.\" Automatically generated by Pod::Man v1.34, Pod::Parser v1.13 .\" .\" Standard preamble: .\" ======================================================================== .de Sh \" Subsection heading .br .if t .Sp .ne 5 .PP \fB\\$1\fR .PP .. .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. | will give a .\" real vertical bar. \*(C+ will give a nicer C++. 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This \s-1POD\s0 itself explains the top-level APIs and general topics at a glance. For other topics and more details, see the PODs below: .PP .Vb 10 \& 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 \& -------------------------------------------------------- .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" The \f(CW\*(C`Encode\*(C'\fR module provides the interfaces between Perl's strings and the rest of the system. Perl strings are sequences of \&\fBcharacters\fR. .PP 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 \f(CW\*(C`ord(ch)\*(C'\fR) is the \*(L"Unicode codepoint\*(R" for the character (the exceptions are those platforms where the legacy encoding is some variant of \s-1EBCDIC\s0 rather than a super-set of \s-1ASCII\s0 \- see perlebcdic). .PP Traditionally, computer data has been moved around in 8\-bit chunks often called \*(L"bytes\*(R". These chunks are also known as \*(L"octets\*(R" 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 \*(L"binary\*(R" data being the machine's representation of numbers, pixels in an image \- or just about anything. .PP When Perl is processing \*(L"binary data\*(R", the programmer wants Perl to process \*(L"sequences of bytes\*(R". This is not a problem for Perl \- as a byte has 256 possible values, it easily fits in Perl's much larger \&\*(L"logical character\*(R". .Sh "\s-1TERMINOLOGY\s0" .IX Subsection "TERMINOLOGY" .IP "\(bu" 2 \&\fIcharacter\fR: a character in the range 0..(2**32\-1) (or more). (What Perl's strings are made of.) .IP "\(bu" 2 \&\fIbyte\fR: a character in the range 0..255 (A special case of a Perl character.) .IP "\(bu" 2 \&\fIoctet\fR: 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.) .SH "PERL ENCODING API" .IX Header "PERL ENCODING API" .ie n .IP "$octets = encode(\s-1ENCODING\s0, $string [, \s-1CHECK\s0])" 2 .el .IP "$octets = encode(\s-1ENCODING\s0, \f(CW$string\fR [, \s-1CHECK\s0])" 2 .IX Item "$octets = encode(ENCODING, $string [, CHECK])" Encodes a string from Perl's internal form into \fI\s-1ENCODING\s0\fR and returns a sequence of octets. \s-1ENCODING\s0 can be either a canonical name or an alias. For encoding names and aliases, see \*(L"Defining Aliases\*(R". For \s-1CHECK\s0, see \*(L"Handling Malformed Data\*(R". .Sp For example, to convert a string from Perl's internal format to iso\-8859\-1 (also known as Latin1), .Sp .Vb 1 \& $octets = encode("iso-8859-1", $string); .Ve .Sp \&\fB\s-1CAVEAT\s0\fR: When you run \f(CW\*(C`$octets = encode("utf8", $string)\*(C'\fR, then \f(CW$octets\fR \&\fBmay not be equal to\fR \f(CW$string\fR. Though they both contain the same data, the utf8 flag for \f(CW$octets\fR is \fBalways\fR off. When you encode anything, utf8 flag of the result is always off, even when it contains completely valid utf8 string. See \*(L"The \s-1UTF\-8\s0 flag\*(R" below. .Sp encode($valid_encoding, undef) is harmless but warns you for \&\f(CW\*(C`Use of uninitialized value in subroutine entry\*(C'\fR. encode($valid_encoding, '') is harmless and warnless. .ie