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1 | # $Id: encoding.pm,v 2.4 2006/06/03 20:28:48 dankogai Exp dankogai $ |
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2 | package encoding; |
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3 | our $VERSION = do { my @r = ( q$Revision: 2.4 $ =~ /\d+/g ); sprintf "%d." . "%02d" x $#r, @r }; |
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4 | |
5 | use Encode; |
046f36bf |
6 | use strict; |
656ebd29 |
7 | use warnings; |
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8 | |
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9 | sub DEBUG () { 0 } |
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10 | |
11 | BEGIN { |
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12 | if ( ord("A") == 193 ) { |
13 | require Carp; |
14 | Carp::croak("encoding: pragma does not support EBCDIC platforms"); |
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15 | } |
16 | } |
17 | |
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18 | our $HAS_PERLIO = 0; |
19 | eval { require PerlIO::encoding }; |
d1256cb1 |
20 | unless ($@) { |
21 | $HAS_PERLIO = ( PerlIO::encoding->VERSION >= 0.02 ); |
0ab8f81e |
22 | } |
b2704119 |
23 | |
d1256cb1 |
24 | sub _exception { |
151b5d36 |
25 | my $name = shift; |
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26 | $] > 5.008 and return 0; # 5.8.1 or higher then no |
27 | my %utfs = map { $_ => 1 } |
28 | qw(utf8 UCS-2BE UCS-2LE UTF-16 UTF-16BE UTF-16LE |
29 | UTF-32 UTF-32BE UTF-32LE); |
30 | $utfs{$name} or return 0; # UTFs or no |
31 | require Config; |
32 | Config->import(); |
33 | our %Config; |
34 | return $Config{perl_patchlevel} ? 0 : 1 # maintperl then no |
151b5d36 |
35 | } |
fa6f41cf |
36 | |
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37 | sub in_locale { $^H & ( $locale::hint_bits || 0 ) } |
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38 | |
39 | sub _get_locale_encoding { |
40 | my $locale_encoding; |
41 | |
42 | # I18N::Langinfo isn't available everywhere |
43 | eval { |
d1256cb1 |
44 | require I18N::Langinfo; |
45 | I18N::Langinfo->import(qw(langinfo CODESET)); |
46 | $locale_encoding = langinfo( CODESET() ); |
b1aeb384 |
47 | }; |
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48 | |
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49 | my $country_language; |
50 | |
51 | no warnings 'uninitialized'; |
52 | |
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53 | if ( not $locale_encoding && in_locale() ) { |
54 | if ( $ENV{LC_ALL} =~ /^([^.]+)\.([^.]+)$/ ) { |
55 | ( $country_language, $locale_encoding ) = ( $1, $2 ); |
56 | } |
57 | elsif ( $ENV{LANG} =~ /^([^.]+)\.([^.]+)$/ ) { |
58 | ( $country_language, $locale_encoding ) = ( $1, $2 ); |
59 | } |
60 | |
61 | # LANGUAGE affects only LC_MESSAGES only on glibc |
62 | } |
63 | elsif ( not $locale_encoding ) { |
64 | if ( $ENV{LC_ALL} =~ /\butf-?8\b/i |
65 | || $ENV{LANG} =~ /\butf-?8\b/i ) |
66 | { |
67 | $locale_encoding = 'utf8'; |
68 | } |
69 | |
70 | # Could do more heuristics based on the country and language |
71 | # parts of LC_ALL and LANG (the parts before the dot (if any)), |
72 | # since we have Locale::Country and Locale::Language available. |
73 | # TODO: get a database of Language -> Encoding mappings |
74 | # (the Estonian database at http://www.eki.ee/letter/ |
75 | # would be excellent!) --jhi |
b1aeb384 |
76 | } |
d1256cb1 |
77 | if ( defined $locale_encoding |
78 | && lc($locale_encoding) eq 'euc' |
79 | && defined $country_language ) |
80 | { |
81 | if ( $country_language =~ /^ja_JP|japan(?:ese)?$/i ) { |
82 | $locale_encoding = 'euc-jp'; |
83 | } |
84 | elsif ( $country_language =~ /^ko_KR|korean?$/i ) { |
85 | $locale_encoding = 'euc-kr'; |
86 | } |
5a1dbf39 |
87 | elsif ( $country_language =~ /^zh_CN|chin(?:a|ese)$/i ) { |
d1256cb1 |
88 | $locale_encoding = 'euc-cn'; |
89 | } |
90 | elsif ( $country_language =~ /^zh_TW|taiwan(?:ese)?$/i ) { |
91 | $locale_encoding = 'euc-tw'; |
92 | } |
93 | else { |
94 | require Carp; |
95 | Carp::croak( |
96 | "encoding: Locale encoding '$locale_encoding' too ambiguous" |
97 | ); |
98 | } |
b1aeb384 |
99 | } |
100 | |
