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1 | # $Id: encoding.pm,v 2.1 2004/10/19 04:55:01 dankogai Exp $ |
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2 | package encoding; |
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3 | our $VERSION = do { my @r = (q$Revision: 2.1 $ =~ /\d+/g); sprintf "%d."."%02d" x $#r, @r }; |
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4 | |
5 | use Encode; |
046f36bf |
6 | use strict; |
b1aeb384 |
7 | |
8f139f4c |
8 | sub DEBUG () { 0 } |
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9 | |
10 | BEGIN { |
11 | if (ord("A") == 193) { |
12 | require Carp; |
b1aeb384 |
13 | Carp::croak("encoding: pragma does not support EBCDIC platforms"); |
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14 | } |
15 | } |
16 | |
0ab8f81e |
17 | our $HAS_PERLIO = 0; |
18 | eval { require PerlIO::encoding }; |
19 | unless ($@){ |
20 | $HAS_PERLIO = (PerlIO::encoding->VERSION >= 0.02); |
21 | } |
b2704119 |
22 | |
151b5d36 |
23 | sub _exception{ |
24 | my $name = shift; |
b5ab1f6f |
25 | $] > 5.008 and return 0; # 5.8.1 or higher then no |
151b5d36 |
26 | my %utfs = map {$_=>1} |
27 | qw(utf8 UCS-2BE UCS-2LE UTF-16 UTF-16BE UTF-16LE |
28 | UTF-32 UTF-32BE UTF-32LE); |
b5ab1f6f |
29 | $utfs{$name} or return 0; # UTFs or no |
151b5d36 |
30 | require Config; Config->import(); our %Config; |
2b6a28d4 |
31 | return $Config{perl_patchlevel} ? 0 : 1 # maintperl then no |
151b5d36 |
32 | } |
fa6f41cf |
33 | |
b1aeb384 |
34 | sub in_locale { $^H & ($locale::hint_bits || 0)} |
35 | |
36 | sub _get_locale_encoding { |
37 | my $locale_encoding; |
38 | |
39 | # I18N::Langinfo isn't available everywhere |
40 | eval { |
41 | require I18N::Langinfo; |
42 | I18N::Langinfo->import(qw(langinfo CODESET)); |
43 | $locale_encoding = langinfo(CODESET()); |
44 | }; |
45 | |
46 | my $country_language; |
47 | |
48 | no warnings 'uninitialized'; |
49 | |
50 | if (not $locale_encoding && in_locale()) { |
51 | if ($ENV{LC_ALL} =~ /^([^.]+)\.([^.]+)$/) { |
52 | ($country_language, $locale_encoding) = ($1, $2); |
53 | } elsif ($ENV{LANG} =~ /^([^.]+)\.([^.]+)$/) { |
54 | ($country_language, $locale_encoding) = ($1, $2); |
55 | } |
56 | # LANGUAGE affects only LC_MESSAGES only on glibc |
57 | } elsif (not $locale_encoding) { |
58 | if ($ENV{LC_ALL} =~ /\butf-?8\b/i || |
59 | $ENV{LANG} =~ /\butf-?8\b/i) { |
60 | $locale_encoding = 'utf8'; |
61 | } |
62 | # Could do more heuristics based on the country and language |
63 | # parts of LC_ALL and LANG (the parts before the dot (if any)), |
64 | # since we have Locale::Country and Locale::Language available. |
65 | # TODO: get a database of Language -> Encoding mappings |
66 | # (the Estonian database at http://www.eki.ee/letter/ |
67 | # would be excellent!) --jhi |
68 | } |
69 | if (defined $locale_encoding && |
70 | lc($locale_encoding) eq 'euc' && |
71 | defined $country_language) { |
72 | if ($country_language =~ /^ja_JP|japan(?:ese)?$/i) { |
73 | $locale_encoding = 'euc-jp'; |
74 | } elsif ($country_language =~ /^ko_KR|korean?$/i) { |
75 | $locale_encoding = 'euc-kr'; |
76 | } elsif ($country_language =~ /^zh_CN|chin(?:a|ese)?$/i) { |
77 | $locale_encoding = 'euc-cn'; |
78 | } elsif ($country_language =~ /^zh_TW|taiwan(?:ese)?$/i) { |
79 | $locale_encoding = 'euc-tw'; |
80 | } else { |
81 | require Carp; |
82 | Carp::croak("encoding: Locale encoding '$locale_encoding' too ambiguous"); |
83 | } |
84 | } |
85 | |
86 | return $locale_encoding; |
87 | } |
88 | |
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89 | sub import { |
90 | my $class = shift; |
91 | my $name = shift; |
b1aeb384 |
92 | if ($name eq ':_get_locale_encoding') { # used by lib/open.pm |
93 | my $caller = caller(); |
94 | { |
95 | no strict 'refs'; |
96 | *{"${caller}::_get_locale_encoding"} = \&_get_locale_encoding; |
97 | } |
98 | return; |
99 | } |
100 | $name = _get_locale_encoding() if $name eq ':locale'; |
3ef515df |
101 | my %arg = @_; |
b1aeb384 |
