[Pharo-project] Alien signature: first attempt

Schwab,Wilhelm K bschwab at anest.ufl.edu
Thu Mar 1 16:52:49 EST 2012


Eliot,

That helps a bit; it's still unfamiliar territory.  I am a little bothered by #wordResult: and #floatResult.  There are times when one is expected to return 16 bit values (rare) and either a float or a double (common).  Does that flexibility exist?

Bill




________________________________
From: pharo-project-bounces at lists.gforge.inria.fr [pharo-project-bounces at lists.gforge.inria.fr] on behalf of Eliot Miranda [eliot.miranda at gmail.com]
Sent: Thursday, March 01, 2012 3:26 PM
To: Pharo-project at lists.gforge.inria.fr
Subject: Re: [Pharo-project] Alien signature: first attempt



On Thu, Mar 1, 2012 at 10:57 AM, Schwab,Wilhelm K <bschwab at anest.ufl.edu<mailto:bschwab at anest.ufl.edu>> wrote:
Esteban,

Will this work?  Even if so, is there a better way to define it?

No it won't work, because you don't understand what it does.


longVoidStarLongRetInt: callbackContext sp: spAlien
       <signature: 'int (*) (long, void *, long)' abi: 'IA32'>
       ^callbackContext wordResult:
               (block
                       value: (Alien newC:4)
                       value: (Alien forPointer: (spAlien unsignedLongAt: 5))
                       value: (Alien newC:4)
               )

The above takes only one parameter's value from the spAlien (the void * value) and passes garbage for the other parameters. The spAlien is a pointer to the incoming C callback stack frame, i.e. a pointer to the callback's parameters.  So spAlien unsignedLongAt: 5 gets the four-byte pointer for the void * parameter, wraps it up in a convenient pointer Alien (so the callback block can e.g. indirect through it to get at the data the pointer is pointing to), and passes it as the second argument of the callback block.  But the two Alien newC: 4's are entirely bogus, passing effectively uninitialized data for the first and third parameters of the callback block.  They're just empty Aliens, when in fact you want to pass two longs to the block for the first and third parameters.

So to pass values in you need something like:

longVoidStarLongRetInt: callbackContext sp: spAlien
       <signature: 'int (*) (long, void *, long)' abi: 'IA32'>
       ^callbackContext wordResult:
               (block
                       value: (spAlien signedLongAt: 1)
                       value: (Alien forPointer: (spAlien unsignedLongAt: 5))
                       value: (spAlien signedLongAt: 9)
               )

You might also need to consider passing the result of the block back out.  If you only want to use it to answer integers then the above is fine.  But take a look at the intcharstarRetint:sp: signature:

intcharstarRetint: callbackContext sp: spAlien
<signature: 'int (*)(int, char *)' abi: 'IA32'>
^callbackContext wordResult:
((block
value: (spAlien signedLongAt: 1) ~= 0
value: (Alien forPointer: (spAlien unsignedLongAt: 5)) strcpyUTF8)
ifNil: [0]
ifNotNil:
[:result|
result isInteger
ifTrue: [result]
ifFalse: [result == true ifTrue: [1] ifFalse: [0]]])

Analogously it passes a signed integer as the first argument and a UTF8 string derived from the second char * parameter. (The method should probably be called intcharstarasUTF8Retint:sp: or some such; forgive me, we're getting there).

But on return it takes the result of the callback block and passes it to the ifNil:ifNotNil: which
- maps a nil result form the block to 0 (ifNil: [0])
- maps integers to integers (which will only deal correctly with integers in the 32-bit range), and
- maps true to 1, mapping all other results to 0.

Does what's going on now make more sense?

HTH,
Eliot


Bill

________________________________________
From: pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr> [pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr>] on behalf of Schwab,Wilhelm K [bschwab at anest.ufl.edu<mailto:bschwab at anest.ufl.edu>]
Sent: Thursday, March 01, 2012 12:15 AM
To: Pharo-project at lists.gforge.inria.fr<mailto:Pharo-project at lists.gforge.inria.fr>
Subject: Re: [Pharo-project] FFI on 1.3: compile fields

thanks!!!!!




