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+#
+# $Id: Encode.pm,v 2.39 2009/11/26 09:23:48 dankogai Exp $
+#
+package Encode;
+use strict;
+use warnings;
+our $VERSION = sprintf "%d.%02d", q$Revision: 2.39 $ =~ /(\d+)/g;
+sub DEBUG () { 0 }
+use XSLoader ();
+XSLoader::load( __PACKAGE__, $VERSION );
+
+require Exporter;
+use base qw/Exporter/;
+
+# Public, encouraged API is exported by default
+
+our @EXPORT = qw(
+ decode decode_utf8 encode encode_utf8 str2bytes bytes2str
+ encodings find_encoding clone_encoding
+);
+our @FB_FLAGS = qw(
+ DIE_ON_ERR WARN_ON_ERR RETURN_ON_ERR LEAVE_SRC
+ PERLQQ HTMLCREF XMLCREF STOP_AT_PARTIAL
+);
+our @FB_CONSTS = qw(
+ FB_DEFAULT FB_CROAK FB_QUIET FB_WARN
+ FB_PERLQQ FB_HTMLCREF FB_XMLCREF
+);
+our @EXPORT_OK = (
+ qw(
+ _utf8_off _utf8_on define_encoding from_to is_16bit is_8bit
+ is_utf8 perlio_ok resolve_alias utf8_downgrade utf8_upgrade
+ ),
+ @FB_FLAGS, @FB_CONSTS,
+);
+
+our %EXPORT_TAGS = (
+ all => [ @EXPORT, @EXPORT_OK ],
+ default => [ @EXPORT ],
+ fallbacks => [ @FB_CONSTS ],
+ fallback_all => [ @FB_CONSTS, @FB_FLAGS ],
+);
+
+# Documentation moved after __END__ for speed - NI-S
+
+our $ON_EBCDIC = ( ord("A") == 193 );
+
+use Encode::Alias;
+
+# Make a %Encoding package variable to allow a certain amount of cheating
+our %Encoding;
+our %ExtModule;
+require Encode::Config;
+# See
+# https://bugzilla.redhat.com/show_bug.cgi?id=435505#c2
+# to find why sig handers inside eval{} are disabled.
+eval {
+ local $SIG{__DIE__};
+ local $SIG{__WARN__};
+ require Encode::ConfigLocal;
+};
+
+sub encodings {
+ my $class = shift;
+ my %enc;
+ if ( @_ and $_[0] eq ":all" ) {
+ %enc = ( %Encoding, %ExtModule );
+ }
+ else {
+ %enc = %Encoding;
+ for my $mod ( map { m/::/o ? $_ : "Encode::$_" } @_ ) {
+ DEBUG and warn $mod;
+ for my $enc ( keys %ExtModule ) {
+ $ExtModule{$enc} eq $mod and $enc{$enc} = $mod;
+ }
+ }
+ }
+ return sort { lc $a cmp lc $b }
+ grep { !/^(?:Internal|Unicode|Guess)$/o } keys %enc;
+}
+
+sub perlio_ok {
+ my $obj = ref( $_[0] ) ? $_[0] : find_encoding( $_[0] );
+ $obj->can("perlio_ok") and return $obj->perlio_ok();
+ return 0; # safety net
+}
+
+sub define_encoding {
+ my $obj = shift;
+ my $name = shift;
+ $Encoding{$name} = $obj;
+ my $lc = lc($name);
+ define_alias( $lc => $obj ) unless $lc eq $name;
+ while (@_) {
+ my $alias = shift;
+ define_alias( $alias, $obj );
+ }
+ return $obj;
+}
+
+sub getEncoding {
+ my ( $class, $name, $skip_external ) = @_;
+
+ ref($name) && $name->can('renew') and return $name;
+ exists $Encoding{$name} and return $Encoding{$name};
+ my $lc = lc $name;
+ exists $Encoding{$lc} and return $Encoding{$lc};
+
+ my $oc = $class->find_alias($name);
+ defined($oc) and return $oc;
+ $lc ne $name and $oc = $class->find_alias($lc);
+ defined($oc) and return $oc;
+
+ unless ($skip_external) {
+ if ( my $mod = $ExtModule{$name} || $ExtModule{$lc} ) {
+ $mod =~ s,::,/,g;
+ $mod .= '.pm';
+ eval { require $mod; };
+ exists $Encoding{$name} and return $Encoding{$name};
+ }
+ }
+ return;
+}
+
+sub find_encoding($;$) {
+ my ( $name, $skip_external ) = @_;
+ return __PACKAGE__->getEncoding( $name, $skip_external );
+}
+
