package Encode;
+use strict;
-$VERSION = 0.01;
+our $VERSION = '0.02';
require DynaLoader;
require Exporter;
-@ISA = qw(Exporter DynaLoader);
+our @ISA = qw(Exporter DynaLoader);
-@EXPORT_OK =
+# Public, encouraged API is exported by default
+our @EXPORT = qw (
+ encode
+ decode
+ encode_utf8
+ decode_utf8
+ find_encoding
+ encodings
+);
+
+our @EXPORT_OK =
qw(
- bytes_to_utf8
- utf8_to_bytes
- chars_to_utf8
- utf8_to_chars
- utf8_to_chars_check
- bytes_to_chars
- chars_to_bytes
+ define_encoding
+ define_alias
from_to
is_utf8
- on_utf8
- off_utf8
- utf_to_utf
- encodings
+ is_8bit
+ is_16bit
+ utf8_upgrade
+ utf8_downgrade
+ _utf8_on
+ _utf8_off
);
bootstrap Encode ();
-=pod
+# Documentation moved after __END__ for speed - NI-S
+
+use Carp;
+
+# Make a %encoding package variable to allow a certain amount of cheating
+our %encoding;
+my @alias; # ordered matching list
+my %alias; # cached known aliases
+ # 0 1 2 3 4 5 6 7 8 9 10
+our @latin2iso_num = ( 0, 1, 2, 3, 4, 9, 10, 13, 14, 15, 16 );
+
+
+sub encodings
+{
+ my ($class) = @_;
+ return keys %encoding;
+}
+
+sub findAlias
+{
+ my $class = shift;
+ local $_ = shift;
+ unless (exists $alias{$_})
+ {
+ for (my $i=0; $i < @alias; $i += 2)
+ {
+ my $alias = $alias[$i];
+ my $val = $alias[$i+1];
+ my $new;
+ if (ref($alias) eq 'Regexp' && $_ =~ $alias)
+ {
+ $new = eval $val;
+ }
+ elsif (ref($alias) eq 'CODE')
+ {
+ $new = &{$alias}($val)
+ }
+ elsif (lc($_) eq lc($alias))
+ {
+ $new = $val;
+ }
+ if (defined($new))
+ {
+ next if $new eq $_; # avoid (direct) recursion on bugs
+ my $enc = (ref($new)) ? $new : find_encoding($new);
+ if ($enc)
+ {
+ $alias{$_} = $enc;
+ last;
+ }
+ }
+ }
+ }
+ return $alias{$_};
+}
+
+sub define_alias
+{
+ while (@_)
+ {
+ my ($alias,$name) = splice(@_,0,2);
+ push(@alias, $alias => $name);
+ }
+}
+
+# Allow variants of iso-8859-1 etc.
+define_alias( qr/^iso[-_]?(\d+)[-_](\d+)$/i => '"iso-$1-$2"' );
+
+# At least HP-UX has these.
+define_alias( qr/^iso8859(\d+)$/i => '"iso-8859-$1"' );
+
+# This is a font issue, not an encoding issue.
+# (The currency symbol of the Latin 1 upper half
+# has been redefined as the euro symbol.)
+define_alias( qr/^(.+)\@euro$/i => '"$1"' );
+
+# Allow latin-1 style names as well
+define_alias( qr/^(?:iso[-_]?)?latin[-_]?(\d+)$/i => '"iso-8859-$latin2iso_num[$1]"' );
+
+# Common names for non-latin prefered MIME names
+define_alias( 'ascii' => 'US-ascii',
+ 'cyrillic' => 'iso-8859-5',
+ 'arabic' => 'iso-8859-6',
+ 'greek' => 'iso-8859-7',
+ 'hebrew' => 'iso-8859-8');
+
+# At least AIX has IBM-NNN (surprisingly...) instead of cpNNN.
+define_alias( qr/^ibm[-_]?(\d\d\d\d?)$/i => '"cp$1"');
+
+# Standardize on the dashed versions.
+define_alias( qr/^utf8$/i => 'utf-8' );
+define_alias( qr/^koi8r$/i => 'koi8-r' );
+
+# TODO: the HP-UX '8' encodings: arabic8 greek8 hebrew8 roman8 turkish8
+# TODO: the Thai Encoding tis620
+# TODO: the Chinese Encoding gb18030
+# TODO: what is the Japanese 'ujis' encoding seen in some Linuxes?
