code: private static NfsPreOpAttributes makePreOpAttributes(Xdr xdr) {
          NfsPreOpAttributes preOpAttributes = null;
          if ((xdr != null) && xdr.getBoolean()) {
              preOpAttributes = new NfsPreOpAttributes(xdr);
          }
          return preOpAttributes;
      }
docs: Extracts the pre-operation attributes.
  @param xdr
  @return The attributes.