package org.lcsim.util.cache;
   
   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
   */
  public class ByteFormat extends Format {
  
      private final static String[] mags = { " B", " kB", " MB", " GB", " TB", " PB" };
      private final static DecimalFormat formatter = new DecimalFormat("#,##0.0");
  
      /**
       * Formats a long which represent a number of bytes.
       */
      public String format(long bytes) {
          return format(new Long(bytes));
      }
  
      /**
       * 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();
              if (numBytes > 1024) {
                  int mag = 1;
                  for (; mag < mags.length; mag++) {
                      if (numBytes < 1024 * 1024)
                          break;
                      numBytes /= 1024;
                  }
  
                  buf.append(formatter.format((double) numBytes / 1024.0)).append(mags[mag]);
              } else {
                  buf.append(numBytes).append(mags[0]);
              }
          }
          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;
      }
  }