Brett W. McCoy <[EMAIL PROTECTED]> writes:
>I am building an embedded Perl scripting environment for a 3D modelling
>package. I have the basic scripting engine working (that was the easy
>part), but now my challenge is to be able to directly interface with C++
>objects inside the application. What I really want to do is to be able
>to build Perl objects on the fly from live C++ objects.
Which can be done if you have a clear policy for how a C++ object
becomes a perl object. The snag is that C++ is compile time typed
so each C++ class needs a "method" to convert itself to/from perl objects.
I have some day-job related code (which I have yet to shake loose into
something I can distribute) which uses g++ -E and then a "parse"
of result to create perl bindings to all the public methods of
a class heirachy. (i.e. you use it instead of xsubpp and it produces Class.cpp).
At bottom of this are the utility functions:
void *
SV_to_object(pTHX_ SV *sv, const char *classname)
{
if (SvOK(sv))
{
if (sv_derived_from(sv,classname) && SvIOK(SvRV(sv))) {
IV tmp = SvIV(SvRV(sv));
return (void *) INT2PTR(void *,tmp);
}
croak("Not a %s (%_)",classname,sv);
}
return 0;
}
void
object_to_SV(pTHX_ SV **svp, const char *classname, IV value)
{
if (value)
{
SV *sv = sv_newmortal();
sv_setref_iv(sv,classname,value);
*svp = sv;
}
else
{
*svp = &PL_sv_undef;
}
}
void
enum_to_SV(pTHX_ SV **svp, const char *classname, IV value, const char *str = 0)
{
SV *sv = sv_newmortal();
*svp = sv;
sv_setref_iv(sv,classname,value);
if (str)
{
sv_upgrade((sv = SvRV(sv)),SVt_PVIV);
sv_setpv(sv,str);
SvIOK_on(sv);
}
}
IV
SV_to_enum(pTHX_ SV *sv, const char *classname)
{
if (sv_derived_from(sv,classname) && SvIOK(SvRV(sv))) {
return SvIV(SvRV(sv));
}
croak("Not a %s (%_)",classname,sv);
return 0;
}
The perl script (which I call findclass) then arranges to pass
right thing to classname args of those. The perl classnames are same
as the C++ ones.
The fun part is handling
overloaded functions - i.e. figuring out from the number and type
of args passed which C++ method to call and producing "XS code"
that calls method with correctly converted args to call that method.
>For instance,
>the user has the application running with an open document with a
>hierarchy of objects, and each level (application, document, object)
>has a certain scripting context associated with it (not too different
>from DOM, I think), so you can run, say, a script that modifies the
>behavior of a group of objects as they are being animated.
>
>I found, on CPAN, an aborted attempt at creating a C++ interface to the
>Perl API, and that might be a good starting point, but I wanted to see
>if anyone else has ventured into this arena.
You can embed perl in C++ using perl's C API. You just have to
to C-ish housekeeping rather than C++-ish housekeeping.
--
Nick Ing-Simmons
http://www.ni-s.u-net.com/
