2 # $Id: Encode.pm,v 2.68 2015/01/22 10:17:32 dankogai Exp dankogai $
7 our $VERSION = sprintf "%d.%02d", q$Revision: 2.68 $ =~ /(\d+)/g;
8 use constant DEBUG => !!$ENV{PERL_ENCODE_DEBUG};
10 XSLoader::load( __PACKAGE__, $VERSION );
12 use Exporter 5.57 'import';
14 # Public, encouraged API is exported by default
17 decode decode_utf8 encode encode_utf8 str2bytes bytes2str
18 encodings find_encoding clone_encoding
21 DIE_ON_ERR WARN_ON_ERR RETURN_ON_ERR LEAVE_SRC
22 PERLQQ HTMLCREF XMLCREF STOP_AT_PARTIAL
25 FB_DEFAULT FB_CROAK FB_QUIET FB_WARN
26 FB_PERLQQ FB_HTMLCREF FB_XMLCREF
30 _utf8_off _utf8_on define_encoding from_to is_16bit is_8bit
31 is_utf8 perlio_ok resolve_alias utf8_downgrade utf8_upgrade
33 @FB_FLAGS, @FB_CONSTS,
37 all => [ @EXPORT, @EXPORT_OK ],
38 default => [ @EXPORT ],
39 fallbacks => [ @FB_CONSTS ],
40 fallback_all => [ @FB_CONSTS, @FB_FLAGS ],
43 # Documentation moved after __END__ for speed - NI-S
45 our $ON_EBCDIC = ( ord("A") == 193 );
49 # Make a %Encoding package variable to allow a certain amount of cheating
52 require Encode::Config;
54 # https://bugzilla.redhat.com/show_bug.cgi?id=435505#c2
55 # to find why sig handlers inside eval{} are disabled.
59 require Encode::ConfigLocal;
64 my $arg = $_[1] || '';
65 if ( $arg eq ":all" ) {
66 %enc = ( %Encoding, %ExtModule );
70 for my $mod ( map { m/::/ ? $_ : "Encode::$_" } @_ ) {
72 for my $enc ( keys %ExtModule ) {
73 $ExtModule{$enc} eq $mod and $enc{$enc} = $mod;
77 return sort { lc $a cmp lc $b }
78 grep { !/^(?:Internal|Unicode|Guess)$/o } keys %enc;
82 my $obj = ref( $_[0] ) ? $_[0] : find_encoding( $_[0] );
83 $obj->can("perlio_ok") and return $obj->perlio_ok();
84 return 0; # safety net
90 $Encoding{$name} = $obj;
92 define_alias( $lc => $obj ) unless $lc eq $name;
95 define_alias( $alias, $obj );
101 my ( $class, $name, $skip_external ) = @_;
103 $name =~ s/\s+//g; # https://rt.cpan.org/Ticket/Display.html?id=65796
105 ref($name) && $name->can('renew') and return $name;
106 exists $Encoding{$name} and return $Encoding{$name};
108 exists $Encoding{$lc} and return $Encoding{$lc};
110 my $oc = $class->find_alias($name);
111 defined($oc) and return $oc;
112 $lc ne $name and $oc = $class->find_alias($lc);
113 defined($oc) and return $oc;
115 unless ($skip_external) {
116 if ( my $mod = $ExtModule{$name} || $ExtModule{$lc} ) {
119 eval { require $mod; };
120 exists $Encoding{$name} and return $Encoding{$name};
126 sub find_encoding($;$) {
127 my ( $name, $skip_external ) = @_;
128 return __PACKAGE__->getEncoding( $name, $skip_external );
131 sub resolve_alias($) {
132 my $obj = find_encoding(shift);
133 defined $obj and return $obj->name;
137 sub clone_encoding($) {
138 my $obj = find_encoding(shift);
140 eval { require Storable };
142 return Storable::dclone($obj);
146 my ( $name, $string, $check ) = @_;
147 return undef unless defined $string;
148 $string .= ''; # stringify;
150 unless ( defined $name ) {
152 Carp::croak("Encoding name should not be undef");
154 my $enc = find_encoding($name);
155 unless ( defined $enc ) {
157 Carp::croak("Unknown encoding '$name'");
159 # For Unicode, warnings need to be caught and re-issued at this level
160 # so that callers can disable utf8 warnings lexically.
