FFI definitions - structs

The FFI documentation states the following in terms of defining a C struct fields when defining subclasses of ExternalStructure:

#####################################

fields 

^#((red   'byte')
   (green 'byte')
   (blue  'byte'))                

##########################################

It only mentions simple data types, int, byte etc, as do the all the examples I've been able to find. 

How do you define pointers to other structs that are fields that are part of the C struct. E.g.

C definition:

....

Thanks

Try something like what appears below.  If you search the Squeak archives, you'll probably find some useful posts by Andreas Raab.  Don't expect too much documentation.  Overall, Squeak/Pharo's FFI still falls far short of Dolphin's (sorry, but it's true), and structure mapping is a big area of relative weakness.

Note that you *might* have to add an instance variable and accessors to allow the struct to hold a reference to the "real" target object - otherwise the GC might pull things out from under you.  Somewhere in the Dolphin image, there are examples of the phenomenon.

HTH.

Bill

==============================

fields
    "
        Gsl_wavelet defineFields
    struct


{
const gsl_wavelet_type *type;
const double *h1;
const double *g1;
const double *h2;
const double *g2;
size_t nc;
size_t offset;
}"
^#(
     ( type 'Gsl_wavelet_type*' )
     ( h1 'double*' )
     ( g1 'double*' )
     ( h2 'double*' )
     ( g2 'double*' )
     ( nc 'long' )
     ( offset 'long' )
)