bakunin has asked for the wisdom of the Perl Monks concerning the following question:

Esteemed Monks,
I have been playing with Inline::C and the Perl API recently. What a fun way to program!!

Here is my question:

Simply put, I'm accessing an external C-Library with Inline::C, and I want the C constructor wrapper to bless a hashref, not a scalar. The object, then, could call other wrappers as well as storing some other data in its slots. Let me illustrate this with some code: 

package Foo;

## Inline part skipped.
__C__

SV* new() 
{
     HV* hv = newHV(); 
     Foo* foo = newFoo(); //C constructor. 
     // Now, do something with hv and foo, then 
    return blessed_hashref;
}

void setName(SV* obj, char* name) 
{
      Foo* foo = get_foo_from(obj); 
     
     // and call the Foo-C method:
     Foo_set_name(foo);
}

package main;

my $foo = Foo->new();
$foo->setName("Lorelai");
$foo->{shortname} = "Rory";

[download]

Does this make sense? Or should I not bother the blessed scalar and simply create a hash based Perl class to wrap it?

Thanks!

Replies are listed 'Best First'.
Re: Perl API,external C library and blessing a hashref
by mpeppler (Vicar) on May 19, 2004 at 16:10 UTC
    Either technique works. I've blessed my objects at the C level (though I use XS, not Inline::C). In addition, I've used the '~' magic to store an SV that holds the pointer to the data for the C struct that describes the object.

    Something like 

    thv = (HV*)sv_2mortal((SV*)newHV());
sv = newSViv((IV)info);
sv_magic((SV*)thv, sv, '~', "CTlib", 5);
SvRMAGICAL_on((SV*)thv);

rv = newRV((SV*)thv);
stash = gv_stashpv("Sybase::CTlib::_attribs", TRUE);
(void)sv_bless(rv, stash);

    [download]
    Then you can get the "info" structure from the hashref via mg_find().

    Note that this code is pretty old, and there might be better ways to do this sort of things in more recent versions of perl.

    Michael

[reply]
[d/l]
      Thanks Michael!! It's working like a charm. My gawd! It's beautiful...

      I need to look into the MAGIC* now. :)

      Ogla
[reply]
        Go read the perlguts and perlapi docs for some information about this...

        Michael

[reply]

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