+
+# Map white space and _ to '-'
+define_alias( qr/^(\S+)[\s_]+(.*)$/i => '"$1-$2"' );
+
+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) = @_;
+ my $enc;
+ if (ref($name) && $name->can('new_sequence'))
+ {
+ return $name;
+ }
+ if (exists $encoding{$name})
+ {
+ return $encoding{$name};
+ }
+ else
+ {
+ return $class->findAlias($name);
+ }
+}
+
+sub find_encoding
+{
+ my ($name) = @_;
+ return __PACKAGE__->getEncoding($name);
+}
+
+sub encode
+{
+ my ($name,$string,$check) = @_;
+ my $enc = find_encoding($name);
+ croak("Unknown encoding '$name'") unless defined $enc;
+ my $octets = $enc->encode($string,$check);
+ return undef if ($check && length($string));
+ return $octets;
+}
+
+sub decode
+{
+ my ($name,$octets,$check) = @_;
+ my $enc = find_encoding($name);
+ croak("Unknown encoding '$name'") unless defined $enc;
+ my $string = $enc->decode($octets,$check);
+ return undef if ($check && length($octets));
+ return $string;
+}
+
+sub from_to
+{
+ my ($string,$from,$to,$check) = @_;
+ my $f = find_encoding($from);
+ croak("Unknown encoding '$from'") unless defined $f;
+ my $t = find_encoding($to);
+ croak("Unknown encoding '$to'") unless defined $t;
+ my $uni = $f->decode($string,$check);
+ return undef if ($check && length($string));
+ $string = $t->encode($uni,$check);
+ return undef if ($check && length($uni));
+ return length($_[0] = $string);
+}
+
+sub encode_utf8
+{
+ my ($str) = @_;
+ utf8::encode($str);
+ return $str;
+}
+
+sub decode_utf8
+{
+ my ($str) = @_;
+ return undef unless utf8::decode($str);
+ return $str;
+}
+
+package Encode::Encoding;
+# Base class for classes which implement encodings
+
+sub Define
+{
+ my $obj = shift;
+ my $canonical = shift;
+ $obj = bless { Name => $canonical },$obj unless ref $obj;
+ # warn "$canonical => $obj\n";
+ Encode::define_encoding($obj, $canonical, @_);
+}
+
+sub name { shift->{'Name'} }
+
+# Temporary legacy methods
+sub toUnicode { shift->decode(@_) }
+sub fromUnicode { shift->encode(@_) }
+
+sub new_sequence { return $_[0] }
+
+package Encode::XS;
+use base 'Encode::Encoding';
+
+package Encode::Internal;
+use base 'Encode::Encoding';
+
+# Dummy package that provides the encode interface but leaves data
+# as UTF-X encoded. It is here so that from_to() works.
+
+__PACKAGE__->Define('Internal');
+
+Encode::define_alias( 'Unicode' => 'Internal' ) if ord('A') == 65;
+
+sub decode
+{
+ my ($obj,$str,$chk) = @_;
+ utf8::upgrade($str);
+ $_[1] = '' if $chk;
+ return $str;
+}
+
+*encode = \&decode;
+
+package Encoding::Unicode;
+use base 'Encode::Encoding';
+
+__PACKAGE__->Define('Unicode') unless ord('A') == 65;
+
+sub decode
+{
+ my ($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 $res;
+}
+
+sub encode
+{
+ my ($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;
+}
+
+
+package Encode::utf8;
+use base 'Encode::Encoding';
+# package to allow long-hand
+# $octets = encode( utf8 => $string );
+#
+
+__PACKAGE__->Define(qw(UTF-8 utf8));
+
+sub decode
+{
+ my ($obj,$octets,$chk) = @_;
+ my $str = Encode::decode_utf8($octets);
+ if (defined $str)
+ {
+ $_[1] = '' if $chk;
+ return $str;
+ }
+ return undef;
+}
+
+sub encode
+{
+ my ($obj,$string,$chk) = @_;
+ my $octets = Encode::encode_utf8($string);
+ $_[1] = '' if $chk;
+ return $octets;
+}
+
+package Encode::iso10646_1;
+use base 'Encode::Encoding';
+# Encoding is 16-bit network order Unicode (no surogates)
+# Used for X font encodings
+
+__PACKAGE__->Define(qw(UCS-2 iso-10646-1));
+
+sub decode
+{
+ my ($obj,$str,$chk) = @_;
+ my $uni = '';
+ while (length($str))
+ {
+ my $code = unpack('n',substr($str,0,2,'')) & 0xffff;
+ $uni .= chr($code);
+ }
+ $_[1] = $str if $chk;
+ utf8::upgrade($uni);
+ return $uni;
+}
+
+sub encode
+{
+ my ($obj,$uni,$chk) = @_;
+ my $str = '';
+ while (length($uni))
+ {
+ my $ch = substr($uni,0,1,'');
+ my $x = ord($ch);
+ unless ($x < 32768)
+ {
+ last if ($chk);
+ $x = 0;
+ }
+ $str .= pack('n',$x);
+ }
+ $_[1] = $uni if $chk;
+ return $str;
+}
+
+# switch back to Encode package in case we ever add AutoLoader
+package Encode;
+
+1;
+
+__END__
=head1 NAME
Encode - character encodings
+=head1 SYNOPSIS
+
+ use Encode;
+
+=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>).
+
+Traditionaly 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 machines 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
+=over 4
=item *
-I<char>: a character in the range 0..maxint (at least 2**32-1)
+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. disk file.)
=back
general meant only for those who think they know what they are doing,
and such details may change in future releases.
-=head2 bytes
+=head1 ENCODINGS
+
+=head2 Characteristics of an Encoding
+
+An encoding has a "repertoire" of characters that it can represent,
+and for each representable character there is at least one sequence of
+octets that represents it.
