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[perl5.git] / ext / Encode / Encode.pm
CommitLineData
10c5ecbb 1#
656ebd29 2# $Id: Encode.pm,v 2.18 2006/06/03 20:28:48 dankogai Exp dankogai $
10c5ecbb 3#
2c674647 4package Encode;
51ef4e11 5use strict;
656ebd29 6use warnings;
4438fa18 7our $VERSION = "2.18_01";
8f139f4c 8sub DEBUG () { 0 }
6d1c0808 9use XSLoader ();
d1256cb1 10XSLoader::load( __PACKAGE__, $VERSION );
2c674647 11
2c674647 12require Exporter;
7e19fb92 13use base qw/Exporter/;
2c674647 14
4411f3b6 15# Public, encouraged API is exported by default
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16
17our @EXPORT = qw(
0a8c69ed 18 decode decode_utf8 encode encode_utf8 str2bytes bytes2str
a0d8a30e 19 encodings find_encoding clone_encoding
4411f3b6 20);
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21our @FB_FLAGS = qw(
22 DIE_ON_ERR WARN_ON_ERR RETURN_ON_ERR LEAVE_SRC
23 PERLQQ HTMLCREF XMLCREF STOP_AT_PARTIAL
24);
25our @FB_CONSTS = qw(
26 FB_DEFAULT FB_CROAK FB_QUIET FB_WARN
27 FB_PERLQQ FB_HTMLCREF FB_XMLCREF
28);
29our @EXPORT_OK = (
30 qw(
31 _utf8_off _utf8_on define_encoding from_to is_16bit is_8bit
32 is_utf8 perlio_ok resolve_alias utf8_downgrade utf8_upgrade
85982a32 33 ),
d1256cb1
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34 @FB_FLAGS, @FB_CONSTS,
35);
85982a32 36
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37our %EXPORT_TAGS = (
38 all => [ @EXPORT, @EXPORT_OK ],
39 fallbacks => [@FB_CONSTS],
40 fallback_all => [ @FB_CONSTS, @FB_FLAGS ],
41);
85982a32 42
4411f3b6 43# Documentation moved after __END__ for speed - NI-S
2c674647 44
d1256cb1 45our $ON_EBCDIC = ( ord("A") == 193 );
f2a2953c 46
5d030b67
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47use Encode::Alias;
48
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49# Make a %Encoding package variable to allow a certain amount of cheating
50our %Encoding;
aae85ceb
DK
51our %ExtModule;
52require Encode::Config;
53eval { require Encode::ConfigLocal };
5129552c 54
d1256cb1 55sub encodings {
5129552c 56 my $class = shift;
fc17bd48 57 my %enc;
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58 if ( @_ and $_[0] eq ":all" ) {
59 %enc = ( %Encoding, %ExtModule );
5129552c 60 }
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61 else {
62 %enc = %Encoding;
63 for my $mod ( map { m/::/o ? $_ : "Encode::$_" } @_ ) {
64 DEBUG and warn $mod;
65 for my $enc ( keys %ExtModule ) {
66 $ExtModule{$enc} eq $mod and $enc{$enc} = $mod;
67 }
68 }
69 }
70 return sort { lc $a cmp lc $b }
71 grep { !/^(?:Internal|Unicode|Guess)$/o } keys %enc;
51ef4e11
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72}
73
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74sub perlio_ok {
75 my $obj = ref( $_[0] ) ? $_[0] : find_encoding( $_[0] );
011b2d2f 76 $obj->can("perlio_ok") and return $obj->perlio_ok();
d1256cb1 77 return 0; # safety net
85982a32
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78}
79
d1256cb1 80sub define_encoding {
18586f54
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81 my $obj = shift;
82 my $name = shift;
5129552c 83 $Encoding{$name} = $obj;
18586f54 84 my $lc = lc($name);
d1256cb1
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85 define_alias( $lc => $obj ) unless $lc eq $name;
86 while (@_) {
87 my $alias = shift;
88 define_alias( $alias, $obj );
18586f54
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89 }
90 return $obj;
656753f8
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91}
92
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93sub getEncoding {
94 my ( $class, $name, $skip_external ) = @_;
10c5ecbb 95
a0d8a30e 96 ref($name) && $name->can('renew') and return $name;
10c5ecbb 97 exists $Encoding{$name} and return $Encoding{$name};
18586f54 98 my $lc = lc $name;
10c5ecbb 99 exists $Encoding{$lc} and return $Encoding{$lc};
c50d192e 100
5129552c 101 my $oc = $class->find_alias($name);
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102 defined($oc) and return $oc;
103 $lc ne $name and $oc = $class->find_alias($lc);
104 defined($oc) and return $oc;
c50d192e 105
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106 unless ($skip_external) {
107 if ( my $mod = $ExtModule{$name} || $ExtModule{$lc} ) {
108 $mod =~ s,::,/,g;
109 $mod .= '.pm';
110 eval { require $mod; };
111 exists $Encoding{$name} and return $Encoding{$name};
