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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: 2.0 $ =~ /\d+/g); sprintf "%d."."%02d" x $#r, @r }; |
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6 | |
7 | my $Canon = 'Guess'; |
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8 | sub 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 | our $UTF8_BOM = pack("C3", 0xef, 0xbb, 0xbf); |
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23 | |
24 | sub import { # Exporter not used so we do it on our own |
25 | my $callpkg = caller; |
26 | for my $item (@EXPORT){ |
27 | no strict 'refs'; |
28 | *{"$callpkg\::$item"} = \&{"$item"}; |
29 | } |
30 | set_suspects(@_); |
31 | } |
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32 | |
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33 | sub set_suspects{ |
34 | my $class = shift; |
35 | my $self = ref($class) ? $class : $Encode::Encoding{$Canon}; |
36 | $self->{Suspects} = { %DEF_SUSPECTS }; |
37 | $self->add_suspects(@_); |
38 | } |
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39 | |
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40 | sub add_suspects{ |
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41 | my $class = shift; |
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42 | my $self = ref($class) ? $class : $Encode::Encoding{$Canon}; |
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43 | for my $c (@_){ |
44 | my $e = find_encoding($c) or die "Unknown encoding: $c"; |
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45 | $self->{Suspects}{$e->name} = $e; |
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46 | DEBUG and warn "Added: ", $e->name; |
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47 | } |
48 | } |
49 | |
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50 | sub decode($$;$){ |
51 | my ($obj, $octet, $chk) = @_; |
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52 | my $guessed = guess($obj, $octet); |
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53 | unless (ref($guessed)){ |
54 | require Carp; |
55 | Carp::croak($guessed); |
56 | } |
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57 | my $utf8 = $guessed->decode($octet, $chk); |
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58 | $_[1] = $octet if $chk; |
59 | return $utf8; |
60 | } |
61 | |
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62 | sub guess_encoding{ |
63 | guess($Encode::Encoding{$Canon}, @_); |
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64 | } |
65 | |
66 | sub guess { |
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67 | my $class = shift; |
68 | my $obj = ref($class) ? $class : $Encode::Encoding{$Canon}; |
69 | my $octet = shift; |
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70 | |
71 | # sanity check |
72 | return unless defined $octet and length $octet; |
73 | |
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74 | # cheat 0: utf8 flag; |
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75 | if ( Encode::is_utf8($octet) ) { |
76 | return find_encoding('utf8') unless $NoUTFAutoGuess; |
77 | Encode::_utf8_off($octet); |
78 | } |
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79 | # cheat 1: BOM |
80 | use Encode::Unicode; |
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81 | unless ($NoUTFAutoGuess) { |
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82 | my $BOM = pack('C3', unpack("C3", $octet)); |
83 | return find_encoding('utf8') |
84 | if (defined $BOM and $BOM eq $UTF8_BOM); |
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85 | $BOM = unpack('N', $octet); |
86 | return find_encoding('UTF-32') |
87 | if (defined $BOM and ($BOM == 0xFeFF or $BOM == 0xFFFe0000)); |
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88 | $BOM = unpack('n', $octet); |
89 | return find_encoding('UTF-16') |
90 | if (defined $BOM and ($BOM == 0xFeFF or $BOM == 0xFFFe)); |
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91 | if ($octet =~ /\x00/o){ # if \x00 found, we assume UTF-(16|32)(BE|LE) |
92 | my $utf; |
93 | my ($be, $le) = (0, 0); |
94 | if ($octet =~ /\x00\x00/o){ # UTF-32(BE|LE) assumed |
95 | $utf = "UTF-32"; |
96 | for my $char (unpack('N*', $octet)){ |
97 | $char & 0x0000ffff and $be++; |
98 | $char & 0xffff0000 and $le++; |
99 | } |
100 | }else{ # UTF-16(BE|LE) assumed |
101 | $utf = "UTF-16"; |
102 | for my $char (unpack('n*', $octet)){ |
103 | $char & 0x00ff and $be++; |
104 | $char & 0xff00 and $le++; |
105 | } |
106 | } |
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107 | DEBUG and warn "$utf, be == $be, le == $le"; |
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108 | $be == $le |
109 | and return |
110 | "Encodings ambiguous between $utf BE and LE ($be, $le)"; |