+sub resolve_alias($) {
+ my $obj = find_encoding(shift);
+ defined $obj and return $obj->name;
+ return;
+}
+
+sub clone_encoding($) {
+ my $obj = find_encoding(shift);
+ ref $obj or return;
+ eval { require Storable };
+ $@ and return;
+ return Storable::dclone($obj);
+}
+
+sub encode($$;$) {
+ my ( $name, $string, $check ) = @_;
+ return undef unless defined $string;
+ $string .= '' if ref $string; # stringify;
+ $check ||= 0;
+ unless ( defined $name ) {
+ require Carp;
+ Carp::croak("Encoding name should not be undef");
+ }
+ my $enc = find_encoding($name);
+ unless ( defined $enc ) {
+ require Carp;
+ Carp::croak("Unknown encoding '$name'");
+ }
+ my $octets = $enc->encode( $string, $check );
+ $_[1] = $string if $check and !ref $check and !( $check & LEAVE_SRC() );
+ return $octets;
+}
+*str2bytes = \&encode;
+
+sub decode($$;$) {
+ my ( $name, $octets, $check ) = @_;
+ return undef unless defined $octets;
+ $octets .= '' if ref $octets;
+ $check ||= 0;
+ my $enc = find_encoding($name);
+ unless ( defined $enc ) {
+ require Carp;
+ Carp::croak("Unknown encoding '$name'");
+ }
+ my $string = $enc->decode( $octets, $check );
+ $_[1] = $octets if $check and !ref $check and !( $check & LEAVE_SRC() );
+ return $string;
+}
+*bytes2str = \&decode;
+
+sub from_to($$$;$) {
+ my ( $string, $from, $to, $check ) = @_;
+ return undef unless defined $string;
+ $check ||= 0;
+ my $f = find_encoding($from);
+ unless ( defined $f ) {
+ require Carp;
+ Carp::croak("Unknown encoding '$from'");
+ }
+ my $t = find_encoding($to);
+ unless ( defined $t ) {
+ require Carp;
+ Carp::croak("Unknown encoding '$to'");
+ }
+ my $uni = $f->decode($string);
+ $_[0] = $string = $t->encode( $uni, $check );
+ return undef if ( $check && length($uni) );
+ return defined( $_[0] ) ? length($string) : undef;
+}
+
+sub encode_utf8($) {
+ my ($str) = @_;
+ utf8::encode($str);
+ return $str;
+}
+
+sub decode_utf8($;$) {
+ my ( $str, $check ) = @_;
+ return $str if is_utf8($str);
+ if ($check) {
+ return decode( "utf8", $str, $check );
+ }
+ else {
+ return decode( "utf8", $str );
+ return $str;
+ }
+}
+
+predefine_encodings(1);
+
+#
+# This is to restore %Encoding if really needed;
+#
+
+sub predefine_encodings {
+ require Encode::Encoding;
+ no warnings 'redefine';
+ my $use_xs = shift;
+ if ($ON_EBCDIC) {
+
+ # was in Encode::UTF_EBCDIC
+ package Encode::UTF_EBCDIC;
+ push @Encode::UTF_EBCDIC::ISA, 'Encode::Encoding';
+ *decode = sub {
+ my ( $obj, $str, $chk ) = @_;
+ my $res = '';
+ for ( my $i = 0 ; $i < length($str) ; $i++ ) {
+ $res .=
+ chr(
+ utf8::unicode_to_native( ord( substr( $str, $i, 1 ) ) )
+ );
+ }
+ $_[1] = '' if $chk;
+ return $res;
+ };
+ *encode = sub {
+ my ( $obj, $str, $chk ) = @_;
+ my $res = '';
+ for ( my $i = 0 ; $i < length($str) ; $i++ ) {
+ $res .=
+ chr(
+ utf8::native_to_unicode( ord( substr( $str, $i, 1 ) ) )
+ );
+ }
+ $_[1] = '' if $chk;
+ return $res;
+ };
+ $Encode::Encoding{Unicode} =
+ bless { Name => "UTF_EBCDIC" } => "Encode::UTF_EBCDIC";
+ }
+ else {
+
+ package Encode::Internal;
+ push @Encode::Internal::ISA, 'Encode::Encoding';
+ *decode = sub {
+ my ( $obj, $str, $chk ) = @_;
+ utf8::upgrade($str);