112 }
d1ed7747 113 }
18586f54 114 return;
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115}
116
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117sub find_encoding($;$) {
118 my ( $name, $skip_external ) = @_;
119 return __PACKAGE__->getEncoding( $name, $skip_external );
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120}
121
d1256cb1 122sub resolve_alias($) {
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123 my $obj = find_encoding(shift);
124 defined $obj and return $obj->name;
125 return;
126}
127
d1256cb1 128sub clone_encoding($) {
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129 my $obj = find_encoding(shift);
130 ref $obj or return;
131 eval { require Storable };
132 $@ and return;
133 return Storable::dclone($obj);
134}
135
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136sub encode($$;$) {
137 my ( $name, $string, $check ) = @_;
0f7c507f 138 return undef unless defined $string;
d1256cb1
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139 $string .= '' if ref $string; # stringify;
140 $check ||= 0;
18586f54 141 my $enc = find_encoding($name);
d1256cb1
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142 unless ( defined $enc ) {
143 require Carp;
144 Carp::croak("Unknown encoding '$name'");
10c5ecbb 145 }
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146 my $octets = $enc->encode( $string, $check );
147 $_[1] = $string if $check and !( $check & LEAVE_SRC() );
18586f54 148 return $octets;
4411f3b6 149}
0a8c69ed 150*str2bytes = \&encode;
4411f3b6 151
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152sub decode($$;$) {
153 my ( $name, $octets, $check ) = @_;
0f7c507f 154 return undef unless defined $octets;
78589665 155 $octets .= '' if ref $octets;
d1256cb1 156 $check ||= 0;
18586f54 157 my $enc = find_encoding($name);
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158 unless ( defined $enc ) {
159 require Carp;
160 Carp::croak("Unknown encoding '$name'");
10c5ecbb 161 }
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162 my $string = $enc->decode( $octets, $check );
163 $_[1] = $octets if $check and !( $check & LEAVE_SRC() );
18586f54 164 return $string;
4411f3b6 165}
0a8c69ed 166*bytes2str = \&decode;
4411f3b6 167
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168sub from_to($$$;$) {
169 my ( $string, $from, $to, $check ) = @_;
0f7c507f 170 return undef unless defined $string;
d1256cb1 171 $check ||= 0;
18586f54 172 my $f = find_encoding($from);
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173 unless ( defined $f ) {
174 require Carp;
175 Carp::croak("Unknown encoding '$from'");
10c5ecbb 176 }
18586f54 177 my $t = find_encoding($to);
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178 unless ( defined $t ) {
179 require Carp;
180 Carp::croak("Unknown encoding '$to'");
10c5ecbb 181 }
41c240f5 182 my $uni = $f->decode($string);
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183 $_[0] = $string = $t->encode( $uni, $check );
184 return undef if ( $check && length($uni) );
185 return defined( $_[0] ) ? length($string) : undef;
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186}
187
d1256cb1 188sub encode_utf8($) {
18586f54 189 my ($str) = @_;
c731e18e 190 utf8::encode($str);
18586f54 191 return $str;
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192}
193
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194sub decode_utf8($;$) {
195 my ( $str, $check ) = @_;
41c240f5 196 return $str if is_utf8($str);
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197 if ($check) {
198 return decode( "utf8", $str, $check );
199 }
200 else {
201 return decode( "utf8", $str );
202 return $str;
c2cbba7d 203 }
5ad8ef52
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204}
205
b536bf57 206predefine_encodings(1);
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207
208#
209# This is to restore %Encoding if really needed;
210#
10c5ecbb 211
d1256cb1 212sub predefine_encodings {
10c5ecbb 213 use Encode::Encoding;
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214 no warnings 'redefine';
215 my $use_xs = shift;
6d1c0808 216 if ($ON_EBCDIC) {
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217
218 # was in Encode::UTF_EBCDIC
219 package Encode::UTF_EBCDIC;
220 push @Encode::UTF_EBCDIC::ISA, 'Encode::Encoding';
221 *decode = sub {
222 my ( $obj, $str, $chk ) = @_;
