Hey Rob,
One approach would be to use a wrapper wrapper:
use Inline C => <<'EOC';
void c_printf(char *format, AV * arguments) {
...
}
EOC
sub wrap_printf {
my $format = shift;
c_printf($format, [EMAIL PROTECTED]);
}
wrap_printf("%d\n", $x);
wrap_printf("%#o\n", $y);
-Ken
> -----Original Message-----
> From: Sisyphus [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, August 18, 2004 10:42 PM
> To: inline
> Subject: Wrapping variable length agument lists
>
>
> Hi,
>
> Suppose I wanted to write a wrapper for the C printf() function -
> something like:
>
>
> use warnings;
> use Inline C => <<'EOC';
>
> void wrap_printf(SV * a, SV * b) {
> if(SvUOK(b)) printf(SvPV_nolen(a), SvUV(b));
> if(SvIOK(b)) printf(SvPV_nolen(a), SvIV(b));
> if(SvNOK(b)) printf(SvPV_nolen(a), SvNV(b));
> }
>
> EOC
>
> $x = -32;
> $y = 40;
>
> wrap_printf("%d\n", $x);
> wrap_printf("%#o\n", $y);
>
> That would work fine (up to a point) - but, of course, instead of
> writing the wrap_printf() function twice, I would want to do
> it as one
> function call, just as you would with the printf() function:
>
> wrap_printf("%d\n%#o\n", $x, $y);
>
> That, of course, no longer works. The wrap_printf() function
> needs to be
> able to accommodate argument lists of varying lengths - so I thought:
>
> void wrap_printf(SV * a, ...) {
> /* Code to transfer the supplied arguments to C's printf() function */
> }
>
> The only trouble now is that I don't know what that "Code" looks like
> and whether that "Code" can be written in a way that performs
> efficiently.
>
> So now I'm thinking that wrap_printf() needs to take a
> reference to an
> array as its argument:
>
> void wrap_printf(AV * arguments) {
> /* Code to transfer the referred arguments to C's printf() function */
> }
>
> I don't know, off the top of my head, exactly what *that*
> "Code" looks
> like either - though I'm confident I can work it out.
>
> A slight problem with this last rendition is that one will
> now have to
> call wrap_printf() from perl as:
>
> wrap_printf(["%d\n%#o\n", $x, $y]);
>
> which is different to the usual printf() argument format -
> which would
> be unfortunate, though tolerable.
>
> Any thoughts on what is the *correct* approach would be appreciated.
>
> (The correct approach is to use perl's printf() function - but let's
> suppose, for the sake of argument, that perl doesn't have
> one. I guess
> that there's also some code somewhere in the perl source that
> would go a
> long way towards showing me the best way to go about it, but
> I'm a bit
> overwhelmed when it comes to actually locating that source code.)
>
> Cheers,
> Rob
>
>
>
>
>
>