+ $_[1] = '' if $chk;
+ return $str;
+ };
+ *encode = \&decode;
+ $Encode::Encoding{Unicode} =
+ bless { Name => "Internal" } => "Encode::Internal";
+ }
+
+ {
+
+ # was in Encode::utf8
+ package Encode::utf8;
+ push @Encode::utf8::ISA, 'Encode::Encoding';
+
+ #
+ if ($use_xs) {
+ Encode::DEBUG and warn __PACKAGE__, " XS on";
+ *decode = \&decode_xs;
+ *encode = \&encode_xs;
+ }
+ else {
+ Encode::DEBUG and warn __PACKAGE__, " XS off";
+ *decode = sub {
+ my ( $obj, $octets, $chk ) = @_;
+ my $str = Encode::decode_utf8($octets);
+ if ( defined $str ) {
+ $_[1] = '' if $chk;
+ return $str;
+ }
+ return undef;
+ };
+ *encode = sub {
+ my ( $obj, $string, $chk ) = @_;
+ my $octets = Encode::encode_utf8($string);
+ $_[1] = '' if $chk;
+ return $octets;
+ };
+ }
+ *cat_decode = sub { # ($obj, $dst, $src, $pos, $trm, $chk)
+ # currently ignores $chk
+ my ( $obj, undef, undef, $pos, $trm ) = @_;
+ my ( $rdst, $rsrc, $rpos ) = \@_[ 1, 2, 3 ];
+ use bytes;
+ if ( ( my $npos = index( $$rsrc, $trm, $pos ) ) >= 0 ) {
+ $$rdst .=
+ substr( $$rsrc, $pos, $npos - $pos + length($trm) );
+ $$rpos = $npos + length($trm);
+ return 1;
+ }
+ $$rdst .= substr( $$rsrc, $pos );
+ $$rpos = length($$rsrc);
+ return '';
+ };
+ $Encode::Encoding{utf8} =
+ bless { Name => "utf8" } => "Encode::utf8";
+ $Encode::Encoding{"utf-8-strict"} =
+ bless { Name => "utf-8-strict", strict_utf8 => 1 } =>
+ "Encode::utf8";
+ }
+}
+
+1;
+
+__END__
+
+=head1 NAME
+
+Encode - character encodings
+
+=head1 SYNOPSIS
+
+ use Encode;
+
+=head2 Table of Contents
+
+Encode consists of a collection of modules whose details are too big
+to fit in one document. This POD itself explains the top-level APIs
+and general topics at a glance. For other topics and more details,
+see the PODs below:
+
+ Name Description
+ --------------------------------------------------------
+ Encode::Alias Alias definitions to encodings
+ Encode::Encoding Encode Implementation Base Class
+ Encode::Supported List of Supported Encodings
+ Encode::CN Simplified Chinese Encodings
+ Encode::JP Japanese Encodings
+ Encode::KR Korean Encodings
+ Encode::TW Traditional Chinese Encodings
+ --------------------------------------------------------
+
+=head1 DESCRIPTION
+
+The C<Encode> module provides the interfaces between Perl's strings
+and the rest of the system. Perl strings are sequences of
+B<characters>.
+
+The repertoire of characters that Perl can represent is at least that
+defined by the Unicode Consortium. On most platforms the ordinal
+values of the characters (as returned by C<ord(ch)>) is the "Unicode
+codepoint" for the character (the exceptions are those platforms where
+the legacy encoding is some variant of EBCDIC rather than a super-set
+of ASCII - see L<perlebcdic>).
+
+Traditionally, computer data has been moved around in 8-bit chunks
+often called "bytes". These chunks are also known as "octets" in
+networking standards. Perl is widely used to manipulate data of many
+types - not only strings of characters representing human or computer
+languages but also "binary" data being the machine's representation of
+numbers, pixels in an image - or just about anything.