101 | return $locale_encoding; |
102 | } |
103 | |
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104 | sub import { |
105 | my $class = shift; |
106 | my $name = shift; |
d1256cb1 |
107 | if ( $name eq ':_get_locale_encoding' ) { # used by lib/open.pm |
108 | my $caller = caller(); |
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109 | { |
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110 | no strict 'refs'; |
111 | *{"${caller}::_get_locale_encoding"} = \&_get_locale_encoding; |
112 | } |
113 | return; |
b1aeb384 |
114 | } |
115 | $name = _get_locale_encoding() if $name eq ':locale'; |
3ef515df |
116 | my %arg = @_; |
b1aeb384 |
117 | $name = $ENV{PERL_ENCODING} unless defined $name; |
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118 | my $enc = find_encoding($name); |
d1256cb1 |
119 | unless ( defined $enc ) { |
120 | require Carp; |
121 | Carp::croak("encoding: Unknown encoding '$name'"); |
122 | } |
123 | $name = $enc->name; # canonize |
124 | unless ( $arg{Filter} ) { |
125 | DEBUG and warn "_exception($name) = ", _exception($name); |
126 | _exception($name) or ${^ENCODING} = $enc; |
127 | $HAS_PERLIO or return 1; |
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128 | } |
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129 | else { |
130 | defined( ${^ENCODING} ) and undef ${^ENCODING}; |
131 | |
132 | # implicitly 'use utf8' |
133 | require utf8; # to fetch $utf8::hint_bits; |
134 | $^H |= $utf8::hint_bits; |
135 | eval { |
136 | require Filter::Util::Call; |
137 | Filter::Util::Call->import; |
138 | filter_add( |
139 | sub { |
140 | my $status = filter_read(); |
141 | if ( $status > 0 ) { |
142 | $_ = $enc->decode( $_, 1 ); |
143 | DEBUG and warn $_; |
144 | } |
145 | $status; |
146 | } |
147 | ); |
148 | }; |
d7fe8a7a |
149 | $@ eq '' and DEBUG and warn "Filter installed"; |
b1aeb384 |
150 | } |
05ef2f67 |
151 | defined ${^UNICODE} and ${^UNICODE} != 0 and return 1; |
d1256cb1 |
152 | for my $h (qw(STDIN STDOUT)) { |
153 | if ( $arg{$h} ) { |
154 | unless ( defined find_encoding( $arg{$h} ) ) { |
155 | require Carp; |
156 | Carp::croak( |
157 | "encoding: Unknown encoding for $h, '$arg{$h}'"); |
158 | } |
159 | eval { binmode( $h, ":raw :encoding($arg{$h})" ) }; |
160 | } |
161 | else { |
162 | unless ( exists $arg{$h} ) { |
163 | eval { |
164 | no warnings 'uninitialized'; |
165 | binmode( $h, ":raw :encoding($name)" ); |
166 | }; |
167 | } |
168 | } |
169 | if ($@) { |
170 | require Carp; |
171 | Carp::croak($@); |
172 | } |
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173 | } |
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174 | return 1; # I doubt if we need it, though |
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175 | } |
176 | |
d1256cb1 |
177 | sub unimport { |
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178 | no warnings; |
179 | undef ${^ENCODING}; |
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180 | if ($HAS_PERLIO) { |
181 | binmode( STDIN, ":raw" ); |
182 | binmode( STDOUT, ":raw" ); |
183 | } |
184 | else { |
185 | binmode(STDIN); |
186 | binmode(STDOUT); |
621b0f8d |
187 | } |
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188 | if ( $INC{"Filter/Util/Call.pm"} ) { |
189 | eval { filter_del() }; |
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190 | } |
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191 | } |
192 | |
193 | 1; |
194 | __END__ |
85982a32 |
195 | |
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196 | =pod |
197 | |
198 | =head1 NAME |
199 | |
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200 | encoding - allows you to write your script in non-ascii or non-utf8 |
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201 | |
202 | =head1 SYNOPSIS |
203 | |
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204 | use encoding "greek"; # Perl like Greek to you? |
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205 | use encoding "euc-jp"; # Jperl! |
206 | |
962111ca |
207 | # or you can even do this if your shell supports your native encoding |
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208 | |
