golden hour

/usr/share/perl/5.30.0

File/Folder	Size	Actions
AnyDBM_File.pm	2.56 KB
App	-
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AutoLoader.pm	15.43 KB
AutoSplit.pm	19.18 KB
B	-
Benchmark.pm	30.3 KB
CORE.pod	3.11 KB
CPAN	-
CPAN.pm	138.75 KB
Carp	-
Carp.pm	35.12 KB
Class	-
Compress	-
Config	-
DB.pm	18.48 KB
DBM_Filter	-
DBM_Filter.pm	14.05 KB
Devel	-
Digest	-
Digest.pm	10.45 KB
DirHandle.pm	2.04 KB
Dumpvalue.pm	17.14 KB
Encode	-
English.pm	4.65 KB
Env.pm	5.39 KB
Exporter	-
Exporter.pm	18.36 KB
ExtUtils	-
Fatal.pm	56.91 KB
File	-
FileCache.pm	5.42 KB
FileHandle.pm	6.63 KB
Filter	-
FindBin.pm	4.45 KB
Getopt	-
HTTP	-
I18N	-
IO	-
IPC	-
Internals.pod	2.51 KB
JSON	-
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Memoize	-
Memoize.pm	35.34 KB
Module	-
NEXT.pm	18.54 KB
Net	-
Params	-
Parse	-
Perl	-
PerlIO	-
PerlIO.pm	10.21 KB
Pod	-
Safe.pm	24.49 KB
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SelectSaver.pm	1.05 KB
SelfLoader.pm	17.27 KB
Symbol.pm	4.69 KB
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Test.pm	29.34 KB
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Test2.pm	6.24 KB
Text	-
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Thread.pm	8.09 KB
Tie	-
Time	-
UNIVERSAL.pm	6.44 KB
Unicode	-
User	-
XSLoader.pm	10.99 KB
_charnames.pm	32.39 KB
autodie	-
autodie.pm	12.58 KB
autouse.pm	4.14 KB
base.pm	10.7 KB
bigint.pm	22.85 KB
bignum.pm	20.64 KB
bigrat.pm	15.78 KB
blib.pm	2.01 KB
bytes.pm	3.65 KB
bytes_heavy.pl	758 B
charnames.pm	20.38 KB
constant.pm	14.38 KB
deprecate.pm	5.07 KB
diagnostics.pm	18.59 KB
dumpvar.pl	15.19 KB
encoding	-
experimental.pm	6.9 KB
feature.pm	17.28 KB
fields.pm	9.25 KB
filetest.pm	3.91 KB
if.pm	3.53 KB
integer.pm	3.18 KB
less.pm	3.13 KB
locale.pm	4.74 KB
meta_notation.pm	2.07 KB
ok.pm	967 B
open.pm	7.83 KB
overload	-
overload.pm	52.04 KB
overloading.pm	1.77 KB
parent.pm	2.51 KB
perl5db.pl	309.69 KB
perlfaq.pm	77 B
pod	-
sigtrap.pm	8.53 KB
sort.pm	3.82 KB
strict.pm	4.63 KB
subs.pm	901 B
unicore	-
utf8.pm	10.18 KB
utf8_heavy.pl	26.66 KB
vars.pm	2.4 KB
version	-
version.pm	1.93 KB
version.pod	9.6 KB
vmsish.pm	4.21 KB
warnings	-
warnings.pm	48.82 KB

Edit: open.pm

package open;
use warnings;

our $VERSION = '1.11';

require 5.008001; # for PerlIO::get_layers()

my $locale_encoding;

sub _get_encname {
    return ($1, Encode::resolve_alias($1)) if $_[0] =~ /^:?encoding$(.+)$$/;
    return;
}