162 if ( ref($enc) eq 'Encode::Unicode' ) {
165 local $SIG{__WARN__} = sub { $warn = shift };
166 $octets = $enc->encode( $string, $check );
168 warnings::warnif('utf8', $warn) if length $warn;
171 $octets = $enc->encode( $string, $check );
173 $_[1] = $string if $check and !ref $check and !( $check & LEAVE_SRC() );
176 *str2bytes = \&encode;
179 my ( $name, $octets, $check ) = @_;
180 return undef unless defined $octets;
183 my $enc = find_encoding($name);
184 unless ( defined $enc ) {
186 Carp::croak("Unknown encoding '$name'");
188 # For Unicode, warnings need to be caught and re-issued at this level
189 # so that callers can disable utf8 warnings lexically.
191 if ( ref($enc) eq 'Encode::Unicode' ) {
194 local $SIG{__WARN__} = sub { $warn = shift };
195 $string = $enc->decode( $octets, $check );
197 warnings::warnif('utf8', $warn) if length $warn;
200 $string = $enc->decode( $octets, $check );
202 $_[1] = $octets if $check and !ref $check and !( $check & LEAVE_SRC() );
205 *bytes2str = \&decode;
208 my ( $string, $from, $to, $check ) = @_;
209 return undef unless defined $string;
211 my $f = find_encoding($from);
212 unless ( defined $f ) {
214 Carp::croak("Unknown encoding '$from'");
216 my $t = find_encoding($to);
217 unless ( defined $t ) {
219 Carp::croak("Unknown encoding '$to'");
221 my $uni = $f->decode($string);
222 $_[0] = $string = $t->encode( $uni, $check );
223 return undef if ( $check && length($uni) );
224 return defined( $_[0] ) ? length($string) : undef;
235 sub decode_utf8($;$) {
236 my ( $octets, $check ) = @_;
237 return undef unless defined $octets;
240 $utf8enc ||= find_encoding('utf8');
241 my $string = $utf8enc->decode( $octets, $check );
242 $_[0] = $octets if $check and !ref $check and !( $check & LEAVE_SRC() );
246 # sub decode_utf8($;$) {
247 # my ( $str, $check ) = @_;
248 # return $str if is_utf8($str);
250 # return decode( "utf8", $str, $check );
253 # return decode( "utf8", $str );
258 predefine_encodings(1);
261 # This is to restore %Encoding if really needed;
264 sub predefine_encodings {
265 require Encode::Encoding;
266 no warnings 'redefine';
270 # was in Encode::UTF_EBCDIC
271 package Encode::UTF_EBCDIC;
272 push @Encode::UTF_EBCDIC::ISA, 'Encode::Encoding';
274 my ( undef, $str, $chk ) = @_;
276 for ( my $i = 0 ; $i < length($str) ; $i++ ) {
279 utf8::unicode_to_native( ord( substr( $str, $i, 1 ) ) )
286 my ( undef, $str, $chk ) = @_;
288 for ( my $i = 0 ; $i < length($str) ; $i++ ) {
291 utf8::native_to_unicode( ord( substr( $str, $i, 1 ) ) )
297 $Encode::Encoding{Unicode} =
298 bless { Name => "UTF_EBCDIC" } => "Encode::UTF_EBCDIC";
302 package Encode::Internal;
303 push @Encode::Internal::ISA, 'Encode::Encoding';
305 my ( undef, $str, $chk ) = @_;
311 $Encode::Encoding{Unicode} =
312 bless { Name => "Internal" } => "Encode::Internal";
317 # was in Encode::utf8
318 package Encode::utf8;
319 push @Encode::utf8::ISA, 'Encode::Encoding';
323 Encode::DEBUG and warn __PACKAGE__, " XS on";
324 *decode = \&decode_xs;
325 *encode = \&encode_xs;
328 Encode::DEBUG and warn __PACKAGE__, " XS off";
330 my ( undef, $octets, $chk ) = @_;
331 my $str = Encode::decode_utf8($octets);
332 if ( defined $str ) {
339 my ( undef, $string, $chk ) = @_;
340 my $octets = Encode::encode_utf8($string);
345 *cat_decode = sub { # ($obj, $dst, $src, $pos, $trm, $chk)
346 # currently ignores $chk
347 my ( undef, undef, undef, $pos, $trm ) = @_;
348 my ( $rdst, $rsrc, $rpos ) = \@_[ 1, 2, 3 ];
350 if ( ( my $npos = index( $$rsrc, $trm, $pos ) ) >= 0 ) {
352 substr( $$rsrc, $pos, $npos - $pos + length($trm) );
353 $$rpos = $npos + length($trm);
