> On 17 Feb 2018, at 02:50, Ben Coman <b...@openinworld.com> wrote: > > > > On 16 February 2018 at 16:38, Esteban Lorenzano <esteba...@gmail.com > <mailto: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) ]. > > 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.
I was thinking to implement the #castTo: for all the “pointer” classes (ByteArray, FFIExternalReference, FFIExternalStructure). #[42 0 0 0] castTo: FFIInt32 -> 42 what do you think? Esteban > > 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 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 > > <mailto: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 > > <http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html> > > > > >