+
+When Perl is processing "binary data", the programmer wants Perl to
+process "sequences of bytes". This is not a problem for Perl - as a
+byte has 256 possible values, it easily fits in Perl's much larger
+"logical character".
+
+=head2 TERMINOLOGY
+
+=over 2
+
+=item *
+
+I<character>: a character in the range 0..(2**32-1) (or more).
+(What Perl's strings are made of.)
+
+=item *
+
+I<byte>: a character in the range 0..255
+(A special case of a Perl character.)
+
+=item *
+
+I<octet>: 8 bits of data, with ordinal values 0..255
+(Term for bytes passed to or from a non-Perl context, e.g. a disk file.)
+
+=back
+
+=head1 PERL ENCODING API
+
+=over 2
+
+=item $octets = encode(ENCODING, $string [, CHECK])
+
+Encodes a string from Perl's internal form into I<ENCODING> and returns
+a sequence of octets. ENCODING can be either a canonical name or
+an alias. For encoding names and aliases, see L</"Defining Aliases">.
+For CHECK, see L</"Handling Malformed Data">.
+
+For example, to convert a string from Perl's internal format to
+iso-8859-1 (also known as Latin1),
+
+ $octets = encode("iso-8859-1", $string);
+
+B<CAVEAT>: When you run C<$octets = encode("utf8", $string)>, then
+$octets B<may not be equal to> $string. Though they both contain the
+same data, the UTF8 flag for $octets is B<always> off. When you
+encode anything, UTF8 flag of the result is always off, even when it
+contains completely valid utf8 string. See L</"The UTF8 flag"> below.
+
+If the $string is C<undef> then C<undef> is returned.
+
+=item $string = decode(ENCODING, $octets [, CHECK])
+
+Decodes a sequence of octets assumed to be in I<ENCODING> into Perl's
+internal form and returns the resulting string. As in encode(),
+ENCODING can be either a canonical name or an alias. For encoding names
+and aliases, see L</"Defining Aliases">. For CHECK, see
+L</"Handling Malformed Data">.
+
+For example, to convert ISO-8859-1 data to a string in Perl's internal format:
+
+ $string = decode("iso-8859-1", $octets);
+
+B<CAVEAT>: When you run C<$string = decode("utf8", $octets)>, then $string
+B<may not be equal to> $octets. Though they both contain the same data,
+the UTF8 flag for $string is on unless $octets entirely consists of
+ASCII data (or EBCDIC on EBCDIC machines). See L</"The UTF8 flag">
+below.
+
+If the $string is C<undef> then C<undef> is returned.
+
+=item [$obj =] find_encoding(ENCODING)
+
+Returns the I<encoding object> corresponding to ENCODING. Returns
+undef if no matching ENCODING is find.
+
+This object is what actually does the actual (en|de)coding.
+
+ $utf8 = decode($name, $bytes);
+
+is in fact
+
+ $utf8 = do{
+ $obj = find_encoding($name);
+ croak qq(encoding "$name" not found) unless ref $obj;
+ $obj->decode($bytes)
+ };
+
+with more error checking.
+
+Therefore you can save time by reusing this object as follows;
+
+ my $enc = find_encoding("iso-8859-1");
+ while(<>){
+ my $utf8 = $enc->decode($_);
+ # and do someting with $utf8;
+ }
+
+Besides C<< ->decode >> and C<< ->encode >>, other methods are
+available as well. For instance, C<< -> name >> returns the canonical
+name of the encoding object.
+
+ find_encoding("latin1")->name; # iso-8859-1
+
+See L<Encode::Encoding> for details.
+
+=item [$length =] from_to($octets, FROM_ENC, TO_ENC [, CHECK])
+
+Converts B<in-place> data between two encodings. The data in $octets
+must be encoded as octets and not as characters in Perl's internal
+format. For example, to convert ISO-8859-1 data to Microsoft's CP1250
+encoding:
+
+ from_to($octets, "iso-8859-1", "cp1250");
+
+and to convert it back:
+
+ from_to($octets, "cp1250", "iso-8859-1");
+
+Note that because the conversion happens in place, the data to be
+converted cannot be a string constant; it must be a scalar variable.
+
+from_to() returns the length of the converted string in octets on
+success, I<undef> on error.
