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package Encode::Guess;
use strict;
use warnings;
use Encode qw(:fallbacks find_encoding);
our $VERSION = do { my @r = ( q$Revision: 2.7 $ =~ /\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
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