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1 | package Encode::Guess; |
2 | use strict; |
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3 | |
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4 | use Encode qw(:fallbacks find_encoding); |
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5 | our $VERSION = do { my @r = (q$Revision: 1.8 $ =~ /\d+/g); sprintf "%d."."%02d" x $#r, @r }; |
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6 | |
7 | my $Canon = 'Guess'; |
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8 | our $DEBUG = 0; |
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9 | our %DEF_SUSPECTS = map { $_ => find_encoding($_) } qw(ascii utf8); |
10 | $Encode::Encoding{$Canon} = |
11 | bless { |
12 | Name => $Canon, |
13 | Suspects => { %DEF_SUSPECTS }, |
14 | } => __PACKAGE__; |
15 | |
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16 | use base qw(Encode::Encoding); |
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17 | sub needs_lines { 1 } |
18 | sub perlio_ok { 0 } |
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19 | |
20 | our @EXPORT = qw(guess_encoding); |
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21 | our $NoUTFAutoGuess = 0; |
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22 | |
23 | sub import { # Exporter not used so we do it on our own |
24 | my $callpkg = caller; |
25 | for my $item (@EXPORT){ |
26 | no strict 'refs'; |
27 | *{"$callpkg\::$item"} = \&{"$item"}; |
28 | } |
29 | set_suspects(@_); |
30 | } |
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31 | |
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32 | sub set_suspects{ |
33 | my $class = shift; |
34 | my $self = ref($class) ? $class : $Encode::Encoding{$Canon}; |
35 | $self->{Suspects} = { %DEF_SUSPECTS }; |
36 | $self->add_suspects(@_); |
37 | } |
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38 | |
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39 | sub add_suspects{ |
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40 | my $class = shift; |
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41 | my $self = ref($class) ? $class : $Encode::Encoding{$Canon}; |
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42 | for my $c (@_){ |
43 | my $e = find_encoding($c) or die "Unknown encoding: $c"; |
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44 | $self->{Suspects}{$e->name} = $e; |
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45 | $DEBUG and warn "Added: ", $e->name; |
46 | } |
47 | } |
48 | |
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49 | sub decode($$;$){ |
50 | my ($obj, $octet, $chk) = @_; |
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51 | my $guessed = guess($obj, $octet); |
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52 | unless (ref($guessed)){ |
53 | require Carp; |
54 | Carp::croak($guessed); |
55 | } |
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56 | my $utf8 = $guessed->decode($octet, $chk); |
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57 | $_[1] = $octet if $chk; |
58 | return $utf8; |
59 | } |
60 | |
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61 | sub guess_encoding{ |
62 | guess($Encode::Encoding{$Canon}, @_); |
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63 | } |
64 | |
65 | sub guess { |
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66 | my $class = shift; |
67 | my $obj = ref($class) ? $class : $Encode::Encoding{$Canon}; |
68 | my $octet = shift; |
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69 | |
70 | # sanity check |
71 | return unless defined $octet and length $octet; |
72 | |
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73 | # cheat 0: utf8 flag; |
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74 | if ( Encode::is_utf8($octet) ) { |
75 | return find_encoding('utf8') unless $NoUTFAutoGuess; |
76 | Encode::_utf8_off($octet); |
77 | } |
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78 | # cheat 1: BOM |
79 | use Encode::Unicode; |
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80 | unless ($NoUTFAutoGuess) { |
81 | my $BOM = unpack('n', $octet); |
82 | return find_encoding('UTF-16') |
83 | if (defined $BOM and ($BOM == 0xFeFF or $BOM == 0xFFFe)); |
84 | $BOM = unpack('N', $octet); |
85 | return find_encoding('UTF-32') |
86 | if (defined $BOM and ($BOM == 0xFeFF or $BOM == 0xFFFe0000)); |
87 | if ($octet =~ /\x00/o){ # if \x00 found, we assume UTF-(16|32)(BE|LE) |
88 | my $utf; |
89 | my ($be, $le) = (0, 0); |
90 | if ($octet =~ /\x00\x00/o){ # UTF-32(BE|LE) assumed |
91 | $utf = "UTF-32"; |
92 | for my $char (unpack('N*', $octet)){ |
93 | $char & 0x0000ffff and $be++; |