223 my $res = '';
224 for ( my $i = 0 ; $i < length($str) ; $i++ ) {
225 $res .=
226 chr(
227 utf8::unicode_to_native( ord( substr( $str, $i, 1 ) ) )
228 );
229 }
230 $_[1] = '' if $chk;
231 return $res;
232 };
233 *encode = sub {
234 my ( $obj, $str, $chk ) = @_;
235 my $res = '';
236 for ( my $i = 0 ; $i < length($str) ; $i++ ) {
237 $res .=
238 chr(
239 utf8::native_to_unicode( ord( substr( $str, $i, 1 ) ) )
240 );
241 }
242 $_[1] = '' if $chk;
243 return $res;
244 };
245 $Encode::Encoding{Unicode} =
246 bless { Name => "UTF_EBCDIC" } => "Encode::UTF_EBCDIC";
247 }
248 else {
249
250 package Encode::Internal;
251 push @Encode::Internal::ISA, 'Encode::Encoding';
252 *decode = sub {
253 my ( $obj, $str, $chk ) = @_;
254 utf8::upgrade($str);
255 $_[1] = '' if $chk;
256 return $str;
257 };
258 *encode = \&decode;
259 $Encode::Encoding{Unicode} =
260 bless { Name => "Internal" } => "Encode::Internal";
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261 }
262
263 {
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264
265 # was in Encode::utf8
266 package Encode::utf8;
267 push @Encode::utf8::ISA, 'Encode::Encoding';
268
269 #
270 if ($use_xs) {
271 Encode::DEBUG and warn __PACKAGE__, " XS on";
272 *decode = \&decode_xs;
273 *encode = \&encode_xs;
274 }
275 else {
276 Encode::DEBUG and warn __PACKAGE__, " XS off";
277 *decode = sub {
278 my ( $obj, $octets, $chk ) = @_;
279 my $str = Encode::decode_utf8($octets);
280 if ( defined $str ) {
281 $_[1] = '' if $chk;
282 return $str;
283 }
284 return undef;
285 };
286 *encode = sub {
287 my ( $obj, $string, $chk ) = @_;
288 my $octets = Encode::encode_utf8($string);
289 $_[1] = '' if $chk;
290 return $octets;
291 };
292 }
293 *cat_decode = sub { # ($obj, $dst, $src, $pos, $trm, $chk)
294 # currently ignores $chk
295 my ( $obj, undef, undef, $pos, $trm ) = @_;
296 my ( $rdst, $rsrc, $rpos ) = \@_[ 1, 2, 3 ];
297 use bytes;
298 if ( ( my $npos = index( $$rsrc, $trm, $pos ) ) >= 0 ) {
299 $$rdst .=
300 substr( $$rsrc, $pos, $npos - $pos + length($trm) );
301 $$rpos = $npos + length($trm);
302 return 1;
303 }
304 $$rdst .= substr( $$rsrc, $pos );
305 $$rpos = length($$rsrc);
306 return '';
307 };
308 $Encode::Encoding{utf8} =
309 bless { Name => "utf8" } => "Encode::utf8";
310 $Encode::Encoding{"utf-8-strict"} =
311 bless { Name => "utf-8-strict", strict_utf8 => 1 } =>
312 "Encode::utf8";
f2a2953c 313 }
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314}
315
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3161;
317
2a936312
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318__END__
319
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320=head1 NAME
321
322Encode - character encodings
323
324=head1 SYNOPSIS
325
326 use Encode;
327
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328=head2 Table of Contents
329
0ab8f81e 330Encode consists of a collection of modules whose details are too big
67d7b5ef 331to fit in one document. This POD itself explains the top-level APIs
6d1c0808 332and general topics at a glance. For other topics and more details,
0ab8f81e 333see the PODs below:
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334
335 Name Description
336 --------------------------------------------------------
6d1c0808 337 Encode::Alias Alias definitions to encodings
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338 Encode::Encoding Encode Implementation Base Class
339 Encode::Supported List of Supported Encodings
340 Encode::CN Simplified Chinese Encodings
341 Encode::JP Japanese Encodings
342 Encode::KR Korean Encodings
343 Encode::TW Traditional Chinese Encodings
344 --------------------------------------------------------
345
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346=head1 DESCRIPTION
347
47bfe92f 348The C<Encode> module provides the interfaces between Perl's strings
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349and the rest of the system. Perl strings are sequences of
350B<characters>.
351
352The repertoire of characters that Perl can represent is at least that
353defined by the Unicode Consortium. On most platforms the ordinal
354values of the characters (as returned by C<ord(ch)>) is the "Unicode
355codepoint" for the character (the exceptions are those platforms where
356the legacy encoding is some variant of EBCDIC rather than a super-set
357of ASCII - see L<perlebcdic>).