356 $$rdst .= substr( $$rsrc, $pos );
357 $$rpos = length($$rsrc);
360 $Encode::Encoding{utf8} =
361 bless { Name => "utf8" } => "Encode::utf8";
362 $Encode::Encoding{"utf-8-strict"} =
363 bless { Name => "utf-8-strict", strict_utf8 => 1 }
374 Encode - character encodings in Perl
378 use Encode qw(decode encode);
379 $characters = decode('UTF-8', $octets, Encode::FB_CROAK);
380 $octets = encode('UTF-8', $characters, Encode::FB_CROAK);
382 =head2 Table of Contents
384 Encode consists of a collection of modules whose details are too extensive
385 to fit in one document. This one itself explains the top-level APIs
386 and general topics at a glance. For other topics and more details,
387 see the documentation for these modules:
391 =item L<Encode::Alias> - Alias definitions to encodings
393 =item L<Encode::Encoding> - Encode Implementation Base Class
395 =item L<Encode::Supported> - List of Supported Encodings
397 =item L<Encode::CN> - Simplified Chinese Encodings
399 =item L<Encode::JP> - Japanese Encodings
401 =item L<Encode::KR> - Korean Encodings
403 =item L<Encode::TW> - Traditional Chinese Encodings
409 The C<Encode> module provides the interface between Perl strings
410 and the rest of the system. Perl strings are sequences of
413 The repertoire of characters that Perl can represent is a superset of those
414 defined by the Unicode Consortium. On most platforms the ordinal
415 values of a character as returned by C<ord(I<S>)> is the I<Unicode
416 codepoint> for that character. The exceptions are platforms where
417 the legacy encoding is some variant of EBCDIC rather than a superset
418 of ASCII; see L<perlebcdic>.
420 During recent history, data is moved around a computer in 8-bit chunks,
421 often called "bytes" but also known as "octets" in standards documents.
422 Perl is widely used to manipulate data of many types: not only strings of
423 characters representing human or computer languages, but also "binary"
424 data, being the machine's representation of numbers, pixels in an image, or
427 When Perl is processing "binary data", the programmer wants Perl to
428 process "sequences of bytes". This is not a problem for Perl: because a
429 byte has 256 possible values, it easily fits in Perl's much larger
432 This document mostly explains the I<how>. L<perlunitut> and L<perlunifaq>
439 A character in the range 0 .. 2**32-1 (or more);
440 what Perl's strings are made of.
444 A character in the range 0..255;
445 a special case of a Perl character.
449 8 bits of data, with ordinal values 0..255;
450 term for bytes passed to or from a non-Perl context, such as a disk file,
451 standard I/O stream, database, command-line argument, environment variable,
454 =head1 THE PERL ENCODING API
460 $octets = encode(ENCODING, STRING[, CHECK])
462 Encodes the scalar value I<STRING> from Perl's internal form into
463 I<ENCODING> and returns a sequence of octets. I<ENCODING> can be either a
464 canonical name or an alias. For encoding names and aliases, see
465 L</"Defining Aliases">. For CHECK, see L</"Handling Malformed Data">.
467 For example, to convert a string from Perl's internal format into
468 ISO-8859-1, also known as Latin1:
470 $octets = encode("iso-8859-1", $string);
472 B<CAVEAT>: When you run C<$octets = encode("utf8", $string)>, then
473 $octets I<might not be equal to> $string. Though both contain the
474 same data, the UTF8 flag for $octets is I<always> off. When you
475 encode anything, the UTF8 flag on the result is always off, even when it
476 contains a completely valid utf8 string. See L</"The UTF8 flag"> below.