94 | $char & 0xffff0000 and $le++; |
95 | } |
96 | }else{ # UTF-16(BE|LE) assumed |
97 | $utf = "UTF-16"; |
98 | for my $char (unpack('n*', $octet)){ |
99 | $char & 0x00ff and $be++; |
100 | $char & 0xff00 and $le++; |
101 | } |
102 | } |
103 | $DEBUG and warn "$utf, be == $be, le == $le"; |
104 | $be == $le |
105 | and return |
106 | "Encodings ambiguous between $utf BE and LE ($be, $le)"; |
107 | $utf .= ($be > $le) ? 'BE' : 'LE'; |
108 | return find_encoding($utf); |
109 | } |
110 | } |
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111 | my %try = %{$obj->{Suspects}}; |
112 | for my $c (@_){ |
113 | my $e = find_encoding($c) or die "Unknown encoding: $c"; |
114 | $try{$e->name} = $e; |
115 | $DEBUG and warn "Added: ", $e->name; |
116 | } |
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117 | my $nline = 1; |
118 | for my $line (split /\r\n?|\n/, $octet){ |
119 | # cheat 2 -- \e in the string |
120 | if ($line =~ /\e/o){ |
121 | my @keys = keys %try; |
122 | delete @try{qw/utf8 ascii/}; |
123 | for my $k (@keys){ |
124 | ref($try{$k}) eq 'Encode::XS' and delete $try{$k}; |
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125 | } |
126 | } |
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127 | my %ok = %try; |
128 | # warn join(",", keys %try); |
129 | for my $k (keys %try){ |
130 | my $scratch = $line; |
131 | $try{$k}->decode($scratch, FB_QUIET); |
132 | if ($scratch eq ''){ |
133 | $DEBUG and warn sprintf("%4d:%-24s ok\n", $nline, $k); |
134 | }else{ |
135 | use bytes (); |
136 | $DEBUG and |
137 | warn sprintf("%4d:%-24s not ok; %d bytes left\n", |
138 | $nline, $k, bytes::length($scratch)); |
139 | delete $ok{$k}; |
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140 | } |
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141 | } |
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142 | %ok or return "No appropriate encodings found!"; |
143 | if (scalar(keys(%ok)) == 1){ |
144 | my ($retval) = values(%ok); |
145 | return $retval; |
146 | } |
147 | %try = %ok; $nline++; |
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148 | } |
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149 | $try{ascii} or |
150 | return "Encodings too ambiguous: ", join(" or ", keys %try); |
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151 | return $try{ascii}; |
152 | } |
153 | |
154 | |
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155 | |
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156 | 1; |
157 | __END__ |
158 | |
159 | =head1 NAME |
160 | |
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161 | Encode::Guess -- Guesses encoding from data |
162 | |
163 | =head1 SYNOPSIS |
164 | |
165 | # if you are sure $data won't contain anything bogus |
166 | |
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167 | use Encode; |
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168 | use Encode::Guess qw/euc-jp shiftjis 7bit-jis/; |
169 | my $utf8 = decode("Guess", $data); |
170 | my $data = encode("Guess", $utf8); # this doesn't work! |
171 | |
172 | # more elaborate way |
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173 | use Encode::Guess; |
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174 | my $enc = guess_encoding($data, qw/euc-jp shiftjis 7bit-jis/); |
175 | ref($enc) or die "Can't guess: $enc"; # trap error this way |
176 | $utf8 = $enc->decode($data); |
177 | # or |
178 | $utf8 = decode($enc->name, $data) |
179 | |
180 | =head1 ABSTRACT |
181 | |
182 | Encode::Guess enables you to guess in what encoding a given data is |
183 | encoded, or at least tries to. |
184 | |
185 | =head1 DESCRIPTION |
186 | |
187 | By default, it checks only ascii, utf8 and UTF-16/32 with BOM. |
188 | |
189 | use Encode::Guess; # ascii/utf8/BOMed UTF |
190 | |
191 | To use it more practically, you have to give the names of encodings to |
192 | check (I<suspects> as follows). The name of suspects can either be |
193 | canonical names or aliases. |
194 | |
195 | # tries all major Japanese Encodings as well |
196 | use Encode::Guess qw/euc-jp shiftjis 7bit-jis/; |
197 | |
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198 | If the C<$Encode::Guess::NoUTFAutoGuess> variable is set to a true |
199 | value, no heuristics will be applied to UTF8/16/32, and the result |
200 | will be limited to the suspects and C<ascii>. |
201 | |
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202 | =over 4 |
203 | |
204 | =item Encode::Guess->set_suspects |
205 | |
206 | You can also change the internal suspects list via C<set_suspects> |
207 | method. |
208 | |
209 | use Encode::Guess; |
210 | Encode::Guess->set_suspects(qw/euc-jp shiftjis 7bit-jis/); |
211 | |
