Re: (tye)Re: XS question: typemap for a pointer to a pointer?

I made the changes as you suggested. My XS file now reads:

int
libnet_init_packet(p_size, buf)
        size_t p_size
        u_char * & buf
    OUTPUT:
        buf
[download]

I also did the same thing for libnet_destory_packet(). It now compiles as I hoped it would, but I get a memory fault when I run this test script:

# Before `make install' is performed this script should be runnable wi
+th
# `make test'. After `make install' it should work as `perl test.pl'

######################### We start with some black magic to print on f
+ailure.

# Change 1..1 below to 1..last_test_to_print .
# (It may become useful if the test is moved to ./t subdirectory.)

BEGIN { $| = 1; print "1..1\n"; }
END {print "not ok 1\n" unless $loaded;}
use Net::LibnetRaw;
$loaded = 1;
print "ok 1\n";

my $buf;
Net::LibnetRaw::libnet_init_packet(IP_H, $buf);
my $dip = Net::LibnetRaw::libnet_name_resolve("10.0.0.4", 1);
my $sip = Net::LibnetRaw::libnet_name_resolve("10.0.0.1", 1);
#my $sock = Net::LibnetRaw::libnet_open_raw_sock(IPPROTO_RAW);
Net::LibnetRaw::libnet_build_ip(ICMP_ECHO_H, 0, 12345, 0, 127, 0, $sip
+, $dip, undef, 0, $buf);
Net::LibnetRaw::libnet_write_ip($sock, $buf, IP_H + ICMP_ECHO_H);
Net::LibnetRaw::libnet_close_raw_sock($sock);
Net::LibnetRaw::libnet_destroy_packet($buf);

######################### End of black magic.

# Insert your test code below (better if it prints "ok 13"
# (correspondingly "not ok 13") depending on the success of chunk 13
# of the test code):
[download]

It appears that the error occurs when I call libnet_build_ip(). It seems pretty clear that there is an issue with the passage and management of buf. Buf is supposed to come back out by reference here. My XSUB for libnet_build_ip() is:

int
libnet_build_ip(len, tos, id, frag, ttl, prot, saddr, daddr, payload, 
+payload_s, buf)
                u_short len
                u_char tos
                u_short id
                u_short frag
                u_char ttl
                u_char prot
                u_long saddr
                u_long daddr
                const u_char * payload
                int payload_s
                u_char & buf
        OUTPUT:
                buf
[download]

It is appropriate for the function prototype. buf is not passed as a C "u_char **" like with libnet_init_packet(). buf should be holding a C pointer to the meory location allocated by libnet_packet_init(), which is basically a wrapper to malloc() which passed the buf back by reference.

My guess is that there is some issue related to storing a pointer to a memory location used in C in a perl reference. If my guess is correction, how do I work around this? If not, then what the hell am I doing wrong? I've considered writing additional C code to simply allow $buf to hold a number which would act sort of like a "buffer descriptor" ala UNIX file I/O and keep the pointers in perl, but I really want to do as much of this in perl as possible.

Your solutions are greatly appreciated.

Comment on Re: (tye)Re: XS question: typemap for a pointer to a pointer? Select or Download Code

