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Yuriy Babah

question about FFI

Hi !

I'm trying to call a very simple function from C ++ lib, writed for the test.
function with prototype:

extern "C" float interpolationFunc(float* xm, float* ym, int size, float x).

In Pharo7 wrote:
FFIExamples class >> interpolationFunc_xm: xM ym: yM size: size x: x
^ self ffiCall: #(float interpolationFunc #(float * xM , float * yM , int size , float x)) module: 'libinterpolationLib.so'

in Playground i'm doing:
xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := xm clone.
#(2 3) doWithIndex: [:each :i | xm at: i put: each].
#(3 4) doWithIndex: [:each :i | ym at: i put: each].
FFIExamples interpolationFunc_xm: xm pointer ym: ym pointer size: 2 x: 2.5 .

last expression returninп me 0.0, but right is 3.5.

I'm dit the same in Python3 ctypes, and there work's fine.

In UnifiedFFI booklet is absent chapter "Arrays", anybody may help with whot i'm doing wrong?

tesonep@gmail.com

Re: question about FFI

Hi,

could be the problem that you are using the same external array for both xm and ym?.

The clone message just creates a shallow copy of the external array.

It does not allocates a new external array, it only copies the address in both xm and ym.

You should better do something like this:

xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := FFIExternalArray externalNewType: 'float' size: 2.

Cheers.

On Mon, Nov 26, 2018 at 9:30 AM Yuriy Babah <[hidden email]> wrote:

Hi !

I'm trying to call a very simple function from C ++ lib, writed for the test.
function with prototype:

extern "C" float interpolationFunc(float* xm, float* ym, int size, float x).

In Pharo7 wrote:
FFIExamples class >> interpolationFunc_xm: xM ym: yM size: size x: x
^ self ffiCall: #(float interpolationFunc #(float * xM , float * yM , int size , float x)) module: 'libinterpolationLib.so'

in Playground i'm doing:
xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := xm clone.
#(2 3) doWithIndex: [:each :i | xm at: i put: each].
#(3 4) doWithIndex: [:each :i | ym at: i put: each].
FFIExamples interpolationFunc_xm: xm pointer ym: ym pointer size: 2 x: 2.5 .

last expression returninп me 0.0, but right is 3.5.

I'm dit the same in Python3 ctypes, and there work's fine.

In UnifiedFFI booklet is absent chapter "Arrays", anybody may help with whot i'm doing wrong?

Pablo Tesone.
[hidden email]

Yuriy Babah

Re: question about FFI

Thank, i'm trued do this, and i'm got

aBoxedFloat64 4.5879913020458836e-41 ,

which is still a very strange value

пн, 26 нояб. 2018 г. в 12:33, [hidden email] <[hidden email]>:

Hi,

could be the problem that you are using the same external array for both xm and ym?.
The clone message just creates a shallow copy of the external array.
It does not allocates a new external array, it only copies the address in both xm and ym.

You should better do something like this:

xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := FFIExternalArray externalNewType: 'float' size: 2.

Cheers.

On Mon, Nov 26, 2018 at 9:30 AM Yuriy Babah <[hidden email]> wrote:
Hi !

I'm trying to call a very simple function from C ++ lib, writed for the test.
function with prototype:

extern "C" float interpolationFunc(float* xm, float* ym, int size, float x).

In Pharo7 wrote:
FFIExamples class >> interpolationFunc_xm: xM ym: yM size: size x: x
^ self ffiCall: #(float interpolationFunc #(float * xM , float * yM , int size , float x)) module: 'libinterpolationLib.so'

in Playground i'm doing:
xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := xm clone.
#(2 3) doWithIndex: [:each :i | xm at: i put: each].
#(3 4) doWithIndex: [:each :i | ym at: i put: each].
FFIExamples interpolationFunc_xm: xm pointer ym: ym pointer size: 2 x: 2.5 .

last expression returninп me 0.0, but right is 3.5.

I'm dit the same in Python3 ctypes, and there work's fine.

In UnifiedFFI booklet is absent chapter "Arrays", anybody may help with whot i'm doing wrong?

--
Pablo Tesone.
[hidden email]

Yuriy Babah

Re: question about FFI

just in case,

and

https://www.virustotal.com/ru/file/738460bb6be71b4615581dad1a787cbb80b188e52fe3480ef54b7bfce500f3dd/analysis/1543226071/

пн, 26 нояб. 2018 г. в 12:50, Yuriy Babah <[hidden email]>:

Thank, i'm trued do this, and i'm got
aBoxedFloat64 4.5879913020458836e-41 ,
which is still a very strange value

пн, 26 нояб. 2018 г. в 12:33, [hidden email] <[hidden email]>:
Hi,

could be the problem that you are using the same external array for both xm and ym?.
The clone message just creates a shallow copy of the external array.
It does not allocates a new external array, it only copies the address in both xm and ym.

You should better do something like this:

xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := FFIExternalArray externalNewType: 'float' size: 2.

Cheers.

On Mon, Nov 26, 2018 at 9:30 AM Yuriy Babah <[hidden email]> wrote:
Hi !