+
+B<CAVEAT>: The following operations look the same but are not quite so;
+
+ from_to($data, "iso-8859-1", "utf8"); #1
+ $data = decode("iso-8859-1", $data); #2
+
+Both #1 and #2 make $data consist of a completely valid UTF-8 string
+but only #2 turns UTF8 flag on. #1 is equivalent to
+
+ $data = encode("utf8", decode("iso-8859-1", $data));
+
+See L</"The UTF8 flag"> below.
+
+Also note that
+
+ from_to($octets, $from, $to, $check);
+
+is equivalent to
+
+ $octets = encode($to, decode($from, $octets), $check);
+
+Yes, it does not respect the $check during decoding. It is
+deliberately done that way. If you need minute control, C<decode>
+then C<encode> as follows;
+
+ $octets = encode($to, decode($from, $octets, $check_from), $check_to);
+
+=item $octets = encode_utf8($string);
+
+Equivalent to C<$octets = encode("utf8", $string);> The characters
+that comprise $string are encoded in Perl's internal format and the
+result is returned as a sequence of octets. All possible
+characters have a UTF-8 representation so this function cannot fail.
+
+
+=item $string = decode_utf8($octets [, CHECK]);
+
+equivalent to C<$string = decode("utf8", $octets [, CHECK])>.
+The sequence of octets represented by
+$octets is decoded from UTF-8 into a sequence of logical
+characters. Not all sequences of octets form valid UTF-8 encodings, so
+it is possible for this call to fail. For CHECK, see
+L</"Handling Malformed Data">.
+
+=back
+
+=head2 Listing available encodings
+
+ use Encode;
+ @list = Encode->encodings();
+
+Returns a list of the canonical names of the available encodings that
+are loaded. To get a list of all available encodings including the
+ones that are not loaded yet, say
+
+ @all_encodings = Encode->encodings(":all");
+
+Or you can give the name of a specific module.
+
+ @with_jp = Encode->encodings("Encode::JP");
+
+When "::" is not in the name, "Encode::" is assumed.
+
+ @ebcdic = Encode->encodings("EBCDIC");
+
+To find out in detail which encodings are supported by this package,
+see L<Encode::Supported>.
+
+=head2 Defining Aliases
+
+To add a new alias to a given encoding, use:
+
+ use Encode;
+ use Encode::Alias;
+ define_alias(newName => ENCODING);
+
+After that, newName can be used as an alias for ENCODING.
+ENCODING may be either the name of an encoding or an
+I<encoding object>
+
+But before you do so, make sure the alias is nonexistent with
+C<resolve_alias()>, which returns the canonical name thereof.
+i.e.
+
+ Encode::resolve_alias("latin1") eq "iso-8859-1" # true
+ Encode::resolve_alias("iso-8859-12") # false; nonexistent
+ Encode::resolve_alias($name) eq $name # true if $name is canonical
+
+resolve_alias() does not need C<use Encode::Alias>; it can be
+exported via C<use Encode qw(resolve_alias)>.
+
+See L<Encode::Alias> for details.
+
+=head2 Finding IANA Character Set Registry names
+
+The canonical name of a given encoding does not necessarily agree with
+IANA IANA Character Set Registry, commonly seen as C<< Content-Type:
+text/plain; charset=I<whatever> >>. For most cases canonical names
+work but sometimes it does not (notably 'utf-8-strict').
+
+Therefore as of Encode version 2.21, a new method C<mime_name()> is added.
+
+ use Encode;
+ my $enc = find_encoding('UTF-8');
+ warn $enc->name; # utf-8-strict
+ warn $enc->mime_name; # UTF-8
+
+See also: L<Encode::Encoding>
+
+=head1 Encoding via PerlIO
+
+If your perl supports I<PerlIO> (which is the default), you can use a
+PerlIO layer to decode and encode directly via a filehandle. The
+following two examples are totally identical in their functionality.
+
+ # via PerlIO
+ open my $in, "<:encoding(shiftjis)", $infile or die;
+ open my $out, ">:encoding(euc-jp)", $outfile or die;
+ while(<$in>){ print $out $_; }
+
+ # via from_to
+ open my $in, "<", $infile or die;
+ open my $out, ">", $outfile or die;
+ while(<$in>){
+ from_to($_, "shiftjis", "euc-jp", 1);
+ print $out $_;
+ }
+
+Unfortunately, it may be that encodings are PerlIO-savvy. You can check
+if your encoding is supported by PerlIO by calling the C<perlio_ok>
+method.