n .IP "$string = decode(\s-1ENCODING\s0, $octets [, \s-1CHECK\s0])" 2 .el .IP "$string = decode(\s-1ENCODING\s0, \f(CW$octets\fR [, \s-1CHECK\s0])" 2 .IX Item "$string = decode(ENCODING, $octets [, CHECK])" Decodes a sequence of octets assumed to be in \fI\s-1ENCODING\s0\fR into Perl's internal form and returns the resulting string. As in \fIencode()\fR, \&\s-1ENCODING\s0 can be either a canonical name or an alias. For encoding names and aliases, see \*(L"Defining Aliases\*(R". For \s-1CHECK\s0, see \&\*(L"Handling Malformed Data\*(R". .Sp For example, to convert \s-1ISO\-8859\-1\s0 data to a string in Perl's internal format: .Sp .Vb 1 \& $string = decode("iso-8859-1", $octets); .Ve .Sp \&\fB\s-1CAVEAT\s0\fR: When you run \f(CW\*(C`$string = decode("utf8", $octets)\*(C'\fR, then \f(CW$string\fR \&\fBmay not be equal to\fR \f(CW$octets\fR. Though they both contain the same data, the utf8 flag for \f(CW$string\fR is on unless \f(CW$octets\fR entirely consists of \&\s-1ASCII\s0 data (or \s-1EBCDIC\s0 on \s-1EBCDIC\s0 machines). See \*(L"The \s-1UTF\-8\s0 flag\*(R" below. .Sp decode($valid_encoding, undef) is harmless but warns you for \&\f(CW\*(C`Use of uninitialized value in subroutine entry\*(C'\fR. decode($valid_encoding, '') is harmless and warnless. .IP "[$length =] from_to($octets, \s-1FROM_ENC\s0, \s-1TO_ENC\s0 [, \s-1CHECK\s0])" 2 .IX Item "[$length =] from_to($octets, FROM_ENC, TO_ENC [, CHECK])" Converts \fBin-place\fR data between two encodings. The data in \f(CW$octets\fR must be encoded as octets and not as characters in Perl's internal format. For example, to convert \s-1ISO\-8859\-1\s0 data to Microsoft's \s-1CP1250\s0 encoding: .Sp .Vb 1 \& from_to($octets, "iso-8859-1", "cp1250"); .Ve .Sp and to convert it back: .Sp .Vb 1 \& from_to($octets, "cp1250", "iso-8859-1"); .Ve .Sp Note that because the conversion happens in place, the data to be converted cannot be a string constant; it must be a scalar variable. .Sp \&\fIfrom_to()\fR returns the length of the converted string in octets on success, undef otherwise. .Sp \&\fB\s-1CAVEAT\s0\fR: The following operations look the same but are not quite so; .Sp .Vb 2 \& from_to($data, "iso-8859-1", "utf8"); #1 \& $data = decode("iso-8859-1", $data); #2 .Ve .Sp Both #1 and #2 make \f(CW$data\fR consist of a completely valid \s-1UTF\-8\s0 string but only #2 turns utf8 flag on. #1 is equivalent to .Sp .Vb 1 \& $data = encode("utf8", decode("iso-8859-1", $data)); .Ve .Sp See \*(L"The \s-1UTF\-8\s0 flag\*(R" below. .IP "$octets = encode_utf8($string);" 2 .IX Item "$octets = encode_utf8($string);" Equivalent to \f(CW\*(C`$octets = encode("utf8", $string);\*(C'\fR The characters that comprise \f(CW$string\fR are encoded in Perl's internal format and the result is returned as a sequence of octets. All possible characters have a \s-1UTF\-8\s0 representation so this function cannot fail. .IP "$string = decode_utf8($octets [, \s-1CHECK\s0]);" 2 .IX Item "$string = decode_utf8($octets [, CHECK]);" equivalent to \f(CW\*(C`$string = decode("utf8", $octets [, CHECK])\*(C'\fR. The sequence of octets represented by \&\f(CW$octets\fR is decoded from \s-1UTF\-8\s0 into a sequence of logical characters. Not all sequences of octets form valid \s-1UTF\-8\s0 encodings, so it is possible for this call to fail. For \s-1CHECK\s0, see \&\*(L"Handling Malformed Data\*(R". .Sh "Listing available encodings" .IX Subsection "Listing available