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.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. Capital omega is used to do unbreakable dashes and .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, .\" nothing in troff, for use with C<>. .tr \(*W- .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' .ie n \{\ . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} .el\{\ . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "B::COW 3" .TH B::COW 3 "2020-04-23" "perl v5.26.3" "User Contributed Perl Documentation" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" B::COW \- B::COW additional B helpers to check COW status .SH "VERSION" .IX Header "VERSION" version 0.004 .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #!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 = ( \*(Aqa\*(Aq .. \*(Aqd\*(Aq ); \& 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; .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" B::COW provides some naive additional B helpers to check the \s-1COW\s0 status of one SvPV. .SS "\s-1COW\s0 or Copy On Write introduction" .IX Subsection "COW or Copy On Write introduction" A COWed SvPV is sharing its string (the \s-1PV\s0) with other SvPVs. It's a (kind of) Read Only C string, that would be Copied On Write (\s-1COW\s0). .PP More than one \s-1SV\s0 can share the same \s-1PV,\s0 but when one \s-1PV\s0 need to alter it, it would perform a copy of it, decrease the \s-1COWREFCNT\s0 counter. .PP One \s-1SV\s0 can then drop the \s-1COW\s0 flag when it's the only one holding a pointer to the \s-1PV.\s0 .PP The \s-1COWREFCNT\s0 is stored at the end of the \s-1PV,\s0 after the the \*(L"\e0\*(R". .PP That value is limited to 255, when we reach 255, a new \s-1PV\s0 would be created, .SH "FUNCTIONS" .IX Header "FUNCTIONS" .SS "\fBcan_cow()\fP" .IX Subsection "can_cow()" Return a boolean value. True if your Perl version support Copy On Write for SvPVs .SS "is_cow( \s-1PV\s0 )" .IX Subsection "is_cow( PV )" Return a boolean value. True if the \s-1SV\s0 is cowed SvPV. (check the \s-1SV FLAGS\s0) .SS "cowrefcnt( \s-1PV\s0 )" .IX Subsection "cowrefcnt( PV )" Return one integer representing the \s-1COW\s0 RefCount value. If the string is not \s-1COW,\s0 then it will return undef. .SS "\fBcowrefcnt_max()\fP" .IX Subsection "cowrefcnt_max()" Will return the \s-1SV_COW_REFCNT_MAX\s0 of your Perl. (if \s-1COW\s0 is supported, this should be 255 unless customized). .SH "AUTHOR" .IX Header "AUTHOR" Nicolas R. <atoomic@cpan.org> .SH "COPYRIGHT AND LICENSE" .IX Header "COPYRIGHT AND LICENSE" This software is copyright (c) 2018 by Nicolas R. .PP This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
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