sub croak {
    require Carp; goto &Carp::croak;
}

sub _drop_oldenc {
    # If by the time we arrive here there already is at the top of the
    # perlio layer stack an encoding identical to what we would like
    # to push via this open pragma, we will pop away the old encoding
    # (+utf8) so that we can push ourselves in place (this is easier
    # than ignoring pushing ourselves because of the way how ${^OPEN}
    # works).  So we are looking for something like
    #
    #   stdio encoding(xxx) utf8
    #
    # in the existing layer stack, and in the new stack chunk for
    #
    #   :encoding(xxx)
    #
    # If we find a match, we pop the old stack (once, since
    # the utf8 is just a flag on the encoding layer)
    my ($h, @new) = @_;
    return unless @new >= 1 && $new[-1] =~ /^:encoding$.+$$/;
    my @old = PerlIO::get_layers($h);
    return unless @old >= 3 &&
	          $old[-1] eq 'utf8' &&
                  $old[-2] =~ /^encoding$.+$$/;
    require Encode;
    my ($loname, $lcname) = _get_encname($old[-2]);
    unless (defined $lcname) { # Should we trust get_layers()?
	croak("open: Unknown encoding '$loname'");
    }
    my ($voname, $vcname) = _get_encname($new[-1]);
    unless (defined $vcname) {
	croak("open: Unknown encoding '$voname'");
    }
    if ($lcname eq $vcname) {
	binmode($h, ":pop"); # utf8 is part of the encoding layer
    }
}

sub import {
    my ($class,@args) = @_;
    croak("open: needs explicit list of PerlIO layers") unless @args;
    my $std;
    my ($in,$out) = split(/\0/,(${^OPEN} || "\0"), -1);
    while (@args) {
	my $type = shift(@args);
	my $dscp;
	if ($type =~ /^:?(utf8|locale|encoding$.+$)$/) {
	    $type = 'IO';
	    $dscp = ":$1";
	} elsif ($type eq ':std') {
	    $std = 1;
	    next;
	} else {
	    $dscp = shift(@args) || '';
	}
	my @val;
	foreach my $layer (split(/\s+/,$dscp)) {
            $layer =~ s/^://;
	    if ($layer eq 'locale') {
		require Encode;
		require encoding;
		$locale_encoding = encoding::_get_locale_encoding()
		    unless defined $locale_encoding;
		(warnings::warnif("layer", "Cannot figure out an encoding to use"), last)
		    unless defined $locale_encoding;
                $layer = "encoding($locale_encoding)";
		$std = 1;
	    } else {
		my $target = $layer;		# the layer name itself
		$target =~ s/^(\w+)$.+$$/$1/;	# strip parameters

unless(PerlIO::Layer::->find($target,1)) {
		    warnings::warnif("layer", "Unknown PerlIO layer '$target'");
		}
	    }
	    push(@val,":$layer");
	    if ($layer =~ /^(crlf|raw)$/) {
		$^H{"open_$type"} = $layer;
	    }
	}
	if ($type eq 'IN') {
	    _drop_oldenc(*STDIN, @val) if $std;
	    $in  = join(' ', @val);
	}
	elsif ($type eq 'OUT') {
	    if ($std) {
		_drop_oldenc(*STDOUT, @val);
		_drop_oldenc(*STDERR, @val);
	    }
	    $out = join(' ', @val);
	}
	elsif ($type eq 'IO') {
	    if ($std) {
		_drop_oldenc(*STDIN, @val);
		_drop_oldenc(*STDOUT, @val);
		_drop_oldenc(*STDERR, @val);
	    }
	    $in = $out = join(' ', @val);
	}
	else {
	    croak "Unknown PerlIO layer class '$type' (need IN, OUT or IO)";
	}
    }
    ${^OPEN} = join("\0", $in, $out);
    if ($std) {
	if ($in) {
	    if ($in =~ /:utf8\b/) {
		    binmode(STDIN,  ":utf8");
		} elsif ($in =~ /(\w+$.+$)/) {
		    binmode(STDIN,  ":$1");
		}
	}
	if ($out) {
	    if ($out =~ /:utf8\b/) {
		binmode(STDOUT,  ":utf8");
		binmode(STDERR,  ":utf8");
	    } elsif ($out =~ /(\w+$.+$)/) {
		binmode(STDOUT,  ":$1");
		binmode(STDERR,  ":$1");
	    }
	}
    }
}

1;
__END__

=head1 NAME

open - perl pragma to set default PerlIO layers for input and output

=head1 SYNOPSIS

use open IN  => ":crlf", OUT => ":bytes";
    use open OUT => ':utf8';
    use open IO  => ":encoding(iso-8859-7)";

use open IO  => ':locale';

use open ':encoding(UTF-8)';
    use open ':locale';
    use open ':encoding(iso-8859-7)';

use open ':std';

=head1 DESCRIPTION

Full-fledged support for I/O layers is now implemented provided
Perl is configured to use PerlIO as its IO system (which is now the
default).