478 If the $string is C<undef>, then C<undef> is returned.
482 $string = decode(ENCODING, OCTETS[, CHECK])
484 This function returns the string that results from decoding the scalar
485 value I<OCTETS>, assumed to be a sequence of octets in I<ENCODING>, into
486 Perl's internal form. As with encode(),
487 I<ENCODING> can be either a canonical name or an alias. For encoding names
488 and aliases, see L</"Defining Aliases">; for I<CHECK>, see L</"Handling
491 For example, to convert ISO-8859-1 data into a string in Perl's
494 $string = decode("iso-8859-1", $octets);
496 B<CAVEAT>: When you run C<$string = decode("utf8", $octets)>, then $string
497 I<might not be equal to> $octets. Though both contain the same data, the
498 UTF8 flag for $string is on. See L</"The UTF8 flag">
501 If the $string is C<undef>, then C<undef> is returned.
505 [$obj =] find_encoding(ENCODING)
507 Returns the I<encoding object> corresponding to I<ENCODING>. Returns
508 C<undef> if no matching I<ENCODING> is find. The returned object is
509 what does the actual encoding or decoding.
511 $utf8 = decode($name, $bytes);
516 $obj = find_encoding($name);
517 croak qq(encoding "$name" not found) unless ref $obj;
518 $obj->decode($bytes);
521 with more error checking.
523 You can therefore save time by reusing this object as follows;
525 my $enc = find_encoding("iso-8859-1");
527 my $utf8 = $enc->decode($_);
528 ... # now do something with $utf8;
531 Besides L</decode> and L</encode>, other methods are
532 available as well. For instance, C<name()> returns the canonical
533 name of the encoding object.
535 find_encoding("latin1")->name; # iso-8859-1
537 See L<Encode::Encoding> for details.
541 [$length =] from_to($octets, FROM_ENC, TO_ENC [, CHECK])
543 Converts I<in-place> data between two encodings. The data in $octets
544 must be encoded as octets and I<not> as characters in Perl's internal
545 format. For example, to convert ISO-8859-1 data into Microsoft's CP1250
548 from_to($octets, "iso-8859-1", "cp1250");
550 and to convert it back:
552 from_to($octets, "cp1250", "iso-8859-1");
554 Because the conversion happens in place, the data to be
555 converted cannot be a string constant: it must be a scalar variable.
557 C<from_to()> returns the length of the converted string in octets on success,
558 and C<undef> on error.
560 B<CAVEAT>: The following operations may look the same, but are not:
562 from_to($data, "iso-8859-1", "utf8"); #1
563 $data = decode("iso-8859-1", $data); #2
565 Both #1 and #2 make $data consist of a completely valid UTF-8 string,
566 but only #2 turns the UTF8 flag on. #1 is equivalent to:
568 $data = encode("utf8", decode("iso-8859-1", $data));
570 See L</"The UTF8 flag"> below.
574 from_to($octets, $from, $to, $check);
578 $octets = encode($to, decode($from, $octets), $check);
580 Yes, it does I<not> respect the $check during decoding. It is
581 deliberately done that way. If you need minute control, use C<decode>
582 followed by C<encode> as follows:
584 $octets = encode($to, decode($from, $octets, $check_from), $check_to);
588 $octets = encode_utf8($string);
590 Equivalent to C<$octets = encode("utf8", $string)>. The characters in
591 $string are encoded in Perl's internal format, and the result is returned
592 as a sequence of octets. Because all possible characters in Perl have a
593 (loose, not strict) UTF-8 representation, this function cannot fail.
597 $string = decode_utf8($octets [, CHECK]);
599 Equivalent to C<$string = decode("utf8", $octets [, CHECK])>.
600 The sequence of octets represented by $octets is decoded
601 from UTF-8 into a sequence of logical characters.
602 Because not all sequences of octets are valid UTF-8,
603 it is quite possible for this function to fail.
604 For CHECK, see L</"Handling Malformed Data">.
606 =head2 Listing available encodings
609 @list = Encode->encodings();
611 Returns a list of canonical names of available encodings that have already
612 been loaded. To get a list of all available encodings including those that
613 have not yet been loaded, say:
615 @all_encodings = Encode->encodings(":all");
617 Or you can give the name of a specific module:
619 @with_jp = Encode->encodings("Encode::JP");
621 When "C<::>" is not in the name, "C<Encode::>" is assumed.
623 @ebcdic = Encode->encodings("EBCDIC");
625 To find out in detail which encodings are supported by this package,
626 see L<Encode::Supported>.
