lib/perl5/5.8.8/open.pm

   1 package open;
   2 use warnings;
   3 use Carp;
   4 $open::hint_bits = 0x20000; # HINT_LOCALIZE_HH
   5
   6 our $VERSION = '1.05';
   7
   8 require 5.008001; # for PerlIO::get_layers()
   9
  10 my $locale_encoding;
  11
  12 sub _get_encname {
  13     return ($1, Encode::resolve_alias($1)) if $_[0] =~ /^:?encoding\((.+)\)$/;
  14     return;
  15 }
  16
  17 sub _drop_oldenc {
  18     # If by the time we arrive here there already is at the top of the
  19     # perlio layer stack an encoding identical to what we would like
  20     # to push via this open pragma, we will pop away the old encoding
  21     # (+utf8) so that we can push ourselves in place (this is easier
  22     # than ignoring pushing ourselves because of the way how ${^OPEN}
  23     # works).  So we are looking for something like
  24     #
  25     #   stdio encoding(xxx) utf8
  26     #
  27     # in the existing layer stack, and in the new stack chunk for
  28     #
  29     #   :encoding(xxx)
  30     #
  31     # If we find a match, we pop the old stack (once, since
  32     # the utf8 is just a flag on the encoding layer)
  33     my ($h, @new) = @_;
  34     return unless @new >= 1 && $new[-1] =~ /^:encoding\(.+\)$/;
  35     my @old = PerlIO::get_layers($h);
  36     return unless @old >= 3 &&
  37                   $old[-1] eq 'utf8' &&
  38                   $old[-2] =~ /^encoding\(.+\)$/;
  39     require Encode;
  40     my ($loname, $lcname) = _get_encname($old[-2]);
  41     unless (defined $lcname) { # Should we trust get_layers()?
  42         require Carp;
  43         Carp::croak("open: Unknown encoding '$loname'");
  44     }
  45     my ($voname, $vcname) = _get_encname($new[-1]);
  46     unless (defined $vcname) {
  47         require Carp;
  48         Carp::croak("open: Unknown encoding '$voname'");
  49     }
  50     if ($lcname eq $vcname) {
  51         binmode($h, ":pop"); # utf8 is part of the encoding layer
  52     }
  53 }
  54
  55 sub import {
  56     my ($class,@args) = @_;
  57     croak("open: needs explicit list of PerlIO layers") unless @args;
  58     my $std;
  59     $^H |= $open::hint_bits;
  60     my ($in,$out) = split(/\0/,(${^OPEN} || "\0"), -1);
  61     while (@args) {
  62         my $type = shift(@args);
  63         my $dscp;
  64         if ($type =~ /^:?(utf8|locale|encoding\(.+\))$/) {
  65             $type = 'IO';
  66             $dscp = ":$1";
  67         } elsif ($type eq ':std') {
  68             $std = 1;
  69             next;
  70         } else {
  71             $dscp = shift(@args) || '';
  72         }
  73         my @val;
  74         foreach my $layer (split(/\s+/,$dscp)) {
  75             $layer =~ s/^://;
  76             if ($layer eq 'locale') {
  77                 require Encode;
  78                 require encoding;
  79                 $locale_encoding = encoding::_get_locale_encoding()
  80                     unless defined $locale_encoding;
  81                 (warnings::warnif("layer", "Cannot figure out an encoding to use"), last)
  82                     unless defined $locale_encoding;
  83                 if ($locale_encoding =~ /^utf-?8$/i) {
  84                     $layer = "utf8";
  85                 } else {
  86                     $layer = "encoding($locale_encoding)";
  87                 }
  88                 $std = 1;
  89             } else {
  90                 my $target = $layer;            # the layer name itself
  91                 $target =~ s/^(\w+)\(.+\)$/$1/; # strip parameters
  92
  93                 unless(PerlIO::Layer::->find($target,1)) {
  94                     warnings::warnif("layer", "Unknown PerlIO layer '$target'");
  95                 }
  96             }
  97             push(@val,":$layer");
  98             if ($layer =~ /^(crlf|raw)$/) {
  99                 $^H{"open_$type"} = $layer;
 100             }
 101         }
 102         if ($type eq 'IN') {
 103             _drop_oldenc(*STDIN, @val);
 104             $in  = join(' ', @val);
 105         }
 106         elsif ($type eq 'OUT') {
 107             _drop_oldenc(*STDOUT, @val);
 108             $out = join(' ', @val);
 109         }
 110         elsif ($type eq 'IO') {
 111             _drop_oldenc(*STDIN,  @val);
 112             _drop_oldenc(*STDOUT, @val);
 113             $in = $out = join(' ', @val);
 114         }
 115         else {
 116             croak "Unknown PerlIO layer class '$type'";
 117         }
 118     }
 119     ${^OPEN} = join("\0", $in, $out);
 120     if ($std) {
 121         if ($in) {
 122             if ($in =~ /:utf8\b/) {
 123                     binmode(STDIN,  ":utf8");
 124                 } elsif ($in =~ /(\w+\(.+\))/) {
 125                     binmode(STDIN,  ":$1");
 126                 }
 127         }
 128         if ($out) {
 129             if ($out =~ /:utf8\b/) {
 130                 binmode(STDOUT,  ":utf8");
 131                 binmode(STDERR,  ":utf8");
 132             } elsif ($out =~ /(\w+\(.+\))/) {
 133                 binmode(STDOUT,  ":$1");
 134                 binmode(STDERR,  ":$1");
 135             }
 136         }
 137     }
 138 }
 139
 140 1;
 141 __END__
 142
 143 =head1 NAME
 144
 145 open - perl pragma to set default PerlIO layers for input and output
 146
 147 =head1 SYNOPSIS
 148
 149     use open IN  => ":crlf", OUT => ":bytes";
 150     use open OUT => ':utf8';
 151     use open IO  => ":encoding(iso-8859-7)";
 152
 153     use open IO  => ':locale';
 154
 155     use open ':utf8';
 156     use open ':locale';
 157     use open ':encoding(iso-8859-7)';
 158
 159     use open ':std';
 160
 161 =head1 DESCRIPTION
 162
 163 Full-fledged support for I/O layers is now implemented provided
 164 Perl is configured to use PerlIO as its IO system (which is now the
 165 default).