+
+=head2 Types of Encodings
+
+Encodings can be divided into the following types:
=over 4
-=item *
+=item * Fixed length 8-bit (or less) encodings.
- bytes_to_utf8(STRING [, FROM])
+Each character is a single octet so may have a repertoire of up to
+256 characters. ASCII and iso-8859-* are typical examples.
-The bytes in STRING are recoded in-place into UTF-8. If no FROM is
-specified the bytes are expected to be encoded in US-ASCII or ISO
-8859-1 (Latin 1). Returns the new size of STRING, or C<undef> if
-there's a failure.
+=item * Fixed length 16-bit encodings
-[INTERNAL] Also the UTF-8 flag of STRING is turned on.
+Each character is two octets so may have a repertoire of up to
+65 536 characters. Unicode's UCS-2 is an example. Also used for
+encodings for East Asian languages.
-=item *
+=item * Fixed length 32-bit encodings.
- utf8_to_bytes(STRING [, TO [, CHECK]])
+Not really very "encoded" encodings. The Unicode code points
+are just represented as 4-octet integers. None the less because
+different architectures use different representations of integers
+(so called "endian") there at least two disctinct encodings.
-The UTF-8 in STRING is decoded in-place into bytes. If no TO encoding
-is specified the bytes are expected to be encoded in US-ASCII or ISO
-8859-1 (Latin 1). Returns the new size of STRING, or C<undef> if
-there's a failure.
+=item * Multi-byte encodings
-What if there are characters > 255? What if the UTF-8 in STRING is
-malformed? See L</"Handling Malformed Data">.
+The number of octets needed to represent a character varies.
+UTF-8 is a particularly complex but regular case of a multi-byte
+encoding. Several East Asian countries use a multi-byte encoding
+where 1-octet is used to cover western roman characters and Asian
+characters get 2-octets.
+(UTF-16 is strictly a multi-byte encoding taking either 2 or 4 octets
+to represent a Unicode code point.)
-[INTERNAL] The UTF-8 flag of STRING is not checked.
+=item * "Escape" encodings.
+
+These encodings embed "escape sequences" into the octet sequence
+which describe how the following octets are to be interpreted.
+The iso-2022-* family is typical. Following the escape sequence
+octets are encoded by an "embedded" encoding (which will be one
+of the above types) until another escape sequence switches to
+a different "embedded" encoding.
+
+These schemes are very flexible and can handle mixed languages but are
+very complex to process (and have state). No escape encodings are
+implemented for Perl yet.
=back
-=head2 chars
+=head2 Specifying Encodings
+
+Encodings can be specified to the API described below in two ways:
=over 4
-=item *
+=item 1. By name
+
+Encoding names are strings with characters taken from a restricted
+repertoire. See L</"Encoding Names">.
+
+=item 2. As an object
- chars_to_utf8(STRING)
+Encoding objects are returned by C<find_encoding($name)>.
-The chars in STRING are encoded in-place into UTF-8. Returns the new
-size of STRING, or C<undef> if there's a failure.
+=back
+
+=head2 Encoding Names
+
+Encoding names are case insensitive. White space in names is ignored.
+In addition an encoding may have aliases. Each encoding has one
+"canonical" name. The "canonical" name is chosen from the names of
+the encoding by picking the first in the following sequence:
+
+=over 4
+
+=item * The MIME name as defined in IETF RFC-XXXX.
-No assumptions are made on the encoding of the chars. If you want to
-assume that the chars are Unicode and to trap illegal Unicode
-characters, you must use C<from_to('Unicode', ...)>.
+=item * The name in the IANA registry.
-[INTERNAL] Also the UTF-8 flag of STRING is turned on.
+=item * The name used by the the organization that defined it.
+
+=back
+
+Because of all the alias issues, and because in the general case
+encodings have state C<Encode> uses the encoding object internally
+once an operation is in progress.
+
+=head1 PERL ENCODING API
+
+=head2 Generic Encoding Interface
=over 4
=item *
- utf8_to_chars(STRING)
+ $bytes = encode(ENCODING, $string[, CHECK])
-The UTF-8 in STRING is decoded in-place into chars. Returns the new
-size of STRING, or C<undef> if there's a failure.
+Encodes string from Perl's internal form into I<ENCODING> and returns
+a sequence of octets. For CHECK see L</"Handling Malformed Data">.
-If the UTF-8 in STRING is malformed C<undef> is returned, and also an
-optional lexical warning (category utf8) is given.
+=item *
-[INTERNAL] The UTF-8 flag of STRING is not checked.
+ $string = decode(ENCODING, $bytes[, CHECK])
+
+Decode sequence of octets assumed to be in I<ENCODING> into Perl's
+internal form and returns the resulting string. For CHECK see
+L</"Handling Malformed Data">.
=item *
- utf8_to_chars_check(STRING [, CHECK])
+ from_to($string, FROM_ENCODING, TO_ENCODING[, CHECK])
+
+Convert B<in-place> the data between two encodings. How did the data
+in $string originally get to be in FROM_ENCODING? Either using
+encode() or through PerlIO: See L</"Encoding and IO">. For CHECK
+see L</"Handling Malformed Data">.
