PerlGuts->PerlEmbed->PerlCall

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PerlGuts-gtPerlEmbed-gtPerlCall

• Calling Perl from your C program

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PerlGuts

• SV the basic variable
• AV Array
• HV Hash
• STASH Package / Namespace

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PerlGuts
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PerlAPI

• newSV, newSVpv, newSViv .
• sv_setpv/iv/nv
• Sv(Flag) SvCUR, SvIOK, SvPOK .
• SvIV, SvPV
• SvREFCNT, SvREFCNT_inc, SvREFCNT_dec
• newAV, av_pop, av_unshift, av_fetch
• newHV, hv_store, hv_fetch

Total 400 API functions tons of macros
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PerlGuts other concepts

• Mortal variables
• sv_2mortal
• Perl Stack
• _at__

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PerlEmbed

• A Simple Embedded Perl

include ltEXTERN.hgt include ltperl.hgt static
PerlInterpreter my_perl int main(int argc,
char argv, char env) PERL_SYS_INIT3(arg
c,argv,env) my_perl perl_alloc()
perl_construct(my_perl) perl_parse(my_perl,
NULL, argc, argv, (char )NULL)
perl_run(my_perl) perl_destruct(my_perl)
perl_free(my_perl) PERL_SYS_TERM()
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• A Simple Embedded Perl

include ltEXTERN.hgt include ltperl.hgt static
PerlInterpreter my_perl int main(int argc,
char argv, char env) PERL_SYS_INIT3(arg
c,argv,env) char my_argv "",
"power.pl" my_perl perl_alloc()
perl_construct(my_perl) perl_parse(my_perl,
NULL, 2, my_argv, (char )NULL)
PL_exit_flags PERL_EXIT_DESTRUCT_END
perl_run(my_perl) perl_destruct(my_perl)
perl_free(my_perl) PERL_SYS_TERM()
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• A Simple Embedded Perl

include ltEXTERN.hgt include ltperl.hgt static
PerlInterpreter my_perl int main(int argc,
char argv, char env) PERL_SYS_INIT3(arg
c,argv,env) char embedding "",
"-e", "0" my_perl perl_alloc()
perl_construct(my_perl) perl_parse(my_perl,
NULL, 3, embedding, NULL) PL_exit_flags
PERL_EXIT_DESTRUCT_END eval_pv(my a5
print a x 3, FALSE) perl_destruct(my_perl)
perl_free(my_perl) PERL_SYS_TERM()
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Conventions

• d define / declare
• a argument
• p parameter
• _ - there should be a comma after
• Example aTHX_

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include ltEXTERN.hgt include ltperl.hgt int
main(int argc, char argv, char env)
PERL_SYS_INIT3(argc,argv,env) char
embedding "", "power.pl"
PerlInterpreter perl_inter perl_inter
perl_alloc() perl_construct(perl_inter)
dTHXa(perl_inter) perl_parse(perl_inter,
NULL, 2, embedding, NULL) PL_exit_flags
PERL_EXIT_DESTRUCT_END char name
MyPackage load_module(PERL_LOADMOD_NOIMPORT
, newSVpvn(name, strlen(name)), Nullsv)
call_func(aTHX_ 7, 5) perl_destruct(perl_i
nter) perl_free(perl_inter)
PERL_SYS_TERM()
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If my function is sub Multiply print
_0_1 void call_func(pTHX_ int x, int y)
dSP char params 5, 7, NULL
call_argv(Multiply, G_DISCARD, params)
Flags G_VOID, G_SCALAR, G_ARRAY, G_DISCARD,
G_NOARGS, G_EVAL, G_KEEPERR
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void call_func(pTHX_ int x, int y) dSP
ENTER SAVETMPS PUSHMARK(SP)
XPUSHs(sv_2mortal(newSViv(x)))
XPUSHs(sv_2mortal(newSViv(y))) PUTBACK
call_pv("Multiply", G_DISCARD) FREETMPS
LEAVE
Now lets add two more functions sub Multiply2
return _0_1 sub some_calcs return
(_0_1, _0-1)
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int call_func(pTHX_ int x, int y) dSP
int count int ret -1 ENTER
SAVETMPS PUSHMARK(SP)
XPUSHs(sv_2mortal(newSViv(x)))
XPUSHs(sv_2mortal(newSViv(y))) PUTBACK
count call_pv("Multiply2", G_SCALAR G_EVAL)
SPAGAIN if (SvTRUE(ERRSV)) //
There was an error char err_str
SvPVX(ERRSV) POPs else ret POPi
FREETMPS LEAVE return ret
Always, even if there was an exception, pop a
value off the stack
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int call_func(pTHX_ int x, int y) ...
count call_pv(some_calcs", G_ARRAY G_EVAL)
SPAGAIN // count can be 0 (exception,
empty list) // One way to access the returned
values is with the // POPx macros but will
receive results in reverse // order. Other
way (should include xsub.h) I32 ax SP
- count ax (SP - PL_stack_base) 1
// And then printf(Added d, Substracted
d\n, SvIV(ST(0)), SvIV(ST(1))) ...
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Dynamic Loader
EXTERN_C void boot_DynaLoader (pTHX_ CV
cv) EXTERN_C void xs_init(pTHX) char file
__FILE__ dXSUB_SYS / DynaLoader is a
special case / newXS("DynaLoaderboot_DynaLoa
der", boot_DynaLoader, file) And
then perl_parse(perl_inter, xs_init, 3, my_argv,
(char )NULL)
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Sources

• Perldoc perlhack, perlguts, perlembed, perlcall,
  perlapi
• PerlGuts Illustrated (http//gisle.aas.no/perl/ill
  guts/)