binary.java

java的小波分析程序

package wavelet_util;

/**
 *

  Calculate power and log functions using fast
  binary operations.

 */
public class binary {
  /**
   *
     Calculate 2<sup>n</sup> where n >= 0

     @param n
        a value between 0..31

     @return power2 returns 2<sup>n</sup>

   */
  public static int power2( byte n)
  {
    int rslt = 0x1 << (n & 0x1f);
    return rslt;
  } // power2


  /**
   *
  <p>
     Calculate floor( log<sub>2</sub>( val ) ), where val > 0
  <p>
     The log function is undefined for 0.
  
     @param val
        a positive value

     @return <tt>floor( log<sub>2</sub>( val ) )</tt>
  
   */
  public static byte log2(int val )
  {
    byte log;

    for (log = 0; val > 0; log++, val = val >> 1)
      ;
  
    log--;
  
    return log;
  } // log2


  /**
    nearestPower2
  <p>
    Given a value "val", where val > 0, nearestPower2 returns
    the power of 2 that is less than or equal to val.

   */
  public static int nearestPower2( int val )
  {
    byte l = log2( val );
    int power = power2( l );

    return power;
  } // nearestPower2

} // class binary