358
0ab8f81e 359Traditionally, computer data has been moved around in 8-bit chunks
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360often called "bytes". These chunks are also known as "octets" in
361networking standards. Perl is widely used to manipulate data of many
362types - not only strings of characters representing human or computer
0ab8f81e 363languages but also "binary" data being the machine's representation of
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364numbers, pixels in an image - or just about anything.
365
0ab8f81e 366When Perl is processing "binary data", the programmer wants Perl to
67d7b5ef 367process "sequences of bytes". This is not a problem for Perl - as a
0ab8f81e 368byte has 256 possible values, it easily fits in Perl's much larger
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369"logical character".
370
371=head2 TERMINOLOGY
4411f3b6 372
7e19fb92 373=over 2
21938dfa 374
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375=item *
376
377I<character>: a character in the range 0..(2**32-1) (or more).
378(What Perl's strings are made of.)
379
380=item *
381
382I<byte>: a character in the range 0..255
383(A special case of a Perl character.)
384
385=item *
386
387I<octet>: 8 bits of data, with ordinal values 0..255
0ab8f81e 388(Term for bytes passed to or from a non-Perl context, e.g. a disk file.)
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389
390=back
4411f3b6 391
67d7b5ef 392=head1 PERL ENCODING API
4411f3b6 393
7e19fb92 394=over 2
4411f3b6 395
b7a5c9de 396=item $octets = encode(ENCODING, $string [, CHECK])
4411f3b6 397
0ab8f81e 398Encodes a string from Perl's internal form into I<ENCODING> and returns
67d7b5ef 399a sequence of octets. ENCODING can be either a canonical name or
0ab8f81e
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400an alias. For encoding names and aliases, see L</"Defining Aliases">.
401For CHECK, see L</"Handling Malformed Data">.
4411f3b6 402
b7a5c9de 403For example, to convert a string from Perl's internal format to
6d1c0808 404iso-8859-1 (also known as Latin1),
681a7c68 405
b7a5c9de 406 $octets = encode("iso-8859-1", $string);
7e19fb92 407
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408B<CAVEAT>: When you run C<$octets = encode("utf8", $string)>, then $octets
409B<may not be equal to> $string. Though they both contain the same data, the utf8 flag
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410for $octets is B<always> off. When you encode anything, utf8 flag of
411the result is always off, even when it contains completely valid utf8
412string. See L</"The UTF-8 flag"> below.
681a7c68 413
7f0d54d7 414If the $string is C<undef> then C<undef> is returned.
4089adc4 415
b7a5c9de 416=item $string = decode(ENCODING, $octets [, CHECK])
4411f3b6 417
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418Decodes a sequence of octets assumed to be in I<ENCODING> into Perl's
419internal form and returns the resulting string. As in encode(),
420ENCODING can be either a canonical name or an alias. For encoding names
421and aliases, see L</"Defining Aliases">. For CHECK, see
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422L</"Handling Malformed Data">.
423
b7a5c9de 424For example, to convert ISO-8859-1 data to a string in Perl's internal format:
681a7c68 425
b7a5c9de 426 $string = decode("iso-8859-1", $octets);
681a7c68 427
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428B<CAVEAT>: When you run C<$string = decode("utf8", $octets)>, then $string
429B<may not be equal to> $octets. Though they both contain the same data,
430the utf8 flag for $string is on unless $octets entirely consists of
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431ASCII data (or EBCDIC on EBCDIC machines). See L</"The UTF-8 flag">
432below.
47bfe92f 433
7f0d54d7 434If the $string is C<undef> then C<undef> is returned.
4089adc4 435
b7a5c9de 436=item [$length =] from_to($octets, FROM_ENC, TO_ENC [, CHECK])
7e19fb92 437
b7a5c9de
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438Converts B<in-place> data between two encodings. The data in $octets
439must be encoded as octets and not as characters in Perl's internal
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440format. For example, to convert ISO-8859-1 data to Microsoft's CP1250
441encoding:
2b106fbe 442
b7a5c9de 443 from_to($octets, "iso-8859-1", "cp1250");
2b106fbe
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444
445and to convert it back:
446
b7a5c9de 447 from_to($octets, "cp1250", "iso-8859-1");
4411f3b6 448
ab97ca19 449Note that because the conversion happens in place, the data to be
0ab8f81e 450converted cannot be a string constant; it must be a scalar variable.
ab97ca19 451
f9d05ba3
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452from_to() returns the length of the converted string in octets on
453success, I<undef> on error.