628 =head2 Defining Aliases
630 To add a new alias to a given encoding, use:
634 define_alias(NEWNAME => ENCODING);
636 After that, I<NEWNAME> can be used as an alias for I<ENCODING>.
637 I<ENCODING> may be either the name of an encoding or an
640 Before you do that, first make sure the alias is nonexistent using
641 C<resolve_alias()>, which returns the canonical name thereof.
644 Encode::resolve_alias("latin1") eq "iso-8859-1" # true
645 Encode::resolve_alias("iso-8859-12") # false; nonexistent
646 Encode::resolve_alias($name) eq $name # true if $name is canonical
648 C<resolve_alias()> does not need C<use Encode::Alias>; it can be
649 imported via C<use Encode qw(resolve_alias)>.
651 See L<Encode::Alias> for details.
653 =head2 Finding IANA Character Set Registry names
655 The canonical name of a given encoding does not necessarily agree with
656 IANA Character Set Registry, commonly seen as C<< Content-Type:
657 text/plain; charset=I<WHATEVER> >>. For most cases, the canonical name
658 works, but sometimes it does not, most notably with "utf-8-strict".
660 As of C<Encode> version 2.21, a new method C<mime_name()> is therefore added.
663 my $enc = find_encoding("UTF-8");
664 warn $enc->name; # utf-8-strict
665 warn $enc->mime_name; # UTF-8
667 See also: L<Encode::Encoding>
669 =head1 Encoding via PerlIO
671 If your perl supports C<PerlIO> (which is the default), you can use a
672 C<PerlIO> layer to decode and encode directly via a filehandle. The
673 following two examples are fully identical in functionality:
675 ### Version 1 via PerlIO
676 open(INPUT, "< :encoding(shiftjis)", $infile)
677 || die "Can't open < $infile for reading: $!";
678 open(OUTPUT, "> :encoding(euc-jp)", $outfile)
679 || die "Can't open > $output for writing: $!";
680 while (<INPUT>) { # auto decodes $_
681 print OUTPUT; # auto encodes $_
683 close(INPUT) || die "can't close $infile: $!";
684 close(OUTPUT) || die "can't close $outfile: $!";
686 ### Version 2 via from_to()
687 open(INPUT, "< :raw", $infile)
688 || die "Can't open < $infile for reading: $!";
689 open(OUTPUT, "> :raw", $outfile)
690 || die "Can't open > $output for writing: $!";
693 from_to($_, "shiftjis", "euc-jp", 1); # switch encoding
694 print OUTPUT; # emit raw (but properly encoded) data
696 close(INPUT) || die "can't close $infile: $!";
697 close(OUTPUT) || die "can't close $outfile: $!";
699 In the first version above, you let the appropriate encoding layer
700 handle the conversion. In the second, you explicitly translate
701 from one encoding to the other.
703 Unfortunately, it may be that encodings are not C<PerlIO>-savvy. You can check
704 to see whether your encoding is supported by C<PerlIO> by invoking the
705 C<perlio_ok> method on it:
707 Encode::perlio_ok("hz"); # false
708 find_encoding("euc-cn")->perlio_ok; # true wherever PerlIO is available
710 use Encode qw(perlio_ok); # imported upon request
713 Fortunately, all encodings that come with C<Encode> core are C<PerlIO>-savvy
714 except for C<hz> and C<ISO-2022-kr>. For the gory details, see
715 L<Encode::Encoding> and L<Encode::PerlIO>.
717 =head1 Handling Malformed Data
719 The optional I<CHECK> argument tells C<Encode> what to do when
720 encountering malformed data. Without I<CHECK>, C<Encode::FB_DEFAULT>
723 As of version 2.12, C<Encode> supports coderef values for C<CHECK>;
726 B<NOTE:> Not all encodings support this feature.
727 Some encodings ignore the I<CHECK> argument. For example,
728 L<Encode::Unicode> ignores I<CHECK> and it always croaks on error.
730 =head2 List of I<CHECK> values
734 I<CHECK> = Encode::FB_DEFAULT ( == 0)
736 If I<CHECK> is 0, encoding and decoding replace any malformed character
737 with a I<substitution character>. When you encode, I<SUBCHAR> is used.
