Currently, a lot of classes could be immutable if it wasn't for the readFrom() method to initialize itself from an input stream.

However, if we had a factory, which reads and constructs immutable instances of classes, then we could turn a lot of classes into immutable classes, for example all headers should be immutable.

The code for marshalling and unmarshalling could be generated, e.g. based on an XML description of the data layout of a class, or via annotations.