NAME
Encode::Guess -- Guesses encoding from data
SYNOPSIS
# if you are sure $data won't contain anything bogus
use
Encode;
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
)
ABSTRACT
Encode::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.
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
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 thatset_suspects
flushes the current suspects list whileadd_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, utf8 and UTF-(16|32) with BOM
my
$decoder
= guess_encoding(
$data
);
CAVEATS
Because of the algorithm used, ISO-8859 series and other 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 explicit when it comes to encodings. But there are some, especially Japanese, environment that guess-coding is a must. Use this module with care.
TO DO
Encode::Guess does not work on EBCDIC platforms.