738 When you decode, the Unicode REPLACEMENT CHARACTER, code point U+FFFD, is
739 used. If the data is supposed to be UTF-8, an optional lexical warning of
740 warning category C<"utf8"> is given.
744 I<CHECK> = Encode::FB_CROAK ( == 1)
746 If I<CHECK> is 1, methods immediately die with an error
747 message. Therefore, when I<CHECK> is 1, you should trap
748 exceptions with C<eval{}>, unless you really want to let it C<die>.
752 I<CHECK> = Encode::FB_QUIET
754 If I<CHECK> is set to C<Encode::FB_QUIET>, encoding and decoding immediately
755 return the portion of the data that has been processed so far when an
756 error occurs. The data argument is overwritten with everything
757 after that point; that is, the unprocessed portion of the data. This is
758 handy when you have to call C<decode> repeatedly in the case where your
759 source data may contain partial multi-byte character sequences,
760 (that is, you are reading with a fixed-width buffer). Here's some sample
761 code to do exactly that:
763 my($buffer, $string) = ("", "");
764 while (read($fh, $buffer, 256, length($buffer))) {
765 $string .= decode($encoding, $buffer, Encode::FB_QUIET);
766 # $buffer now contains the unprocessed partial character
771 I<CHECK> = Encode::FB_WARN
773 This is the same as C<FB_QUIET> above, except that instead of being silent
774 on errors, it issues a warning. This is handy for when you are debugging.
776 =head3 FB_PERLQQ FB_HTMLCREF FB_XMLCREF
780 =item perlqq mode (I<CHECK> = Encode::FB_PERLQQ)
782 =item HTML charref mode (I<CHECK> = Encode::FB_HTMLCREF)
784 =item XML charref mode (I<CHECK> = Encode::FB_XMLCREF)
788 For encodings that are implemented by the C<Encode::XS> module, C<CHECK> C<==>
789 C<Encode::FB_PERLQQ> puts C<encode> and C<decode> into C<perlqq> fallback mode.
791 When you decode, C<\xI<HH>> is inserted for a malformed character, where
792 I<HH> is the hex representation of the octet that could not be decoded to
793 utf8. When you encode, C<\x{I<HHHH>}> will be inserted, where I<HHHH> is
794 the Unicode code point (in any number of hex digits) of the character that
795 cannot be found in the character repertoire of the encoding.
797 The HTML/XML character reference modes are about the same. In place of
798 C<\x{I<HHHH>}>, HTML uses C<&#I<NNN>;> where I<NNN> is a decimal number, and
799 XML uses C<&#xI<HHHH>;> where I<HHHH> is the hexadecimal number.
801 In C<Encode> 2.10 or later, C<LEAVE_SRC> is also implied.
805 These modes are all actually set via a bitmask. Here is how the C<FB_I<XXX>>
806 constants are laid out. You can import the C<FB_I<XXX>> constants via
807 C<use Encode qw(:fallbacks)>, and you can import the generic bitmask
808 constants via C<use Encode qw(:fallback_all)>.
810 FB_DEFAULT FB_CROAK FB_QUIET FB_WARN FB_PERLQQ
813 RETURN_ON_ERR 0x0004 X X
823 If the C<Encode::LEAVE_SRC> bit is I<not> set but I<CHECK> is set, then the
824 source string to encode() or decode() will be overwritten in place.
