Re: Need to pass an unsigned char array from an xsub back to Perl

Your code is somewhat confusing as to whether you want to return the unsigned char[16] as a Perl array/list (16 individual values), or as a scalar (Perl string of length 16).

Assuming the latter, I think you're approaching things in a much too complicated way. Simply create a char[16] buffer in C, let XSessionID() fill it, and place a copy of it in an SV, which you then return:

#!/usr/bin/perl -wl
use strict;
use Inline C => <<'END_C';

SV* GenerateSessionID() {

    char uuid[16];    // buffer

    // fill buffer, i.e. mimic your XSessionID()
    int i;
    for (i=0; i<16; i++) {
        uuid[i] = 0xA0 + i;
    }

    return newSVpvn(uuid, 16);
}
END_C

my $uuid = GenerateSessionID();
print join ' ', unpack("(H2)*", $uuid);
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Output:

$ ./962624.pl
a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af
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Not using Inline::C (i.e. using a normal XSUB instead), this should translate to something like

SV *
GenerateSessionID()
    PREINIT:
        char uuid[16];
    CODE:
        XSessionID((uuid_t*)uuid);
        RETVAL = newSVpvn(uuid, 16);
    OUTPUT:
        RETVAL
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Or, if you want to use PPCODE:

void
GenerateSessionID()
    PREINIT:
        char uuid[16];
    PPCODE:
        XSessionID((uuid_t*)uuid);
        ST(0) = newSVpvn(uuid, 16);
        sv_2mortal(ST(0));
        XSRETURN(1);
[download]

Comment on Re: Need to pass an unsigned char array from an xsub back to Perl Select or Download Code

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Re^2: Need to pass an unsigned char array from an xsub back to Perl by Anonymous Monk on Mar 30, 2012 at 17:19 UTC
Thank you so much for the quick reply. Indeed, your solution is very elegant. I am a newbie in xsubb. I did use the second method. `PREINIT: unsigned char uuid_arr[16]; CODE: char convert_arr[33]; int i; XGenerateSessionID((uuid_t) &uuid_arr); memset(convert_arr,'\0',33); for(i=0; i< 16; i++){ snprintf(&convert_arr[i2], sizeof(convert_arr)-(i*2), "%02X" +, uuid_arr[i]); } RETVAL = newSVpvn(convert_arr,33); OUTPUT: RETVAL` [download] If I had not converted the unsigned char back to char, the compiler complains of signedness.	[reply] [d/l]
Re^2: Need to pass an unsigned char array from an xsub back to Perl by bulk88 (Priest) on Apr 01, 2012 at 16:57 UTC
Or, if you want to use PPCODE: `void GenerateSessionID() PREINIT: char uuid[16]; PPCODE: XSessionID((uuid_t)uuid); ST(0) = newSVpvn(uuid, 16); sv_2mortal(ST(0)); XSRETURN(1);` [download] Thats quite bloated. This is less bloated. `void GenerateSessionID() PREINIT: char uuid[16] = {0); //zero fill PPCODE: XSessionID((uuid_t)uuid); PUSHs(sv_2mortal((newSVpvn(uuid, 16)));` [download] Also the OP might want to zero his UUID since we are not checking the return value of XSessionID to determine failure.	[reply] [d/l] [select]