102 | $name = $ENV{PERL_ENCODING} unless defined $name; |
3ef515df |
103 | my $enc = find_encoding($name); |
104 | unless (defined $enc) { |
105 | require Carp; |
b1aeb384 |
106 | Carp::croak("encoding: Unknown encoding '$name'"); |
3ef515df |
107 | } |
fa6f41cf |
108 | $name = $enc->name; # canonize |
0f7c507f |
109 | unless ($arg{Filter}) { |
8f139f4c |
110 | DEBUG and warn "_exception($name) = ", _exception($name); |
151b5d36 |
111 | _exception($name) or ${^ENCODING} = $enc; |
85982a32 |
112 | $HAS_PERLIO or return 1; |
aae85ceb |
113 | }else{ |
114 | defined(${^ENCODING}) and undef ${^ENCODING}; |
151b5d36 |
115 | # implicitly 'use utf8' |
116 | require utf8; # to fetch $utf8::hint_bits; |
117 | $^H |= $utf8::hint_bits; |
aae85ceb |
118 | eval { |
119 | require Filter::Util::Call ; |
120 | Filter::Util::Call->import ; |
aae85ceb |
121 | filter_add(sub{ |
151b5d36 |
122 | my $status = filter_read(); |
123 | if ($status > 0){ |
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124 | $_ = $enc->decode($_, 1); |
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125 | DEBUG and warn $_; |
aae85ceb |
126 | } |
127 | $status ; |
128 | }); |
129 | }; |
d7fe8a7a |
130 | $@ eq '' and DEBUG and warn "Filter installed"; |
b1aeb384 |
131 | } |
05ef2f67 |
132 | defined ${^UNICODE} and ${^UNICODE} != 0 and return 1; |
151b5d36 |
133 | for my $h (qw(STDIN STDOUT)){ |
134 | if ($arg{$h}){ |
135 | unless (defined find_encoding($arg{$h})) { |
136 | require Carp; |
b1aeb384 |
137 | Carp::croak("encoding: Unknown encoding for $h, '$arg{$h}'"); |
151b5d36 |
138 | } |
6be7c101 |
139 | eval { binmode($h, ":raw :encoding($arg{$h})") }; |
151b5d36 |
140 | }else{ |
141 | unless (exists $arg{$h}){ |
142 | eval { |
143 | no warnings 'uninitialized'; |
6be7c101 |
144 | binmode($h, ":raw :encoding($name)"); |
151b5d36 |
145 | }; |
146 | } |
147 | } |
148 | if ($@){ |
149 | require Carp; |
150 | Carp::croak($@); |
151 | } |
3ef515df |
152 | } |
153 | return 1; # I doubt if we need it, though |
154 | } |
155 | |
156 | sub unimport{ |
157 | no warnings; |
158 | undef ${^ENCODING}; |
621b0f8d |
159 | if ($HAS_PERLIO){ |
160 | binmode(STDIN, ":raw"); |
161 | binmode(STDOUT, ":raw"); |
162 | }else{ |
6be7c101 |
163 | binmode(STDIN); |
164 | binmode(STDOUT); |
621b0f8d |
165 | } |
aae85ceb |
166 | if ($INC{"Filter/Util/Call.pm"}){ |
167 | eval { filter_del() }; |
168 | } |
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169 | } |
170 | |
171 | 1; |
172 | __END__ |
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173 | |
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174 | =pod |
175 | |
176 | =head1 NAME |
177 | |
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178 | encoding - allows you to write your script in non-ascii or non-utf8 |
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179 | |
180 | =head1 SYNOPSIS |
181 | |
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182 | use encoding "greek"; # Perl like Greek to you? |
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183 | use encoding "euc-jp"; # Jperl! |
184 | |
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185 | # or you can even do this if your shell supports your native encoding |
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186 | |
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187 | perl -Mencoding=latin2 -e '...' # Feeling centrally European? |
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188 | perl -Mencoding=euc-kr -e '...' # Or Korean? |
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189 | |
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190 | # more control |
191 | |
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192 | # A simple euc-cn => utf-8 converter |
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193 | use encoding "euc-cn", STDOUT => "utf8"; while(<>){print}; |
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194 | |
195 | # "no encoding;" supported (but not scoped!) |
