Encode::Guess(3pm)					 Perl Programmers Reference Guide					Encode::Guess(3pm)

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 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:

	   o   Two or more suspects remain

	   o   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

       o   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).

       o   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.

       o   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/);

       o   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, Encode::Encoding

perl v5.12.1							    2010-04-26							Encode::Guess(3pm)