________________________________________
From: pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr> [pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr>] on behalf of Esteban Lorenzano [estebanlm at gmail.com<mailto:estebanlm at gmail.com>]
Sent: Wednesday, February 29, 2012 10:18 PM
To: Pharo-project at lists.gforge.inria.fr<mailto:Pharo-project at lists.gforge.inria.fr>
Subject: Re: [Pharo-project] FFI on 1.3: compile fields

you need to define a signature... not at home now, but wait 'til tomorrow and I'll send an example

best,
Esteban

El 29/02/2012, a las 11:21p.m., Schwab,Wilhelm K escribió:

> What does "cannot find callback signature" mean from #signature:block:?  I'm stuck.
>
>
>
>
> ________________________________________
> From: pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr> [pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr>] on behalf of Esteban Lorenzano [estebanlm at gmail.com<mailto:estebanlm at gmail.com>]
> Sent: Wednesday, February 29, 2012 6:54 PM
> To: Pharo-project at lists.gforge.inria.fr<mailto:Pharo-project at lists.gforge.inria.fr>
> Subject: Re: [Pharo-project] FFI on 1.3: compile fields
>
> yeah... sorry about that
> is a bug on FFI... I managed to worked around it for HPDF, for a customer's project... but of course is not a good and definitive solution.
>
> best,
> Esteban
>
> El 29/02/2012, a las 8:37p.m., Schwab,Wilhelm K escribió:
>
>> This is gonna take a while...   I had structs flying around as void* and was moderately happy.  Nonetheless, your suggestion worked, provided I add a lot getHandle asInteger and change the void* to long :(
>>
>>
>>
>>
>> ________________________________________
>> From: pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr> [pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr>] on behalf of Esteban Lorenzano [estebanlm at gmail.com<mailto:estebanlm at gmail.com>]
>> Sent: Wednesday, February 29, 2012 6:23 PM
>> To: Pharo-project at lists.gforge.inria.fr<mailto:Pharo-project at lists.gforge.inria.fr>
>> Subject: Re: [Pharo-project] FFI on 1.3: compile fields
>>
>> I also found some problems using void* in linux... maybe you want to use long (which has same size)... I "fixed" my problems that way.
>>
>> yes... maybe we need to look at FFI to see why void* has problems some times, but well, that can help you atm (sorry for not having a better answer)
>>
>> Esteban
>>
>> El 29/02/2012, a las 8:11p.m., Igor Stasenko escribió:
>>
>>> On 1 March 2012 00:58, Schwab,Wilhelm K <bschwab at anest.ufl.edu<mailto:bschwab at anest.ufl.edu>> wrote:
>>>> Another glitch: is there any problem passing things as void*?  I'm getting failure to coerce errors that did not arise before.
>>>>
>>> No idea. As you may suspect, i stopped using FFI/Alien once i got
>>> NativeBoost toy to play with.
>>>
>>> Please file the issue, describing the problem. so we can look over it
>>> and fix it.
>>>
>>>>
>>>>
>>>> ________________________________________
>>>> From: pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr> [pharo-project-bounces at lists.gforge.inria.fr<mailto:pharo-project-bounces at lists.gforge.inria.fr>] on behalf of Igor Stasenko [siguctua at gmail.com<mailto:siguctua at gmail.com>]
>>>> Sent: Wednesday, February 29, 2012 5:51 PM
>>>> To: Pharo-project at lists.gforge.inria.fr<mailto:Pharo-project at lists.gforge.inria.fr>
>>>> Subject: Re: [Pharo-project] FFI on 1.3: compile fields
>>>>
>>>> On 1 March 2012 00:37, Schwab,Wilhelm K <bschwab at anest.ufl.edu<mailto:bschwab at anest.ufl.edu>> wrote:
>>>>> Does 1.3 by default not create field accessors?  Why is that?  I thought
>>>>> nothing was happening.
>>>>>
>>>>
>>>> Good question, i'd like to know the answer too.
>>>> It is related to MC final 'installation' phase,
>>>> where it initializing all classes.
>>>>
>>>> In NativeBoost i was also using
>>>>
>>>> noteCompilationOf: aSelector meta: isMeta
>>>>      "A hook allowing some classes to react to recompilation of certain selectors"
>>>>
>>>> but there was a big question, at which point this hook is triggered,
>>>> and looks like some changes in MC stop triggering it/triggering at
>>>> wrong time (not all methods get into a class/ class not initialized
>>>> etc),
>>>> which makes it not very useful.
>>>>
>>>> So i ended up creating a DNU handler on instance side, then on DNU i
>>>> check if i have field accessors and if not,
>>>> compile them on the fly.
>>>>
>>>>
>>>>> Bill
>>>>>
>>>>
>>>>
>>>> --
>>>> Best regards,
>>>> Igor Stasenko.
>>>>
>>>>
>>>
>>>
>>>
>>> --
>>> Best regards,
>>> Igor Stasenko.
>>>
>>
>>
>>
>
>
>







--
best,
Eliot

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