+
+ Encode::perlio_ok("hz"); # False
+ find_encoding("euc-cn")->perlio_ok; # True where PerlIO is available
+
+ use Encode qw(perlio_ok); # exported upon request
+ perlio_ok("euc-jp")
+
+Fortunately, all encodings that come with Encode core are PerlIO-savvy
+except for hz and ISO-2022-kr. For gory details, see
+L<Encode::Encoding> and L<Encode::PerlIO>.
+
+=head1 Handling Malformed Data
+
+The optional I<CHECK> argument tells Encode what to do when it
+encounters malformed data. Without CHECK, Encode::FB_DEFAULT ( == 0 )
+is assumed.
+
+As of version 2.12 Encode supports coderef values for CHECK. See below.
+
+=over 2
+
+=item B<NOTE:> Not all encoding support this feature
+
+Some encodings ignore I<CHECK> argument. For example,
+L<Encode::Unicode> ignores I<CHECK> and it always croaks on error.
+
+=back
+
+Now here is the list of I<CHECK> values available
+
+=over 2
+
+=item I<CHECK> = Encode::FB_DEFAULT ( == 0)
+
+If I<CHECK> is 0, (en|de)code will put a I<substitution character> in
+place of a malformed character. When you encode, E<lt>subcharE<gt>
+will be used. When you decode the code point C<0xFFFD> is used. If
+the data is supposed to be UTF-8, an optional lexical warning
+(category utf8) is given.
+
+=item I<CHECK> = Encode::FB_CROAK ( == 1)
+
+If I<CHECK> is 1, methods will die on error immediately with an error
+message. Therefore, when I<CHECK> is set to 1, you should trap the
+error with eval{} unless you really want to let it die.
+
+=item I<CHECK> = Encode::FB_QUIET
+
+If I<CHECK> is set to Encode::FB_QUIET, (en|de)code will immediately
+return the portion of the data that has been processed so far when an
+error occurs. The data argument will be overwritten with everything
+after that point (that is, the unprocessed part of data). This is
+handy when you have to call decode repeatedly in the case where your
+source data may contain partial multi-byte character sequences,
+(i.e. you are reading with a fixed-width buffer). Here is a sample
+code that does exactly this:
+
+ my $buffer = ''; my $string = '';
+ while(read $fh, $buffer, 256, length($buffer)){
+ $string .= decode($encoding, $buffer, Encode::FB_QUIET);
+ # $buffer now contains the unprocessed partial character
+ }
+
+=item I<CHECK> = Encode::FB_WARN
+
+This is the same as above, except that it warns on error. Handy when
+you are debugging the mode above.
+
+=item perlqq mode (I<CHECK> = Encode::FB_PERLQQ)
+
+=item HTML charref mode (I<CHECK> = Encode::FB_HTMLCREF)
+
+=item XML charref mode (I<CHECK> = Encode::FB_XMLCREF)
+
+For encodings that are implemented by Encode::XS, CHECK ==
+Encode::FB_PERLQQ turns (en|de)code into C<perlqq> fallback mode.
+
+When you decode, C<\xI<HH>> will be inserted for a malformed character,
+where I<HH> is the hex representation of the octet that could not be
+decoded to utf8. And when you encode, C<\x{I<HHHH>}> will be inserted,
+where I<HHHH> is the Unicode ID of the character that cannot be found
+in the character repertoire of the encoding.
+
+HTML/XML character reference modes are about the same, in place of
+C<\x{I<HHHH>}>, HTML uses C<&#I<NNN>;> where I<NNN> is a decimal number and
+XML uses C<&#xI<HHHH>;> where I<HHHH> is the hexadecimal number.
+
+In Encode 2.10 or later, C<LEAVE_SRC> is also implied.
+
+=item The bitmask
+
+These modes are actually set via a bitmask. Here is how the FB_XX
+constants are laid out. You can import the FB_XX constants via
+C<use Encode qw(:fallbacks)>; you can import the generic bitmask
+constants via C<use Encode qw(:fallback_all)>.