encodings" .Vb 2 \& use Encode; \& @list = Encode->encodings(); .Ve .PP 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 .PP .Vb 1 \& @all_encodings = Encode->encodings(":all"); .Ve .PP Or you can give the name of a specific module. .PP .Vb 1 \& @with_jp = Encode->encodings("Encode::JP"); .Ve .PP When \*(L"::\*(R" is not in the name, \*(L"Encode::\*(R" is assumed. .PP .Vb 1 \& @ebcdic = Encode->encodings("EBCDIC"); .Ve .PP To find out in detail which encodings are supported by this package, see Encode::Supported. .Sh "Defining Aliases" .IX Subsection "Defining Aliases" To add a new alias to a given encoding, use: .PP .Vb 3 \& use Encode; \& use Encode::Alias; \& define_alias(newName => ENCODING); .Ve .PP After that, newName can be used as an alias for \s-1ENCODING\s0. \&\s-1ENCODING\s0 may be either the name of an encoding or an \&\fIencoding object\fR .PP But before you do so, make sure the alias is nonexistent with \&\f(CW\*(C`resolve_alias()\*(C'\fR, which returns the canonical name thereof. i.e. .PP .Vb 3 \& 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 .Ve .PP \&\fIresolve_alias()\fR does not need \f(CW\*(C`use Encode::Alias\*(C'\fR; it can be exported via \f(CW\*(C`use Encode qw(resolve_alias)\*(C'\fR. .PP See Encode::Alias for details. .SH "Encoding via PerlIO" .IX Header "Encoding via PerlIO" If your perl supports \fIPerlIO\fR (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. .PP .Vb 4 \& # via PerlIO \& open my $in, "<:encoding(shiftjis)", $infile or die; \& open my $out, ">:encoding(euc-jp)", $outfile or die; \& while(<$in>){ print $out $_; } .Ve .PP .Vb 7 \& # 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 $_; \& } .Ve .PP Unfortunately, it may be that encodings are PerlIO\-savvy. You can check if your encoding is supported by PerlIO by calling the \f(CW\*(C`perlio_ok\*(C'\fR method. .PP .Vb 2 \& Encode::perlio_ok("hz"); # False \& find_encoding("euc-cn")->perlio_ok; # True where PerlIO is available .Ve .PP .Vb 2 \& use Encode qw(perlio_ok); # exported upon request \& perlio_ok("euc-jp") .Ve .PP Fortunately, all encodings that come with Encode core are PerlIO-savvy except for hz and ISO\-2022\-kr. For gory details, see Encode::Encoding and Encode::PerlIO. .SH "Handling Malformed Data" .IX Header "Handling Malformed Data" .RS 2 The \fI\s-1CHECK\s0\fR argument is used as follows. When you omit it, the behaviour is the same as if you had passed a value of 0 for \&\fI\s-1CHECK\s0\fR. .RE .IP "\fI\s-1CHECK\s0\fR = Encode::FB_DEFAULT ( == 0)" 2 .IX Item "CHECK = Encode::FB_DEFAULT ( == 0)" If \fI\s-1CHECK\s0\fR is 0, (en|de)code will put a \fIsubstitution character\fR in place of a malformed character. For UCM-based encodings, will be used. For Unicode, the code point \f(CW0xFFFD\fR is used. If the data is supposed to be \s-1UTF\-8\s0, an optional lexical warning (category utf8) is given. .IP "\fI\s-1CHECK\s0\fR = Encode::FB_CROAK ( == 1)" 2 .IX Item "CHECK = Encode::FB_CROAK ( == 1)" If \fI\s-1CHECK\s0\fR is 1, methods will die on error immediately with an error message. Therefore, when \fI\s-1CHECK\s0\fR is set to 1, you should trap the fatal error with eval{} unless you really want to let it die on error. .IP "\fI\s-1CHECK\s0\fR = Encode::FB_QUIET" 2 .IX Item "CHECK = Encode::FB_QUIET" If \fI\s-1CHECK\s0\fR 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, for example because you are reading with a fixed-width buffer. Here is some sample code that does exactly this: .Sp .Vb 7 \& my $data = ''; my $utf8 = ''; \& while(defined(read $fh, $buffer, 256)){ \& # buffer may end in a partial character so we append \& $data .