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209 | perl -Mencoding=latin2 -e '...' # Feeling centrally European? |
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210 | perl -Mencoding=euc-kr -e '...' # Or Korean? |
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211 | |
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212 | # more control |
213 | |
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214 | # A simple euc-cn => utf-8 converter |
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215 | use encoding "euc-cn", STDOUT => "utf8"; while(<>){print}; |
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216 | |
217 | # "no encoding;" supported (but not scoped!) |
218 | no encoding; |
219 | |
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220 | # an alternate way, Filter |
221 | use encoding "euc-jp", Filter=>1; |
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222 | # now you can use kanji identifiers -- in euc-jp! |
223 | |
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224 | # switch on locale - |
225 | # note that this probably means that unless you have a complete control |
226 | # over the environments the application is ever going to be run, you should |
227 | # NOT use the feature of encoding pragma allowing you to write your script |
228 | # in any recognized encoding because changing locale settings will wreck |
229 | # the script; you can of course still use the other features of the pragma. |
230 | use encoding ':locale'; |
231 | |
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232 | =head1 ABSTRACT |
233 | |
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234 | Let's start with a bit of history: Perl 5.6.0 introduced Unicode |
235 | support. You could apply C<substr()> and regexes even to complex CJK |
236 | characters -- so long as the script was written in UTF-8. But back |
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237 | then, text editors that supported UTF-8 were still rare and many users |
238 | instead chose to write scripts in legacy encodings, giving up a whole |
239 | new feature of Perl 5.6. |
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240 | |
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241 | Rewind to the future: starting from perl 5.8.0 with the B<encoding> |
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242 | pragma, you can write your script in any encoding you like (so long |
243 | as the C<Encode> module supports it) and still enjoy Unicode support. |
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244 | This pragma achieves that by doing the following: |
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245 | |
246 | =over |
247 | |
248 | =item * |
249 | |
250 | Internally converts all literals (C<q//,qq//,qr//,qw///, qx//>) from |
251 | the encoding specified to utf8. In Perl 5.8.1 and later, literals in |
252 | C<tr///> and C<DATA> pseudo-filehandle are also converted. |
253 | |
254 | =item * |
255 | |
256 | Changing PerlIO layers of C<STDIN> and C<STDOUT> to the encoding |
257 | specified. |
258 | |
259 | =back |
260 | |
261 | =head2 Literal Conversions |
262 | |
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263 | You can write code in EUC-JP as follows: |
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264 | |
265 | my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji |
266 | #<-char-><-char-> # 4 octets |
267 | s/\bCamel\b/$Rakuda/; |
268 | |
269 | And with C<use encoding "euc-jp"> in effect, it is the same thing as |
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270 | the code in UTF-8: |
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271 | |
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272 | my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characters |
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273 | s/\bCamel\b/$Rakuda/; |
274 | |
05ef2f67 |
275 | =head2 PerlIO layers for C<STD(IN|OUT)> |
276 | |
277 | The B<encoding> pragma also modifies the filehandle layers of |
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278 | STDIN and STDOUT to the specified encoding. Therefore, |
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279 | |