I'm trying to call a very simple function from C ++ lib, writed for the test.
function with prototype:

extern "C" float interpolationFunc(float* xm, float* ym, int size, float x).

In Pharo7 wrote:
FFIExamples class >> interpolationFunc_xm: xM ym: yM size: size x: x
^ self ffiCall: #(float interpolationFunc #(float * xM , float * yM , int size , float x)) module: 'libinterpolationLib.so'

in Playground i'm doing:
xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := xm clone.
#(2 3) doWithIndex: [:each :i | xm at: i put: each].
#(3 4) doWithIndex: [:each :i | ym at: i put: each].
FFIExamples interpolationFunc_xm: xm pointer ym: ym pointer size: 2 x: 2.5 .

last expression returninп me 0.0, but right is 3.5.

I'm dit the same in Python3 ctypes, and there work's fine.

In UnifiedFFI booklet is absent chapter "Arrays", anybody may help with whot i'm doing wrong?

--
Pablo Tesone.
[hidden email]

libinterpolationLib.so (133K) Download Attachment

Pharo Smalltalk Users mailing list

Re: question about FFI

In reply to this post by Yuriy Babah

Yuriy Babah wrote
> in Playground i'm doing:
*
> #(2 3) doWithIndex: [:each :i | xm at: i put: each].
> #(3 4) doWithIndex: [:each :i | ym at: i put: each].
*
>
> whot i'm doing wrong?

So, you're putting 2 at index 2 of xm, and then writing 3 past end of array,
and in ym you're putting 3 and 4 at offsets past the end of array?

It's a wonder your image didn't crash, rather than return interpolation of
the uninitialized values...

Cheers,
Henry

--
Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

Pharo Smalltalk Users mailing list

Re: question about FFI

In reply to this post by Yuriy Babah

Nevermind me, hadn't had my coffee yet, for some reason I didn't see it was
doWithIndex: you were using :/

Still a bit scary that FFIExternalArray at:put: doesn't perform bounds
checks...

Cheers,
Henry

--
Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html

EstebanLM

Re: question about FFI

In reply to this post by Yuriy Babah

Hi,

On 26 Nov 2018, at 09:28, Yuriy Babah <[hidden email]> wrote:

Hi !

I'm trying to call a very simple function from C ++ lib, writed for the test.
function with prototype:

extern "C" float interpolationFunc(float* xm, float* ym, int size, float x).

In Pharo7 wrote:
FFIExamples class >> interpolationFunc_xm: xM ym: yM size: size x: x
^ self ffiCall: #(float interpolationFunc #(float * xM , float * yM , int size , float x)) module: 'libinterpolationLib.so'

in Playground i'm doing:
xm := FFIExternalArray externalNewType: 'float' size: 2.
ym := xm clone.
#(2 3) doWithIndex: [:each :i | xm at: i put: each].
#(3 4) doWithIndex: [:each :i | ym at: i put: each].
FFIExamples interpolationFunc_xm: xm pointer ym: ym pointer size: 2 x: 2.5 .

This is incorrect. “xm” and “ym” are already pointers (references)

When you pass "xm pointer” you are actually passing a pointer to a pointer (a float** in this case)

This looks better:

FFIExamples

interpolationFunc_xm: xm getHandle

ym: ym getHandle

size: 2

x: 2.5 .

Still, you need to do something with those arrays after using them, since you are creating them with externalNewType:… (which mean it allocates the memory space).

You will need to send #free to them.

Other solution would be to not use #externalNewType:size: but plain #newType:size:

Cheers,

Esteban

last expression returninп me 0.0, but right is 3.5.

I'm dit the same in Python3 ctypes, and there work's fine.

In UnifiedFFI booklet is absent chapter "Arrays", anybody may help with whot i'm doing wrong?

Yuriy Babah

Re: question about FFI

FFIExamples
interpolationFunc_xm: xm getHandle
ym: ym getHandle
size: 2
x: 2.5 .

cool! it worked !! Thank Esteban Lorenzano and everyone else )

EstebanLM

Re: question about FFI

In reply to this post by Pharo Smalltalk Users mailing list

On 26 Nov 2018, at 11:14, Henrik Sperre Johansen via Pharo-users <[hidden email]> wrote:

From: Henrik Sperre Johansen <[hidden email]>
Subject: Re: question about FFI
Date: 26 November 2018 at 11:14:26 CET
To: [hidden email]

Yuriy Babah wrote
in Playground i'm doing:
*
#(2 3) doWithIndex: [:each :i | xm at: i put: each].
#(3 4) doWithIndex: [:each :i | ym at: i put: each].
*

whot i'm doing wrong?

So, you're putting 2 at index 2 of xm, and then writing 3 past end of array,
and in ym you're putting 3 and 4 at offsets past the end of array?

It's a wonder your image didn't crash, rather than return interpolation of
the uninitialized values…

He is not doing that.

He is using #doWithIndex:

So he is passing 2 at index 1 and 3 at index 2, then 3 at index 1 and 4 at index 2.

Esteban

Cheers,
Henry

--
Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html