On Tue, Apr 20, 2004 at 09:18:12AM +0100 Nick Ing-Simmons wrote:
> Scott T. Hildreth <[EMAIL PROTECTED]> writes:
> >> >
> >> > .. so the address of $fldnm is always the same (static). Therefore the
> >> > fld->names that are sent in all point to the same address. How do I get
> >> > a new SV so that the memory area is different.
> >>
> >> By making a copy:
> >>
> >> fld->name = savepv( SvPV(name, len) );
>
> There is another useful function - sharepvn()
> This returns a char * (which should be considered readonly) but
> the _same_ char * will be returned for same string.
>
> So set_name($obj,'foo')
> and
> set_name($obj,f =>('o' x 2));
>
> Would both give C "foo" calling sharepvn() on that would however look
> up that string and return a pointer to shared copy.
>
> This is used by perl's hashes etc. so that you can just compare
> the PV values to get a fast proof of equality.
>
> (You should unsharepvn() when you don't need it anymore - they are refcounted.)
Cool! So that's another treasure not to be found in perlapi.pod:
#define Perl_sharepvn(sv, len, hash)
What about its third argument, though? It's an U32...so should 'hash' by
used as a sort of ID to unambiguously identify pointers? I suppose I
can't just set it to zero, can I?
Tassilo
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