280 | use encoding "euc-jp"; |
281 | my $message = "Camel is the symbol of perl.\n"; |
282 | my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji |
283 | $message =~ s/\bCamel\b/$Rakuda/; |
284 | print $message; |
285 | |
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286 | Will print "\xF1\xD1\xF1\xCC is the symbol of perl.\n", |
287 | not "\x{99F1}\x{99DD} is the symbol of perl.\n". |
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288 | |
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289 | You can override this by giving extra arguments; see below. |
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290 | |
990e18f7 |
291 | =head2 Implicit upgrading for byte strings |
292 | |
293 | By default, if strings operating under byte semantics and strings |
294 | with Unicode character data are concatenated, the new string will |
295 | be created by decoding the byte strings as I<ISO 8859-1 (Latin-1)>. |
296 | |
297 | The B<encoding> pragma changes this to use the specified encoding |
298 | instead. For example: |
299 | |
300 | use encoding 'utf8'; |
301 | my $string = chr(20000); # a Unicode string |
302 | utf8::encode($string); # now it's a UTF-8 encoded byte string |
303 | # concatenate with another Unicode string |
304 | print length($string . chr(20000)); |
305 | |
306 | Will print C<2>, because C<$string> is upgraded as UTF-8. Without |
307 | C<use encoding 'utf8';>, it will print C<4> instead, since C<$string> |
308 | is three octets when interpreted as Latin-1. |
309 | |
05ef2f67 |
310 | =head1 FEATURES THAT REQUIRE 5.8.1 |
311 | |
312 | Some of the features offered by this pragma requires perl 5.8.1. Most |
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313 | of these are done by Inaba Hiroto. Any other features and changes |
05ef2f67 |
314 | are good for 5.8.0. |
315 | |
316 | =over |
317 | |
318 | =item "NON-EUC" doublebyte encodings |
319 | |
0f29a567 |
320 | Because perl needs to parse script before applying this pragma, such |
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321 | encodings as Shift_JIS and Big-5 that may contain '\' (BACKSLASH; |
322 | \x5c) in the second byte fails because the second byte may |
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323 | accidentally escape the quoting character that follows. Perl 5.8.1 |
05ef2f67 |
324 | or later fixes this problem. |
325 | |
326 | =item tr// |
327 | |
328 | C<tr//> was overlooked by Perl 5 porters when they released perl 5.8.0 |
329 | See the section below for details. |
330 | |
331 | =item DATA pseudo-filehandle |
332 | |
333 | Another feature that was overlooked was C<DATA>. |
334 | |
335 | =back |
336 | |
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337 | =head1 USAGE |
338 | |
339 | =over 4 |
340 | |
341 | =item use encoding [I<ENCNAME>] ; |
342 | |
05ef2f67 |
343 | Sets the script encoding to I<ENCNAME>. And unless ${^UNICODE} |
344 | exists and non-zero, PerlIO layers of STDIN and STDOUT are set to |
345 | ":encoding(I<ENCNAME>)". |
346 | |
347 | Note that STDERR WILL NOT be changed. |
348 | |
349 | Also note that non-STD file handles remain unaffected. Use C<use |
350 | open> or C<binmode> to change layers of those. |
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351 | |
352 | If no encoding is specified, the environment variable L<PERL_ENCODING> |
962111ca |
353 | is consulted. If no encoding can be found, the error C<Unknown encoding |
354 | 'I<ENCNAME>'> will be thrown. |
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355 | |
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356 | =item use encoding I<ENCNAME> [ STDIN =E<gt> I<ENCNAME_IN> ...] ; |
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357 | |
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358 | You can also individually set encodings of STDIN and STDOUT via the |
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359 | C<< STDIN => I<ENCNAME> >> form. In this case, you cannot omit the |
360 | first I<ENCNAME>. C<< STDIN => undef >> turns the IO transcoding |
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361 | completely off. |
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362 | |