111 | $utf .= ($be > $le) ? 'BE' : 'LE'; |
112 | return find_encoding($utf); |
113 | } |
114 | } |
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115 | my %try = %{$obj->{Suspects}}; |
116 | for my $c (@_){ |
117 | my $e = find_encoding($c) or die "Unknown encoding: $c"; |
118 | $try{$e->name} = $e; |
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119 | DEBUG and warn "Added: ", $e->name; |
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120 | } |
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121 | my $nline = 1; |
122 | for my $line (split /\r\n?|\n/, $octet){ |
123 | # cheat 2 -- \e in the string |
124 | if ($line =~ /\e/o){ |
125 | my @keys = keys %try; |
126 | delete @try{qw/utf8 ascii/}; |
127 | for my $k (@keys){ |
128 | ref($try{$k}) eq 'Encode::XS' and delete $try{$k}; |
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129 | } |
130 | } |
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131 | my %ok = %try; |
132 | # warn join(",", keys %try); |
133 | for my $k (keys %try){ |
134 | my $scratch = $line; |
135 | $try{$k}->decode($scratch, FB_QUIET); |
136 | if ($scratch eq ''){ |
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137 | DEBUG and warn sprintf("%4d:%-24s ok\n", $nline, $k); |
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138 | }else{ |
139 | use bytes (); |
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140 | DEBUG and |
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141 | warn sprintf("%4d:%-24s not ok; %d bytes left\n", |
142 | $nline, $k, bytes::length($scratch)); |
143 | delete $ok{$k}; |
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144 | } |
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145 | } |
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146 | %ok or return "No appropriate encodings found!"; |
147 | if (scalar(keys(%ok)) == 1){ |
148 | my ($retval) = values(%ok); |
149 | return $retval; |
150 | } |
151 | %try = %ok; $nline++; |
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152 | } |
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153 | $try{ascii} or |
154 | return "Encodings too ambiguous: ", join(" or ", keys %try); |
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155 | return $try{ascii}; |
156 | } |
157 | |
158 | |
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159 | |
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160 | 1; |
161 | __END__ |
162 | |
163 | =head1 NAME |
164 | |
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165 | Encode::Guess -- Guesses encoding from data |
166 | |
167 | =head1 SYNOPSIS |
168 | |
169 | # if you are sure $data won't contain anything bogus |
170 | |
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171 | use Encode; |
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172 | use Encode::Guess qw/euc-jp shiftjis 7bit-jis/; |
173 | my $utf8 = decode("Guess", $data); |
174 | my $data = encode("Guess", $utf8); # this doesn't work! |
175 | |
176 | # more elaborate way |
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177 | use Encode::Guess; |
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178 | my $enc = guess_encoding($data, qw/euc-jp shiftjis 7bit-jis/); |
179 | ref($enc) or die "Can't guess: $enc"; # trap error this way |
180 | $utf8 = $enc->decode($data); |
181 | # or |
182 | $utf8 = decode($enc->name, $data) |
183 | |
184 | =head1 ABSTRACT |
185 | |
186 | Encode::Guess enables you to guess in what encoding a given data is |
187 | encoded, or at least tries to. |
188 | |
189 | =head1 DESCRIPTION |
190 | |
191 | By default, it checks only ascii, utf8 and UTF-16/32 with BOM. |
192 | |
193 | use Encode::Guess; # ascii/utf8/BOMed UTF |
194 | |
195 | To use it more practically, you have to give the names of encodings to |
196 | check (I<suspects> as follows). The name of suspects can either be |
197 | canonical names or aliases. |
198 | |
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199 | CAVEAT: Unlike UTF-(16|32), BOM in utf8 is NOT AUTOMATICALLY STRIPPED. |
200 | |
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201 | # tries all major Japanese Encodings as well |
202 | use Encode::Guess qw/euc-jp shiftjis 7bit-jis/; |
203 | |
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204 | If the C<$Encode::Guess::NoUTFAutoGuess> variable is set to a true |
205 | value, no heuristics will be applied to UTF8/16/32, and the result |
206 | will be limited to the suspects and C<ascii>. |
207 | |
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208 | =over 4 |
209 | |
210 | =item Encode::Guess->set_suspects |
211 | |
212 | You can also change the internal suspects list via C<set_suspects> |
213 | method. |
214 | |
215 | use Encode::Guess; |
