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File Content: `Guess.pm`

package Encode::Guess;
use strict;
use warnings;
use Encode qw(:fallbacks find_encoding);
our $VERSION = do { my @r = ( q$Revision: 2.8 $ =~ /\d+/g ); sprintf "%d." . "%02d" x $#r, @r };

my $Canon = 'Guess';
use constant DEBUG => !!$ENV{PERL_ENCODE_DEBUG};
our %DEF_SUSPECTS = map { $_ => find_encoding($_) } qw(ascii utf8);
my $obj = bless {
    Name     => $Canon,
    Suspects => {%DEF_SUSPECTS},
} => __PACKAGE__;
Encode::define_encoding($obj, $Canon);

use parent qw(Encode::Encoding);
sub needs_lines { 1 }
sub perlio_ok   { 0 }

our @EXPORT         = qw(guess_encoding);
our $NoUTFAutoGuess = 0;
our $UTF8_BOM       = pack( "C3", 0xef, 0xbb, 0xbf );

sub import {    # Exporter not used so we do it on our own
    my $callpkg = caller;
    for my $item (@EXPORT) {
        no strict 'refs';
        *{"$callpkg\::$item"} = \&{"$item"};
    }
    set_suspects(@_);
}

sub set_suspects {
    my $class = shift;
    my $self = ref($class) ? $class : $Encode::Encoding{$Canon};
    $self->{Suspects} = {%DEF_SUSPECTS};
    $self->add_suspects(@_);
}

sub add_suspects {
    my $class = shift;
    my $self = ref($class) ? $class : $Encode::Encoding{$Canon};
    for my $c (@_) {
        my $e = find_encoding($c) or die "Unknown encoding: $c";
        $self->{Suspects}{ $e->name } = $e;
        DEBUG and warn "Added: ", $e->name;
    }
}

sub decode($$;$) {
    my ( $obj, $octet, $chk ) = @_;
    my $guessed = guess( $obj, $octet );
    unless ( ref($guessed) ) {
        require Carp;
        Carp::croak($guessed);
    }
    my $utf8 = $guessed->decode( $octet, $chk || 0 );
    $_[1] = $octet if $chk;
    return $utf8;
}

sub guess_encoding {
    guess( $Encode::Encoding{$Canon}, @_ );
}

sub guess {
    my $class = shift;
    my $obj   = ref($class) ? $class : $Encode::Encoding{$Canon};
    my $octet = shift;

    # sanity check
    return "Empty string, empty guess" unless defined $octet and length $octet;

    # cheat 0: utf8 flag;
    if ( Encode::is_utf8($octet) ) {
        return find_encoding('utf8') unless $NoUTFAutoGuess;
        Encode::_utf8_off($octet);
    }

    # cheat 1: BOM
    use Encode::Unicode;
    unless ($NoUTFAutoGuess) {
        my $BOM = pack( 'C3', unpack( "C3", $octet ) );
        return find_encoding('utf8')
          if ( defined $BOM and $BOM eq $UTF8_BOM );
        $BOM = unpack( 'N', $octet );
        return find_encoding('UTF-32')
          if ( defined $BOM and ( $BOM == 0xFeFF or $BOM == 0xFFFe0000 ) );
        $BOM = unpack( 'n', $octet );
        return find_encoding('UTF-16')
          if ( defined $BOM and ( $BOM == 0xFeFF or $BOM == 0xFFFe ) );
        if ( $octet =~ /\x00/o )
        {    # if \x00 found, we assume UTF-(16|32)(BE|LE)
            my $utf;
            my ( $be, $le ) = ( 0, 0 );
            if ( $octet =~ /\x00\x00/o ) {    # UTF-32(BE|LE) assumed
                $utf = "UTF-32";
                for my $char ( unpack( 'N*', $octet ) ) {
                    $char & 0x0000ffff and $be++;
                    $char & 0xffff0000 and $le++;
                }
            }
            else {                            # UTF-16(BE|LE) assumed
                $utf = "UTF-16";
                for my $char ( unpack( 'n*', $octet ) ) {
                    $char & 0x00ff and $be++;
                    $char & 0xff00 and $le++;
                }
            }
            DEBUG and warn "$utf, be == $be, le == $le";
            $be == $le
              and return
              "Encodings ambiguous between $utf BE and LE ($be, $le)";
            $utf .= ( $be > $le ) ? 'BE' : 'LE';
            return find_encoding($utf);
        }
    }
    my %try = %{ $obj->{Suspects} };
    for my $c (@_) {
        my $e = find_encoding($c) or die "Unknown encoding: $c";
        $try{ $e->name } = $e;
        DEBUG and warn "Added: ", $e->name;
    }
    my $nline = 1;
    for my $line ( split /\r\n?|\n/, $octet ) {