05ef2f67 |
363 | When ${^UNICODE} exists and non-zero, these options will completely |
364 | ignored. ${^UNICODE} is a variable introduced in perl 5.8.1. See |
365 | L<perlrun> see L<perlvar/"${^UNICODE}"> and L<perlrun/"-C"> for |
366 | details (perl 5.8.1 and later). |
367 | |
151b5d36 |
368 | =item use encoding I<ENCNAME> Filter=E<gt>1; |
369 | |
370 | This turns the encoding pragma into a source filter. While the |
371 | default approach just decodes interpolated literals (in qq() and |
372 | qr()), this will apply a source filter to the entire source code. See |
05ef2f67 |
373 | L</"The Filter Option"> below for details. |
151b5d36 |
374 | |
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375 | =item no encoding; |
376 | |
05ef2f67 |
377 | Unsets the script encoding. The layers of STDIN, STDOUT are |
962111ca |
378 | reset to ":raw" (the default unprocessed raw stream of bytes). |
3ef515df |
379 | |
380 | =back |
381 | |
151b5d36 |
382 | =head1 The Filter Option |
383 | |
384 | The magic of C<use encoding> is not applied to the names of |
385 | identifiers. In order to make C<${"\x{4eba}"}++> ($human++, where human |
386 | is a single Han ideograph) work, you still need to write your script |
387 | in UTF-8 -- or use a source filter. That's what 'Filter=>1' does. |
388 | |
151b5d36 |
389 | What does this mean? Your source code behaves as if it is written in |
390 | UTF-8 with 'use utf8' in effect. So even if your editor only supports |
391 | Shift_JIS, for example, you can still try examples in Chapter 15 of |
392 | C<Programming Perl, 3rd Ed.>. For instance, you can use UTF-8 |
393 | identifiers. |
394 | |
395 | This option is significantly slower and (as of this writing) non-ASCII |
396 | identifiers are not very stable WITHOUT this option and with the |
397 | source code written in UTF-8. |
398 | |
399 | =head2 Filter-related changes at Encode version 1.87 |
400 | |
401 | =over |
402 | |
403 | =item * |
404 | |
405 | The Filter option now sets STDIN and STDOUT like non-filter options. |
406 | And C<< STDIN=>I<ENCODING> >> and C<< STDOUT=>I<ENCODING> >> work like |
407 | non-filter version. |
408 | |
409 | =item * |
410 | |
411 | C<use utf8> is implicitly declared so you no longer have to C<use |
412 | utf8> to C<${"\x{4eba}"}++>. |
413 | |
414 | =back |
415 | |
3ef515df |
416 | =head1 CAVEATS |
417 | |
418 | =head2 NOT SCOPED |
419 | |
420 | The pragma is a per script, not a per block lexical. Only the last |
621b0f8d |
421 | C<use encoding> or C<no encoding> matters, and it affects |
422 | B<the whole script>. However, the <no encoding> pragma is supported and |
423 | B<use encoding> can appear as many times as you want in a given script. |
424 | The multiple use of this pragma is discouraged. |
425 | |
0f29a567 |
426 | By the same reason, the use this pragma inside modules is also |
3c4b39be |
427 | discouraged (though not as strongly discouraged as the case above. |
0f29a567 |
428 | See below). |
05ef2f67 |
429 | |
430 | If you still have to write a module with this pragma, be very careful |
431 | of the load order. See the codes below; |
432 | |
433 | # called module |
434 | package Module_IN_BAR; |
435 | use encoding "bar"; |
436 | # stuff in "bar" encoding here |
437 | 1; |
438 | |
439 | # caller script |
440 | use encoding "foo" |
441 | use Module_IN_BAR; |
442 | # surprise! use encoding "bar" is in effect. |
443 | |
444 | The best way to avoid this oddity is to use this pragma RIGHT AFTER |
445 | other modules are loaded. i.e. |
446 | |
447 | use Module_IN_BAR; |
448 | use encoding "foo"; |
3ef515df |
449 | |
450 | =head2 DO NOT MIX MULTIPLE ENCODINGS |
451 | |
452 | Notice that only literals (string or regular expression) having only |
453 | legacy code points are affected: if you mix data like this |
454 | |
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455 | \xDF\x{100} |
3ef515df |
456 | |
457 | the data is assumed to be in (Latin 1 and) Unicode, not in your native |
458 | encoding. In other words, this will match in "greek": |
459 | |
d1256cb1 |
460 | "\xDF" =~ /\x{3af}/ |
3ef515df |
461 | |
462 | but this will not |
463 | |
d1256cb1 |