The C<open> pragma serves as one of the interfaces to declare default
"layers" (also known as "disciplines") for all I/O. Any two-argument
open(), readpipe() (aka qx//) and similar operators found within the
lexical scope of this pragma will use the declared defaults.
Even three-argument opens may be affected by this pragma
when they don't specify IO layers in MODE.

With the C<IN> subpragma you can declare the default layers
of input streams, and with the C<OUT> subpragma you can declare
the default layers of output streams.  With the C<IO>  subpragma
you can control both input and output streams simultaneously.

If you have a legacy encoding, you can use the C<:encoding(...)> tag.

If you want to set your encoding layers based on your
locale environment variables, you can use the C<:locale> tag.
For example:

$ENV{LANG} = 'ru_RU.KOI8-R';
    # the :locale will probe the locale environment variables like LANG
    use open OUT => ':locale';
    open(O, ">koi8");
    print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1
    close O;
    open(I, "<koi8");
    printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1
    close I;

These are equivalent

use open ':encoding(UTF-8)';
    use open IO => ':encoding(UTF-8)';

as are these

use open ':locale';
    use open IO => ':locale';

and these

use open ':encoding(iso-8859-7)';
    use open IO => ':encoding(iso-8859-7)';

The matching of encoding names is loose: case does not matter, and
many encodings have several aliases.  See L<Encode::Supported> for
details and the list of supported locales.

When open() is given an explicit list of layers (with the three-arg
syntax), they override the list declared using this pragma.  open() can
also be given a single colon (:) for a layer name, to override this pragma
and use the default (C<:raw> on Unix, C<:crlf> on Windows).

The C<:std> subpragma on its own has no effect, but if combined with
the C<:utf8> or C<:encoding> subpragmas, it converts the standard
filehandles (STDIN, STDOUT, STDERR) to comply with encoding selected
for input/output handles.  For example, if both input and out are
chosen to be C<:encoding(UTF-8)>, a C<:std> will mean that STDIN, STDOUT,
and STDERR are also in C<:encoding(UTF-8)>.  On the other hand, if only
output is chosen to be in C<< :encoding(koi8r) >>, a C<:std> will cause
only the STDOUT and STDERR to be in C<koi8r>.  The C<:locale> subpragma
implicitly turns on C<:std>.

The logic of C<:locale> is described in full in L<encoding>,
but in short it is first trying nl_langinfo(CODESET) and then
guessing from the LC_ALL and LANG locale environment variables.

Directory handles may also support PerlIO layers in the future.

=head1 NONPERLIO FUNCTIONALITY

If Perl is not built to use PerlIO as its IO system then only the two
pseudo-layers C<:bytes> and C<:crlf> are available.

The C<:bytes> layer corresponds to "binary mode" and the C<:crlf>
layer corresponds to "text mode" on platforms that distinguish
between the two modes when opening files (which is many DOS-like
platforms, including Windows).  These two layers are no-ops on
platforms where binmode() is a no-op, but perform their functions
everywhere if PerlIO is enabled.

=head1 IMPLEMENTATION DETAILS

There is a class method in C<PerlIO::Layer> C<find> which is
implemented as XS code.  It is called by C<import> to validate the
layers:

PerlIO::Layer::->find("perlio")

The return value (if defined) is a Perl object, of class
C<PerlIO::Layer> which is created by the C code in F<perlio.c>.  As
yet there is nothing useful you can do with the object at the perl
level.

=head1 SEE ALSO

L<perlfunc/"binmode">, L<perlfunc/"open">, L<perlunicode>, L<PerlIO>,
L<encoding>

=cut