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https://github.com/atoomic/b-cow
Perl B Module to check Cow and CowRefcnt
https://github.com/atoomic/b-cow
Last synced: 3 months ago
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Perl B Module to check Cow and CowRefcnt
- Host: GitHub
- URL: https://github.com/atoomic/b-cow
- Owner: atoomic
- Created: 2018-10-26T15:16:26.000Z (about 6 years ago)
- Default Branch: master
- Last Pushed: 2024-04-27T15:33:26.000Z (9 months ago)
- Last Synced: 2024-06-19T00:35:58.053Z (7 months ago)
- Language: Perl
- Size: 37.1 KB
- Stars: 3
- Watchers: 3
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: Changes
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README
# NAME
B::COW - B::COW additional B helpers to check COW status
# VERSION
version 0.007
# SYNOPSIS
```perl
#!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;
```
# DESCRIPTION
B::COW provides some naive additional B helpers to check the COW status of one SvPV.
## 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,
[](https://github.com/atoomic/B-COW/actions) [](https://github.com/atoomic/B-COW/actions) [](https://github.com/atoomic/B-COW/actions)
# FUNCTIONS
## can\_cow()
Return a boolean value. True if your Perl version support Copy On Write for SvPVs
## is\_cow( PV )
Return a boolean value. True if the SV is cowed SvPV. (check the SV FLAGS)
## cowrefcnt( PV )
Return one integer representing the COW RefCount value.
If the string is not COW, then it will return undef.
## cowrefcnt\_max()
Will return the SV\_COW\_REFCNT\_MAX of your Perl. (if COW is supported, this should
be 255 unless customized).
# AUTHOR
Nicolas R.
# 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.