464 | "\xDF\x{100}" =~ /\x{3af}\x{100}/ |
3ef515df |
465 | |
962111ca |
466 | since the C<\xDF> (ISO 8859-7 GREEK SMALL LETTER IOTA WITH TONOS) on |
467 | the left will B<not> be upgraded to C<\x{3af}> (Unicode GREEK SMALL |
468 | LETTER IOTA WITH TONOS) because of the C<\x{100}> on the left. You |
469 | should not be mixing your legacy data and Unicode in the same string. |
3ef515df |
470 | |
471 | This pragma also affects encoding of the 0x80..0xFF code point range: |
472 | normally characters in that range are left as eight-bit bytes (unless |
473 | they are combined with characters with code points 0x100 or larger, |
474 | in which case all characters need to become UTF-8 encoded), but if |
475 | the C<encoding> pragma is present, even the 0x80..0xFF range always |
476 | gets UTF-8 encoded. |
477 | |
478 | After all, the best thing about this pragma is that you don't have to |
0ab8f81e |
479 | resort to \x{....} just to spell your name in a native encoding. |
480 | So feel free to put your strings in your encoding in quotes and |
481 | regexes. |
3ef515df |
482 | |
151b5d36 |
483 | =head2 tr/// with ranges |
4b291ae6 |
484 | |
485 | The B<encoding> pragma works by decoding string literals in |
151b5d36 |
486 | C<q//,qq//,qr//,qw///, qx//> and so forth. In perl 5.8.0, this |
4b291ae6 |
487 | does not apply to C<tr///>. Therefore, |
488 | |
489 | use encoding 'euc-jp'; |
490 | #.... |
491 | $kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/; |
492 | # -------- -------- -------- -------- |
493 | |
494 | Does not work as |
495 | |
496 | $kana =~ tr/\x{3041}-\x{3093}/\x{30a1}-\x{30f3}/; |
497 | |
498 | =over |
499 | |
500 | =item Legend of characters above |
501 | |
502 | utf8 euc-jp charnames::viacode() |
503 | ----------------------------------------- |
504 | \x{3041} \xA4\xA1 HIRAGANA LETTER SMALL A |
505 | \x{3093} \xA4\xF3 HIRAGANA LETTER N |
506 | \x{30a1} \xA5\xA1 KATAKANA LETTER SMALL A |
507 | \x{30f3} \xA5\xF3 KATAKANA LETTER N |
508 | |
509 | =back |
510 | |
05ef2f67 |
511 | This counterintuitive behavior has been fixed in perl 5.8.1. |
151b5d36 |
512 | |
4b291ae6 |
513 | =head3 workaround to tr///; |
514 | |
ce16148b |
515 | In perl 5.8.0, you can work around as follows; |
4b291ae6 |
516 | |
517 | use encoding 'euc-jp'; |
151b5d36 |
518 | # .... |
4b291ae6 |
519 | eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ }; |
520 | |
ce16148b |
521 | Note the C<tr//> expression is surrounded by C<qq{}>. The idea behind |
4b291ae6 |
522 | is the same as classic idiom that makes C<tr///> 'interpolate'. |
523 | |
524 | tr/$from/$to/; # wrong! |
525 | eval qq{ tr/$from/$to/ }; # workaround. |
526 | |
527 | Nevertheless, in case of B<encoding> pragma even C<q//> is affected so |
528 | C<tr///> not being decoded was obviously against the will of Perl5 |
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529 | Porters so it has been fixed in Perl 5.8.1 or later. |
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530 | |
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531 | =head1 EXAMPLE - Greekperl |
532 | |
533 | use encoding "iso 8859-7"; |
534 | |
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535 | # \xDF in ISO 8859-7 (Greek) is \x{3af} in Unicode. |
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536 | |
537 | $a = "\xDF"; |
538 | $b = "\x{100}"; |
539 | |
540 | printf "%#x\n", ord($a); # will print 0x3af, not 0xdf |
541 | |
542 | $c = $a . $b; |
543 | |
544 | # $c will be "\x{3af}\x{100}", not "\x{df}\x{100}". |
545 | |
546 | # chr() is affected, and ... |
547 | |
548 | print "mega\n" if ord(chr(0xdf)) == 0x3af; |
549 | |
550 | # ... ord() is affected by the encoding pragma ... |
551 | |
552 | print "tera\n" if ord(pack("C", 0xdf)) == 0x3af; |
553 | |
554 | # ... as are eq and cmp ... |
555 | |
556 | print "peta\n" if "\x{3af}" eq pack("C", 0xdf); |
557 | print "exa\n" if "\x{3af}" cmp pack("C", 0xdf) == 0; |
558 | |
559 | # ... but pack/unpack C are not affected, in case you still |
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560 | # want to go back to your native encoding |
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561 | |