216 | Encode::Guess->set_suspects(qw/euc-jp shiftjis 7bit-jis/); |
217 | |
218 | =item Encode::Guess->add_suspects |
219 | |
220 | Or you can use C<add_suspects> method. The difference is that |
221 | C<set_suspects> flushes the current suspects list while |
222 | C<add_suspects> adds. |
223 | |
224 | use Encode::Guess; |
225 | Encode::Guess->add_suspects(qw/euc-jp shiftjis 7bit-jis/); |
226 | # now the suspects are euc-jp,shiftjis,7bit-jis, AND |
227 | # euc-kr,euc-cn, and big5-eten |
228 | Encode::Guess->add_suspects(qw/euc-kr euc-cn big5-eten/); |
229 | |
230 | =item Encode::decode("Guess" ...) |
231 | |
232 | When you are content with suspects list, you can now |
233 | |
234 | my $utf8 = Encode::decode("Guess", $data); |
235 | |
236 | =item Encode::Guess->guess($data) |
237 | |
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238 | But it will croak if: |
239 | |
240 | =over |
241 | |
242 | =item * |
243 | |
244 | Two or more suspects remain |
245 | |
246 | =item * |
247 | |
248 | No suspects left |
249 | |
250 | =back |
251 | |
252 | So you should instead try this; |
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253 | |
254 | my $decoder = Encode::Guess->guess($data); |
255 | |
256 | On success, $decoder is an object that is documented in |
257 | L<Encode::Encoding>. So you can now do this; |
258 | |
259 | my $utf8 = $decoder->decode($data); |
260 | |
261 | On failure, $decoder now contains an error message so the whole thing |
262 | would be as follows; |
263 | |
264 | my $decoder = Encode::Guess->guess($data); |
265 | die $decoder unless ref($decoder); |
266 | my $utf8 = $decoder->decode($data); |
267 | |
268 | =item guess_encoding($data, [, I<list of suspects>]) |
269 | |
270 | You can also try C<guess_encoding> function which is exported by |
271 | default. It takes $data to check and it also takes the list of |
272 | suspects by option. The optional suspect list is I<not reflected> to |
273 | the internal suspects list. |
274 | |
275 | my $decoder = guess_encoding($data, qw/euc-jp euc-kr euc-cn/); |
276 | die $decoder unless ref($decoder); |
277 | my $utf8 = $decoder->decode($data); |
278 | # check only ascii and utf8 |
279 | my $decoder = guess_encoding($data); |
280 | |
281 | =back |
282 | |
283 | =head1 CAVEATS |
284 | |
285 | =over 4 |
286 | |
287 | =item * |
288 | |
289 | Because of the algorithm used, ISO-8859 series and other single-byte |
290 | encodings do not work well unless either one of ISO-8859 is the only |
291 | one suspect (besides ascii and utf8). |
292 | |
293 | use Encode::Guess; |
294 | # perhaps ok |
295 | my $decoder = guess_encoding($data, 'latin1'); |
296 | # definitely NOT ok |
297 | my $decoder = guess_encoding($data, qw/latin1 greek/); |
298 | |
299 | The reason is that Encode::Guess guesses encoding by trial and error. |
300 | It first splits $data into lines and tries to decode the line for each |
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301 | suspect. It keeps it going until all but one encoding is eliminated |
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302 | out of suspects list. ISO-8859 series is just too successful for most |
303 | cases (because it fills almost all code points in \x00-\xff). |
304 | |
305 | =item * |
306 | |
307 | Do not mix national standard encodings and the corresponding vendor |
308 | encodings. |
309 | |
310 | # a very bad idea |
311 | my $decoder |
312 | = guess_encoding($data, qw/shiftjis MacJapanese cp932/); |
313 | |
314 | The reason is that vendor encoding is usually a superset of national |
315 | standard so it becomes too ambiguous for most cases. |
316 | |
317 | =item * |
318 | |
319 | On the other hand, mixing various national standard encodings |
320 | automagically works unless $data is too short to allow for guessing. |
321 | |
322 | # This is ok if $data is long enough |
323 | my $decoder = |
324 | guess_encoding($data, qw/euc-cn |
325 | euc-jp shiftjis 7bit-jis |
326 | euc-kr |
327 | big5-eten/); |
328 | |
329 | =item * |
330 | |
331 | DO NOT PUT TOO MANY SUSPECTS! Don't you try something like this! |
332 | |
333 | my $decoder = guess_encoding($data, |
334 | Encode->encodings(":all")); |
335 | |
336 | =back |
337 | |
338 | It is, after all, just a guess. You should alway be explicit when it |
339 | comes to encodings. But there are some, especially Japanese, |
340 | environment that guess-coding is a must. Use this module with care. |
341 | |
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342 | =head1 TO DO |
343 | |
344 | Encode::Guess does not work on EBCDIC platforms. |
345 | |
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346 | =head1 SEE ALSO |
347 | |
348 | L<Encode>, L<Encode::Encoding> |
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349 | |
350 | =cut |
351 | |