On Apr 26, 2008, at 12:55 PM, Marvin Humphrey wrote:
This isn't a truly hard problem. There are definitely many ways to
make this introspection data available using C. But all the ways
I've thought of so far are ugly.
I've gotten this working. On its own, it's mildly ugly -- not too bad.
Things are improving step by step. At first, you couldn't override
anything. Then you could implement abstract methods using the host
language. Now you can override public methods.
There's one significant problem left that I'm aware of: Perl's SUPER
mechanism is broken with the vtable override.
Say you use the host language to override a method which was
implemented in C. The original binding invoked the implementing
function via the vtable. The override has now changed that vtable
pointer to be a callback. If you invoke SUPER from the subclass, it
invokes the callback, which invokes the native method again, and you
end up in an infinite loop.
sub serialize {
my ( $self, $outstream ) = @_;
$self->SUPER::serialize($outstream); # BOOM! Infinite recursion.
...
}
The solution, I believe, is to have the XS bindings not invoke via the
vtable, but instead invoke the implementing function directly.
Unfortunately, that means a lot more binding code, because each
override requires its own binding.
Now:
MODULE = KinoSearch PACKAGE = KinoSearch::Index::PostingList
chy_u32_t
get_doc_num(self)
kino_PostingList *self;
CODE:
RETVAL = Kino_PList_Get_Doc_Num(self);
OUTPUT: RETVAL
Fixed:
MODULE = KinoSearch PACKAGE = KinoSearch::Index::PostingList
chy_u32_t
get_doc_num(self)
kino_PostingList *self;
CODE:
RETVAL = kino_PList_get_doc_num(self);
OUTPUT: RETVAL
MODULE = KinoSearch PACKAGE = KinoSearch::Index::SegPostingList
chy_u32_t
get_doc_num(self)
kino_SegPostingList *self;
CODE:
RETVAL = kino_SegPList_get_doc_num(self);
OUTPUT: RETVAL
MODULE = KinoSearch PACKAGE = KinoSearch::Index::MultiPostingList
chy_u32_t
get_doc_num(self)
kino_MultiPostingList *self;
CODE:
RETVAL = kino_MultiPList_get_doc_num(self);
OUTPUT: RETVAL
Fortunately, most of the binding code gets auto-generated these days,
so once the auto-generation code gets patched the suffering will
primarily take the form of slower compiles rather than increased
maintenance costs.
Marvin Humphrey
Rectangular Research
http://www.rectangular.com/