562 | print "zetta\n" if unpack("C", (pack("C", 0xdf))) == 0xdf; |
563 | |
564 | =head1 KNOWN PROBLEMS |
565 | |
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566 | =over |
567 | |
0f29a567 |
568 | =item literals in regex that are longer than 127 bytes |
151b5d36 |
569 | |
0ab8f81e |
570 | For native multibyte encodings (either fixed or variable length), |
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571 | the current implementation of the regular expressions may introduce |
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572 | recoding errors for regular expression literals longer than 127 bytes. |
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573 | |
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574 | =item EBCDIC |
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575 | |
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576 | The encoding pragma is not supported on EBCDIC platforms. |
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577 | (Porters who are willing and able to remove this limitation are |
578 | welcome.) |
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579 | |
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580 | =item format |
581 | |
582 | This pragma doesn't work well with format because PerlIO does not |
583 | get along very well with it. When format contains non-ascii |
584 | characters it prints funny or gets "wide character warnings". |
585 | To understand it, try the code below. |
586 | |
587 | # Save this one in utf8 |
588 | # replace *non-ascii* with a non-ascii string |
589 | my $camel; |
590 | format STDOUT = |
591 | *non-ascii*@>>>>>>> |
592 | $camel |
593 | . |
594 | $camel = "*non-ascii*"; |
595 | binmode(STDOUT=>':encoding(utf8)'); # bang! |
596 | write; # funny |
597 | print $camel, "\n"; # fine |
598 | |
599 | Without binmode this happens to work but without binmode, print() |
600 | fails instead of write(). |
601 | |
602 | At any rate, the very use of format is questionable when it comes to |
603 | unicode characters since you have to consider such things as character |
604 | width (i.e. double-width for ideographs) and directions (i.e. BIDI for |
605 | Arabic and Hebrew). |
606 | |
151b5d36 |
607 | =back |
608 | |
b1aeb384 |
609 | =head2 The Logic of :locale |
610 | |
611 | The logic of C<:locale> is as follows: |
612 | |
613 | =over 4 |
614 | |
615 | =item 1. |
616 | |
617 | If the platform supports the langinfo(CODESET) interface, the codeset |
618 | returned is used as the default encoding for the open pragma. |
619 | |
620 | =item 2. |
621 | |
622 | If 1. didn't work but we are under the locale pragma, the environment |
623 | variables LC_ALL and LANG (in that order) are matched for encodings |
624 | (the part after C<.>, if any), and if any found, that is used |
625 | as the default encoding for the open pragma. |
626 | |
627 | =item 3. |
628 | |
629 | If 1. and 2. didn't work, the environment variables LC_ALL and LANG |
630 | (in that order) are matched for anything looking like UTF-8, and if |
631 | any found, C<:utf8> is used as the default encoding for the open |
632 | pragma. |
633 | |
634 | =back |
635 | |
636 | If your locale environment variables (LC_ALL, LC_CTYPE, LANG) |
637 | contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching), |
638 | the default encoding of your STDIN, STDOUT, and STDERR, and of |
639 | B<any subsequent file open>, is UTF-8. |
640 | |
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641 | =head1 HISTORY |
642 | |
643 | This pragma first appeared in Perl 5.8.0. For features that require |
644 | 5.8.1 and better, see above. |
645 | |
b1aeb384 |
646 | The C<:locale> subpragma was implemented in 2.01, or Perl 5.8.6. |
647 | |
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648 | =head1 SEE ALSO |
649 | |
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650 | L<perlunicode>, L<Encode>, L<open>, L<Filter::Util::Call>, |
651 | |
652 | Ch. 15 of C<Programming Perl (3rd Edition)> |
653 | by Larry Wall, Tom Christiansen, Jon Orwant; |
654 | O'Reilly & Associates; ISBN 0-596-00027-8 |
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655 | |
656 | =cut |