825 If you're not interested in this, then bitwise-OR it with the bitmask.
827 =head2 coderef for CHECK
829 As of C<Encode> 2.12, C<CHECK> can also be a code reference which takes the
830 ordinal value of the unmapped character as an argument and returns
831 octets that represent the fallback character. For instance:
833 $ascii = encode("ascii", $utf8, sub{ sprintf "<U+%04X>", shift });
835 Acts like C<FB_PERLQQ> but U+I<XXXX> is used instead of C<\x{I<XXXX>}>.
837 Even the fallback for C<decode> must return octets, which are
838 then decoded with the character encoding that C<decode> accepts. So for
839 example if you wish to decode octets as UTF-8, and use ISO-8859-15 as
840 a fallback for bytes that are not valid UTF-8, you could write
842 $str = decode 'UTF-8', $octets, sub {
844 from_to $tmp, 'ISO-8859-15', 'UTF-8';
848 =head1 Defining Encodings
850 To define a new encoding, use:
852 use Encode qw(define_encoding);
853 define_encoding($object, CANONICAL_NAME [, alias...]);
855 I<CANONICAL_NAME> will be associated with I<$object>. The object
856 should provide the interface described in L<Encode::Encoding>.
857 If more than two arguments are provided, additional
858 arguments are considered aliases for I<$object>.
860 See L<Encode::Encoding> for details.
864 Before the introduction of Unicode support in Perl, The C<eq> operator
865 just compared the strings represented by two scalars. Beginning with
866 Perl 5.8, C<eq> compares two strings with simultaneous consideration of
867 I<the UTF8 flag>. To explain why we made it so, I quote from page 402 of
868 I<Programming Perl, 3rd ed.>
874 Old byte-oriented programs should not spontaneously break on the old
875 byte-oriented data they used to work on.
879 Old byte-oriented programs should magically start working on the new
880 character-oriented data when appropriate.
884 Programs should run just as fast in the new character-oriented mode
885 as in the old byte-oriented mode.
889 Perl should remain one language, rather than forking into a
890 byte-oriented Perl and a character-oriented Perl.
894 When I<Programming Perl, 3rd ed.> was written, not even Perl 5.6.0 had been
895 born yet, many features documented in the book remained unimplemented for a
896 long time. Perl 5.8 corrected much of this, and the introduction of the
897 UTF8 flag is one of them. You can think of there being two fundamentally
898 different kinds of strings and string-operations in Perl: one a
899 byte-oriented mode for when the internal UTF8 flag is off, and the other a
900 character-oriented mode for when the internal UTF8 flag is on.
902 Here is how C<Encode> handles the UTF8 flag.
908 When you I<encode>, the resulting UTF8 flag is always B<off>.
912 When you I<decode>, the resulting UTF8 flag is B<on>--I<unless> you can
913 unambiguously represent data. Here is what we mean by "unambiguously".
914 After C<$utf8 = decode("foo", $octet)>,
916 When $octet is... The UTF8 flag in $utf8 is
917 ---------------------------------------------
918 In ASCII only (or EBCDIC only) OFF
920 In any other Encoding ON
921 ---------------------------------------------
923 As you see, there is one exception: in ASCII. That way you can assume
924 Goal #1. And with C<Encode>, Goal #2 is assumed but you still have to be
925 careful in the cases mentioned in the B<CAVEAT> paragraphs above.
927 This UTF8 flag is not visible in Perl scripts, exactly for the same reason
928 you cannot (or rather, you I<don't have to>) see whether a scalar contains
929 a string, an integer, or a floating-point number. But you can still peek
930 and poke these if you will. See the next section.
934 =head2 Messing with Perl's Internals
936 The following API uses parts of Perl's internals in the current
937 implementation. As such, they are efficient but may change in a future
942 is_utf8(STRING [, CHECK])
944 [INTERNAL] Tests whether the UTF8 flag is turned on in the I<STRING>.
945 If I<CHECK> is true, also checks whether I<STRING> contains well-formed
946 UTF-8. Returns true if successful, false otherwise.
948 As of Perl 5.8.1, L<utf8> also has the C<utf8::is_utf8> function.
954 [INTERNAL] Turns the I<STRING>'s internal UTF8 flag B<on>. The I<STRING>
955 is I<not> checked for containing only well-formed UTF-8. Do not use this
956 unless you I<know with absolute certainty> that the STRING holds only
957 well-formed UTF-8. Returns the previous state of the UTF8 flag (so please
958 don't treat the return value as indicating success or failure), or C<undef>
959 if I<STRING> is not a string.
