> -----Original Message-----
> From: Mik Firestone [mailto:[EMAIL PROTECTED]
> Sent: Thursday, July 29, 2004 9:00 AM
> To: [EMAIL PROTECTED]
> Subject: Returning reference to C structures
>
>
> I am just looking for a URL or an example of how to return a
> reference to a C
> structure to perl. I have read the Cookbook, and I can get
> my code to work if
> I actually create a blessed reference. I would prefer to
> bless it - I just
> want a reference that I can later pass to other C functions.
Here's how I do it. I've got a perl object that I want to store some C context in (so
it can maintain state between calls), so I create a "_context" slot in the $self
object like so:
HV *self_hash = (HV*) SvRV(self);
SV **fetched = hv_fetch(self_hash, "_context", 8, 1);
if (fetched == NULL)
croak("Couldn't create the _context slot in $self");
sv_setiv(*fetched, (IV) my_struct_pointer);
SvREADONLY_on(*fetched);
The SvREADONLY_on() call is important because I want this thing to be immutable in
perl-land. Then when I want to retrieve the context struct again, I use a little
helper function:
/* A pure-c function, not visible from perl */
context_struct *get_context_struct (SV *self) {
HV *self_hash = (HV*) SvRV(self);
SV **fetched = hv_fetch(self_hash, "_context", 8, 0);
if (fetched == NULL)
croak("Couldn't fetch the _context slot in $self");
return (context_struct *) SvIV(*fetched);
}
...
/* An XS function visible to perl */
void
foo( self )
SV * self
CODE:
{
context_struct *c = get_context_struct(self);
...
}
Theoretically I could put this helper function in a typemap too, to make things look a
little cleaner.
-Ken
