JezK
Edit File: 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