package B::COW;
use strict;
use warnings;
# ABSTRACT: B::COW additional B helpers to check COW status
use base 'Exporter';
our $VERSION = '0.004'; # VERSION: generated by DZP::OurPkgVersion
use XSLoader;
XSLoader::load(__PACKAGE__);
my @all_export = qw{ can_cow is_cow cowrefcnt cowrefcnt_max };
our @EXPORT_OK = (
@all_export,
);
our %EXPORT_TAGS = (
all => [@all_export],
);
1;
__END__
=pod
=encoding utf-8
=head1 NAME
B::COW - B::COW additional B helpers to check COW status
=head1 VERSION
version 0.004
=head1 SYNOPSIS
#!perl
use strict;
use warnings;
use Test::More; # just used for illustration purpose
use B::COW qw{:all};
if ( can_cow() ) { # $] >= 5.020
ok !is_cow(undef);
my $str = "abcdef";
ok is_cow($str);
is cowrefcnt($str), 1;
my @a;
push @a, $str for 1 .. 100;
ok is_cow($str);
ok is_cow( $a[0] );
ok is_cow( $a[99] );
is cowrefcnt($str), 101;
is cowrefcnt( $a[-1] ), 101;
delete $a[99];
is cowrefcnt($str), 100;
is cowrefcnt( $a[-1] ), 100;
{
my %h = ( 'a' .. 'd' );
foreach my $k ( sort keys %h ) {
ok is_cow($k);
is cowrefcnt($k), 0;
}
}
}
else {
my $str = "abcdef";
is is_cow($str), undef;
is cowrefcnt($str), undef;
is cowrefcnt_max(), undef;
}
done_testing;
=head1 DESCRIPTION
B::COW provides some naive additional B helpers to check the COW status of one SvPV.
=head2 COW or Copy On Write introduction
A COWed SvPV is sharing its string (the PV) with other SvPVs.
It's a (kind of) Read Only C string, that would be Copied On Write (COW).
More than one SV can share the same PV, but when one PV need to alter it,
it would perform a copy of it, decrease the COWREFCNT counter.
One SV can then drop the COW flag when it's the only one holding a pointer
to the PV.
The COWREFCNT is stored at the end of the PV, after the the "\0".
That value is limited to 255, when we reach 255, a new PV would be created,
=for markdown [](https://github.com/atoomic/B-COW/actions) [](https://github.com/atoomic/B-COW/actions) [](https://github.com/atoomic/B-COW/actions)
=head1 FUNCTIONS
=head2 can_cow()
Return a boolean value. True if your Perl version support Copy On Write for SvPVs
=head2 is_cow( PV )
Return a boolean value. True if the SV is cowed SvPV. (check the SV FLAGS)
=head2 cowrefcnt( PV )
Return one integer representing the COW RefCount value.
If the string is not COW, then it will return undef.
=head2 cowrefcnt_max()
Will return the SV_COW_REFCNT_MAX of your Perl. (if COW is supported, this should
be 255 unless customized).
=head1 AUTHOR
Nicolas R. <atoomic@cpan.org>
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2018 by Nicolas R.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut