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Encode::Guess

Section: Perl Programmers Reference Guide (3pm)
Updated: 2014-10-30
Index

NAME

Encode::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)

ABSTRACT

Encode::Guess enables you to guess in what encoding a given data isencoded, 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 tocheck (suspects as follows). The name of suspects can either becanonical 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 truevalue, no heuristics will be applied to UTF8/16/32, and the resultwill 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 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 inEncode::Encoding. So you can now do this;

  my $utf8 = $decoder->decode($data);

On failure, $decoder now contains an error message so the whole thingwould 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 bydefault. It takes $data to check and it also takes the list ofsuspects by option. The optional suspect list is not reflected tothe 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 single-byteencodings do not work well unless either one of ISO-8859 is the onlyone 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 eachsuspect. It keeps it going until all but one encoding is eliminatedout of suspects list. ISO-8859 series is just too successful for mostcases (because it fills almost all code points in \x00-\xff).

•

Do not mix national standard encodings and the corresponding vendorencodings.

  # a very bad idea  my $decoder     = guess_encoding($data, qw/shiftjis MacJapanese cp932/);

The reason is that vendor encoding is usually a superset of nationalstandard so it becomes too ambiguous for most cases.

•

On the other hand, mixing various national standard encodingsautomagically 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 itcomes 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.

This document was created byman2html,using the manual pages.

Encode::Guess

NAME

SYNOPSIS

ABSTRACT

DESCRIPTION

CAVEATS

TO DO

SEE ALSO

Index