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/workflows/linux/badge.svg)](https://github.com/atoomic/B-COW/actions) [![](https://github.com/atoomic/B-COW/workflows/macos/badge.svg)](https://github.com/atoomic/B-COW/actions) [![](https://github.com/atoomic/B-COW/workflows/windows/badge.svg)](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