3ef515df 454
b7a5c9de 455B<CAVEAT>: The following operations look the same but are not quite so;
7e19fb92 456
b7a5c9de 457 from_to($data, "iso-8859-1", "utf8"); #1
7e19fb92 458 $data = decode("iso-8859-1", $data); #2
4411f3b6 459
b7a5c9de 460Both #1 and #2 make $data consist of a completely valid UTF-8 string
7e19fb92 461but only #2 turns utf8 flag on. #1 is equivalent to
f2a2953c 462
7e19fb92 463 $data = encode("utf8", decode("iso-8859-1", $data));
f2a2953c 464
7e19fb92 465See L</"The UTF-8 flag"> below.
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466
467=item $octets = encode_utf8($string);
468
7e19fb92 469Equivalent to C<$octets = encode("utf8", $string);> The characters
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470that comprise $string are encoded in Perl's internal format and the
471result is returned as a sequence of octets. All possible
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472characters have a UTF-8 representation so this function cannot fail.
473
f2a2953c
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474
475=item $string = decode_utf8($octets [, CHECK]);
476
7e19fb92 477equivalent to C<$string = decode("utf8", $octets [, CHECK])>.
b7a5c9de 478The sequence of octets represented by
7e19fb92
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479$octets is decoded from UTF-8 into a sequence of logical
480characters. Not all sequences of octets form valid UTF-8 encodings, so
481it is possible for this call to fail. For CHECK, see
482L</"Handling Malformed Data">.
f2a2953c
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483
484=back
485
51ef4e11
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486=head2 Listing available encodings
487
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488 use Encode;
489 @list = Encode->encodings();
490
491Returns a list of the canonical names of the available encodings that
492are loaded. To get a list of all available encodings including the
493ones that are not loaded yet, say
494
495 @all_encodings = Encode->encodings(":all");
496
0ab8f81e 497Or you can give the name of a specific module.
5129552c 498
c731e18e
JH
499 @with_jp = Encode->encodings("Encode::JP");
500
501When "::" is not in the name, "Encode::" is assumed.
51ef4e11 502
c731e18e 503 @ebcdic = Encode->encodings("EBCDIC");
5d030b67 504
0ab8f81e 505To find out in detail which encodings are supported by this package,
5d030b67 506see L<Encode::Supported>.
51ef4e11
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507
508=head2 Defining Aliases
509
0ab8f81e 510To add a new alias to a given encoding, use:
67d7b5ef 511
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512 use Encode;
513 use Encode::Alias;
a63c962f 514 define_alias(newName => ENCODING);
51ef4e11 515
3ef515df 516After that, newName can be used as an alias for ENCODING.
f2a2953c
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517ENCODING may be either the name of an encoding or an
518I<encoding object>
51ef4e11 519
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520But before you do so, make sure the alias is nonexistent with
521C<resolve_alias()>, which returns the canonical name thereof.
522i.e.
523
524 Encode::resolve_alias("latin1") eq "iso-8859-1" # true
525 Encode::resolve_alias("iso-8859-12") # false; nonexistent
526 Encode::resolve_alias($name) eq $name # true if $name is canonical
527
0ab8f81e
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528resolve_alias() does not need C<use Encode::Alias>; it can be
529exported via C<use Encode qw(resolve_alias)>.
fcb875d4 530
0ab8f81e 531See L<Encode::Alias> for details.
51ef4e11 532
85982a32 533=head1 Encoding via PerlIO
4411f3b6 534
b7a5c9de 535If your perl supports I<PerlIO> (which is the default), you can use a PerlIO layer to decode
0ab8f81e
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536and encode directly via a filehandle. The following two examples
537are totally identical in their functionality.
4411f3b6 538
85982a32
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539 # via PerlIO
540 open my $in, "<:encoding(shiftjis)", $infile or die;
541 open my $out, ">:encoding(euc-jp)", $outfile or die;
b7a5c9de 542 while(<$in>){ print $out $_; }
8e86646e 543
85982a32 544 # via from_to
0ab8f81e
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545 open my $in, "<", $infile or die;
546 open my $out, ">", $outfile or die;
b7a5c9de 547 while(<$in>){
0ab8f81e 548 from_to($_, "shiftjis", "euc-jp", 1);
b7a5c9de 549 print $out $_;
85982a32 550 }
4411f3b6 551
b7a5c9de 552Unfortunately, it may be that encodings are PerlIO-savvy. You can check
0ab8f81e
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553if your encoding is supported by PerlIO by calling the C<perlio_ok>
554method.
