libvenus has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks

I m trying to call a C function stored in a library via perlXS. The signature of the C function is as under and the last two parameters are ouput parameters and contain a list 

int rcv_msg(char *query, int readlen, char *testHost, char *testPort, 
+char *prodHost, char *prodPort, char *testMsg, char *prodMsg)

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The XS code is as under :-

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

#include "ppport.h"

#include "const-c.inc"

MODULE = REGTEST                PACKAGE = REGTEST

INCLUDE: const-xs.inc
int
rcv_msg(query,queryLen,testHost,testPort,prodHost,prodPort,testMsg,pro
+dMsg)
        char *query
        int  queryLen
        char *testHost
        char *testPort
        char *prodHost
        char *prodPort
        char *testMsg = NO_INIT
        char *prodMsg = NO_INIT
    OUTPUT:
        testMsg
        prodMsg
        RETVAL

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The c fuction returns a list value (i.e. the o/p of the query). I m not sure how do i store the list value in XS

the Perl code is as under :- 

use ExtUtils::testlib;
use REGTEST;

local $/ = undef;
my $query = "select symbol from SEC where symbol=\'IBM\'\;";
my $queryLen = split//,$query;
my $testHost = "pisas392";
my $testPort = 50071;
my $prodHost = "pisas392";
my $prodPort = 50071;
my ($prodRes,$testRes);
($testRes,$prodRes) = REGTEST::rcv_msg($query,$queryLen,$testHost,$tes
+tPort,$pro
dHost,$prodPort,$testRes,$prodRes);

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Any help is highly appreciated Thanks

Replies are listed 'Best First'.
Re: Return list from C to PerlXS
by Anonymous Monk on Oct 17, 2008 at 09:16 UTC
    Try 'xsubpp yourfile.xs' and you'll see 
    XS(XS_REGTEST_rcv_msg)
{
    dXSARGS;
    if (items != 8)
    Perl_croak(aTHX_ "Usage: REGTEST::rcv_msg(query, queryLen, testHos
+t, testPort, prodHost, prodPort, testMsg, prodMsg)");
    {
    char *    int    char *    char *    char *    char *    char *   
+ testMsg;
    char *    prodMsg;
    int    RETVAL;

    RETVAL = rcv_msg(query, queryLen, testHost, testPort, prodHost, pr
+odPort, testMsg, prodMsg);
    }
    XSRETURN(1);
}

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    XSRETURN(1) means it returns one. So XSRETURN(3) site:search.cpan.org and you'll find some examples, like 
    void
GetBorders(handle)
    HWND handle
PREINIT:
    int aBorders [3];
PPCODE:
    if(SendMessage(handle, SB_GETBORDERS, (WPARAM) 0, (LPARAM) aBorder
+s) == TRUE) {
        EXTEND(SP,3);
        XST_mIV(0,aBorders[0]);
        XST_mIV(1,aBorders[1]);
        XST_mIV(2,aBorders[2]);
        XSRETURN(3);
    }
    else {
        XSRETURN_UNDEF;
    }

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    or 
    void
tdxs_wait_for_response()
    PPCODE:
        I32 result = EM_OK;
        I32 sessid = 0;
        I32 token = 0;
        char *cnta = NULL;
        DBCHWAT(&result, cnta, &sessid, &token);
        EXTEND(SP, 3);
        if (result != EM_OK) {
            PUSHs(&PL_sv_undef);
            PUSHs(sv_2mortal(newSViv(result)));
            PUSHs(&PL_sv_undef);
            XSRETURN(3);
        }
        PUSHs(sv_2mortal(newSViv(sessid)));
        PUSHs(sv_2mortal(newSViv(0)));
        PUSHs(&PL_sv_undef);
        XSRETURN(3);

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