Re: Stringwise comparisons (Inline::C)

----- Original Message ----- 
From: "David Oswald"

> sub compare {
>    return $_[0] cmp $_[1];
> }
>
> .... A C stub:
>
> int compare( SV* left, SV* right ) {
>    int result;
>    // Compare the two SV's stringwise.
>    return result;
> }
>
>
> ....and....
>
> sub lessthan {
>    return $_[0] lt $_[1];
> }
>
> A C stub:
>
> int lessthan( SV* left, SV* right ) {
>    int result;
>    // Less-than compare the two SV's stringwise.
>    return result;
> }
>

I think a callback to a perl subroutine is what you're after. See the 
perlcall documentation.

The following demo is taken from one of the examples in the perlcall docs - 
but it prints out the result of the comparison, rather than returning it.

I couldn't quickly modify it to return the value .... though it shouldn't be 
that difficult. I think you'll need to replace "dSP" with "dXSARGS" and then 
somehow XSRETURN the value off the stack. I'll leave my quick and wrong 
attempt in there - it simply returns 'hello'.
There might even be some example in perlcall that demonstrates how to 
correctly return a value - I didn't look all the way thru it.

##############################
use warnings;

use Inline C => Config =>
    BUILD_NOISY => 1;

use Inline C => <<'EOC';

void call_Compare(char * a, char * b) {
  dSP;
  int count;

  ENTER;
  SAVETMPS;

  PUSHMARK(SP);
  XPUSHs(sv_2mortal(newSVpv(a, 0)));
  XPUSHs(sv_2mortal(newSVpv(b, 0)));
  PUTBACK;

  count = call_pv("Compare", G_SCALAR);

  SPAGAIN;

  if (count != 1)
    croak("Big trouble\n");

  printf ("Comparison of %s and %s yields %d\n", a, b, POPi);

  PUTBACK;
  FREETMPS;
  LEAVE;

}


void return_Compare(char * a, char * b) {
  dXSARGS;
  int count;

  ENTER;
  SAVETMPS;

  PUSHMARK(SP);
  XPUSHs(sv_2mortal(newSVpv(a, 0)));
  XPUSHs(sv_2mortal(newSVpv(b, 0)));
  PUTBACK;

  count = call_pv("Compare", G_SCALAR);

  SPAGAIN;

  if (count != 1)
    croak("Big trouble\n");

  PUTBACK;
  FREETMPS;
  XSRETURN(1);

}

EOC

call_Compare ('hello', 'world');
call_Compare ('hello', 'hello');
call_Compare ('hello', 'hell');

print return_Compare ('hello', 'world'), "\n";
print return_Compare ('hello', 'hello'), "\n";
print return_Compare ('hello', 'hell'), "\n";


sub Compare {
    return $_[0] cmp $_[1];
}

##############################

Cheers,
Rob