1. Embedding Perl in C and the other way around
Marian Co-Founder and CIO of 1H Ltd.

2. Embedding C in Perl Why would I want to do that?
Get some performance by using native C for some of the processing
Embed parts of your existing C application into your Perl app without rewriting it completely

3. The XS way... It cannot be seen, cannot be felt,
Cannot be heard, cannot be smelt.
It lies behind stars and under hills,
And empty holes it fills.
- J.R.R. Tolkien, The Hobbit
Answer: dark.
XS is an interface description file format used to create an extension interface between Perl and C code
extremely hard to learn
even the smallest program must be implemented as additional module
There is another, similar way using SWIG... I don't know how it works :(
If someone is interested...

4. perlman:perlxstut man perlxs man perlguts man perlapi man h2xs
XS Docs
perlman:perlxstut
man perlxs
man perlguts
man perlapi
man h2xs .

5. XS Basics SV – Scalar Value SV* newSVsv(SV*); AV – Array Value
HV – Hash Value
IV – Integer Value SV* newSViv(IV);
UV – Unsigned Integer Value SV* newSVuv(UV);
NV – Double Value SV* newSVnv(double);
PV – String Value
SV* newSVpv(const char*, STRLEN);
SV* newSVpvn(const char*, STRLEN);
SV* newSVpvf(const char*, ...);
SvIV(SV*)
SvUV(SV*)
SvNV(SV*)
SvPV(SV*, STRLEN len)
SvPV_nolen(SV*)
Scalar, Hash and Arrays are typedefs which can include any of the following types.
You create the value with the coresponding newSV* function.
You access the value with the coresponding Sv* function.

6. Inline::C $ cat inline.pl #!/usr/bin/perl use Inline C=>'
void some_func() {
printf("Hello World\n");
}';
&some_func
$ ./inline.pl
Hello World
Examples from Inline::C-Cookbook
Describe the way we add and execute the C code.

7. fun way of using Inline::C
$ cat perl-sign.pl
#!/usr/bin/perl
use Inline C=>'
void C() {
int m,u,e=0;float l,_,I;
for(;1840-e;putchar((++e>907&&942>e?61- drahnreB"]))
for(u=_=l=0;79-(m=e%80)&&I*l+_*_<6&&26- ++u;_=2*l*_+e/80*.09-1,l=I)
I=l*l-_*_-2+m/27.;
}';
&C

8. mmmmmmmmooooooooooooooooooooooooocccccccccc. is@zrre i
i.cccccccoooooooooommmmm
mmmmmmoooooooooooooooooooooooccccccccccc.....iiscrr
zMesii....cccccoooooooooom
erccsiiiii..ccccooooooooo
uMeu r e
e eci..cccooooooo
ooooooooooccccccc..iiiiiiiiiiiiisscz z
s..cccoooooo
bnneree eci..ccccooooo
occcccccc.....iisccrnb m nci..ccccooooo
cii..cccccoooo
Bernhard ercsi...cccccoooo
rnz esi...cccccoooo
( esi..ccccooooo
bneze
es..cccoooooo
urcsi..cccoooooo
zsi..cccooooooo
nu er eznri.cccoooooooo
rrsii.....ccccoooooooooom
rrcsi....ccccccoooooooooomm
mmmmmmmmoooooooooooooooooooooooocccccccccc....iisceeeusi..cccccccooooooooommmmm

9. Multiple Return Values
print map {"$_\n"} get_localtime(time);
use Inline C => <<'END_OF_C_CODE';
#include <time.h>
void get_localtime(int utc) {
struct tm *ltime = localtime(&utc);
Inline_Stack_Vars;
Inline_Stack_Reset;
Inline_Stack_Push(sv_2mortal(newSViv(ltime->tm_year)));
Inline_Stack_Push(sv_2mortal(newSViv(ltime->tm_mon)));
Inline_Stack_Push(sv_2mortal(newSViv(ltime->tm_mday)));
Inline_Stack_Push(sv_2mortal(newSViv(ltime->tm_hour)));
Inline_Stack_Push(sv_2mortal(newSViv(ltime->tm_min)));
Inline_Stack_Push(sv_2mortal(newSViv(ltime->tm_sec)));
Inline_Stack_Push(sv_2mortal(newSViv(ltime->tm_isdst)));
Inline_Stack_Done; }
END_OF_C_CODE
Describe the way we add and execute the code.
We begin the function with Inline_Stack_Vars
This defines some internal variables including Inline_Stack_Items
Inline_Stack_* variables can be used only when we use ... in the argument list or the return type of the function is VOID.
sv_2mortal() – marks a variable as ready for destroy
newSViv() - creates a Scalar Value from integer

10. Variable Argument Lists
greet(qw(Sarathy Jan Sparky Murray Mike));
use Inline C => <<'END_OF_C_CODE';
void greet(SV* name1, ...) {
Inline_Stack_Vars;
int i;
for (i = 0; i < Inline_Stack_Items; i++)
printf("Hello %s!\n",
SvPV(Inline_Stack_Item(i), PL_na));
Inline_Stack_Void; }
END_OF_C_CODE
We begin the function with Inline_Stack_Vars
This defines some internal variables including Inline_Stack_Items
Inline_Stack_* variables can be used only when we use ... in the argument list or the return type of the function is VOID.
We have to have at least one argument before the variable length argument because of the XS parsing.

