Continuations

[Patrick Lightbody-3]

Geert,
Got it almost completely working. I don't know how reusable this code
will be though, as EngineClassLoader does many things besides just
continuation support. I think we should break the responsibilities up,
such as ContinuationClassLoader, CompilingClassLoader, etc.

Anyway, the only problem I have now is that I think the pause() method
should take an argument (String) and I want to pass that string back
through the PauseException that is thrown, either directly or within
the ContinuationContext. This would be needed in WebWork to tell it
what result to render.

Any idea how to do that? I'm looking at the bytecode/ASM logic, but it
is a little confusing as the pause() method is popped off right away,
so i'm not sure how to get a handle on that parameter.

[Geert Bevin]

Hi Patrick,

> Got it almost completely working. I don't know how reusable this code

Great!

> will be though, as EngineClassLoader does many things besides just
> continuation support. I think we should break the responsibilities up,
> such as ContinuationClassLoader, CompilingClassLoader, etc.

I was actually not planning on making it reusable on classloader  
level. Imho RIFE/continuations should extract the code from  
EngineClassLoader from line 389 until 430 into a  
ContinuationInstrumentor class or something like that. Like this, the  
actual functionality can be used anywhere.

> Anyway, the only problem I have now is that I think the pause() method
> should take an argument (String) and I want to pass that string back
> through the PauseException that is thrown, either directly or within
> the ContinuationContext. This would be needed in WebWork to tell it
> what result to render.

I think that should be abstracted a bit better then. Maybe we should  
support any kind of parameters dynamically, since RIFE doesn't need  
any, Webwork needs a String, another framework might need something  
else. The check here:
if ("pause".equals(name) && "()V".equals(desc))

could just look for the method name and parse the description to find  
out what parameters are actually used. ASM's Type class can help a  
lot here. The parameters can then be put into an Object array (null  
if there are no parameters) and provide that to PauseException.

> Any idea how to do that? I'm looking at the bytecode/ASM logic, but it
> is a little confusing as the pause() method is popped off right away,
> so i'm not sure how to get a handle on that parameter.

Look at how the call method is handled, you can use this to retrieve  
the parameter and afterwards pop the method call off.
mMethodVisitor.visitVarInsn(ASTORE, mCallNameIndex);

Can you give me a preferred login and password so that I can setup a  
Subversion account for you and RIFE/continuations? Like this I can  
see where you're going and make quick changes if I see the need for  
them.

Best regards,

Geert

--
Geert Bevin                       Uwyn bvba
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