+
+For example to convert ISO 8859-1 data to UTF-8:
-(Note that special naming of this interface since a two-argument
-utf8_to_chars() has different semantics.)
+ from_to($data, "iso-8859-1", "utf-8");
-The UTF-8 in STRING is decoded in-place into chars. Returns the new
-size of STRING, or C<undef> if there is a failure.
+and to convert it back:
-If the UTF-8 in STRING is malformed? See L</"Handling Malformed Data">.
+ from_to($data, "utf-8", "iso-8859-1");
-[INTERNAL] The UTF-8 flag of STRING is not checked.
+Note that because the conversion happens in place, the data to be
+converted cannot be a string constant, it must be a scalar variable.
=back
-=head2 chars With Encoding
+=head2 Handling Malformed Data
+
+If CHECK is not set, C<undef> is returned. If the data is supposed to
+be UTF-8, an optional lexical warning (category utf8) is given. If
+CHECK is true but not a code reference, dies.
+
+It would desirable to have a way to indicate that transform should use
+the encodings "replacement character" - no such mechanism is defined yet.
+
+It is also planned to allow I<CHECK> to be a code reference.
+
+This is not yet implemented as there are design issues with what its
+arguments should be and how it returns its results.
=over 4
-=item *
+=item Scheme 1
- chars_to_utf8(STRING, FROM [, CHECK])
+Passed remaining fragment of string being processed.
+Modifies it in place to remove bytes/characters it can understand
+and returns a string used to represent them.
+e.g.
-The chars in STRING encoded in FROM are recoded in-place into UTF-8.
-Returns the new size of STRING, or C<undef> if there's a failure.
+ sub fixup {
+ my $ch = substr($_[0],0,1,'');
+ return sprintf("\x{%02X}",ord($ch);
+ }
-No assumptions are made on the encoding of the chars. If you want to
-assume that the chars are Unicode and to trap illegal Unicode
-characters, you must use C<from_to('Unicode', ...)>.
+This scheme is close to how underlying C code for Encode works, but gives
+the fixup routine very little context.
-[INTERNAL] Also the UTF-8 flag of STRING is turned on.
+=item Scheme 2
-=item *
+Passed original string, and an index into it of the problem area, and
+output string so far. Appends what it will to output string and
+returns new index into original string. For example:
- utf8_to_chars(STRING, TO [, CHECK])
+ sub fixup {
+ # my ($s,$i,$d) = @_;
+ my $ch = substr($_[0],$_[1],1);
+ $_[2] .= sprintf("\x{%02X}",ord($ch);
+ return $_[1]+1;
+ }
-The UTF-8 in STRING is decoded in-place into chars encoded in TO.
-Returns the new size of STRING, or C<undef> if there's a failure.
+This scheme gives maximal control to the fixup routine but is more
+complicated to code, and may need internals of Encode to be tweaked to
+keep original string intact.
-If the UTF-8 in STRING is malformed? See L</"Handling Malformed Data">.
+=item Other Schemes
-[INTERNAL] The UTF-8 flag of STRING is not checked.
+Hybrids of above.
-=item *
+Multiple return values rather than in-place modifications.
- bytes_to_chars(STRING, FROM [, CHECK])
+Index into the string could be pos($str) allowing s/\G...//.
-The bytes in STRING encoded in FROM are recoded in-place into chars.
-Returns the new size of STRING in bytes, or C<undef> if there's a
-failure.
+=back
-If the mapping is impossible? See L</"Handling Malformed Data">.
+=head2 UTF-8 / utf8
-=item *
+The Unicode consortium defines the UTF-8 standard as a way of encoding
+the entire Unicode repertiore as sequences of octets. This encoding is
+expected to become very widespread. Perl can use this form internaly
+to represent strings, so conversions to and from this form are
+particularly efficient (as octets in memory do not have to change,
+just the meta-data that tells Perl how to treat them).
- chars_to_bytes(STRING, TO [, CHECK])
+=over 4
+
+=item *
-The chars in STRING are recoded in-place to bytes encoded in TO.
-Returns the new size of STRING in bytes, or C<undef> if there's a
-failure.
+ $bytes = encode_utf8($string);
-If the mapping is impossible? See L</"Handling Malformed Data">.
+The characters that comprise string are encoded in Perl's superset of UTF-8
+and the resulting octets returned as a sequence of bytes. All possible
+characters have a UTF-8 representation so this function cannot fail.
=item *
- from_to(STRING, FROM, TO [, CHECK])
+ $string = decode_utf8($bytes [,CHECK]);
+
+The sequence of octets represented by $bytes is decoded from UTF-8
+into a sequence of logical characters. Not all sequences of octets
+form valid UTF-8 encodings, so it is possible for this call to fail.
+For CHECK see L</"Handling Malformed Data">.
+
+=back
+
+=head2 Other Encodings of Unicode
+
+UTF-16 is similar to UCS-2, 16 bit or 2-byte chunks. UCS-2 can only
+represent 0..0xFFFF, while UTF-16 has a "surrogate pair" scheme which
+allows it to cover the whole Unicode range.
+
+Encode implements big-endian UCS-2 aliased to "iso-10646-1" as that
+happens to be the name used by that representation when used with X11
+fonts.
-The chars in STRING encoded in FROM are recoded in-place into TO.
-Returns the new size of STRING, or C<undef> if there's a failure.
+UTF-32 or UCS-4 is 32-bit or 4-byte chunks. Perl's logical characters
+can be considered as being in this form without encoding. An encoding
+to transfer strings in this form (e.g. to write them to a file) would
+need to
-If mapping between the encodings is impossible?
-See L</"Handling Malformed Data">.
+ pack('L',map(chr($_),split(//,$string))); # native
+ or
+ pack('V',map(chr($_),split(//,$string))); # little-endian
+ or
+ pack('N',map(chr($_),split(//,$string))); # big-endian
-[INTERNAL] If TO is UTF-8, also the UTF-8 flag of STRING is turned on.
+depending on the endian required.
+
+No UTF-32 encodings are implemented yet.
+
+Both UCS-2 and UCS-4 style encodings can have "byte order marks" by
+representing the code point 0xFFFE as the very first thing in a file.
+
+=head2 Listing available encodings
+
+ use Encode qw(encodings);
+ @list = encodings();
+
+Returns a list of the canonical names of the available encodings.
+
+=head2 Defining Aliases
+
+ use Encode qw(define_alias);
+ define_alias( newName => ENCODING);
+
+Allows newName to be used as am alias for ENCODING. ENCODING may be
+either the name of an encoding or and encoding object (as above).
+
+Currently I<newName> can be specified in the following ways:
+
+=over 4
+
+=item As a simple string.
+
+=item As a qr// compiled regular expression, e.g.:
+
+ define_alias( qr/^iso8859-(\d+)$/i => '"iso-8859-$1"' );
+
+In this case if I<ENCODING> is not a reference it is C<eval>-ed to
+allow C<$1> etc. to be subsituted. The example is one way to names as
+used in X11 font names to alias the MIME names for the iso-8859-*
+family.
+
+=item As a code reference, e.g.:
+
+ define_alias( sub { return /^iso8859-(\d+)$/i ? "iso-8859-$1" : undef } , '');
+
+In this case C<$_> will be set to the name that is being looked up and
+I<ENCODING> is passed to the sub as its first argument. The example
+is another way to names as used in X11 font names to alias the MIME
+names for the iso-8859-* family.
=back
-=head2 Testing For UTF-8
+=head2 Defining Encodings
+
+ use Encode qw(define_alias);
+ define_encoding( $object, 'canonicalName' [,alias...]);
+
+Causes I<canonicalName> to be associated with I<$object>. The object
+should provide the interface described in L</"IMPLEMENTATION CLASSES">
+below. If more than two arguments are provided then additional
+arguments are taken as aliases for I<$object> as for C<define_alias>.
+
+=head1 Encoding and IO
+
+It is very common to want to do encoding transformations when
+reading or writing files, network connections, pipes etc.
+If Perl is configured to use the new 'perlio' IO system then
+C<Encode> provides a "layer" (See L<perliol>) which can transform
+data as it is read or written.
+
+Here is how the blind poet would modernise the encoding:
+
+ use Encode;
+ open(my $iliad,'<:encoding(iso-8859-7)','iliad.greek');
+ open(my $utf8,'>:utf8','iliad.utf8');
+ my @epic = <$iliad>;
+ print $utf8 @epic;
+ close($utf8);
+ close($illiad);
+
+In addition the new IO system can also be configured to read/write
+UTF-8 encoded characters (as noted above this is efficient):
+
+ open(my $fh,'>:utf8','anything');
+ print $fh "Any \x{0021} string \N{SMILEY FACE}\n";
+
+Either of the above forms of "layer" specifications can be made the default
+for a lexical scope with the C<use open ...> pragma. See L<open>.
+
+Once a handle is open is layers can be altered using C<binmode>.
+
+Without any such configuration, or if Perl itself is built using
+system's own IO, then write operations assume that file handle accepts
+only I<bytes> and will C<die> if a character larger than 255 is
+written to the handle. When reading, each octet from the handle
+becomes a byte-in-a-character. Note that this default is the same
+behaviour as bytes-only languages (including Perl before v5.6) would
+have, and is sufficient to handle native 8-bit encodings
+e.g. iso-8859-1, EBCDIC etc. and any legacy mechanisms for handling
+other encodings and binary data.
+
+In other cases it is the programs responsibility to transform
+characters into bytes using the API above before doing writes, and to
+transform the bytes read from a handle into characters before doing
+"character operations" (e.g. C<lc>, C</\W+/>, ...).