196 | no encoding; |
197 | |
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198 | # an alternate way, Filter |
199 | use encoding "euc-jp", Filter=>1; |
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200 | # now you can use kanji identifiers -- in euc-jp! |
201 | |
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202 | # switch on locale - |
203 | # note that this probably means that unless you have a complete control |
204 | # over the environments the application is ever going to be run, you should |
205 | # NOT use the feature of encoding pragma allowing you to write your script |
206 | # in any recognized encoding because changing locale settings will wreck |
207 | # the script; you can of course still use the other features of the pragma. |
208 | use encoding ':locale'; |
209 | |
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210 | =head1 ABSTRACT |
211 | |
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212 | Let's start with a bit of history: Perl 5.6.0 introduced Unicode |
213 | support. You could apply C<substr()> and regexes even to complex CJK |
214 | characters -- so long as the script was written in UTF-8. But back |
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215 | then, text editors that supported UTF-8 were still rare and many users |
216 | instead chose to write scripts in legacy encodings, giving up a whole |
217 | new feature of Perl 5.6. |
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218 | |
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219 | Rewind to the future: starting from perl 5.8.0 with the B<encoding> |
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220 | pragma, you can write your script in any encoding you like (so long |
221 | as the C<Encode> module supports it) and still enjoy Unicode support. |
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222 | This pragma achieves that by doing the following: |
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223 | |
224 | =over |
225 | |
226 | =item * |
227 | |
228 | Internally converts all literals (C<q//,qq//,qr//,qw///, qx//>) from |
229 | the encoding specified to utf8. In Perl 5.8.1 and later, literals in |
230 | C<tr///> and C<DATA> pseudo-filehandle are also converted. |
231 | |
232 | =item * |
233 | |
234 | Changing PerlIO layers of C<STDIN> and C<STDOUT> to the encoding |
235 | specified. |
236 | |
237 | =back |
238 | |
239 | =head2 Literal Conversions |
240 | |
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241 | You can write code in EUC-JP as follows: |
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242 | |
243 | my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji |
244 | #<-char-><-char-> # 4 octets |
245 | s/\bCamel\b/$Rakuda/; |
246 | |
247 | And with C<use encoding "euc-jp"> in effect, it is the same thing as |
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248 | the code in UTF-8: |
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249 | |
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250 | my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characters |
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251 | s/\bCamel\b/$Rakuda/; |
252 | |
05ef2f67 |
253 | =head2 PerlIO layers for C<STD(IN|OUT)> |
254 | |
255 | The B<encoding> pragma also modifies the filehandle layers of |
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256 | STDIN and STDOUT to the specified encoding. Therefore, |
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257 | |
258 | use encoding "euc-jp"; |
259 | my $message = "Camel is the symbol of perl.\n"; |
260 | my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji |
261 | $message =~ s/\bCamel\b/$Rakuda/; |
262 | print $message; |
263 | |
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264 | Will print "\xF1\xD1\xF1\xCC is the symbol of perl.\n", |
265 | not "\x{99F1}\x{99DD} is the symbol of perl.\n". |
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266 | |