555
556 Encode::perlio_ok("hz"); # False
557 find_encoding("euc-cn")->perlio_ok; # True where PerlIO is available
558
559 use Encode qw(perlio_ok); # exported upon request
560 perlio_ok("euc-jp")
4411f3b6 561
0ab8f81e 562Fortunately, all encodings that come with Encode core are PerlIO-savvy
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563except for hz and ISO-2022-kr. For gory details, see
564L<Encode::Encoding> and L<Encode::PerlIO>.
4411f3b6 565
85982a32 566=head1 Handling Malformed Data
4411f3b6 567
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568The optional I<CHECK> argument tells Encode what to do when it
569encounters malformed data. Without CHECK, Encode::FB_DEFAULT ( == 0 )
570is assumed.
571
572As of version 2.12 Encode supports coderef values for CHECK. See below.
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573
574=over 2
575
3c4b39be 576=item B<NOTE:> Not all encoding support this feature
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577
578Some encodings ignore I<CHECK> argument. For example,
579L<Encode::Unicode> ignores I<CHECK> and it always croaks on error.
580
581=back
582
583Now here is the list of I<CHECK> values available
47bfe92f 584
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585=over 2
586
85982a32 587=item I<CHECK> = Encode::FB_DEFAULT ( == 0)
47bfe92f 588
f9d05ba3 589If I<CHECK> is 0, (en|de)code will put a I<substitution character> in
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590place of a malformed character. When you encode, E<lt>subcharE<gt>
591will be used. When you decode the code point C<0xFFFD> is used. If
592the data is supposed to be UTF-8, an optional lexical warning
593(category utf8) is given.
e9692b5b 594
7e19fb92 595=item I<CHECK> = Encode::FB_CROAK ( == 1)
e9692b5b 596
b7a5c9de 597If I<CHECK> is 1, methods will die on error immediately with an error
0ab8f81e 598message. Therefore, when I<CHECK> is set to 1, you should trap the
f9d05ba3 599error with eval{} unless you really want to let it die.
47bfe92f 600
85982a32 601=item I<CHECK> = Encode::FB_QUIET
47bfe92f 602
85982a32 603If I<CHECK> is set to Encode::FB_QUIET, (en|de)code will immediately
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604return the portion of the data that has been processed so far when an
605error occurs. The data argument will be overwritten with everything
606after that point (that is, the unprocessed part of data). This is
607handy when you have to call decode repeatedly in the case where your
608source data may contain partial multi-byte character sequences,
609(i.e. you are reading with a fixed-width buffer). Here is a sample
610code that does exactly this:
4411f3b6 611
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612 my $buffer = ''; my $string = '';
613 while(read $fh, $buffer, 256, length($buffer)){
614 $string .= decode($encoding, $buffer, Encode::FB_QUIET);
615 # $buffer now contains the unprocessed partial character
85982a32 616 }
1768d7eb 617
85982a32 618=item I<CHECK> = Encode::FB_WARN
67d7b5ef 619
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620This is the same as above, except that it warns on error. Handy when
621you are debugging the mode above.
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622
623=item perlqq mode (I<CHECK> = Encode::FB_PERLQQ)
624
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625=item HTML charref mode (I<CHECK> = Encode::FB_HTMLCREF)
626
627=item XML charref mode (I<CHECK> = Encode::FB_XMLCREF)
628
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629For encodings that are implemented by Encode::XS, CHECK ==
630Encode::FB_PERLQQ turns (en|de)code into C<perlqq> fallback mode.
631
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632When you decode, C<\xI<HH>> will be inserted for a malformed character,
633where I<HH> is the hex representation of the octet that could not be
634decoded to utf8. And when you encode, C<\x{I<HHHH>}> will be inserted,
635where I<HHHH> is the Unicode ID of the character that cannot be found
0ab8f81e 636in the character repertoire of the encoding.
85982a32 637
af1f55d9 638HTML/XML character reference modes are about the same, in place of
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639C<\x{I<HHHH>}>, HTML uses C<&#I<NNN>;> where I<NNN> is a decimal number and
640XML uses C<&#xI<HHHH>;> where I<HHHH> is the hexadecimal number.
af1f55d9 641
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642In Encode 2.10 or later, C<LEAVE_SRC> is also implied.
643
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644=item The bitmask
645
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646These modes are actually set via a bitmask. Here is how the FB_XX
647constants are laid out. You can import the FB_XX constants via
648C<use Encode qw(:fallbacks)>; you can import the generic bitmask
649constants via C<use Encode qw(:fallback_all)>.
