Perl XS Rosetta Stone

The following is meant as a quick-and-dirty “cheat sheet” reference for XSUB authors. Many of the “translations” below can take multiple forms; the below is not a substitute for reading and digesting the relevant Perl documentation: perlxs, perlxstut, perlapi, perlguts, etc.

The following assumes knowledge of C, including use of pointers.

Scalars: assignment

Perl	XS
my $v	SV *mysv = newSV(0)
$v = undef	sv_set_undef(mysv)
my $v = 1	SV *mysv = newSVuv(1)
$v = 1	sv_setuv(mysv, 1)
$v = -1	sv_setiv(mysv, -1)
$v = 'literal'	sv_setpvs(mysv, "literal")
$v = $other_str	sv_setpvn(mysv, otherstr, length_of_otherstr)

Scalars: concatenation

Perl	XS
$v .= 'literal'	sv_catpvs(mysv, "literal")
$v .= $other_str	sv_catpvn(mysv, otherstr, length_of_otherstr)

Scalars: length

Perl	XS
length $a	sv_len_utf8(mysv)

Arrays

Perl	XS
my @a	AV *myav = newAV()
@a = ()	av_clear(myav)
push @a, $foo	av_push(myav, foo)
$foo = pop @a	SV *foo = av_pop(myav)
$foo = shift @a	SV *foo = av_shift(myav)
($old) = splice(@a, 2, 1, $foo)	SV **old = av_store(myav, 2, foo)
my ($el) = splice(@, 2, 1)	SV *myel = av_delete(myav, 2, 0)
() = splice(@, 2, 1)	av_delete(myav, 2, G_DISCARD)
@INC	get_av("main::INC") or (GvAV(PL_incgv))

Packages/Namespaces

Perl	XS
__PACKAGE__	HvNAME( (HV*)CopSTASH(PL_curcop) )

Global State

Perl	XS
${^GLOBAL_PHASE}	PL_phase / PL_dirty