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267 | You can override this by giving extra arguments; see below. |
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268 | |
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269 | =head2 Implicit upgrading for byte strings |
270 | |
271 | By default, if strings operating under byte semantics and strings |
272 | with Unicode character data are concatenated, the new string will |
273 | be created by decoding the byte strings as I<ISO 8859-1 (Latin-1)>. |
274 | |
275 | The B<encoding> pragma changes this to use the specified encoding |
276 | instead. For example: |
277 | |
278 | use encoding 'utf8'; |
279 | my $string = chr(20000); # a Unicode string |
280 | utf8::encode($string); # now it's a UTF-8 encoded byte string |
281 | # concatenate with another Unicode string |
282 | print length($string . chr(20000)); |
283 | |
284 | Will print C<2>, because C<$string> is upgraded as UTF-8. Without |
285 | C<use encoding 'utf8';>, it will print C<4> instead, since C<$string> |
286 | is three octets when interpreted as Latin-1. |
287 | |
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288 | =head1 FEATURES THAT REQUIRE 5.8.1 |
289 | |
290 | Some of the features offered by this pragma requires perl 5.8.1. Most |
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291 | of these are done by Inaba Hiroto. Any other features and changes |
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292 | are good for 5.8.0. |
293 | |
294 | =over |
295 | |
296 | =item "NON-EUC" doublebyte encodings |
297 | |
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298 | Because perl needs to parse script before applying this pragma, such |
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299 | encodings as Shift_JIS and Big-5 that may contain '\' (BACKSLASH; |
300 | \x5c) in the second byte fails because the second byte may |
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301 | accidentally escape the quoting character that follows. Perl 5.8.1 |
05ef2f67 |
302 | or later fixes this problem. |
303 | |
304 | =item tr// |
305 | |
306 | C<tr//> was overlooked by Perl 5 porters when they released perl 5.8.0 |
307 | See the section below for details. |
308 | |
309 | =item DATA pseudo-filehandle |
310 | |
311 | Another feature that was overlooked was C<DATA>. |
312 | |
313 | =back |
314 | |
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315 | =head1 USAGE |
316 | |
317 | =over 4 |
318 | |
319 | =item use encoding [I<ENCNAME>] ; |
320 | |
05ef2f67 |
321 | Sets the script encoding to I<ENCNAME>. And unless ${^UNICODE} |
322 | exists and non-zero, PerlIO layers of STDIN and STDOUT are set to |
323 | ":encoding(I<ENCNAME>)". |
324 | |
325 | Note that STDERR WILL NOT be changed. |
326 | |
327 | Also note that non-STD file handles remain unaffected. Use C<use |
328 | open> or C<binmode> to change layers of those. |
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329 | |
330 | If no encoding is specified, the environment variable L<PERL_ENCODING> |
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331 | is consulted. If no encoding can be found, the error C<Unknown encoding |
332 | 'I<ENCNAME>'> will be thrown. |
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333 | |
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334 | =item use encoding I<ENCNAME> [ STDIN =E<gt> I<ENCNAME_IN> ...] ; |
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335 | |
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336 | You can also individually set encodings of STDIN and STDOUT via the |
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337 | C<< STDIN => I<ENCNAME> >> form. In this case, you cannot omit the |
338 | first I<ENCNAME>. C<< STDIN => undef >> turns the IO transcoding |
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339 | completely off. |
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340 | |