= $buffer; \& $utf8 .= decode($encoding, $data, Encode::FB_QUIET); \& # $data now contains the unprocessed partial character \& } .Ve .IP "\fI\s-1CHECK\s0\fR = Encode::FB_WARN" 2 .IX Item "CHECK = Encode::FB_WARN" This is the same as above, except that it warns on error. Handy when you are debugging the mode above. .IP "perlqq mode (\fI\s-1CHECK\s0\fR = Encode::FB_PERLQQ)" 2 .IX Item "perlqq mode (CHECK = Encode::FB_PERLQQ)" .PD 0 .IP "\s-1HTML\s0 charref mode (\fI\s-1CHECK\s0\fR = Encode::FB_HTMLCREF)" 2 .IX Item "HTML charref mode (CHECK = Encode::FB_HTMLCREF)" .IP "\s-1XML\s0 charref mode (\fI\s-1CHECK\s0\fR = Encode::FB_XMLCREF)" 2 .IX Item "XML charref mode (CHECK = Encode::FB_XMLCREF)" .PD For encodings that are implemented by Encode::XS, \s-1CHECK\s0 == Encode::FB_PERLQQ turns (en|de)code into \f(CW\*(C`perlqq\*(C'\fR fallback mode. .Sp When you decode, \f(CW\*(C`\ex\f(CI\s-1HH\s0\f(CW\*(C'\fR will be inserted for a malformed character, where \fI\s-1HH\s0\fR is the hex representation of the octet that could not be decoded to utf8. And when you encode, \f(CW\*(C`\ex{\f(CI\s-1HHHH\s0\f(CW}\*(C'\fR will be inserted, where \fI\s-1HHHH\s0\fR is the Unicode \s-1ID\s0 of the character that cannot be found in the character repertoire of the encoding. .Sp \&\s-1HTML/XML\s0 character reference modes are about the same, in place of \&\f(CW\*(C`\ex{\f(CI\s-1HHHH\s0\f(CW}\*(C'\fR, \s-1HTML\s0 uses \f(CW\*(C`&#\f(CI\s-1NNNN\s0\f(CW\*(C'\fR; where \fI\s-1NNNN\s0\fR is a decimal digit and \&\s-1XML\s0 uses \f(CW\*(C`&#x\f(CI\s-1HHHH\s0\f(CW\*(C'\fR; where \fI\s-1HHHH\s0\fR is the hexadecimal digit. .IP "The bitmask" 2 .IX Item "The bitmask" These modes are actually set via a bitmask. Here is how the \s-1FB_XX\s0 constants are laid out. You can import the \s-1FB_XX\s0 constants via \&\f(CW\*(C`use Encode qw(:fallbacks)\*(C'\fR; you can import the generic bitmask constants via \f(CW\*(C`use Encode qw(:fallback_all)\*(C'\fR. .Sp .Vb 8 \& 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 \& PERLQQ 0x0100 X \& HTMLCREF 0x0200 \& XMLCREF 0x0400 .Ve .Sh "Unimplemented fallback schemes" .IX Subsection "Unimplemented fallback schemes" In the future, you will be able to use a code reference to a callback function for the value of \fI\s-1CHECK\s0\fR but its \s-1API\s0 is still undecided. .Sp The fallback scheme does not work on \s-1EBCDIC\s0 platforms. .SH "Defining Encodings" .IX Header "Defining Encodings" To define a new encoding, use: .Sp .Vb 2 \& use Encode qw(define_encoding); \& define_encoding($object, 'canonicalName' [, alias...]); .Ve .Sp \&\fIcanonicalName\fR will be associated with \fI$object\fR. The object should provide the interface described in Encode::Encoding. If more than two arguments are provided then additional arguments are taken as aliases for \fI$object\fR. .Sp See Encode::Encoding for more details. .SH "The UTF\-8 flag" .IX Header "The UTF-8 flag" Before the introduction of utf8 support in perl, The \f(CW\*(C`eq\*(C'\fR operator just compared the strings represented by two scalars. Beginning with perl 5.8, \f(CW\*(C`eq\*(C'\fR compares two strings with simultaneous consideration of \fIthe utf8 flag\fR. To explain why we made it so, I will quote page 402 of \f(CW\*(C`Programming Perl, 3rd ed.