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