MirOS Manual: Encode::Guess(3p)


ext::Encode::lib:PerloProgrammeerxst:R:Encode::lib::Encode::Guess(3p)

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.

     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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TO DO

     Encode::Guess does not work on EBCDIC platforms.

SEE ALSO

     Encode, Encode::Encoding

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