use Encode;
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 --------------------------------------------------------
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 "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 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''.
For example, to convert a string from Perl's internal format to iso-8859-1 (also known as Latin1),
$octets = encode("iso-8859-1", $string);
CAVEAT: When you run "$octets = encode("utf8", $string)", then $octets may not be equal to $string. Though they both contain the same data, the utf8 flag for $octets is always off. When you encode anything, utf8 flag of the result is always off, even when it contains completely valid utf8 string. See ``The UTF-8 flag'' below.
encode($valid_encoding, undef) is harmless but warns you for "Use of uninitialized value in subroutine entry". encode($valid_encoding, '') is harmless and warnless.
For example, to convert ISO-8859-1 data to a string in Perl's internal format:
$string = decode("iso-8859-1", $octets);
CAVEAT: When you run "$string = decode("utf8", $octets)", then $string may not be equal to $octets. Though they both contain the same data, the utf8 flag for $string is on unless $octets entirely consists of ASCII data (or EBCDIC on EBCDIC machines). See ``The UTF-8 flag'' below.
decode($valid_encoding, undef) is harmless but warns you for "Use of uninitialized value in subroutine entry". decode($valid_encoding, '') is harmless and warnless.
from_to($octets, "iso-8859-1", "cp1250");
and to convert it back:
from_to($octets, "cp1250", "iso-8859-1");
Note that because the conversion happens in place, the data to be converted cannot be a string constant; it must be a scalar variable.
from_to() returns the length of the converted string in octets on success, undef on error.
CAVEAT: The following operations look the same but are not quite so;
from_to($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", $data));
See ``The UTF-8 flag'' below.
use Encode; @list = Encode->encodings();
Returns a list of the canonical names of the available encodings that are loaded. To get a list of all available encodings including the ones that are not loaded yet, say
@all_encodings = Encode->encodings(":all");
Or you can give the name of a specific module.
@with_jp = Encode->encodings("Encode::JP");
When ``::'' is not in the name, ``Encode::'' is assumed.
@ebcdic = Encode->encodings("EBCDIC");
To find out in detail which encodings are supported by this package, see Encode::Supported.
use Encode; use Encode::Alias; define_alias(newName => ENCODING);
After that, newName can be used as an alias for ENCODING. ENCODING may be either the name of an encoding or an encoding object
But before you do so, make sure the alias is nonexistent with "resolve_alias()", which returns the canonical name thereof. i.e.
Encode::resolve_alias("latin1") eq "iso-8859-1" # true
Encode::resolve_alias("iso-8859-12") # false; nonexistent
Encode::resolve_alias($name) eq $name # true if $name is canonical
resolve_alias() does not need "use Encode::Alias"; it can be exported via "use Encode qw(resolve_alias)".
See Encode::Alias for details.
# 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 "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 Encode::Encoding and Encode::PerlIO.
Now here is the list of CHECK values available
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);
# $data now contains the unprocessed partial character
}
When you decode, "\xHH" will be inserted for a malformed character, where HH is the hex representation of the octet that could not be decoded to utf8. And when you encode, "\x{HHHH}" will be inserted, where HHHH is the Unicode ID of the character that cannot be found in the character repertoire of the encoding.
HTML/XML character reference modes are about the same, in place of "\x{HHHH}", HTML uses "&#NNNN;" where NNNN is a decimal digit and XML uses "&#xHHHH;" where HHHH is the hexadecimal digit.
FB_DEFAULT FB_CROAK FB_QUIET FB_WARN FB_PERLQQ
DIE_ON_ERR 0x0001 X
WARN_ON_ERR 0x0002 X
RETURN_ON_ERR 0x0004 X X
LEAVE_SRC 0x0008
PERLQQ 0x0100 X
HTMLCREF 0x0200
XMLCREF 0x0400
The fallback scheme does not work on EBCDIC platforms.
use Encode qw(define_encoding);
define_encoding($object, 'canonicalName' [, alias...]);
canonicalName will be associated with $object. 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 $object.
See Encode::Encoding for more details.
Back when "Programming Perl, 3rd ed." was written, not even Perl 5.6.0 was born and many features documented in the book remained unimplemented for a long time. Perl 5.8 corrected this and the introduction of the UTF-8 flag is one of them. You can think of this perl notion as of a byte-oriented mode (utf8 flag off) and a character-oriented mode (utf8 flag on).
Here is how Encode takes care of the utf8 flag.
After "$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 assue Goal #1. And with Encode Goal #2 is assumed but you still have to be careful in such cases mentioned in CAVEAT paragraphs.
This utf8 flag is not visible in perl scripts, exactly for the same reason you cannot (or you 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.
As of perl 5.8.1, utf8 also has utf8::is_utf8().