@Override
                public void writeTo(Output output, T message)
                        throws IOException
                {
                    Date value = (Date) us.getObject(message, offset);
                    if (value != null)
                        output.writeFixed64(number, value.getTime(), false);
                }
Field factory via sun.misc.Unsafe.

@author David Yu
@created Jul 7, 2011
protostuff-runtime/src/main/java/io/protostuff/runtime/RuntimeUnsafeFieldFactory.java