Editing: COW.pm
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
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