Well that blew my mind

[Chris Cunnington]

I understood yesterday that Spoon doesn't send objects to be recreated 
on the other side of a remote message, it sends information about 
objects. It encodes objects.

I see tags go over the wire and the tag types are related to classes in 
the EncodingClasses classvar in MessagingSession class>>initialize.

OK, a tag called methodTag goes over the wire. Now what?
It is connected in the dictionary to CompiledMethod. OK, we are going to 
make an instance of a compiled method on this side from the info coming 
over the wire. It's a little generic, isn't it? Don't we need to be a 
little more specific about what's in it? All those byte codes and literals?

Then it occurred to me that a new instance of CM could be populated... 
with the literals and material that are in a CM. What would we do that 
with? The whole class category in Spoon called LiteralMarkers. I'm 
guessing the markers go over the wire after the tag. Then they get 
installed into the CM. Bang. You've created a CM from a blueprint of one.

That' blew my mind. CM's always seemed immutable. Seems I've just never 
spent much time with CompiledMethod>>#newMethod:header: Let's just make 
one with a bag of literals.

And if we can make CMs from a stream of information, then we can make 
anything. Classes are just collections of CMs with some variables.

Here's were we do just that: we make a CM and fill it full of literals 
from literal markers.

MethodEdition>>#method
     "Answer the method I prescribe in the local system."

     | method |

*method* := (
*CompiledMethod*
             newMethod: (endPC - initialPC + 2)
             header: header).

     1
         to: literalMarkers size
         do: [:literalIndex |
*method*
                 literalAt: literalIndex
                 put: (literalMarkers at: literalIndex) *literal*].

    .. snip ...

     ^method

It seems to me these tools of tags and markers are a complete way to 
describe classes and instances. They can be stored as data and then 
re-instantiated on need. And I guess you could take a snapshot of any 
object or set of objects to have a history or version record.

Have a nice weekend,

Chris
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