ByteFormat.java

package hep.io.root.daemon.xrootd;

import java.text.DecimalFormat;
import java.text.FieldPosition;
import java.text.Format;
import java.text.ParsePosition;

/**
 * A formatter for formatting byte sizes. For example, formatting 12345 byes results in
 * "12.1 kB" and 1234567 results in "1.18 MB".
 *
 * @author Bill Lynch
 * @author Tony Johnson
 */
class ByteFormat extends Format
{
   
   private final static String[] mags = {" B"," kB"," MB"," GB"," TB"," PB"};
   private final static DecimalFormat formatter = new DecimalFormat("#,##0.0");
   public String format(long numBytes)
   {
      if (numBytes > 1024)
      {
         int mag = 1;
         for (; mag<mags.length-1; mag++)
         {
            if (numBytes < 1024*1024) break;
            numBytes /= 1024;
         }

         return formatter.format((double)numBytes / 1024.0)+mags[mag];
      }
      else
      {
         return numBytes+mags[0];
      }
   }

   /**
    * Format the given object (must be a Long).
    *
    * @param obj assumed to be the number of bytes as a Long.
    * @param buf the StringBuffer to append to.
    * @param pos
    * @return A formatted string representing the given bytes in more human-readable form.
    */
   public StringBuffer format(Object obj, StringBuffer buf, FieldPosition pos)
   {
      if (obj instanceof Long)
      {
         long numBytes = ((Long)obj).longValue();
         buf.append(format(numBytes));
      }
      return buf;
   }
   
   /**
    * In this implementation, returns null always.
    *
    * @param source
    * @param pos
    * @return returns null in this implementation.
    */
   public Object parseObject(String source, ParsePosition pos)
   {
      return null;
   }
}