in reply to Re: perl c++ perlembed question
in thread perl c++ perlembed question

thank you for your answer but that does not explain how to call a function from perl that is defined in the c++ code that embedded the perl code ... i only found "How to export functions from C++ to embedded perl. Options" http://groups.google.com/group/perl.xs/browse_thread/thread/190893fecc6bdc52

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Re^3: perl c++ perlembed question
by syphilis (Archbishop) on Jun 27, 2009 at 10:30 UTC
    I'm not exactly sure of your requirements - you would be better off to provide some simple/minimalist test program that demonstrates what you're attempting to achieve. (Since you have not yet worked out how to achieve what you're after, that test script would presumably not work - but if it gave us some hints regarding the essence of your aims, that might help.)

    Here's a basic, contrived example of how the return values of C functions (namely, the foo() and bar() functions) could be fed into the embedded perl process. It's just a slight modification of the 'power.c' example from perlembed: 
     
#include <EXTERN.h>
#include <perl.h>

static PerlInterpreter *my_perl;

static void
PerlPower(int a, int b)
{
  dSP;                           
  ENTER;                         
  SAVETMPS;                      
  PUSHMARK(SP);                  
  XPUSHs(sv_2mortal(newSViv(a)));
  XPUSHs(sv_2mortal(newSViv(b)));
  PUTBACK;                      
  call_pv("expo", G_SCALAR);    
  SPAGAIN;                      
                                
  printf ("%d to the %dth power is %d.\n", a, b, POPi);
  PUTBACK;
  FREETMPS;
  LEAVE;  
}

int foo(void) {
    unsigned long t = (unsigned)time( NULL );
    return (t % 5) + 3;
}

int bar(void) {
    unsigned long t = (unsigned)time( NULL );
    return (t % 4) + 2;
}

int main (int argc, char **argv, char **env)
{
  char *my_argv[] = { "", "power.pl" };

  PERL_SYS_INIT3(&argc,&argv,&env);
  my_perl = perl_alloc();
  perl_construct( my_perl );

  perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL);
  PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
  perl_run(my_perl);

  PerlPower(foo(), bar()); /* foo() ** bar() */

  perl_destruct(my_perl);
  perl_free(my_perl);
  PERL_SYS_TERM();
}

    [download]
    For that program to work, 'power.pl' needs to be also in the cwd - and needs to contain the following: 
    sub expo {
  my ($a, $b) = @_;
  return $a ** $b;
}

    [download]
    Cheers,
    Rob
[reply]
[d/l]
[select]
      i cant provide a test script ... all i got is what youve already postet ... a working embedded perl script that IS NOT ABLE to call functions from the part of the programm/code that embedded the actual perl script :-)

      i got a c++ project that defines a function

      foobar()

      and also embeds a perl script larry.pl

      ok?

      now the c++ code will embed perl and run larry.pl ... now i want larry.pl to be able to access the foobar() function that was declared in the c++ code that actually embedded the larry.pl script. NOT any other laying around c++/c code r module.
[reply]
      wow, that was "easy" :-) thanks a ton rob! i couldnt find ANY example for calling back into c++ from an embedded perl script anywhere ... thanks again :-) you made my day
[reply]
      hm but that also does not call a function from the c++ code from within the power.pl script?

      i wanted
      c++ with a func bla() and an embedded perl interpreter
      this c++ programm is executed and running
      it embeds a perl interpreter that runs foo.pl invoked with some param
      foo.pl runs and executes bla() from the c++ script and gets some return value from the bla() func
      foo.pl returns something to the c++ program
      ...
[reply]
        that also does not call a function from the c++ code from within the power.pl script

        That's correct - sub expo is simply being passed values that come from the C code (subs foo and bar).

        foo.pl runs and executes bla() from the c++ script and gets some return value from the bla() func

        That's the tricky bit ... well, "impossible" rather than "tricky", one suspects. I don't know how foo.pl could run bla() directly.

        I also don't know why foo.pl would *need* to run bla() directly, given that bla()'s return value could be passed to foo.pl as an argument (as per the power.pl example already supplied). If the need to have foo.pl call bla() is a non-negotiable requirement, then I can't help at all with that aspect.
        UPDATE: I now think I *can* envisage circumstances where it would be nice if foo.pl could call bla() directly - but I still have no idea how that could be achieved.

        Thanks for an interesting question, btw. (I learned something in trying to answer it.)

        Cheers,
        Rob
[reply]
Re^3: perl c++ perlembed question
by Anonymous Monk on Jun 27, 2009 at 05:47 UTC
    thank you for your answer but that does not explain how to call a function from perl that is defined in the c++ code

    I thought it did. You use Win32::API (or C::DynaLib) from perl to load/call c functions

    or you write your own c++ dispatcher function, and you make it available to perl through xs/Inline::C/pickle.

[reply]
      i dont want to call JUST ANY c function ... i want to call MY OWN functions that got defined/declared in the code that after declaring those functions embedded the perl script. and i want to access those functions from within the embedded perl script

      i.e.
      blubb.cpp does 2 things ... declaring foobar() and embedding lalala.pl

      now i want to call foobar() from within the embedded lalala.pl

      i really dont know how else i should explain it ... it seems nobody understands me :-(
[reply]
        Hmm, didn't I just describe that exact scenario?
[reply]

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