ext::Encode::lib:PerloProgrammext::Encode::lib::Encode::Guess(3p)NAMEEncode::Guess-- Guesses encoding from data
SYNOPSIS
# if you are sure $data won't contain anything bogus
use Encode;
use Encode::Guess qw/euc-jp shiftjis 7bit-jis/;
my $utf8 = decode("Guess", $data);
my $data = encode("Guess", $utf8); # this doesn't work!
# more elaborate way
use Encode::Guess;
my $enc = guess_encoding($data, qw/euc-jp shiftjis 7bit-jis/);
ref($enc) or die "Can't guess: $enc"; # trap error this way
$utf8 = $enc->decode($data);
# or
$utf8 = decode($enc->name, $data)
ABSTRACTEncode::Guess enables you to guess in what encoding a given
data is encoded, or at least tries to.
DESCRIPTION
By default, it checks only ascii, utf8 and UTF-16/32 with
BOM.
use Encode::Guess; # ascii/utf8/BOMed UTF
To use it more practically, you have to give the names of
encodings to check (suspects as follows). The name of
suspects can either be canonical names or aliases.
CAVEAT: Unlike UTF-(16|32), BOM in utf8 is NOT AUTOMATICALLY
STRIPPED.
# tries all major Japanese Encodings as well
use Encode::Guess qw/euc-jp shiftjis 7bit-jis/;
If the $Encode::Guess::NoUTFAutoGuess variable is set to a
true value, no heuristics will be applied to UTF8/16/32, and
the result will be limited to the suspects and "ascii".
Encode::Guess->set_suspects
You can also change the internal suspects list via
"set_suspects" method.
use Encode::Guess;
Encode::Guess->set_suspects(qw/euc-jp shiftjis 7bit-jis/);
Encode::Guess->add_suspects
Or you can use "add_suspects" method. The difference is
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that "set_suspects" flushes the current suspects list
while "add_suspects" adds.
use Encode::Guess;
Encode::Guess->add_suspects(qw/euc-jp shiftjis 7bit-jis/);
# now the suspects are euc-jp,shiftjis,7bit-jis, AND
# euc-kr,euc-cn, and big5-eten
Encode::Guess->add_suspects(qw/euc-kr euc-cn big5-eten/);
Encode::decode("Guess" ...)
When you are content with suspects list, you can now
my $utf8 = Encode::decode("Guess", $data);
Encode::Guess->guess($data)
But it will croak if:
* Two or more suspects remain
* No suspects left
So you should instead try this;
my $decoder = Encode::Guess->guess($data);
On success, $decoder is an object that is documented in
Encode::Encoding. So you can now do this;
my $utf8 = $decoder->decode($data);
On failure, $decoder now contains an error message so
the whole thing would be as follows;
my $decoder = Encode::Guess->guess($data);
die $decoder unless ref($decoder);
my $utf8 = $decoder->decode($data);
guess_encoding($data, [, list of suspects])
You can also try "guess_encoding" function which is
exported by default. It takes $data to check and it
also takes the list of suspects by option. The optional
suspect list is not reflected to the internal suspects
list.
my $decoder = guess_encoding($data, qw/euc-jp euc-kr euc-cn/);
die $decoder unless ref($decoder);
my $utf8 = $decoder->decode($data);
# check only ascii and utf8
my $decoder = guess_encoding($data);
CAVEATS
+ Because of the algorithm used, ISO-8859 series and other
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single-byte encodings do not work well unless either one
of ISO-8859 is the only one suspect (besides ascii and
utf8).
use Encode::Guess;
# perhaps ok
my $decoder = guess_encoding($data, 'latin1');
# definitely NOT ok
my $decoder = guess_encoding($data, qw/latin1 greek/);
The reason is that Encode::Guess guesses encoding by
trial and error. It first splits $data into lines and
tries to decode the line for each suspect. It keeps it
going until all but one encoding is eliminated out of
suspects list. ISO-8859 series is just too successful
for most cases (because it fills almost all code points
in \x00-\xff).
+ Do not mix national standard encodings and the
corresponding vendor encodings.
# a very bad idea
my $decoder
= guess_encoding($data, qw/shiftjis MacJapanese cp932/);
The reason is that vendor encoding is usually a superset
of national standard so it becomes too ambiguous for
most cases.
+ On the other hand, mixing various national standard
encodings automagically works unless $data is too short
to allow for guessing.
# This is ok if $data is long enough
my $decoder =
guess_encoding($data, qw/euc-cn
euc-jp shiftjis 7bit-jis
euc-kr
big5-eten/);
+ DO NOT PUT TOO MANY SUSPECTS! Don't you try something
like this!
my $decoder = guess_encoding($data,
Encode->encodings(":all"));
It is, after all, just a guess. You should alway be expli-
cit when it comes to encodings. But there are some, espe-
cially Japanese, environment that guess-coding is a must.
Use this module with care.
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SEE ALSO
Encode, Encode::Encoding
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