212 | =item Encode::Guess->add_suspects |
213 | |
214 | Or you can use C<add_suspects> method. The difference is that |
215 | C<set_suspects> flushes the current suspects list while |
216 | C<add_suspects> adds. |
217 | |
218 | use Encode::Guess; |
219 | Encode::Guess->add_suspects(qw/euc-jp shiftjis 7bit-jis/); |
220 | # now the suspects are euc-jp,shiftjis,7bit-jis, AND |
221 | # euc-kr,euc-cn, and big5-eten |
222 | Encode::Guess->add_suspects(qw/euc-kr euc-cn big5-eten/); |
223 | |
224 | =item Encode::decode("Guess" ...) |
225 | |
226 | When you are content with suspects list, you can now |
227 | |
228 | my $utf8 = Encode::decode("Guess", $data); |
229 | |
230 | =item Encode::Guess->guess($data) |
231 | |
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232 | But it will croak if: |
233 | |
234 | =over |
235 | |
236 | =item * |
237 | |
238 | Two or more suspects remain |
239 | |
240 | =item * |
241 | |
242 | No suspects left |
243 | |
244 | =back |
245 | |
246 | So you should instead try this; |
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247 | |
248 | my $decoder = Encode::Guess->guess($data); |
249 | |
250 | On success, $decoder is an object that is documented in |
251 | L<Encode::Encoding>. So you can now do this; |
252 | |
253 | my $utf8 = $decoder->decode($data); |
254 | |
255 | On failure, $decoder now contains an error message so the whole thing |
256 | would be as follows; |
257 | |
258 | my $decoder = Encode::Guess->guess($data); |
259 | die $decoder unless ref($decoder); |
260 | my $utf8 = $decoder->decode($data); |
261 | |
262 | =item guess_encoding($data, [, I<list of suspects>]) |
263 | |
264 | You can also try C<guess_encoding> function which is exported by |
265 | default. It takes $data to check and it also takes the list of |
266 | suspects by option. The optional suspect list is I<not reflected> to |
267 | the internal suspects list. |
268 | |
269 | my $decoder = guess_encoding($data, qw/euc-jp euc-kr euc-cn/); |
270 | die $decoder unless ref($decoder); |
271 | my $utf8 = $decoder->decode($data); |
272 | # check only ascii and utf8 |
273 | my $decoder = guess_encoding($data); |
274 | |
275 | =back |
276 | |
277 | =head1 CAVEATS |
278 | |
279 | =over 4 |
280 | |
281 | =item * |
282 | |
283 | Because of the algorithm used, ISO-8859 series and other single-byte |
284 | encodings do not work well unless either one of ISO-8859 is the only |
285 | one suspect (besides ascii and utf8). |
286 | |
287 | use Encode::Guess; |
288 | # perhaps ok |
289 | my $decoder = guess_encoding($data, 'latin1'); |
290 | # definitely NOT ok |
291 | my $decoder = guess_encoding($data, qw/latin1 greek/); |
292 | |
293 | The reason is that Encode::Guess guesses encoding by trial and error. |
294 | It first splits $data into lines and tries to decode the line for each |
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295 | suspect. It keeps it going until all but one encoding is eliminated |
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296 | out of suspects list. ISO-8859 series is just too successful for most |
297 | cases (because it fills almost all code points in \x00-\xff). |
298 | |
299 | =item * |
300 | |
301 | Do not mix national standard encodings and the corresponding vendor |
302 | encodings. |
303 | |
304 | # a very bad idea |
305 | my $decoder |
306 | = guess_encoding($data, qw/shiftjis MacJapanese cp932/); |
307 | |
308 | The reason is that vendor encoding is usually a superset of national |
309 | standard so it becomes too ambiguous for most cases. |
310 | |
311 | =item * |
312 | |
313 | On the other hand, mixing various national standard encodings |
314 | automagically works unless $data is too short to allow for guessing. |
315 | |
316 | # This is ok if $data is long enough |
317 | my $decoder = |
318 | guess_encoding($data, qw/euc-cn |
319 | euc-jp shiftjis 7bit-jis |
320 | euc-kr |
321 | big5-eten/); |
322 | |
323 | =item * |
324 | |
325 | DO NOT PUT TOO MANY SUSPECTS! Don't you try something like this! |
326 | |
327 | my $decoder = guess_encoding($data, |
328 | Encode->encodings(":all")); |
329 | |
330 | =back |
331 | |
332 | It is, after all, just a guess. You should alway be explicit when it |
333 | comes to encodings. But there are some, especially Japanese, |
334 | environment that guess-coding is a must. Use this module with care. |
335 | |
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336 | =head1 TO DO |
337 | |
338 | Encode::Guess does not work on EBCDIC platforms. |
339 | |
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340 | =head1 SEE ALSO |
341 | |
342 | L<Encode>, L<Encode::Encoding> |
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343 | |
344 | =cut |
345 | |