public void
restoreActive(int pos) {
	if (pos > byteBuffer.capacity()) {
		throw new IllegalArgumentException("cannot set active " +
						   "region past end of input");
	}
	byteBuffer.limit(byteBuffer.position());
}
Restores the previously set active region.  This differs from setActive() in
that restoreActive() takes an absolute position, and setActive takes an
offset from the current location.
@param pos The end of the active region.
src/main/java/core/org/xbill/DNS/DNSInput.java