Hernán Morales Durand wrote:
> I have a couple of questions, I started to play with FFI, so these
> are newbie ones, my intention is to port the ZOOM library. I was there
> happily writing ExternalStructure's until I found one that kills the
> VM. Then I've realized I have some basic doubts about FFI:
> ZOOMODR class>> fields
> 	"  self defineFields  "
> 	^ #(
> 		(direction  'long')
> 		(error      'long')
> 		(buf        'char *')
> 		(top         'long')
> 		(size        'long')
> 		(pos         'long')
> 		(bp          'char *')
> 		(mem       'ZOOMNMem')
> 		(odrPrivate 'void *')  " ========= HERE ========= "
> 	)
> 
> I don't know if this exists, the HERE means

Yes, this will work fine.

> 2)
>     Z_NamePlusRecord Struct Reference
>     =================================
>     Z_DatabaseName * 	databaseName
>     int 	which
>     union {
>        Z_External *   databaseRecord
>        Z_DiagRec *   surrogateDiagnostic
>        Z_FragmentSyntax *   startingFragment
>        Z_FragmentSyntax *   intermediateFragment
>        Z_FragmentSyntax *   finalFragment
>     }	u
> 
> Is there something special to do about an union in the #fields method?

Just declare it as any pointer you'd like and provide methods for the 
particular conversions you need.

Cheers,
   - Andreas