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341 | When ${^UNICODE} exists and non-zero, these options will completely |
342 | ignored. ${^UNICODE} is a variable introduced in perl 5.8.1. See |
343 | L<perlrun> see L<perlvar/"${^UNICODE}"> and L<perlrun/"-C"> for |
344 | details (perl 5.8.1 and later). |
345 | |
151b5d36 |
346 | =item use encoding I<ENCNAME> Filter=E<gt>1; |
347 | |
348 | This turns the encoding pragma into a source filter. While the |
349 | default approach just decodes interpolated literals (in qq() and |
350 | qr()), this will apply a source filter to the entire source code. See |
05ef2f67 |
351 | L</"The Filter Option"> below for details. |
151b5d36 |
352 | |
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353 | =item no encoding; |
354 | |
05ef2f67 |
355 | Unsets the script encoding. The layers of STDIN, STDOUT are |
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356 | reset to ":raw" (the default unprocessed raw stream of bytes). |
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357 | |
358 | =back |
359 | |
151b5d36 |
360 | =head1 The Filter Option |
361 | |
362 | The magic of C<use encoding> is not applied to the names of |
363 | identifiers. In order to make C<${"\x{4eba}"}++> ($human++, where human |
364 | is a single Han ideograph) work, you still need to write your script |
365 | in UTF-8 -- or use a source filter. That's what 'Filter=>1' does. |
366 | |
151b5d36 |
367 | What does this mean? Your source code behaves as if it is written in |
368 | UTF-8 with 'use utf8' in effect. So even if your editor only supports |
369 | Shift_JIS, for example, you can still try examples in Chapter 15 of |
370 | C<Programming Perl, 3rd Ed.>. For instance, you can use UTF-8 |
371 | identifiers. |
372 | |
373 | This option is significantly slower and (as of this writing) non-ASCII |
374 | identifiers are not very stable WITHOUT this option and with the |
375 | source code written in UTF-8. |
376 | |
377 | =head2 Filter-related changes at Encode version 1.87 |
378 | |
379 | =over |
380 | |
381 | =item * |
382 | |
383 | The Filter option now sets STDIN and STDOUT like non-filter options. |
384 | And C<< STDIN=>I<ENCODING> >> and C<< STDOUT=>I<ENCODING> >> work like |
385 | non-filter version. |
386 | |
387 | =item * |
388 | |
389 | C<use utf8> is implicitly declared so you no longer have to C<use |
390 | utf8> to C<${"\x{4eba}"}++>. |
391 | |
392 | =back |
393 | |
3ef515df |
394 | =head1 CAVEATS |
395 | |
396 | =head2 NOT SCOPED |
397 | |
398 | The pragma is a per script, not a per block lexical. Only the last |
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399 | C<use encoding> or C<no encoding> matters, and it affects |
400 | B<the whole script>. However, the <no encoding> pragma is supported and |
401 | B<use encoding> can appear as many times as you want in a given script. |
402 | The multiple use of this pragma is discouraged. |
403 | |
0f29a567 |
404 | By the same reason, the use this pragma inside modules is also |
3c4b39be |
405 | discouraged (though not as strongly discouraged as the case above. |
0f29a567 |
406 | See below). |
05ef2f67 |
407 | |
408 | If you still have to write a module with this pragma, be very careful |
409 | of the load order. See the codes below; |
410 | |
411 | # called module |
412 | package Module_IN_BAR; |
413 | use encoding "bar"; |
414 | # stuff in "bar" encoding here |
415 | 1; |
416 | |
417 | # caller script |
418 | use encoding "foo" |
419 | use Module_IN_BAR; |
420 | # surprise! use encoding "bar" is in effect. |
421 | |
422 | The best way to avoid this oddity is to use this pragma RIGHT AFTER |
423 | other modules are loaded. i.e. |
424 | |
425 | use Module_IN_BAR; |
426 | use encoding "foo"; |
3ef515df |
427 | |
428 | =head2 DO NOT MIX MULTIPLE ENCODINGS |
429 | |
430 | Notice that only literals (string or regular expression) having only |
431 | legacy code points are affected: if you mix data like this |
432 | |
