Alternative to java.io.Externalizable that is HiearichalStream aware

Following on from XSTR-211, an alternative to java.io.Externalizable that works with HierarichalStreams instead of standard ObjectStreams.

This would follow the same contact as java.io.Externalizable in that a default constructor is required and subclasses that require extra serialized information must explicitly provide the data.

Something like:

package com.thoughtworks.xstream;

public interface ?????able {
void writeExternal(HierarchicalStreamWriter writer, MarshallingContext context);
void readExternal(HierarchicalStreamReader reader, UnmarshallingContext context);
}