Hi esteban do you plan to add this explanation to the documentation of uFFI?
Stef On Fri, Feb 16, 2018 at 9:38 AM, Esteban Lorenzano <esteba...@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) ]. > ^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 voilà, 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 <shirof...@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 >> > >