 166
 167 The C<open> pragma serves as one of the interfaces to declare default
 168 "layers" (also known as "disciplines") for all I/O. Any two-argument
 169 open(), readpipe() (aka qx//) and similar operators found within the
 170 lexical scope of this pragma will use the declared defaults.
 171 Even three-argument opens may be affected by this pragma
 172 when they don't specify IO layers in MODE.
 173
 174 With the C<IN> subpragma you can declare the default layers
 175 of input streams, and with the C<OUT> subpragma you can declare
 176 the default layers of output streams.  With the C<IO>  subpragma
 177 you can control both input and output streams simultaneously.
 178
 179 If you have a legacy encoding, you can use the C<:encoding(...)> tag.
 180
 181 If you want to set your encoding layers based on your
 182 locale environment variables, you can use the C<:locale> tag.
 183 For example:
 184
 185     $ENV{LANG} = 'ru_RU.KOI8-R';
 186     # the :locale will probe the locale environment variables like LANG
 187     use open OUT => ':locale';
 188     open(O, ">koi8");
 189     print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1
 190     close O;
 191     open(I, "<koi8");
 192     printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1
 193     close I;
 194
 195 These are equivalent
 196
 197     use open ':utf8';
 198     use open IO => ':utf8';
 199
 200 as are these
 201
 202     use open ':locale';
 203     use open IO => ':locale';
 204
 205 and these
 206
 207     use open ':encoding(iso-8859-7)';
 208     use open IO => ':encoding(iso-8859-7)';
 209
 210 The matching of encoding names is loose: case does not matter, and
 211 many encodings have several aliases.  See L<Encode::Supported> for
 212 details and the list of supported locales.
 213
 214 Note that C<:utf8> PerlIO layer must always be specified exactly like
 215 that, it is not subject to the loose matching of encoding names.
 216
 217 When open() is given an explicit list of layers (with the three-arg
 218 syntax), they override the list declared using this pragma.
 219
 220 The C<:std> subpragma on its own has no effect, but if combined with
 221 the C<:utf8> or C<:encoding> subpragmas, it converts the standard
 222 filehandles (STDIN, STDOUT, STDERR) to comply with encoding selected
 223 for input/output handles.  For example, if both input and out are
 224 chosen to be C<:utf8>, a C<:std> will mean that STDIN, STDOUT, and
 225 STDERR are also in C<:utf8>.  On the other hand, if only output is
 226 chosen to be in C<< :encoding(koi8r) >>, a C<:std> will cause only the
 227 STDOUT and STDERR to be in C<koi8r>.  The C<:locale> subpragma
 228 implicitly turns on C<:std>.
 229
 230 The logic of C<:locale> is described in full in L<encoding>,
 231 but in short it is first trying nl_langinfo(CODESET) and then
 232 guessing from the LC_ALL and LANG locale environment variables.
 233
 234 Directory handles may also support PerlIO layers in the future.
 235
 236 =head1 NONPERLIO FUNCTIONALITY
 237
 238 If Perl is not built to use PerlIO as its IO system then only the two
 239 pseudo-layers C<:bytes> and C<:crlf> are available.
 240
 241 The C<:bytes> layer corresponds to "binary mode" and the C<:crlf>
 242 layer corresponds to "text mode" on platforms that distinguish
 243 between the two modes when opening files (which is many DOS-like
 244 platforms, including Windows).  These two layers are no-ops on
 245 platforms where binmode() is a no-op, but perform their functions
 246 everywhere if PerlIO is enabled.
 247
 248 =head1 IMPLEMENTATION DETAILS
 249
 250 There is a class method in C<PerlIO::Layer> C<find> which is
 251 implemented as XS code.  It is called by C<import> to validate the
 252 layers:
 253
 254    PerlIO::Layer::->find("perlio")
 255
 256 The return value (if defined) is a Perl object, of class
 257 C<PerlIO::Layer> which is created by the C code in F<perlio.c>.  As
 258 yet there is nothing useful you can do with the object at the perl
 259 level.
 260
 261 =head1 SEE ALSO
 262
 263 L<perlfunc/"binmode">, L<perlfunc/"open">, L<perlunicode>, L<PerlIO>,
 264 L<encoding>
 265
 266 =cut