+
+You can also use PerlIO to convert larger amounts of data you don't
+want to bring into memory. For example to convert between ISO 8859-1
+(Latin 1) and UTF-8 (or UTF-EBCDIC in EBCDIC machines):
+
+ open(F, "<:encoding(iso-8859-1)", "data.txt") or die $!;
+ open(G, ">:utf8", "data.utf") or die $!;
+ while (<F>) { print G }
+
+ # Could also do "print G <F>" but that would pull
+ # the whole file into memory just to write it out again.
+
+More examples:
+
+ open(my $f, "<:encoding(cp1252)")
+ open(my $g, ">:encoding(iso-8859-2)")
+ open(my $h, ">:encoding(latin9)") # iso-8859-15
+
+See L<PerlIO> for more information.
+
+=head1 Encoding How to ...
+
+To do:
=over 4
-=item *
+=item * IO with mixed content (faking iso-2020-*)
- is_utf8(STRING [, CHECK])
+=item * MIME's Content-Length:
-[INTERNAL] Test whether the UTF-8 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.
+=item * UTF-8 strings in binary data.
+
+=item * Perl/Encode wrappers on non-Unicode XS modules.
=back
-=head2 Toggling UTF-8-ness
+=head1 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 4
+=item * is_utf8(STRING [, CHECK])
+
+[INTERNAL] Test whether the UTF-8 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.
+
+=item * valid_utf8(STRING)
+
+[INTERNAL] Test whether STRING is in a consistent state. Will return
+true if string is held as bytes, or is well-formed UTF-8 and has the
+UTF-8 flag on. Main reason for this routine is to allow Perl's
+testsuite to check that operations have left strings in a consistent
+state.
+
=item *
- on_utf8(STRING)
+ _utf8_on(STRING)
[INTERNAL] Turn on the UTF-8 flag in STRING. The data in STRING is
B<not> checked for being well-formed UTF-8. Do not use unless you
=item *
- off_utf8(STRING)
+ _utf8_off(STRING)
[INTERNAL] Turn off the UTF-8 flag in STRING. Do not use frivolously.
Returns the previous state of the UTF-8 flag (so please don't test the
=back
-=head2 UTF-16 and UTF-32 Encodings
-
-=over 4
-
-=item *
-
- utf_to_utf(STRING, FROM, TO [, CHECK])
-
-The data in STRING is converted from Unicode Transfer Encoding FROM to
-Unicode Transfer Encoding TO. Both FROM and TO may be any of the
-following tags (case-insensitive, with or without 'utf' or 'utf-' prefix):
-
- tag meaning
+=head1 IMPLEMENTATION CLASSES
- '7' UTF-7
- '8' UTF-8
- '16be' UTF-16 big-endian
- '16le' UTF-16 little-endian
- '16' UTF-16 native-endian
- '32be' UTF-32 big-endian
- '32le' UTF-32 little-endian
- '32' UTF-32 native-endian
+As mentioned above encodings are (in the current implementation at least)
+defined by objects. The mapping of encoding name to object is via the
+C<%encodings> hash.
-UTF-16 is also known as UCS-2, 16 bit or 2-byte chunks, and UTF-32 as
-UCS-4, 32-bit or 4-byte chunks. Returns the new size of STRING, or
-C<undef> is there's a failure.
+The values of the hash can currently be either strings or objects.
+The string form may go away in the future. The string form occurs
+when C<encodings()> has scanned C<@INC> for loadable encodings but has
+not actually loaded the encoding in question. This is because the
+current "loading" process is all Perl and a bit slow.
-If FROM is UTF-8 and the UTF-8 in STRING is malformed? See
-L</"Handling Malformed Data">.
-
-[INTERNAL] Even if CHECK is true and FROM is UTF-8, the UTF-8 flag of
-STRING is not checked. If TO is UTF-8, also the UTF-8 flag of STRING is
-turned on. Identical FROM and TO are fine.
-
-=back
-
-=head2 Handling Malformed Data
+Once an encoding is loaded then value of the hash is object which
+implements the encoding. The object should provide the following
+interface:
-If CHECK is not set, C<undef> is returned. If the data is supposed to
-be UTF-8, an optional lexical warning (category utf8) is given. If
-CHECK is true but not a code reference, dies. If CHECK is a code
-reference, it is called with the arguments
+=over 4
- (MALFORMED_STRING, STRING_FROM_SO_FAR, STRING_TO_SO_FAR)
+=item -E<gt>name
-Two return values are expected from the call: the string to be used in
-the result string in place of the malformed section, and the length of
-the malformed section in bytes.
+Should return the string representing the canonical name of the encoding.
-=cut
+=item -E<gt>new_sequence
-sub bytes_to_utf8 {
- &_bytes_to_utf8;
-}
+This is a placeholder for encodings with state. It should return an
+object which implements this interface, all current implementations
+return the original object.
-sub utf8_to_bytes {
- &_utf8_to_bytes;
-}
+=item -E<gt>encode($string,$check)
-sub chars_to_utf8 {
- &C_to_utf8;
-}
+Should return the octet sequence representing I<$string>. If I<$check>
+is true it should modify I<$string> in place to remove the converted
+part (i.e. the whole string unless there is an error). If an error
+occurs it should return the octet sequence for the fragment of string
+that has been converted, and modify $string in-place to remove the
+converted part leaving it starting with the problem fragment.
