On Thu, Sep 03, 2015 at 09:05:07PM -0400, Chris Cunnington wrote:
> This community needs a repository for plugins. A directory at 
> http://ftp.squeak.org ought to do it.
> 
> If I want to try Alien I need the plugin. Where am I going to get that? 
> I could get VMMaker, read NewSqueakIA32ABIPlugin three times to see it 
> is not saying Newspeak and realize it compiles a plugin called IA32ABI, 
> which - coincidentally - is the name of the plugin the error Alien 
> exampleCqsort will gives me. (NewSqueakIA32ABIPlugin class>> moduleName 
> returns IA32ABI).
> 
> Does anybody know what the Genie plugin does? Does Paul DeBrucker need 
> to store a BerkeleyDB plugin dll he got by emailing somebody on GitHub?
> 
> If I understand this correctly, if such a directory existed, then all a 
> person would need to do to try the above Alien code would be to download 
> a pre-compiled plugin from - say - 
> http://ftp.squeak/plugins/Alien/fooVersion, put it in their VM directory 
> and start the image. Then check with SmalltalkImage current 
> listLoadedModules to see if you're ready to go.
> 
> I nominate Fabio Niephaus to be the person the community can send 
> pre-compiled plugins for inclusion in such a directory. Eliot's been 
> banging away about Alien for some time [1]. If a person could go, get 
> the plugin and give the code shot, he could have more productive 
> conversations about Alien.
> 
> So, if, Eliot, you have a pre-compiled plugin for Alien, perhaps in an 
> idle moment, you could email it to Fabio? And when, Fabio, you've 
> created the directory in http://ftp.squeak.org you could announce it 
> here on Squeak-dev?
> 
> FWIW,
> 
> Chris

A word of caution:

I think the idea is good in principle, but it needs to be accompanied
by a commitment by someone to do the hard work of keeping track of
dependencies on the various flavors of OS, image word size, VM word size,
spur/V3, and so forth. If someone would like to take that on, great.
That said, we don't want to start a project that gets 80% completed, and
then expect "the community" to do the rest of the work.

I cannot speak for Fabio, but I don't think it is fair for us to expect
him to take on this kind of workload unless he has indicated an interest
in doing it.

Maybe a restricted repository focused just on compiled plugins known
to work with the Spur VM on a limited range of OS flavors would be helpful
at this stage. It probably does not belong on ftp.squeak.org, but it could
be a very useful resource if someone (Chris Cunnington?) wants to set it up.