85982a32 650
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651 FB_DEFAULT FB_CROAK FB_QUIET FB_WARN FB_PERLQQ
652 DIE_ON_ERR 0x0001 X
4089adc4 653 WARN_ON_ERR 0x0002 X
b0b300a3 654 RETURN_ON_ERR 0x0004 X X
7f0d54d7 655 LEAVE_SRC 0x0008 X
b0b300a3 656 PERLQQ 0x0100 X
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657 HTMLCREF 0x0200
658 XMLCREF 0x0400
67d7b5ef 659
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660=back
661
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662=head2 coderef for CHECK
663
664As of Encode 2.12 CHECK can also be a code reference which takes the
665ord value of unmapped caharacter as an argument and returns a string
666that represents the fallback character. For instance,
67d7b5ef 667
8e180e82 668 $ascii = encode("ascii", $utf8, sub{ sprintf "<U+%04X>", shift });
67d7b5ef 669
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670Acts like FB_PERLQQ but E<lt>U+I<XXXX>E<gt> is used instead of
671\x{I<XXXX>}.
982a4085 672
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673=head1 Defining Encodings
674
675To define a new encoding, use:
676
b7a5c9de 677 use Encode qw(define_encoding);
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678 define_encoding($object, 'canonicalName' [, alias...]);
679
680I<canonicalName> will be associated with I<$object>. The object
0ab8f81e 681should provide the interface described in L<Encode::Encoding>.
67d7b5ef 682If more than two arguments are provided then additional
b7a5c9de 683arguments are taken as aliases for I<$object>.
67d7b5ef 684
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685See L<Encode::Encoding> for more details.
686
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687=head1 The UTF-8 flag
688
689Before the introduction of utf8 support in perl, The C<eq> operator
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690just compared the strings represented by two scalars. Beginning with
691perl 5.8, C<eq> compares two strings with simultaneous consideration
692of I<the utf8 flag>. To explain why we made it so, I will quote page
693402 of C<Programming Perl, 3rd ed.>
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694
695=over 2
696
697=item Goal #1:
698
699Old byte-oriented programs should not spontaneously break on the old
700byte-oriented data they used to work on.
701
702=item Goal #2:
703
704Old byte-oriented programs should magically start working on the new
705character-oriented data when appropriate.
706
707=item Goal #3:
708
709Programs should run just as fast in the new character-oriented mode
710as in the old byte-oriented mode.
711
712=item Goal #4:
713
714Perl should remain one language, rather than forking into a
715byte-oriented Perl and a character-oriented Perl.
716
717=back
718
719Back when C<Programming Perl, 3rd ed.> was written, not even Perl 5.6.0
720was born and many features documented in the book remained
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721unimplemented for a long time. Perl 5.8 corrected this and the introduction
722of the UTF-8 flag is one of them. You can think of this perl notion as of a
723byte-oriented mode (utf8 flag off) and a character-oriented mode (utf8
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724flag on).
725
726Here is how Encode takes care of the utf8 flag.
727
4bdf5738 728=over 2
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729
730=item *
731
732When you encode, the resulting utf8 flag is always off.
733
151b5d36 734=item *
7e19fb92 735
b7a5c9de 736When you decode, the resulting utf8 flag is on unless you can
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737unambiguously represent data. Here is the definition of
738dis-ambiguity.
739
b7a5c9de 740After C<$utf8 = decode('foo', $octet);>,
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741
742 When $octet is... The utf8 flag in $utf8 is
743 ---------------------------------------------
744 In ASCII only (or EBCDIC only) OFF
745 In ISO-8859-1 ON
746 In any other Encoding ON
747 ---------------------------------------------
748
3c4b39be 749As you see, there is one exception, In ASCII. That way you can assume
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750Goal #1. And with Encode Goal #2 is assumed but you still have to be
751careful in such cases mentioned in B<CAVEAT> paragraphs.
752
753This utf8 flag is not visible in perl scripts, exactly for the same
754reason you cannot (or you I<don't have to>) see if a scalar contains a
755string, integer, or floating point number. But you can still peek
756and poke these if you will. See the section below.
757
758=back
759
760=head2 Messing with Perl's Internals
4411f3b6 761
47bfe92f 762The following API uses parts of Perl's internals in the current
0ab8f81e 763implementation. As such, they are efficient but may change.
4411f3b6 764
7e19fb92 765=over 2
4411f3b6 766
a63c962f 767=item is_utf8(STRING [, CHECK])
4411f3b6 768
0ab8f81e 769[INTERNAL] Tests whether the UTF-8 flag is turned on in the STRING.
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770If CHECK is true, also checks the data in STRING for being well-formed
771UTF-8. Returns true if successful, false otherwise.
