Hi Ronie,
Great that you work on a threaded FFI because it is a pain for some
libraries. FFI ODBC for example, works very well but is not usable in
real applications because of sql locks that locks the pharo vm.
I don't like FFI too much, NativeBoost is much better, unfortunately I don't
know about other libraries you are talking about (Alien, LowCode and UFFI),
but if you achieve doing something better than NativeBoost, it will be a
great thing.
I wish you succeed.
Regards,
Alain
Le 01/11/2014 00:54, Ronie Salgado a écrit :
Ronie is working on unifying all the api and proposing one syntax
mechanism for
- nativeBoost back-end
- FFI
and may be Alien
I had a skype session with Eliot the last. He taught me about the
callback mechanism and I am actually going to use Alien for the
callbacks, by adapting it to perform the marshalling into the
UFFI/NativeBoost types.
In the future, I am planning in using Lowcode to perform the whole
callback process, but now for simplicity I am just going to piggy back
in Alien.
I still have to finish the callout by fixing a complicated bug. With
Eliot we discussed a workaround for this bug. I haven't implemented
those workaround yet, because I have been a bit busy with my university
studies.
As long as we keep what is working, ahem, working. I now depend on
quite a couple of FFI related libs.
What I need is an easy FFI wrapping tool, like
https://github.com/ronsaldo/swig. Is UFFI going that way?
Well, I made the swig adaptation for NativeBoost. Making it for the UFFI
is actually something trivial. So, we are going to have a powerful FFI
and a binding generator for it.
The only problem with Swig, is that the bindings generated by it are not
perfect, because it exposes the exact same C API. A C library that uses
some kind of object model, cannot be exposed in a clean object oriented
way cleanly by a generic automatic tool.
The FFI situation is not good and we know we should improve it.
For the record, the current FFI situation can be traced to the
historical origins of Smalltalk and even Squeak. The original Smalltalk
was an actual operating system, and Squeak was also made as an operating
system. Because of this, they were not designed to interact with other
languages.
Getting a perfect FFI is going to take a lot of time, because of other
problems, such as Multi-threading and the mandatory use of non-blocking
IO. Fortunately, Eliot made a way to have a threaded FFI, in which a
single thread owns the VM at a single time. With this threaded FFI we
can have things such as a callback from a different thread, which is
required by some libraries such as the sound API of SDL2.
Of course the UFFI is going to support this threaded FFI in some point
of time. To support the threaded FFI I only have to pin/unpin some
object, and call two VM functions, disownVM() and ownVM().
As for getting some actual parallelism in Pharo, this is something that
I think is going to take a big amount of time. For now the best thing we
can do is to use OpenCL. This week I have been doing some experimenting
in making an API for linear algebra, that uses OpenCL to perform
computations in parallel. Later I will publish a video.
Greetings,
Ronie
2014-10-31 19:23 GMT-03:00 Alain Rastoul
<alf.mmm....@gmail.com
<mailto:alf.mmm....@gmail.com>>:
Hi Annick,
you can't pass smalltalk strings or objects to ffi as parameters,
you have to allocate the buffer member of your structure
on the external heap ( plus to avoid being gc'd before ffi call)
with ExternalAddress allocate: <your buffer/string size +1 for
string null termination>
fill your buffer with byteAt:put: method,
and release this memory with free when you have finished.
not sure, but you could try something like:
s := '05:45' copyWith: (Character value: 0).
a := ExternalAddress allocate: s size.
s asByteArray withIndexDo: [ :b :i | a byteAt: i put: b ].
myStruct time: a.
... call your ffi ...
a free
Regards,
Alain
Le 29/10/2014 11:59, Annick Fron a écrit :
I I have a C struct with a char*
struct result {
char* time }
I define an ExternalStructure in FFI , with one field of type
char* (note that the syntax char [5] is not accepted ! ).
defineFields generates the accessors time and time:
If I use
time: ’05:45’
I get an error.
How do I set a string value in an ExternalStructure ?
Annick
