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From "Geir Magnusson Jr." <g...@pobox.com>
Subject Re: [classlib][pack200] Status update - able to parse (some) bytecode now
Date Fri, 02 Mar 2007 18:51:22 GMT

On Feb 27, 2007, at 6:26 PM, Alex Blewitt wrote:

> On 20/02/07, Alex Blewitt <alex.blewitt@gmail.com> wrote:
>> Good news everyone,
>> I've just managed to decode a class file with its constituent  
>> bytecode
>> out to a Jar. There's a few bugs (it doesn't calculate the max stack)
>> and the byteccode is replaced with 'return' -- but that's only  
>> because
>> pack200 does some extra mangling on the bytecode (e.g. 'super()' is
>> normally 2 bytes, but it's so common that there's a special 1 byte
>> marker for it).
> I've addressed this issue, and I can now generate a subset of the
> bytecode (e.g. getstatic/putstatic/invokevirtual/areturn etc.) from an
> input pack file into an output Jar. There's still the tricky problem
> of the arguments; essentially, each argument type (e.g. methodref,
> classref, constant pool) is encoded in their own separate set of bands
> which I've yet to decode/overlay).
> So, whilst the EclipseCon deadline of a 'hello world' isn't that far
> off, it's only going to work with a particular special set of bytecode
> (though I should be able to change the message and re-run it to show
> it's not a pre-recorded demo). But I want to set everyone's
> expectations suitably low, because although I may have reached the
> peak of the complexity, I've still got to come down the other side and
> pick up all the remnants that are yet to be done. I don't see a full
> implementation any time soon -- and I've been off for about a week
> recently too.

Cool stuff.

> Whilst I'm at EclipseCon with the wireless, I'll spend some spare time
> creating/submitting a patch for the work that's done so far. I'll then
> be off for a holiday and will pick up the trail again towards the end
> of March ...

What, you take one vacation a month?  I wish I lived in the UK :)


> Alex.

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