433 | \xDF\x{100} |
434 | |
435 | the data is assumed to be in (Latin 1 and) Unicode, not in your native |
436 | encoding. In other words, this will match in "greek": |
437 | |
438 | "\xDF" =~ /\x{3af}/ |
439 | |
440 | but this will not |
441 | |
442 | "\xDF\x{100}" =~ /\x{3af}\x{100}/ |
443 | |
962111ca |
444 | since the C<\xDF> (ISO 8859-7 GREEK SMALL LETTER IOTA WITH TONOS) on |
445 | the left will B<not> be upgraded to C<\x{3af}> (Unicode GREEK SMALL |
446 | LETTER IOTA WITH TONOS) because of the C<\x{100}> on the left. You |
447 | should not be mixing your legacy data and Unicode in the same string. |
3ef515df |
448 | |
449 | This pragma also affects encoding of the 0x80..0xFF code point range: |
450 | normally characters in that range are left as eight-bit bytes (unless |
451 | they are combined with characters with code points 0x100 or larger, |
452 | in which case all characters need to become UTF-8 encoded), but if |
453 | the C<encoding> pragma is present, even the 0x80..0xFF range always |
454 | gets UTF-8 encoded. |
455 | |
456 | After all, the best thing about this pragma is that you don't have to |
0ab8f81e |
457 | resort to \x{....} just to spell your name in a native encoding. |
458 | So feel free to put your strings in your encoding in quotes and |
459 | regexes. |
3ef515df |
460 | |
151b5d36 |
461 | =head2 tr/// with ranges |
4b291ae6 |
462 | |
463 | The B<encoding> pragma works by decoding string literals in |
151b5d36 |
464 | C<q//,qq//,qr//,qw///, qx//> and so forth. In perl 5.8.0, this |
4b291ae6 |
465 | does not apply to C<tr///>. Therefore, |
466 | |
467 | use encoding 'euc-jp'; |
468 | #.... |
469 | $kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/; |
470 | # -------- -------- -------- -------- |
471 | |
472 | Does not work as |
473 | |
474 | $kana =~ tr/\x{3041}-\x{3093}/\x{30a1}-\x{30f3}/; |
475 | |
476 | =over |
477 | |
478 | =item Legend of characters above |
479 | |
480 | utf8 euc-jp charnames::viacode() |
481 | ----------------------------------------- |
482 | \x{3041} \xA4\xA1 HIRAGANA LETTER SMALL A |
483 | \x{3093} \xA4\xF3 HIRAGANA LETTER N |
484 | \x{30a1} \xA5\xA1 KATAKANA LETTER SMALL A |
485 | \x{30f3} \xA5\xF3 KATAKANA LETTER N |
486 | |
487 | =back |
488 | |
05ef2f67 |
489 | This counterintuitive behavior has been fixed in perl 5.8.1. |
151b5d36 |
490 | |
4b291ae6 |
491 | =head3 workaround to tr///; |
492 | |
ce16148b |
493 | In perl 5.8.0, you can work around as follows; |
4b291ae6 |
494 | |
495 | use encoding 'euc-jp'; |
151b5d36 |
496 | # .... |
4b291ae6 |
497 | eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ }; |
498 | |
ce16148b |
499 | Note the C<tr//> expression is surrounded by C<qq{}>. The idea behind |
4b291ae6 |
500 | is the same as classic idiom that makes C<tr///> 'interpolate'. |
501 | |
502 | tr/$from/$to/; # wrong! |
503 | eval qq{ tr/$from/$to/ }; # workaround. |
504 | |
505 | Nevertheless, in case of B<encoding> pragma even C<q//> is affected so |
506 | C<tr///> not being decoded was obviously against the will of Perl5 |
05ef2f67 |
507 | Porters so it has been fixed in Perl 5.8.1 or later. |
aae85ceb |
508 | |
3ef515df |
509 | =head1 EXAMPLE - Greekperl |
510 | |
511 | use encoding "iso 8859-7"; |
512 | |
0ab8f81e |
513 | # \xDF in ISO 8859-7 (Greek) is \x{3af} in Unicode. |
3ef515df |
514 | |
515 | $a = "\xDF"; |
516 | $b = "\x{100}"; |
517 | |
518 | printf "%#x\n", ord($a); # will print 0x3af, not 0xdf |
519 | |
520 | $c = $a . $b; |
521 | |
522 | # $c will be "\x{3af}\x{100}", not "\x{df}\x{100}". |
523 | |
524 | # chr() is affected, and ... |
525 | |
526 | print "mega\n" if ord(chr(0xdf)) == 0x3af; |
527 | |
528 | # ... ord() is affected by the encoding pragma ... |
529 | |
530 | print "tera\n" if ord(pack("C", 0xdf)) == 0x3af; |
531 | |
532 | # ... as are eq and cmp ... |
533 | |
534 | print "peta\n" if "\x{3af}" eq pack("C", 0xdf); |
535 | print "exa\n" if "\x{3af}" cmp pack("C", 0xdf) == 0; |
536 | |