4411f3b6 772
2c246b25 773As of perl 5.8.1, L<utf8> also has utf8::is_utf8().
b5ab1f6f 774
a63c962f 775=item _utf8_on(STRING)
4411f3b6 776
0ab8f81e 777[INTERNAL] Turns on the UTF-8 flag in STRING. The data in STRING is
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778B<not> checked for being well-formed UTF-8. Do not use unless you
779B<know> that the STRING is well-formed UTF-8. Returns the previous
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780state of the UTF-8 flag (so please don't treat the return value as
781indicating success or failure), or C<undef> if STRING is not a string.
4411f3b6 782
a63c962f 783=item _utf8_off(STRING)
4411f3b6 784
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785[INTERNAL] Turns off the UTF-8 flag in STRING. Do not use frivolously.
786Returns the previous state of the UTF-8 flag (so please don't treat the
787return value as indicating success or failure), or C<undef> if STRING is
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788not a string.
789
790=back
791
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792=head1 UTF-8 vs. utf8
793
794 ....We now view strings not as sequences of bytes, but as sequences
795 of numbers in the range 0 .. 2**32-1 (or in the case of 64-bit
796 computers, 0 .. 2**64-1) -- Programming Perl, 3rd ed.
797
798That has been the perl's notion of UTF-8 but official UTF-8 is more
799strict; Its ranges is much narrower (0 .. 10FFFF), some sequences are
800not allowed (i.e. Those used in the surrogate pair, 0xFFFE, et al).
801
802Now that is overruled by Larry Wall himself.
803
804 From: Larry Wall <larry@wall.org>
805 Date: December 04, 2004 11:51:58 JST
806 To: perl-unicode@perl.org
807 Subject: Re: Make Encode.pm support the real UTF-8
808 Message-Id: <20041204025158.GA28754@wall.org>
809
810 On Fri, Dec 03, 2004 at 10:12:12PM +0000, Tim Bunce wrote:
811 : I've no problem with 'utf8' being perl's unrestricted uft8 encoding,
812 : but "UTF-8" is the name of the standard and should give the
813 : corresponding behaviour.
814
815 For what it's worth, that's how I've always kept them straight in my
816 head.
8e180e82 817
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818 Also for what it's worth, Perl 6 will mostly default to strict but
819 make it easy to switch back to lax.
820
821 Larry
822
823Do you copy? As of Perl 5.8.7, B<UTF-8> means strict, official UTF-8
824while B<utf8> means liberal, lax, version thereof. And Encode version
8252.10 or later thus groks the difference between C<UTF-8> and C"utf8".
826
827 encode("utf8", "\x{FFFF_FFFF}", 1); # okay
828 encode("UTF-8", "\x{FFFF_FFFF}", 1); # croaks
829
830C<UTF-8> in Encode is actually a canonical name for C<utf-8-strict>.
831Yes, the hyphen between "UTF" and "8" is important. Without it Encode
832goes "liberal"
833
834 find_encoding("UTF-8")->name # is 'utf-8-strict'
835 find_encoding("utf-8")->name # ditto. names are case insensitive
50c1ac04 836 find_encoding("utf_8")->name # ditto. "_" are treated as "-"
7f0d54d7
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837 find_encoding("UTF8")->name # is 'utf8'.
838
839
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840=head1 SEE ALSO
841
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842L<Encode::Encoding>,
843L<Encode::Supported>,
6d1c0808 844L<Encode::PerlIO>,
5d030b67 845L<encoding>,
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846L<perlebcdic>,
847L<perlfunc/open>,
848L<perlunicode>,
849L<utf8>,
5d030b67 850the Perl Unicode Mailing List E<lt>perl-unicode@perl.orgE<gt>
4411f3b6 851
85982a32 852=head1 MAINTAINER
aae85ceb
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853
854This project was originated by Nick Ing-Simmons and later maintained
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855by Dan Kogai E<lt>dankogai@dan.co.jpE<gt>. See AUTHORS for a full
856list of people involved. For any questions, use
b7a5c9de 857E<lt>perl-unicode@perl.orgE<gt> so we can all share.
aae85ceb 858
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859While Dan Kogai retains the copyright as a maintainer, the credit
860should go to all those involoved. See AUTHORS for those submitted
861codes.
862
863=head1 COPYRIGHT
864
865Copyright 2002-2006 Dan Kogai E<lt>dankogai@dan.co.jpE<gt>
866
867This library is free software; you can redistribute it and/or modify
868it under the same terms as Perl itself.
869
4411f3b6 870=cut