Dear Ladies and Gentlemen,
I am writing to ask some advice about returning a variable number of
results from an XS in which the callled C function has a (callback)
function pointer argument that it calls to produce the results.
The situation is this,
/* callback */
void server_fn(struct print_job_info *p) {
printf() /* I would like this to replaced by
pushing the formatted string onto the Perl
stack.
eg XPUSHs(sv_2mortal(newSVpvf()))
*/
}
/* This is the function wrapped by the XS */
int cli_print_queue(struct cli_state *cli,
void (*fn)(struct print_job_info *))
It seems to me that
1 I can only return results to Perl by an explicit XSRETURN(items) after
the XPUSHs.
Therefore I have to accumulate the number of XPUSHs in a global variable
updated by the C callback (server_fn() above)).
Is that correct ?
2 Otherwise, the C callback should either
2.1 update a global C structure that will then be accessed by the
calling XS (cli_print_queue)
2.2 update a global Perl structure (eg an AV *) that will be returned by
the calling XS
What is 'the recommended way' or what are some of the less obvious
tradeoffs in each of these ways ?
Thank you,
--
------------------------------------------------------------------------
Stanley Hopcroft
------------------------------------------------------------------------
'...No man is an island, entire of itself; every man is a piece of the
continent, a part of the main. If a clod be washed away by the sea,
Europe is the less, as well as if a promontory were, as well as if a
manor of thy friend's or of thine own were. Any man's death diminishes
me, because I am involved in mankind; and therefore never send to know
for whom the bell tolls; it tolls for thee...'
from Meditation 17, J Donne.
