[Pharo-project] Status of Alien FFI

Igor Stasenko siguctua at gmail.com
Sat Sep 19 02:46:43 EDT 2009


2009/9/19 Stéphane Ducasse <stephane.ducasse at inria.fr>:
> in fact the meta level interface of the VM is missing.
> And I would love to have what you describe.
> When I was tired by smalltalk I was thikning to build one on top of lua.
>

Lua is SLOW :)
Once i recommended one game developer to use Lua for scripting..
and he wired it into C project pretty easily.. but instead of writing
glue code which precompiling
all scripts, he decided to not spend much time on it and parse the
scripts from source each time he may need to run it..
The surprise was, that despite this crappy binding, game running at a
decent frame rate :)
But still - you can go and see the speed comparison of different
numerical algorythms implemented in different languages.
Squeak leaves Lua far behind..
Especially, i think, if you use language for scripting, so scripts
will tend to contain more logic than heavy numeric crunching (because
for numerical crunching hardcore devs using C & GPU) - smalltalk will
win even more.

> Stef
>
> On Sep 19, 2009, at 5:28 AM, Igor Stasenko wrote:
>
>> 2009/9/18 Stéphane Ducasse <stephane.ducasse at inria.fr>:
>>> yes this is one of my dream but ....
>>> I'm not good enough to make it come true.
>>>
>>
>> Lua is specifically designed from the very starting to live well as
>> embedded system, written in C. No wonder that its having very good C
>> interoperability.
>> And that's why, at the time i found the smalltalk, first thing i
>> thought, that
>> creating an interoperability layer between C and smalltalk will
>> unleash its potential
>> for use in scripting.
>> Unfortunately, almost every implementation i found & read about
>> smalltalk vere designed as a
>> self-sustained (or self-sufficient) sandboxed environment with a
>> little care about host interoperability in mind.
>> Even existence of FFI in Squeak doesn't changes that, because Squeak
>> VM architecture
>> as well as language-side design prevents you from controlling
>> interpreter from outside.
>> A less painful way for achieving a kind of embedding, as Andreas
>> mentioned, that you can write the
>> plugin which using callback machinery and create an image which simpli
>> 'listening' for calls from outside
>> then handle them and put response back.
>> But i can't tell, how efficient it could be comparing to Lua scripting
>> interface.
>>
>> For instance, if i would want to enable the dynamic primitive
>> publishing (which host application may want to
>> use), then this would require VM changes.
>> That's why i proposed , some time ago, to modify the VM internal
>> infrastructure to have a kind of namespace,
>> which is dynamically built-up using associations of symbols (C
>> strings) with some pointer/values.
>> Then you can publish primitives at any time you wanting to, replace
>> them at run time and do many other
>> kind of tricks, which is possible, when function pointer is not bound
>> at compile time, but discovered by VM
>> at run time. At some point we could even use a JIT to generate the
>> primitives and then let VM to pick them up at run time.
>> This means, that at some point you could JIT everything you need, and
>> replace the C-compiled VM stuff after booting the
>> image, and from now on, VM is not something which is made from stone
>> like all C-compiled binaries. So different
>> images could carry own system inside which, once its booted up, no
>> longer needs the statically compiled crap.
>> This also means, that by having a good JIT and VM tuned for this, we
>> don't really need writing any C code anymore, because
>> main reason why we doing this is speed and easy interoperability with
>> host environment. :)
>>
>>> Stef
>>>
>>> On Sep 18, 2009, at 6:40 PM, Lawson English wrote:
>>>
>>>> Johan Brichau wrote:
>>>>> On 16 Sep 2009, at 20:37, Ken Treis wrote:
>>>>>
>>>>>
>>>>>> * I'm creating a partial Alien library for GemStone so that I can
>>>>>> use the CairoGraphics package in both Pharo and GLASS. But on
>>>>>> x86-64, there there's a size difference between a pointer/long and
>>>>>> an integer. It'd be nice to have some more explicit APIs on Alien,
>>>>>> so I could say "Alien newCInteger" or "Alien newCLong" and have
>>>>>> the
>>>>>> platform return me the proper size Alien. Even without the
>>>>>> platform
>>>>>> size differences, it seems awkward to use "Alien newC: 4"
>>>>>> everywhere
>>>>>> I want an integer, "Alien newC: 8" where I want a double, etc.
>>>>>>
>>>>>
>>>>> Exactly.
>>>>>
>>>>> It becomes worse once you start having structs and nested structs
>>>>> or
>>>>> structs with pointers to structs ;-)
>>>>>
>>>>> I'm using Alien as the FFI to port JavaConnect from Visualworks to
>>>>> Pharo/Squeak. As you say, it is a pain to work at such a low-level
>>>>> compared to the DLLCC in VW. I am planning to do some work on
>>>>> creating
>>>>> a higher-level interface for it such that we can operate it as you
>>>>> mention, including the correct bytesizes for all platforms.
>>>>>
>>>>> At the moment, I'm mostly focusing on getting the port to work
>>>>> right
>>>>> before I start creating an interface on top of the current Alien
>>>>> interface.
>>>>>
>>>>>
>>>>>
>>>>
>>>> Something to keep in mind is the need for a straightforward way of
>>>> going
>>>> the other way: John Mcintosh's port of the Squeak VM to iPhone
>>>> implies
>>>> that the same thing could be done in other Lua-ish situations,
>>>> allowing
>>>> people to use smalltalk syntax for game scripting. With the right
>>>> libraries for an IDE, I would think squeak could be very
>>>> attractive to
>>>> at least some people in place of/in addition to using Lua.
>>>>
>>>>
>>>> Lawson
>>>>
>>>>
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>>>
>>>
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>>
>>
>>
>> --
>> Best regards,
>> Igor Stasenko AKA sig.
>>
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-- 
Best regards,
Igor Stasenko AKA sig.




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