Mass Deface
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(utf8)';
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 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 subpragma you can declare the default layers
of input streams, and with the C subpragma you can declare
the default layers of output streams. With the C 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, "), "\n"; # this should print 0xc1
close I;
These are equivalent
use open ':encoding(utf8)';
use open IO => ':encoding(utf8)';
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 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(utf8)>, a C<:std> will mean that STDIN, STDOUT,
and STDERR are also in C<:encoding(utf8)>. 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. The C<:locale> subpragma
implicitly turns on C<:std>.
The logic of C<:locale> is described in full in L,
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 C which is
implemented as XS code. It is called by C to validate the
layers:
PerlIO::Layer::->find("perlio")
The return value (if defined) is a Perl object, of class
C which is created by the C code in F. As
yet there is nothing useful you can do with the object at the perl
level.
=head1 SEE ALSO
L, L, L, L,
L
=cut