Storing external data in PMCs
Arthur Bergman
So I am currently trying to do a Perl5LVALUE pmc, a stumbling block is
however that I need to pass the PMC the thing that it is lvalueling, I
was planning to use the pmc data field for storing this but I cannot
access it as a extender without violating the API and guessing at
layouts which is kind of bad (Dan says so ;)
Arthur
Melvin Smith
I don't know Perl5 internals enough to know exactly what Perl5LVALUE
does. Do you want a way to pass a value to the PMC and let the PMC type morph
itself based on the data representation?
-Melvin
Arthur Bergman
An lvalue holds usually a function, and when set is called that
function is called. So no morthing required at all!
For example:
perl -le '$foo = hi; $bar = \substr($foo,1); print "$bar-$foo"; $$bar =
"b"; print "$bar-$foo"';
LVALUE(0x513ec)-hi
LVALUE(0x513ec)-hb
so the reference points to a lvalue which has a reference to $bar and a
special function on the set to actually execute the substr.
The reason I am starting with this is that it is so obscure that it is
hardly used anywhere and is limited to a few small areas in the core
making it a good testing ground.
Arthur
Arthur Bergman
On Monday, October 27, 2003, at 04:44 pm, Melvin Smith wrote:
>
> In this case I assume the function can either be Perl5 or Parrot?
> Sounds like a custom PMC to me. Given the PMC that
> could stash function pointers and correctly dispatch gets/sets
> you have the option of writing a PNI method for setting the stashed
> routine from C or we have to add a call to the extension API to stash a
> raw pointer.
>
> -Melvin
>
The function is a C function. And yes it is a custom PMC which I have
already created.
Dan pointed out the unmanagedstruct.pmc which but I fail to see how
that would help me, I think we need an external API for stashing raw
pointers.
(I don't know what PNI is, but I assume it is to execute bytecode from
C and I do not want to do that).
Arthur
Arthur Bergman
On Monday, October 27, 2003, at 05:20 pm, Melvin Smith wrote:
> Apologies for the formatting of these replies, I'm at work with Lotus
> Notes.
>
> PNI (Parrot Native Interface) is for writing native extensions in C.
> So, what I meant is you can write a method for stashing a raw pointer
> with
> the API today (probably using char *). I'm not sure if it is your
> preferred method,
> and I understand your wariness of bytecode in this case. I was 1/2
> asleep
> this morning on IRC when I suggested it, not understanding the case
> you were dealing with.
>
> You can see samples that Dan has played with such as ncurses somewhere
> in the examples area. (I'm still not saying you don't need API added
> to extend.h
> though, but I'd have to be very clear on what you are asking for...)
>
> -Melvin
>
I just want to be able to say
Parrot_PMC_attach_data(Parrot, PMC, *void);
so the PMC code can get to it
Arthur
Leopold Toetsch
> The function is a C function. And yes it is a custom PMC which I have
> already created.
The interface for calling C code from PASM is NCI (native call
interface). s. e.g. library/*.pasm or t/pmc/nci.t.
But inside your custom PMC you can do all kinds of things, to stuff a
pointer into e.g. data.
- at init time init_pmc() has an extra pointer argument
- via a customized vtable method:
e.g. set_pmc, set_pmc_keyed or push or whatever
Vtable calls seem still to be missing in the extension interface though.
> Dan pointed out the unmanagedstruct.pmc which but I fail to see how
> that would help me, I think we need an external API for stashing raw
> pointers.
unmanagaged struct isn't finished yet. But extending the switch
statements by an enum_type_ptr case is really simple.
library/libpcre.imc has an example to get match results via an
unmanagedstruct PMC.
> Arthur
leo