+
+ FB_DEFAULT FB_CROAK FB_QUIET FB_WARN FB_PERLQQ
+ DIE_ON_ERR 0x0001 X
+ WARN_ON_ERR 0x0002 X
+ RETURN_ON_ERR 0x0004 X X
+ LEAVE_SRC 0x0008 X
+ PERLQQ 0x0100 X
+ HTMLCREF 0x0200
+ XMLCREF 0x0400
+
+=back
+
+=over 2
+
+=item Encode::LEAVE_SRC
+
+If the C<Encode::LEAVE_SRC> bit is not set, but I<CHECK> is, then the second
+argument to C<encode()> or C<decode()> may be assigned to by the functions. If
+you're not interested in this, then bitwise-or the bitmask with it.
+
+=back
+
+=head2 coderef for CHECK
+
+As of Encode 2.12 CHECK can also be a code reference which takes the
+ord value of unmapped caharacter as an argument and returns a string
+that represents the fallback character. For instance,
+
+ $ascii = encode("ascii", $utf8, sub{ sprintf "<U+%04X>", shift });
+
+Acts like FB_PERLQQ but E<lt>U+I<XXXX>E<gt> is used instead of
+\x{I<XXXX>}.
+
+=head1 Defining Encodings
+
+To define a new encoding, use:
+
+ use Encode qw(define_encoding);
+ define_encoding($object, 'canonicalName' [, alias...]);
+
+I<canonicalName> will be associated with I<$object>. The object
+should provide the interface described in L<Encode::Encoding>.
+If more than two arguments are provided then additional
+arguments are taken as aliases for I<$object>.
+
+See L<Encode::Encoding> for more details.
+
+=head1 The UTF8 flag
+
+Before the introduction of Unicode support in perl, The C<eq> operator
+just compared the strings represented by two scalars. Beginning with
+perl 5.8, C<eq> compares two strings with simultaneous consideration of
+I<the UTF8 flag>. To explain why we made it so, I will quote page 402 of
+C<Programming Perl, 3rd ed.>
+
+=over 2
+
+=item Goal #1:
+
+Old byte-oriented programs should not spontaneously break on the old
+byte-oriented data they used to work on.
+
+=item Goal #2:
+
+Old byte-oriented programs should magically start working on the new
+character-oriented data when appropriate.
+
+=item Goal #3:
+
+Programs should run just as fast in the new character-oriented mode
+as in the old byte-oriented mode.
+
+=item Goal #4:
+
+Perl should remain one language, rather than forking into a
+byte-oriented Perl and a character-oriented Perl.
+
+=back
+
+Back when C<Programming Perl, 3rd ed.> was written, not even Perl 5.6.0
+was born and many features documented in the book remained
+unimplemented for a long time. Perl 5.8 corrected this and the introduction
+of the UTF8 flag is one of them. You can think of this perl notion as of a
+byte-oriented mode (UTF8 flag off) and a character-oriented mode (UTF8
+flag on).
+
+Here is how Encode takes care of the UTF8 flag.
+
+=over 2
+
+=item *
+
+When you encode, the resulting UTF8 flag is always off.
+
+=item *
+
+When you decode, the resulting UTF8 flag is on unless you can
+unambiguously represent data. Here is the definition of
+dis-ambiguity.
+
+After C<$utf8 = decode('foo', $octet);>,
+
+ When $octet is... The UTF8 flag in $utf8 is
+ ---------------------------------------------
+ In ASCII only (or EBCDIC only) OFF
+ In ISO-8859-1 ON
+ In any other Encoding ON
+ ---------------------------------------------
+
+As you see, there is one exception, In ASCII. That way you can assume
+Goal #1. And with Encode Goal #2 is assumed but you still have to be
+careful in such cases mentioned in B<CAVEAT> paragraphs.
+
+This UTF8 flag is not visible in perl scripts, exactly for the same
+reason you cannot (or you I<don't have to>) see if a scalar contains a
+string, integer, or floating point number. But you can still peek
+and poke these if you will. See the section below.
+
+=back
+
+=head2 Messing with Perl's Internals
+
+The following API uses parts of Perl's internals in the current
+implementation. As such, they are efficient but may change.
+
+=over 2
+
+=item is_utf8(STRING [, CHECK])
+
+[INTERNAL] Tests whether the UTF8 flag is turned on in the STRING.
+If CHECK is true, also checks the data in STRING for being well-formed
+UTF-8. Returns true if successful, false otherwise.
+
+As of perl 5.8.1, L<utf8> also has utf8::is_utf8().
