Bitexp function
 * returns an integer value equivalent to the exponential. For numbers > 16,  
bitexp(x) approx = 2^(x/8 + 1) */

unsigned long bitexp(unsigned short n)
{
   unsigned short b = n/8;
   unsigned long retval;

   // make sure no overflow
   if(n > 247)
      return 0xf0000000;

   // shorten computation for small numbers
   if(n <= 16)
      return (unsigned long)(n / 2);

   retval = n & 7;
   retval |= 8;
   cout << dec << b << ' ' << hex << retval << endl;

   return (retval << (b - 2));
}