Dave


> 
> [1] http://wiki.squeak.org/squeak/uploads/6100/
> 
> On 2015-09-03 7:07 PM, Eliot Miranda wrote:
> >Hi Craig,
> >
> >    you need Alien-eem.24
> >
> >Here's Alien class>>exampleCqsort
> >"Call the libc qsort function (which requires a callback)."
> >"Alien exampleCqsort"
> >"(Time millisecondsToRun: [100 timesRepeat: [Alien exampleCqsort]]) / 
> >100.0"
> >| cb rand nElements sizeofDouble values orig sort |
> >rand := Random new.
> >values := Alien newC: (nElements := 100) * (sizeofDouble := 8).
> >1 to: values dataSize by: sizeofDouble do:
> >[:i| values doubleAt: i put: rand next].
> >orig := (1 to: values dataSize by: sizeofDouble) collect: [:i| values 
> >doubleAt: i].
> >cb := Callback
> >signature:  #(int (*)(const void *, const void *))
> >block: [ :arg1 :arg2 | ((arg1 doubleAt: 1) - (arg2 doubleAt: 1)) sign].
> >(Alien lookup: 'qsort' inLibrary: Alien libcName)
> >primFFICallResult: nil
> >with: values pointer
> >with: nElements
> >with: sizeofDouble
> >with: cb thunk.
> >sort := (1 to: values dataSize by: sizeofDouble) collect: [:i| values 
> >doubleAt: i].
> >values free.
> >^orig -> sort
> >
> >The above example uses Alien to make the callout.  To use it with the 
> >FFI simply pass cb pointer as the argument as is done above.
> >
> >
> >Implementation:
> >
> >The way that it works is in two parts
> >- the VM passes up a pointer to a structure from which all arguments, 
> >stacked and in registers (because the VM has copied the register args 
> >into the struct) can be accessed, and through which the result can be 
> >returned.
> >- the image level provides marshalling methods that match the 
> >signature in the callback
> >
> >So e.g. with a callback of
> >Callback
> >signature:  #(int (*)(const void *, const void *))
> >block: [ :arg1 :arg2 | ((arg1 doubleAt: 1) - (arg2 doubleAt: 1)) sign]
> >the marshalling methods are in Callback's signature protocol:
> >
> >Callback>>voidstarvoidstarRetint: callbackContext sp: spAlien
> ><signature: #(int (*)(const void *, const void *)) abi: 'IA32'>
> >^callbackContext wordResult:
> >(block
> >value: (Alien forPointer: (spAlien unsignedLongAt: 1))
> >value: (Alien forPointer: (spAlien unsignedLongAt: 5)))
> >
> >where spAlien is an Alien pointing to a VMCallbackContext32.
> >
> >For ARM support we would add
> >
> >Callback>>voidstarvoidstarRetint: callbackContext sp: spAlien 
> >intRegArgs: regsAlien
> ><signature: #(int (*)(const void *, const void *)) abi: 'ARMV5'>
> >^callbackContext wordResult:
> >(block
> >value: (Alien forPointer: (regsAlien unsignedLongAt: 1))
> >value: (Alien forPointer: (regsAlien unsignedLongAt: 5)))
> >
> >Basically the idea is that the selector of the method doesn't matter 
> >except for the number of arguments.  What's important is the pragma 
> >which defines the signature and the ABI for which this is a valid 
> >marshalling method.
> >
> >When the callback is instantiated, Callback introspects to find the 
> >marshalling method that matches the signature.  If one doesn't already 
> >exist you can write one.  Hopefully we'll write an ABI compiler that 
> >will automatically generate these marshalling methods according to the 
> >platform's ABI, but for now its a manual process.  But at least it's 
> >open and flexible.  When the callback is invoked the evaluator is 
> >performed with the current callbackContext and pointer(s) to the 
> >arguments. There is a 32-bit and a 64-bit callback context, and it can 
> >have a stack pointer, integer register args and floating point 
> >register args.  So it's general enough for any callback.
> >
> >To pass back the result, a value is assigned into the struct via the 
> >accessor in the marshalling method and control returns to teh point 
> >where teh callback comes in, and this uses a primitive to return.  
> >Inside the callbackCOntext is a jmpbuf from a setjmp.  The primitive 
> >longjmp's back to the entry point in the VM which extracts the result 
> >and the code for the kind of result and returns:
> >
> >Callback class>>invokeCallbackContext: vmCallbackContextAddress 
> >"<Integer>" "^<FFICallbackReturnValue>"
> >"The low-level entry-point for callbacks sent from the VM/IA32ABI plugin.
> >Return via primReturnFromContext:through:.  thisContext's sender is the
> >call-out context."
> >| callbackAlien type |
> >callbackAlien := (Smalltalk wordSize = 4
> >ifTrue: [VMCallbackContext32]
> >ifFalse: [VMCallbackContext64])
> >atAddress: vmCallbackContextAddress.
> >[type := Callback evaluateCallbackForContext: callbackAlien]
> >ifCurtailed: [self error: 'attempt to non-local return across a 
> >callback'].
> >type ifNil:
> >[type := 1. callbackAlien wordResult: -1].
> >callbackAlien primReturnAs: type fromContext: thisContext
> >
> >On Thu, Sep 3, 2015 at 5:22 AM, Craig Latta <craig at netjam.org 
> ><mailto:craig at netjam.org>> wrote:
> >
> >
> >    Hi all--
> >
> >         I'd like to use a C shared library via FFI from Squeak or Pharo.
> >    Specifically, I want to call a C function which takes as one of its
> >    parameters a pointer to an array of callback function addresses. Does
> >    one of the FFI approaches floating around handle that, and provide a
> >    relatively pleasant mapping between Smalltalk block closures and C
> >    callback function addresses?
> >
> >         I was doing this so far in GemStone, but apparently its FFI only
> >    supports passing callback function addresses one at a time as direct
> >    parameters of C callouts. I suppose I could write a wrapper C library
> >    around the one I really want to use, that provides the callback setup
> >    interface that GemStone expects, but whenever I have to write actual C
> >    code I start to think "Hm, why don't I just use a Smalltalk VM for
> >    which
> >    I have the source?" :)  All the fancy distributed object-database
> >    stuff
> >    that my project also wants can wait for a bit.
> >
> >
> >         thanks!
> >
> >    -C
> >
> >    --
> >    Craig Latta
> >    netjam.org <http://netjam.org>
> >    +31 6 2757 7177 <tel:%2B31%20%20%206%202757%207177> (SMS ok)
> >    + 1 415 287 3547 <tel:%2B%201%20415%20%20287%203547> (no SMS)
> >
> >
> >
> >
> >
> >-- 
> >_,,,^..^,,,_
> >best, Eliot
> >
> >
> 

>