537 | # ... but pack/unpack C are not affected, in case you still |
0ab8f81e |
538 | # want to go back to your native encoding |
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539 | |
540 | print "zetta\n" if unpack("C", (pack("C", 0xdf))) == 0xdf; |
541 | |
542 | =head1 KNOWN PROBLEMS |
543 | |
151b5d36 |
544 | =over |
545 | |
0f29a567 |
546 | =item literals in regex that are longer than 127 bytes |
151b5d36 |
547 | |
0ab8f81e |
548 | For native multibyte encodings (either fixed or variable length), |
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549 | the current implementation of the regular expressions may introduce |
0ab8f81e |
550 | recoding errors for regular expression literals longer than 127 bytes. |
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551 | |
05ef2f67 |
552 | =item EBCDIC |
151b5d36 |
553 | |
3ef515df |
554 | The encoding pragma is not supported on EBCDIC platforms. |
0ab8f81e |
555 | (Porters who are willing and able to remove this limitation are |
556 | welcome.) |
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557 | |
05ef2f67 |
558 | =item format |
559 | |
560 | This pragma doesn't work well with format because PerlIO does not |
561 | get along very well with it. When format contains non-ascii |
562 | characters it prints funny or gets "wide character warnings". |
563 | To understand it, try the code below. |
564 | |
565 | # Save this one in utf8 |
566 | # replace *non-ascii* with a non-ascii string |
567 | my $camel; |
568 | format STDOUT = |
569 | *non-ascii*@>>>>>>> |
570 | $camel |
571 | . |
572 | $camel = "*non-ascii*"; |
573 | binmode(STDOUT=>':encoding(utf8)'); # bang! |
574 | write; # funny |
575 | print $camel, "\n"; # fine |
576 | |
577 | Without binmode this happens to work but without binmode, print() |
578 | fails instead of write(). |
579 | |
580 | At any rate, the very use of format is questionable when it comes to |
581 | unicode characters since you have to consider such things as character |
582 | width (i.e. double-width for ideographs) and directions (i.e. BIDI for |
583 | Arabic and Hebrew). |
584 | |
151b5d36 |
585 | =back |
586 | |
b1aeb384 |
587 | =head2 The Logic of :locale |
588 | |
589 | The logic of C<:locale> is as follows: |
590 | |
591 | =over 4 |
592 | |
593 | =item 1. |
594 | |
595 | If the platform supports the langinfo(CODESET) interface, the codeset |
596 | returned is used as the default encoding for the open pragma. |
597 | |
598 | =item 2. |
599 | |
600 | If 1. didn't work but we are under the locale pragma, the environment |
601 | variables LC_ALL and LANG (in that order) are matched for encodings |
602 | (the part after C<.>, if any), and if any found, that is used |
603 | as the default encoding for the open pragma. |
604 | |
605 | =item 3. |
606 | |
607 | If 1. and 2. didn't work, the environment variables LC_ALL and LANG |
608 | (in that order) are matched for anything looking like UTF-8, and if |
609 | any found, C<:utf8> is used as the default encoding for the open |
610 | pragma. |
611 | |
612 | =back |
613 | |
614 | If your locale environment variables (LC_ALL, LC_CTYPE, LANG) |
615 | contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching), |
616 | the default encoding of your STDIN, STDOUT, and STDERR, and of |
617 | B<any subsequent file open>, is UTF-8. |
618 | |
05ef2f67 |
619 | =head1 HISTORY |
620 | |
621 | This pragma first appeared in Perl 5.8.0. For features that require |
622 | 5.8.1 and better, see above. |
623 | |
b1aeb384 |
624 | The C<:locale> subpragma was implemented in 2.01, or Perl 5.8.6. |
625 | |
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626 | =head1 SEE ALSO |
627 | |
aae85ceb |
628 | L<perlunicode>, L<Encode>, L<open>, L<Filter::Util::Call>, |
629 | |
630 | Ch. 15 of C<Programming Perl (3rd Edition)> |
631 | by Larry Wall, Tom Christiansen, Jon Orwant; |
632 | O'Reilly & Associates; ISBN 0-596-00027-8 |
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633 | |
634 | =cut |