-sub utf8_to_chars {
- &_utf8_to_chars;
-}
+If check is is false then C<encode> should make a "best effort" to
+convert the string - for example by using a replacement character.
-sub utf8_to_chars_check {
- &_utf8_to_chars_check;
-}
+=item -E<gt>decode($octets,$check)
-sub bytes_to_chars {
- &_bytes_to_chars;
-}
+Should return the string that I<$octets> represents. If I<$check> is
+true it should modify I<$octets> in place to remove the converted part
+(i.e. the whole sequence unless there is an error). If an error
+occurs it should return the fragment of string that has been
+converted, and modify $octets in-place to remove the converted part
+leaving it starting with the problem fragment.
-sub chars_to_bytes {
- &_chars_to_bytes;
-}
+If check is is false then C<decode> should make a "best effort" to
+convert the string - for example by using Unicode's "\x{FFFD}" as a
+replacement character.
-sub is_utf8 {
- &_is_utf8;
-}
+=back
-sub on_utf8 {
- &_on_utf8;
-}
+It should be noted that the check behaviour is different from the
+outer public API. The logic is that the "unchecked" case is useful
+when encoding is part of a stream which may be reporting errors
+(e.g. STDERR). In such cases it is desirable to get everything
+through somehow without causing additional errors which obscure the
+original one. Also the encoding is best placed to know what the
+correct replacement character is, so if that is the desired behaviour
+then letting low level code do it is the most efficient.
+
+In contrast if check is true, the scheme above allows the encoding to
+do as much as it can and tell layer above how much that was. What is
+lacking at present is a mechanism to report what went wrong. The most
+likely interface will be an additional method call to the object, or
+perhaps (to avoid forcing per-stream objects on otherwise stateless
+encodings) and additional parameter.
+
+It is also highly desirable that encoding classes inherit from
+C<Encode::Encoding> as a base class. This allows that class to define
+additional behaviour for all encoding objects. For example built in
+Unicode, UCS-2 and UTF-8 classes use :
+
+ package Encode::MyEncoding;
+ use base qw(Encode::Encoding);
+
+ __PACKAGE__->Define(qw(myCanonical myAlias));
+
+To create an object with bless {Name => ...},$class, and call
+define_encoding. They inherit their C<name> method from
+C<Encode::Encoding>.
+
+=head2 Compiled Encodings
+
+F<Encode.xs> provides a class C<Encode::XS> which provides the
+interface described above. It calls a generic octet-sequence to
+octet-sequence "engine" that is driven by tables (defined in
+F<encengine.c>). The same engine is used for both encode and
+decode. C<Encode:XS>'s C<encode> forces Perl's characters to their
+UTF-8 form and then treats them as just another multibyte
+encoding. C<Encode:XS>'s C<decode> transforms the sequence and then
+turns the UTF-8-ness flag as that is the form that the tables are
+defined to produce. For details of the engine see the comments in
+F<encengine.c>.
+
+The tables are produced by the Perl script F<compile> (the name needs
+to change so we can eventually install it somewhere). F<compile> can
+currently read two formats:
-sub off_utf8 {
- &_off_utf8;
-}
+=over 4
-sub utf_to_utf {
- &_utf_to_utf;
-}
+=item *.enc
-use Carp;
+This is a coined format used by Tcl. It is documented in
+Encode/EncodeFormat.pod.
-sub from_to
-{
- my ($string,$from,$to,$check) = @_;
- my $f = __PACKAGE__->getEncoding($from);
- croak("Unknown encoding '$from'") unless $f;
- my $t = __PACKAGE__->getEncoding($to);
- croak("Unknown encoding '$to'") unless $t;
- my $uni = $f->toUnicode($string,$check);
- return undef if ($check && length($string));
- $string = $t->fromUnicode($uni,$check);
- return undef if ($check && length($uni));
- return length($_[0] = $string);
-}
+=item *.ucm
-sub encodings
-{
- my ($class) = @_;
- my ($dir) = __FILE__ =~ /^(.*)\.pm$/;
- my @names = ('Unicode');
- if (opendir(my $dh,$dir))
- {
- while (defined(my $name = readdir($dh)))
- {
- push(@names,$1) if ($name =~ /^(.*)\.enc$/);
- }
- closedir($dh);
- }
- else
- {
- die "Cannot open $dir:$!";
- }
- return @names;
-}
+This is the semi-standard format used by IBM's ICU package.
-my %encoding = ( Unicode => 'Encode::Unicode' );
+=back
-sub getEncoding
-{
- my ($class,$name) = @_;
- unless (exists $encoding{$name})
- {
- my $file;
- foreach my $dir (@INC)
- {
- last if -f ($file = "$dir/Encode/$name.enc");
- }
- if (open(my $fh,$file))
- {
- my $type;
- while (1)
- {
- my $line = <$fh>;
- $type = substr($line,0,1);
- last unless $type eq '#';
- }
- $class .= ('::'.(($type eq 'E') ? 'Escape' : 'Table'));
- $encoding{$name} = $class->read($fh,$name,$type);
- }
- }
- return $encoding{$name};
-}
+F<compile> can write the following forms:
-package Encode::Unicode;
+=over 4
-# Dummy package that provides the encode interface
+=item *.ucm
-sub name { 'Unicode' }
+See above - the F<Encode/*.ucm> files provided with the distribution have
+been created from the original Tcl .enc files using this approach.