        # cheat 2 -- \e in the string
        if ( $line =~ /\e/o ) {
            my @keys = keys %try;
            delete @try{qw/utf8 ascii/};
            for my $k (@keys) {
                ref( $try{$k} ) eq 'Encode::XS' and delete $try{$k};
            }
        }
        my %ok = %try;

        # warn join(",", keys %try);
        for my $k ( keys %try ) {
            my $scratch = $line;
            $try{$k}->decode( $scratch, FB_QUIET );
            if ( $scratch eq '' ) {
                DEBUG and warn sprintf( "%4d:%-24s ok\n", $nline, $k );
            }
            else {
                use bytes ();
                DEBUG
                  and warn sprintf( "%4d:%-24s not ok; %d bytes left\n",
                    $nline, $k, bytes::length($scratch) );
                delete $ok{$k};
            }
        }
        %ok or return "No appropriate encodings found!";
        if ( scalar( keys(%ok) ) == 1 ) {
            my ($retval) = values(%ok);
            return $retval;
        }
        %try = %ok;
        $nline++;
    }
    $try{ascii}
      or return "Encodings too ambiguous: " . join( " or ", keys %try );
    return $try{ascii};
}

1;
__END__

=head1 NAME

Encode::Guess -- Guesses encoding from data

=head1 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)

=head1 ABSTRACT

Encode::Guess enables you to guess in what encoding a given data is
encoded, or at least tries to.  

=head1 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 (I<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 C<$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 C<ascii>.

=over 4

=item Encode::Guess->set_suspects

You can also change the internal suspects list via C<set_suspects>
method. 

  use Encode::Guess;
  Encode::Guess->set_suspects(qw/euc-jp shiftjis 7bit-jis/);

=item Encode::Guess->add_suspects

Or you can use C<add_suspects> method.  The difference is that
C<set_suspects> flushes the current suspects list while
C<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/);

=item Encode::decode("Guess" ...)

When you are content with suspects list, you can now

  my $utf8 = Encode::decode("Guess", $data);

=item Encode::Guess->guess($data)

But it will croak if:

=over

=item *

Two or more suspects remain

=item *

No suspects left

=back

So you should instead try this;

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

On success, $decoder is an object that is documented in
L<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);

=item guess_encoding($data, [, I<list of suspects>])

You can also try C<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 I<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);

=back

=head1 CAVEATS

=over 4

=item *

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).

=item *

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.

=item *

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/);

=item *

DO NOT PUT TOO MANY SUSPECTS!  Don't you try something like this!

  my $decoder = guess_encoding($data, 
                               Encode->encodings(":all"));

=back

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. 

=head1 TO DO

Encode::Guess does not work on EBCDIC platforms.

=head1 SEE ALSO

L<Encode>, L<Encode::Encoding>

=cut
Name	Size	Permission
CN	---	0755
JP	---	0755
KR	---	0755
MIME	---	0755
Unicode	---	0755
Alias.pm	12545 bytes	0644
Byte.pm	2430 bytes	0644
CJKConstants.pm	1683 bytes	0644
CN.pm	2042 bytes	0644
Changes.e2x	179 bytes	0644
Config.pm	6065 bytes	0644
ConfigLocal_PM.e2x	184 bytes	0644
EBCDIC.pm	865 bytes	0644
Encoder.pm	6316 bytes	0644
Encoding.pm	9063 bytes	0644
GSM0338.pm	12865 bytes	0644
Guess.pm	10114 bytes	0644
JP.pm	2682 bytes	0644
KR.pm	1960 bytes	0644
Makefile_PL.e2x	5168 bytes	0644
PerlIO.pod	6060 bytes	0644
README.e2x	553 bytes	0644
Supported.pod	28732 bytes	0644
Symbol.pm	847 bytes	0644
TW.pm	2292 bytes	0644
Unicode.pm	8928 bytes	0644
_PM.e2x	250 bytes	0644
_T.e2x	151 bytes	0644
encode.h	49302 bytes	0644
File Content: Guess.pm

File Content: `Guess.pm`
