/** This class includes static methods for calculating the logarithm (to
**  base 2).
**
**  @author R. McCloskey
**  @version November 2006
*/

public class Log2Calc {


   /** Calculates the floor of the logarithm (to the base two) of 
   **  the specified natural number.  
   **  pre: m>=0
   **  @return floor of lg m (we define lg 0 to be -1)
   */
   public static int floorLog2(int m) {
      int result;
      if (m == 0)
         { result = -1; }
      else {
         result = 0;
         while (m != 1) {
            m = m / 2;
            result++;
         }
      }
      return result;
   }

   /** Calculates the floor of the logarithm (to the base two) of 
   **  the specified natural number.  (Recursive version)
   **  pre:  m>=0
   **  @return floor of lg m (we define lg 0 to be -1)
   */
   public static int floorLog2Rec(int m) {

      int result;
      if (m == 0)
         { result = -1; }
      else 
         { result = 1 + floorLog2Rec(m/2); }
      return result;
   }

   /** Calculates the ceiling of the logarithm (to the base two) of 
   **  the specified natural number.  
   **  pre: m >= 0
   **  @return ceiling of lg m (we define lg 0 to be -1)
   */
   public static int ceilingLog2(int m) {
      int result;
      if (m == 0)
         { result = floorLog2(0); }
      else
         { result = floorLog2(m + m - 1); }
      return result;
   }

}