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(tye)Re2: XS question: typemap for a pointer to a pointer? by tye (Sage) on Apr 11, 2001 at 08:01 UTC
Can you post the generated C code that relates to the processing of the problem argument (near the top and bottom of each generated subroutine)? You want the pointer to be stashed as an opaque value (usually an unsigned long integer, UV). If you have the typemap class wrong then the C code might be trying to copy the data in the allocated buffer rather than just stashing the pointer's value. I don't recall which typemap class is meant to do this and looking at the generated C code prevents me from having to assembly the pieces myself and possible get confused in the process (I'm often easily confused). - tye (but my friends call me "Tye")	[reply]
Re: (tye)Re2: XS question: typemap for a pointer to a pointer? by Big Willy (Scribe) on Apr 11, 2001 at 09:51 UTC
This what you're asking for? /* * This file was generated automatically by xsubpp version 1.9507 from + the * contents of LibnetRaw.xs. Do not edit this file, edit LibnetRaw.xs +instead. * * ANY CHANGES MADE HERE WILL BE LOST! * / #line 1 "LibnetRaw.xs" #include "EXTERN.h" #include "perl.h" #include "XSUB.h" #include "libnet.h" #line 17 "LibnetRaw.c" XS(XS_Net__LibnetRaw_libnet_open_raw_sock) { dXSARGS; if (items != 1) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_open_raw_sock( +protocol)"); { int protocol = (int)SvIV(ST(0)); int RETVAL; dXSTARG; RETVAL = libnet_open_raw_sock(protocol); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_close_raw_sock) { dXSARGS; if (items != 1) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_close_raw_sock +(fd)"); { int fd = (int)SvIV(ST(0)); int RETVAL; dXSTARG; RETVAL = libnet_close_raw_sock(fd); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_write_ip) { dXSARGS; if (items != 3) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_write_ip(sock, + packet, len)"); { int sock = (int)SvIV(ST(0)); u_char packet = (u_char )SvPV(ST(1),PL_na); int len = (int)SvIV(ST(2)); int RETVAL; dXSTARG; RETVAL = libnet_write_ip(sock, packet, len); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_do_checksum) { dXSARGS; if (items != 3) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_do_checksum(bu +f, protocol, len)"); { u_char buf = (u_char)SvUV(ST(0)); int protocol = (int)SvIV(ST(1)); int len = (int)SvIV(ST(2)); int RETVAL; dXSTARG; RETVAL = libnet_do_checksum(&buf, protocol, len); sv_setuv(ST(0), (UV)buf); SvSETMAGIC(ST(0)); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_init_packet) { dXSARGS; if (items != 2) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_init_packet(p_ +size, buf)"); { size_t p_size = (size_t)SvIV(ST(0)); u_char buf = (u_char )SvPV(ST(1),PL_na); int RETVAL; dXSTARG; RETVAL = libnet_init_packet(p_size, &buf); sv_setpv((SV)ST(1), buf); SvSETMAGIC(ST(1)); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_destroy_packet) { dXSARGS; if (items != 1) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_destroy_packet +(buf)"); { u_char * buf = (u_char )SvPV(ST(0),PL_na); int RETVAL; dXSTARG; RETVAL = libnet_destroy_packet(&buf); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_name_resolve) { dXSARGS; if (items != 2) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_name_resolve(h +ostname, use_name)"); { u_char hostname = (u_char )SvPV(ST(0),PL_na); u_short use_name = (u_short)SvUV(ST(1)); u_long RETVAL; dXSTARG; RETVAL = libnet_name_resolve(hostname, use_name); XSprePUSH; PUSHu((UV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_build_ip) { dXSARGS; if (items != 11) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_build_ip(len, +tos, id, frag, ttl, prot, saddr, daddr, payload, payload_s, buf)"); { u_short len = (u_short)SvUV(ST(0)); u_char tos = (u_char)SvUV(ST(1)); u_short id = (u_short)SvUV(ST(2)); u_short frag = (u_short)SvUV(ST(3)); u_char ttl = (u_char)SvUV(ST(4)); u_char prot = (u_char)SvUV(ST(5)); u_long saddr = (u_long)SvUV(ST(6)); u_long daddr = (u_long)SvUV(ST(7)); const u_char payload = (const u_char )SvPV(ST(8),PL_na); int payload_s = (int)SvIV(ST(9)); u_char buf = (u_char)SvUV(ST(10)); int RETVAL; dXSTARG; RETVAL = libnet_build_ip(len, tos, id, frag, ttl, prot, saddr, + daddr, payload, payload_s, &buf); sv_setuv(ST(10), (UV)buf); SvSETMAGIC(ST(10)); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } XS(XS_Net__LibnetRaw_libnet_build_tcp) { dXSARGS; if (items != 10) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_build_tcp(spor +t, dport, seq, ack, control, win, urg, payload, payload_s, buf)"); { u_short sport = (u_short)SvUV(ST(0)); u_short dport = (u_short)SvUV(ST(1)); u_long seq = (u_long)SvUV(ST(2)); u_long ack = (u_long)SvUV(ST(3)); u_char control = (u_char)SvUV(ST(4)); u_short win = (u_short)SvUV(ST(5)); u_short urg = (u_short)SvUV(ST(6)); const u_char payload = (const u_char )SvPV(ST(7),PL_na); int payload_s = (int)SvIV(ST(8)); u_char buf = (u_char)SvUV(ST(9)); int RETVAL; dXSTARG; RETVAL = libnet_build_tcp(sport, dport, seq, ack, control, win +, urg, payload, payload_s, &buf); sv_setuv(ST(9), (UV)buf); SvSETMAGIC(ST(9)); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); } #ifdef __cplusplus extern "C" #endif XS(boot_Net__LibnetRaw) { dXSARGS; char file = __FILE__; XS_VERSION_BOOTCHECK ; newXS("Net::LibnetRaw::libnet_open_raw_sock", XS_Net__LibnetRa +w_libnet_open_raw_sock, file); newXS("Net::LibnetRaw::libnet_close_raw_sock", XS_Net__LibnetR +aw_libnet_close_raw_sock, file); newXS("Net::LibnetRaw::libnet_write_ip", XS_Net__LibnetRaw_lib +net_write_ip, file); newXS("Net::LibnetRaw::libnet_do_checksum", XS_Net__LibnetRaw_ +libnet_do_checksum, file); newXS("Net::LibnetRaw::libnet_init_packet", XS_Net__LibnetRaw_ +libnet_init_packet, file); newXS("Net::LibnetRaw::libnet_destroy_packet", XS_Net__LibnetR +aw_libnet_destroy_packet, file); newXS("Net::LibnetRaw::libnet_name_resolve", XS_Net__LibnetRaw +_libnet_name_resolve, file); newXS("Net::LibnetRaw::libnet_build_ip", XS_Net__LibnetRaw_lib +net_build_ip, file); newXS("Net::LibnetRaw::libnet_build_tcp", XS_Net__LibnetRaw_li +bnet_build_tcp, file); XSRETURN_YES; } [download] Just for concenience, the typemap: `u_char * T_PV u_char T_UV u_short T_UV u_long T_UV const u_char * T_PV` [download] Perhaps I am thinking of a pointer to a pointer in the wrong fashion or I am confusing the ways in which perl reference work that I am not clear on. I truly appreciate your help!	[reply] [d/l] [select]
(tye)Re3: XS question: typemap for a pointer to a pointer? by tye (Sage) on Apr 11, 2001 at 18:24 UTC
Yeah, that's it! Now for the relavent bits: `XS(XS_Net__LibnetRaw_libnet_do_checksum) [...] u_char buf = (u_char)SvUV(ST(0)); [...] RETVAL = libnet_do_checksum(&buf, protocol, len); sv_setuv(ST(0), (UV)buf); SvSETMAGIC(ST(0));` [download] The above is exactly what you want. You need to make the other functions handle `buf` the same way this one does. You also got it correct for `Net__LibnetRaw_libnet_build_ip` and `Net__LibnetRaw_libnet_build_tcp`. `XS(XS_Net__LibnetRaw_libnet_destroy_packet) [...] u_char * buf = (u_char )SvPV(ST(0),PL_na); RETVAL = libnet_destroy_packet(&buf);` [download] You want to add some code here that destroys the `buf` object. Probably just: `OUTPUT: buf sv_setsv(ST(0),&PL_sv_undef);` [download] Now for the source of your problem (I think): `XS(XS_Net__LibnetRaw_libnet_init_packet) [...] u_char buf = (u_char )SvPV(ST(1),PL_na); [...] RETVAL = libnet_init_packet(p_size, &buf); sv_setpv((SV)ST(1), buf);` [download] This function seems to have used a different typemap for `buf` which is trying to extract the '\0'-terminated string that it is supposed to point to. I think all you need to do is fix this typemap to be like the other functions. I'm going to check some other things I noticed and I'll reply separately if I detect any problems. - tye (but my friends call me "Tye")	[reply] [d/l] [select]
(tye)Re4: XS question: typemap for a pointer to a pointer? by tye (Sage) on Apr 11, 2001 at 19:02 UTC
`XS(XS_Net__LibnetRaw_libnet_write_ip) { dXSARGS; if (items != 3) Perl_croak(aTHX_ "Usage: Net::LibnetRaw::libnet_write_ip(sock, + packet, len)"); { int sock = (int)SvIV(ST(0)); u_char * packet = (u_char )SvPV(ST(1),PL_na); int len = (int)SvIV(ST(2)); int RETVAL; dXSTARG; RETVAL = libnet_write_ip(sock, packet, len); XSprePUSH; PUSHi((IV)RETVAL); } XSRETURN(1); }` [download]* I'd make `len` default to 0 (change "`len`" to "`len=0`" the first place it is mentioned) and add: `INIT: if( 0 == len ) len= SvCUR(ST(1));` [download] so that `write_ip($sock,$packet)` works. - tye (but my friends call me "Tye")	[reply] [d/l] [select]
Re: (tye)Re4: XS question: typemap for a pointer to a pointer? by Big Willy (Scribe) on Apr 11, 2001 at 22:13 UTC
(tye)Re5: XS question: typemap for a pointer to a pointer? by tye (Sage) on Apr 11, 2001 at 22:22 UTC
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