\*(C'\fR .RS 2 .IP "Goal #1:" 2 .IX Item "Goal #1:" Old byte-oriented programs should not spontaneously break on the old byte-oriented data they used to work on. .IP "Goal #2:" 2 .IX Item "Goal #2:" Old byte-oriented programs should magically start working on the new character-oriented data when appropriate. .IP "Goal #3:" 2 .IX Item "Goal #3:" Programs should run just as fast in the new character-oriented mode as in the old byte-oriented mode. .IP "Goal #4:" 2 .IX Item "Goal #4:" Perl should remain one language, rather than forking into a byte-oriented Perl and a character-oriented Perl. .RE .RS 2 .Sp Back when \f(CW\*(C`Programming Perl, 3rd ed.\*(C'\fR 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 \s-1UTF\-8\s0 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). .Sp Here is how Encode takes care of the utf8 flag. .IP "\(bu" 2 When you encode, the resulting utf8 flag is always off. .IP "\(bu" 2 When you decode, the resulting utf8 flag is on unless you can unambiguously represent data. Here is the definition of dis\-ambiguity. .Sp After \f(CW\*(C`$utf8 = decode('foo', $octet);\*(C'\fR, .Sp .Vb 6 \& 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 \& --------------------------------------------- .Ve .Sp As you see, there is one exception, In \s-1ASCII\s0. That way you can assue Goal #1. And with Encode Goal #2 is assumed but you still have to be careful in such cases mentioned in \fB\s-1CAVEAT\s0\fR paragraphs. .Sp This utf8 flag is not visible in perl scripts, exactly for the same reason you cannot (or you \fIdon't have to\fR) 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. .RE .RS 2 .Sh "Messing with Perl's Internals" .IX Subsection "Messing with Perl's Internals" The following \s-1API\s0 uses parts of Perl's internals in the current implementation. As such, they are efficient but may change. .IP "is_utf8(\s-1STRING\s0 [, \s-1CHECK\s0])" 2 .IX Item "is_utf8(STRING [, CHECK])" [\s-1INTERNAL\s0] Tests whether the \s-1UTF\-8\s0 flag is turned on in the \s-1STRING\s0. If \s-1CHECK\s0 is true, also checks the data in \s-1STRING\s0 for being well-formed \&\s-1UTF\-8\s0. Returns true if successful, false otherwise. .IP "_utf8_on(\s-1STRING\s0)" 2 .IX Item "_utf8_on(STRING)" [\s-1INTERNAL\s0] Turns on the \s-1UTF\-8\s0 flag in \s-1STRING\s0. The data in \s-1STRING\s0 is \&\fBnot\fR checked for being well-formed \s-1UTF\-8\s0. Do not use unless you \&\fBknow\fR that the \s-1STRING\s0 is well-formed \s-1UTF\-8\s0. Returns the previous state of the \s-1UTF\-8\s0 flag (so please don't treat the return value as indicating success or failure), or \f(CW\*(C`undef\*(C'\fR if \s-1STRING\s0 is not a string. .IP "_utf8_off(\s-1STRING\s0)" 2 .IX Item "_utf8_off(STRING)" [\s-1INTERNAL\s0] Turns off the \s-1UTF\-8\s0 flag in \s-1STRING\s0. Do not use frivolously. Returns the previous state of the \s-1UTF\-8\s0 flag (so please don't treat the return value as indicating success or failure), or \f(CW\*(C`undef\*(C'\fR if \s-1STRING\s0 is not a string. .RE .RS 2 .SH "SEE ALSO" .IX Header "SEE ALSO" Encode::Encoding, Encode::Supported, Encode::PerlIO, encoding, perlebcdic, \&\*(L"open\*(R" in perlfunc, perlunicode, utf8, the Perl Unicode Mailing List .SH "MAINTAINER" .IX Header "MAINTAINER" This project was originated by Nick Ing-Simmons and later maintained by Dan Kogai . See \s-1AUTHORS\s0 for a full list of people involved. For any questions, use so we can all share.