On 17 Feb 2018, at 02:50, Ben Coman <btc@openInWorld.com> wrote:

On 16 February 2018 at 16:38, Esteban Lorenzano <estebanlm@gmail.com> wrote:

hi,

���casting��� is not necessary in general since is just a way to tell the C compiler that a pointer is form a certain type (but is always a pointer, and in machine code is always the same).

So, here you will do something like this:

Iterator >> asCollectionOfType: aTypeName
        | result address typeClass |

        result := OrderedCollection new.
        address := ExternalAddress new.
        typeClass := FFIExternalType resolveType: aTypeName.
        [self iterator_next: address]
                whileTrue: [ result add: (typeClass fromHandle: address) ].

Perhaps this is a bit about discover-ability.  People with C experience may

naturally search for "cast".  If I Spotter search for..... cast #i

it turns up only four... "broadcast" under Socket class

If that was instead like...  (typeClass castFromHandle: address)

then people may be more likely to find it themselves.

cheers -ben

  

 

   ^result

Iterator >> iterator_next: data
        ^ self ffiCall: #(Boolean iterator_next (Iterator self, void** data))

now��� you have a problem if your type if your type is an ���atomic��� type, like int, long, etc. because those values are passed ���by value��� and not by pointer, so you will need to decode them.
in this case, I would implement a  method extension (probably it worths to add it to UFFI):

FFIExternalType class >> valueFromHandle: anAddress
        ^ self new handle: anAddress at: 1 ���This is used for structures, but we can reuse them :)"

FFIExternalReference class >> valueFromHandle: anAddress
        ^ self fromHandle: anAddress

FFIExternalStructure class >> valueFromHandle: anAddress
        ^ self fromHandle: anAddress

So your function will be like something like this:

Iterator >> asCollectionOfType: aTypeName
        | result address typeClass |

        result := OrderedCollection new.
        address := ExternalAddress new.
        typeClass := FFIExternalType resolveType: aTypeName.
        [self iterator_next: address]
                whileTrue: [ result add: (typeClass valueFromHandle:: address) ].
   ^result

and voil��, you have your cast :)

Esteban

ps: (some errors can be found here, since I���m ���programming at mail client���, but you get the idea ;) )

> On 15 Feb 2018, at 19:59, Egor Scorik <shirofaii@gmail.com> wrote:
>
> Hi,
>
> I'm trying to play with new UFFI system. It looks much easier then
> NativeBoost, but unfortunately its hard to find any docs or examples.
> I have problem with casting void* (ExternalAddress) into smalltalk object if
> there is no hardcoded type in ffi method. And I really dislike the idea of
> making many ffi methods, one for each required type.
> In this example i can't understand how to make something like `address
> castTo: type`
>
> FFIExternalObject subclass: #Iterator
>
> Iterator >> asCollectionOfType: aTypeName
>       | result address type |
>
>       result := OrderedCollection new.
>       address := ExternalAddress new.
>       type := FFIExternalType resolveType: aTypeName.
>       [self iterator_next: address] whileTrue: [
>               result add: (address castTo: type).
>       ].
>    ^result
>
> Iterator >> iterator_next: data
>       ^ self ffiCall: #(Boolean iterator_next (Iterator self, void** data))
>
>
>
>
> --
> Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html
>