@Override
                public void writeTo(Output output, T message)
                        throws IOException
                {
                    if (primitive)
                        output.writeDouble(number,
                                us.getDouble(message, offset), false);
                    else
                    {
                        Double value = (Double) us.getObject(message, offset);
                        if (value != null)
                            output.writeDouble(number, value.doubleValue(),
                                    false);
                    }
                }
Field factory via sun.misc.Unsafe.

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