+
+=item _utf8_on(STRING)
+
+[INTERNAL] Turns on the UTF8 flag in STRING. The data in STRING is
+B<not> checked for being well-formed UTF-8. Do not use unless you
+B<know> that the STRING is well-formed UTF-8. Returns the previous
+state of the UTF8 flag (so please don't treat the return value as
+indicating success or failure), or C<undef> if STRING is not a string.
+
+This function does not work on tainted values.
+
+=item _utf8_off(STRING)
+
+[INTERNAL] Turns off the UTF8 flag in STRING. Do not use frivolously.
+Returns the previous state of the UTF8 flag (so please don't treat the
+return value as indicating success or failure), or C<undef> if STRING is
+not a string.
+
+This function does not work on tainted values.
+
+=back
+
+=head1 UTF-8 vs. utf8 vs. UTF8
+
+ ....We now view strings not as sequences of bytes, but as sequences
+ of numbers in the range 0 .. 2**32-1 (or in the case of 64-bit
+ computers, 0 .. 2**64-1) -- Programming Perl, 3rd ed.
+
+That has been the perl's notion of UTF-8 but official UTF-8 is more
+strict; Its ranges is much narrower (0 .. 10FFFF), some sequences are
+not allowed (i.e. Those used in the surrogate pair, 0xFFFE, et al).
+
+Now that is overruled by Larry Wall himself.
+
+ From: Larry Wall <larry@wall.org>
+ Date: December 04, 2004 11:51:58 JST
+ To: perl-unicode@perl.org
+ Subject: Re: Make Encode.pm support the real UTF-8
+ Message-Id: <20041204025158.GA28754@wall.org>
+
+ On Fri, Dec 03, 2004 at 10:12:12PM +0000, Tim Bunce wrote:
+ : I've no problem with 'utf8' being perl's unrestricted uft8 encoding,
+ : but "UTF-8" is the name of the standard and should give the
+ : corresponding behaviour.
+
+ For what it's worth, that's how I've always kept them straight in my
+ head.
+
+ Also for what it's worth, Perl 6 will mostly default to strict but
+ make it easy to switch back to lax.
+
+ Larry
+
+Do you copy? As of Perl 5.8.7, B<UTF-8> means strict, official UTF-8
+while B<utf8> means liberal, lax, version thereof. And Encode version
+2.10 or later thus groks the difference between C<UTF-8> and C"utf8".
+
+ encode("utf8", "\x{FFFF_FFFF}", 1); # okay
+ encode("UTF-8", "\x{FFFF_FFFF}", 1); # croaks
+
+C<UTF-8> in Encode is actually a canonical name for C<utf-8-strict>.
+Yes, the hyphen between "UTF" and "8" is important. Without it Encode
+goes "liberal"
+
+ find_encoding("UTF-8")->name # is 'utf-8-strict'
+ find_encoding("utf-8")->name # ditto. names are case insensitive
+ find_encoding("utf_8")->name # ditto. "_" are treated as "-"
+ find_encoding("UTF8")->name # is 'utf8'.
+
+The UTF8 flag is internally called UTF8, without a hyphen. It indicates
+whether a string is internally encoded as utf8, also without a hypen.
+
+=head1 SEE ALSO
+
+L<Encode::Encoding>,
+L<Encode::Supported>,
+L<Encode::PerlIO>,
+L<encoding>,
+L<perlebcdic>,
+L<perlfunc/open>,
+L<perlunicode>, L<perluniintro>, L<perlunifaq>, L<perlunitut>
+L<utf8>,
+the Perl Unicode Mailing List E<lt>perl-unicode@perl.orgE<gt>
+
+=head1 MAINTAINER
+
+This project was originated by Nick Ing-Simmons and later maintained
+by Dan Kogai E<lt>dankogai@dan.co.jpE<gt>. See AUTHORS for a full
+list of people involved. For any questions, use
+E<lt>perl-unicode@perl.orgE<gt> so we can all share.
+
+While Dan Kogai retains the copyright as a maintainer, the credit
+should go to all those involoved. See AUTHORS for those submitted
+codes.
+
+=head1 COPYRIGHT
+
+Copyright 2002-2006 Dan Kogai E<lt>dankogai@dan.co.jpE<gt>
+
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself.
+
+=cut