-sub toUnicode { $_[1] }
+=item *.c
-sub fromUnicode { $_[1] }
+Produces tables as C data structures - this is used to build in encodings
+into F<Encode.so>/F<Encode.dll>.
-package Encode::Table;
+=item *.xs
-sub read
-{
- my ($class,$fh,$name,$type) = @_;
- my $rep = $class->can("rep_$type");
- my ($def,$sym,$pages) = split(/\s+/,scalar(<$fh>));
- my @touni;
- my %fmuni;
- my $count = 0;
- $def = hex($def);
- $def = pack(&$rep($def),$def);
- while ($pages--)
- {
- my $page = hex(<$fh>);
- my @page;
- my $ch = $page * 256;
- for (my $i = 0; $i < 16; $i++)
- {
- my $line = <$fh>;
- for (my $j = 0; $j < 16; $j++)
- {
- my $val = hex(substr($line,0,4,''));
- if ($val || !$ch)
- {
- my $uch = chr($val);
- push(@page,$uch);
- $fmuni{$uch} = pack(&$rep($ch),$ch);
- $count++;
- }
- else
- {
- push(@page,undef);
- }
- $ch++;
- }
- }
- $touni[$page] = \@page;
- }
+In theory this allows encodings to be stand-alone loadable Perl
+extensions. The process has not yet been tested. The plan is to use
+this approach for large East Asian encodings.
- return bless {Name => $name,
- Rep => $rep,
- ToUni => \@touni,
- FmUni => \%fmuni,
- Def => $def,
- Num => $count,
- },$class;
-}
+=back
-sub name { shift->{'Name'} }
+The set of encodings built-in to F<Encode.so>/F<Encode.dll> is
+determined by F<Makefile.PL>. The current set is as follows:
-sub rep_S { 'C' }
+=over 4
-sub rep_D { 'S' }
+=item ascii and iso-8859-*
-sub rep_M { ($_[0] > 255) ? 'S' : 'C' }
+That is all the common 8-bit "western" encodings.
-sub representation
-{
- my ($obj,$ch) = @_;
- $ch = 0 unless @_ > 1;
- $obj-{'Rep'}->($ch);
-}
+=item IBM-1047 and two other variants of EBCDIC.
-sub toUnicode
-{
- my ($obj,$str,$chk) = @_;
- my $rep = $obj->{'Rep'};
- my $touni = $obj->{'ToUni'};
- my $uni = '';
- while (length($str))
- {
- my $ch = ord(substr($str,0,1,''));
- my $x;
- if (&$rep($ch) eq 'C')
- {
- $x = $touni->[0][$ch];
- }
- else
- {
- $x = $touni->[$ch][ord(substr($str,0,1,''))];
- }
- unless (defined $x)
- {
- last if $chk;
- # What do we do here ?
- $x = '';
- }
- $uni .= $x;
- }
- $_[1] = $str if $chk;
- return $uni;
-}
+These are the same variants that are supported by EBCDIC Perl as
+"native" encodings. They are included to prove "reversibility" of
+some constructs in EBCDIC Perl.
-sub fromUnicode
-{
- my ($obj,$uni,$chk) = @_;
- my $fmuni = $obj->{'FmUni'};
- my $str = '';
- my $def = $obj->{'Def'};
- while (length($uni))
- {
- my $ch = substr($uni,0,1,'');
- my $x = $fmuni->{$ch};
- unless (defined $x)
- {
- last if ($chk);
- $x = $def;
- }
- $str .= $x;
- }
- $_[1] = $uni if $chk;
- return $str;
-}
+=item symbol and dingbats as used by Tk on X11.
-package Encode::Escape;
-use Carp;
+(The reason Encode got started was to support Perl/Tk.)
-sub read
-{
- my ($class,$fh,$name) = @_;
- my %self = (Name => $name, Num => 0);
- while (<$fh>)
- {
- my ($key,$val) = /^(\S+)\s+(.*)$/;
- $val =~ s/^\{(.*?)\}/$1/g;
- $val =~ s/\\x([0-9a-f]{2})/chr(hex($1))/ge;
- $self{$key} = $val;
- }
- return bless \%self,$class;
-}
+=back
-sub name { shift->{'Name'} }
+That set is rather ad hoc and has been driven by the needs of the
+tests rather than the needs of typical applications. It is likely
+to be rationalized.
-sub toUnicode
-{
- croak("Not implemented yet");
-}
+=head1 SEE ALSO
-sub fromUnicode
-{
- croak("Not implemented yet");
-}
+L<perlunicode>, L<perlebcdic>, L<perlfunc/open>, L<PerlIO>
-1;
+=cut
-__END__
https://perl5.git.perl.org / perl5.git / blobdiff