code: public long getCrc64()
    {
      try {
        if (isDirectory()) {
          String []list = list();
  
          long digest = 0x1;
  
          for (int i = 0; i < list.length; i++) {
            digest = Crc64.generate(digest, list[i]);
          }
  
          return digest;
        }
        else if (canRead()) {
          ReadStreamOld is = openRead();
  
          try {
            long digest = 0x1;
  
            byte []buffer = is.buffer();
            while (is.fillBuffer() > 0) {
              int length = is.getLength();
  
              digest = Crc64.generate(digest, buffer, 0, length);
            }
  
            return digest;
          } finally {
            is.close();
          }
        }
        else {
          return 0; // Depend requires -1
        }
      } catch (IOException e) {
        // XXX: log
        e.printStackTrace();
  
        return -1;
      }
    }
docs: Returns the crc64 code.