961 B<NOTE>: For security reasons, this function does not work on tainted values.
967 [INTERNAL] Turns the I<STRING>'s internal UTF8 flag B<off>. Do not use
968 frivolously. Returns the previous state of the UTF8 flag, or C<undef> if
969 I<STRING> is not a string. Do not treat the return value as indicative of
970 success or failure, because that isn't what it means: it is only the
973 B<NOTE>: For security reasons, this function does not work on tainted values.
975 =head1 UTF-8 vs. utf8 vs. UTF8
977 ....We now view strings not as sequences of bytes, but as sequences
978 of numbers in the range 0 .. 2**32-1 (or in the case of 64-bit
979 computers, 0 .. 2**64-1) -- Programming Perl, 3rd ed.
981 That has historically been Perl's notion of UTF-8, as that is how UTF-8 was
982 first conceived by Ken Thompson when he invented it. However, thanks to
983 later revisions to the applicable standards, official UTF-8 is now rather
984 stricter than that. For example, its range is much narrower (0 .. 0x10_FFFF
985 to cover only 21 bits instead of 32 or 64 bits) and some sequences
986 are not allowed, like those used in surrogate pairs, the 31 non-character
987 code points 0xFDD0 .. 0xFDEF, the last two code points in I<any> plane
988 (0xI<XX>_FFFE and 0xI<XX>_FFFF), all non-shortest encodings, etc.
990 The former default in which Perl would always use a loose interpretation of
991 UTF-8 has now been overruled:
993 From: Larry Wall <larry@wall.org>
994 Date: December 04, 2004 11:51:58 JST
995 To: perl-unicode@perl.org
996 Subject: Re: Make Encode.pm support the real UTF-8
997 Message-Id: <20041204025158.GA28754@wall.org>
999 On Fri, Dec 03, 2004 at 10:12:12PM +0000, Tim Bunce wrote:
1000 : I've no problem with 'utf8' being perl's unrestricted uft8 encoding,
1001 : but "UTF-8" is the name of the standard and should give the
1002 : corresponding behaviour.
1004 For what it's worth, that's how I've always kept them straight in my
1007 Also for what it's worth, Perl 6 will mostly default to strict but
1008 make it easy to switch back to lax.
1012 Got that? As of Perl 5.8.7, B<"UTF-8"> means UTF-8 in its current
1013 sense, which is conservative and strict and security-conscious, whereas
1014 B<"utf8"> means UTF-8 in its former sense, which was liberal and loose and
1015 lax. C<Encode> version 2.10 or later thus groks this subtle but critically
1016 important distinction between C<"UTF-8"> and C<"utf8">.
1018 encode("utf8", "\x{FFFF_FFFF}", 1); # okay
1019 encode("UTF-8", "\x{FFFF_FFFF}", 1); # croaks
1021 In the C<Encode> module, C<"UTF-8"> is actually a canonical name for
1022 C<"utf-8-strict">. That hyphen between the C<"UTF"> and the C<"8"> is
1023 critical; without it, C<Encode> goes "liberal" and (perhaps overly-)permissive:
1025 find_encoding("UTF-8")->name # is 'utf-8-strict'
1026 find_encoding("utf-8")->name # ditto. names are case insensitive
1027 find_encoding("utf_8")->name # ditto. "_" are treated as "-"
1028 find_encoding("UTF8")->name # is 'utf8'.
1030 Perl's internal UTF8 flag is called "UTF8", without a hyphen. It indicates
1031 whether a string is internally encoded as "utf8", also without a hyphen.
1035 L<Encode::Encoding>,
1036 L<Encode::Supported>,
1041 L<perlunicode>, L<perluniintro>, L<perlunifaq>, L<perlunitut>
1043 the Perl Unicode Mailing List L<http://lists.perl.org/list/perl-unicode.html>
1047 This project was originated by the late Nick Ing-Simmons and later
1048 maintained by Dan Kogai I<< <dankogai@cpan.org> >>. See AUTHORS
1049 for a full list of people involved. For any questions, send mail to
1050 I<< <perl-unicode@perl.org> >> so that we can all share.
1052 While Dan Kogai retains the copyright as a maintainer, credit
1053 should go to all those involved. See AUTHORS for a list of those
1054 who submitted code to the project.
1058 Copyright 2002-2014 Dan Kogai I<< <dankogai@cpan.org> >>.
1060 This library is free software; you can redistribute it and/or modify
1061 it under the same terms as Perl itself.