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Encode::Guess -- Guesses encoding from data

Encode::Guess -- Guesses encoding from data


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 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.


 # tries all major Japanese Encodings as well

  use Encode::Guess qw/euc-jp shiftjis 7bit-jis/;
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 Encode::Guess fails to eliminate all other suspects but the right one or no suspect was good. So you should instead try this;

  my $decoder = Encode::Guess->guess($data);

On success, $decoder is an object that is documented in the Encode::Encoding manpage. 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 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 was 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.


SEE ALSO

Encode, the Encode::Encoding manpage

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