11. Another way of using Inline::C
use Inline C;
$vp = string_scan($text); # call our function
__END__
__C__ /*
* Our C code goes here */
int string_scan(char* str) { }
We begin the function with Inline_Stack_Vars
This defines some internal variables including Inline_Stack_Items
Inline_Stack_* variables can be used only when we use ... in the argument list or the return type of the function is VOID.
We have to have at least one argument before the variable length argument because of the XS parsing.

12. Embedding Perl in C Why would I want to do that? Use Perl's RE
Package your software into a single binary
Use some of the nice Perl already working perl modules in your C application

13. How you can do it? ExtUtils::Embed
perl -MExtUtils::Embed -e ccopts -e ldopts
B::C
The only way... XS
In all cases ExtUtils::Embed will help with the compilation flags.
B::C is used for direct compile (perlcc) but is available only for perl or 5.13.x.
Using XS seams the only portable/compatible way...

14. man perlembed man perlcall man perlguts man perlapi man perlxs
Docs
man perlembed
man perlcall
man perlguts
man perlapi
man perlxs

15. B::C/perlcc Works with Perl 5.6.0 Works with Perl 5.13.x
#!/usr/bin/perl
use strict;
use warnings;
use lib '.';
use parse_config;
my $a = 'some text';
my $b = 13;
my %config = parse_config('/etc/guardian.conf');
#my %config = ( df => 13, hj => 18);
printf "%s %d\n", $a, $b;
while (my ($k,$v) = each %config) {
print "$k :: $v\n"; }
it should work with perl >=5.10 but i haven't made it to work :(

16. $ perlcc -o em em.pl
$ ./em
Segmentation fault
some text 13
df :: 13
hj :: 18

17. #include "embed.h"
int main (int argc, char **argv, char **env) {
char *embedding[] = { "", "-e", "0" };
unsigned char *perlPlain;
size_t len = 0;
int err = 0;
PERL_SYS_INIT3(&argc,&argv,&env);
my_perl = perl_alloc();
perl_construct( my_perl );
perl_parse(my_perl, xs_init, 3, embedding, NULL);
PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
perl_run(my_perl);
perlPlain=spc_base64_decode(&perl64,&len,0,&err);
eval_pv(perlPlain, TRUE);
perl_destruct(my_perl);
perl_free(my_perl);
PERL_SYS_TERM();
return 0; }

18. #ifndef _EMBED_H
#define _EMBED_H
#include <EXTERN.h>
#include <perl.h>
#include "base64.h"
#include "code_64.h"
static PerlInterpreter *my_perl;
static void xs_init (pTHX);
EXTERN_C void boot_DynaLoader (pTHX_ CV* cv);
EXTERN_C void boot_Socket (pTHX_ CV* cv);
EXTERN_C void xs_init(pTHX) {
char *file = __FILE__;
/* DynaLoader is a special case */
newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file); }
#endif

19. $ ./embed --version
This is perl, v (*) built for i386-linux-thread-multi
Copyright , Larry Wall
Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.
Complete documentation for Perl, including FAQ lists, should be found on
this system using "man perl" or "perldoc perl". If you have access to the
Internet, point your browser at the Perl Home Page.

20. # perl -MExtUtils::Embed -e ccopts -e ldopts
-Wl,-E -Wl,-rpath,/usr/lib/perl5/5.8.8/i386-linux-thread- multi/CORE -L/usr/local/lib /usr/lib/perl5/5.8.8/i386-linux- thread-multi/auto/DynaLoader/DynaLoader.a - L/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE -lperl - lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe - Wdeclaration-after-statement -I/usr/local/include - D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm - I/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE
# gcc -o embed embed.c $(perl -MExtUtils::Embed -e ccopts -e ldopts)

21. call_argv("showtime", G_DISCARD | G_NOARGS, args);
eval_pv(perlPlain, TRUE);
/** Treat $a as an integer **/
eval_pv("$a = 3; $a **= 2", TRUE);
printf("a = %d\n", SvIV(get_sv("a", 0)));
/** Treat $a as a float **/
eval_pv("$a = 3.14; $a **= 2", TRUE);
printf("a = %f\n", SvNV(get_sv("a", 0)));
/** Treat $a as a string **/
eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE);
printf("a = %s\n", SvPV_nolen(get_sv("a", 0)));