CVSROOT/scripts/jcode.pl

package jcode;
;######################################################################
;#
;# jcode.pl: Perl library for Japanese character code conversion
;#
;# Copyright (c) 1995-2000 Kazumasa Utashiro <utashiro@iij.ad.jp>
;# Internet Initiative Japan Inc.
;# 3-13 Kanda Nishiki-cho, Chiyoda-ku, Tokyo 101-0054, Japan
;#
;# Copyright (c) 1992,1993,1994 Kazumasa Utashiro
;# Software Research Associates, Inc.
;#
;# Use and redistribution for ANY PURPOSE are granted as long as all
;# copyright notices are retained.  Redistribution with modification
;# is allowed provided that you make your modified version obviously
;# distinguishable from the original one.  THIS SOFTWARE IS PROVIDED
;# BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES ARE
;# DISCLAIMED.
;#
;# Original version was developed under the name of srekcah@sra.co.jp
;# February 1992 and it was called kconv.pl at the beginning.  This
;# address was a pen name for group of individuals and it is no longer
;# valid.
;#
;# The latest version is available here:
;#
;#      ftp://ftp.iij.ad.jp/pub/IIJ/dist/utashiro/perl/
;#
;; $rcsid = q$Id: jcode.pl,v 1.1 2005/12/26 08:20:19 tigercat Exp $;
;#
;######################################################################
;#
;# PERL4 INTERFACE:
;#
;#      &jcode'getcode(*line)
;#              Return 'jis', 'sjis', 'euc' or undef according to
;#              Japanese character code in $line.  Return 'binary' if
;#              the data has non-character code.
;#
;#              When evaluated in array context, it returns a list
;#              contains two items.  First value is the number of
;#              characters which matched to the expected code, and
;#              second value is the code name.  It is useful if and
;#              only if the number is not 0 and the code is undef;
;#              that case means it couldn't tell 'euc' or 'sjis'
;#              because the evaluation score was exactly same.  This
;#              interface is too tricky, though.
;#
;#              Code detection between euc and sjis is very difficult
;#              or sometimes impossible or even lead to wrong result
;#              when it includes JIS X0201 KANA characters.  So JIS
;#              X0201 KANA is ignored for automatic code detection.
;#
;#      &jcode'convert(*line, $ocode [, $icode [, $option]])
;#              Convert the contents of $line to the specified
;#              Japanese code given in the second argument $ocode.
;#              $ocode can be any of "jis", "sjis" or "euc", or use
;#              "noconv" when you don't want the code conversion.
;#              Input code is recognized automatically from the line
;#              itself when $icode is not supplied (JIS X0201 KANA is
;#              ignored in code detection.  See the above descripton
;#              of &getcode).  $icode also can be specified, but
;#              xxx2yyy routine is more efficient when both codes are
;#              known.
;#
;#              It returns the code of input string in scalar context,
;#              and a list of pointer of convert subroutine and the
;#              input code in array context.
;#
;#              Japanese character code JIS X0201, X0208, X0212 and
;#              ASCII code are supported.  X0212 characters can not be
;#              represented in SJIS and they will be replased by
;#              "geta" character when converted to SJIS.
;#
;#              See next paragraph for $option parameter.
;#
;#      &jcode'xxx2yyy(*line [, $option])
;#              Convert the Japanese code from xxx to yyy.  String xxx
;#              and yyy are any convination from "jis", "euc" or
;#              "sjis".  They return *approximate* number of converted
;#              bytes.  So return value 0 means the line was not
;#              converted at all.
;#
;#              Optional parameter $option is used to specify optional
;#              conversion method.  String "z" is for JIS X0201 KANA
;#              to X0208 KANA, and "h" is for reverse.
;#
;#      $jcode'convf{'xxx', 'yyy'}
;#              The value of this associative array is pointer to the
;#              subroutine jcode'xxx2yyy().
;#
;#      &jcode'to($ocode, $line [, $icode [, $option]])
;#      &jcode'jis($line [, $icode [, $option]])
;#      &jcode'euc($line [, $icode [, $option]])
;#      &jcode'sjis($line [, $icode [, $option]])
;#              These functions are prepared for easy use of
;#              call/return-by-value interface.  You can use these
;#              funcitons in s///e operation or any other place for
;#              convenience.
;#
;#      &jcode'jis_inout($in, $out)
;#              Set or inquire JIS start and end sequences.  Default
;#              is "ESC-$-B" and "ESC-(-B".  If you supplied only one
;#              character, "ESC-$" or "ESC-(" is prepended for each
;#              character respectively.  Acutually "ESC-(-B" is not a
;#              sequence to end JIS code but a sequence to start ASCII
;#              code set.  So `in' and `out' are somewhat misleading.
;#
;#      &jcode'get_inout($string)
;#              Get JIS start and end sequences from $string.
;#
;#      &jcode'cache()
;#      &jcode'nocache()
;#      &jcode'flush()
;#              Usually, converted character is cached in memory to
;#              avoid same calculations have to be done many times.
;#              To disable this caching, call &jcode'nocache().  It
;#              can be revived by &jcode'cache() and cache is flushed
;#              by calling &jcode'flush().  &cache() and &nocache()
;#              functions return previous caching state.
;#
;#      ---------------------------------------------------------------
;#
;#      &jcode'h2z_xxx(*line)
;#              JIS X0201 KANA (so-called Hankaku-KANA) to X0208 KANA
;#              (Zenkaku-KANA) code conversion routine.  String xxx is
;#              any of "jis", "sjis" and "euc".  From the difficulty
;#              of recognizing code set from 1-byte KATAKANA string,
;#              automatic code recognition is not supported.
;#
;#      &jcode'z2h_xxx(*line)
;#              X0208 to X0201 KANA code conversion routine.  String
;#              xxx is any of "jis", "sjis" and "euc".
;#
;#      $jcode'z2hf{'xxx'}
;#      $jcode'h2zf{'xxx'}
;#              These are pointer to the corresponding function just
;#              as $jcode'convf.
;#
;#      ---------------------------------------------------------------
;#
;#      &jcode'tr(*line, $from, $to [, $option])
;#              &jcode'tr emulates tr operator for 2 byte code.  Only 'd'
;#              is interpreted as an option.
;#
;#              Range operator like `A-Z' for 2 byte code is partially
;#              supported.  Code must be JIS or EUC, and first byte
;#              have to be same on first and last character.
;#
;#              CAUTION: Handling range operator is a kind of trick
;#              and it is not perfect.  So if you need to transfer `-' 
;#              character, please be sure to put it at the beginning
;#              or the end of $from and $to strings.
;#
;#      &jcode'trans($line, $from, $to [, $option)
;#              Same as &jcode'tr but accept string and return string
;#              after translation.
;#
;#      ---------------------------------------------------------------
;#
;#      &jcode'init()
;#              Initialize the variables used in this package.  You
;#              don't have to call this when using jocde.pl by `do' or
;#              `require' interface.  Call it first if you embedded
;#              the jcode.pl at the end of your script.
;#
;######################################################################
;#
;# PERL5 INTERFACE:
;#
;# Current jcode.pl is written in Perl 4 but it is possible to use
;# from Perl 5 using `references'.  Fully perl5 capable version is
;# future issue.
;#
;# Since lexical variable is not a subject of typeglob, *string style
;# call doesn't work if the variable is declared as `my'.  Same thing
;# happens to special variable $_ if the perl is compiled to use
;# thread capability.  So using reference is generally recommented to
;# avoid the mysterious error.
;#
;#      jcode::getcode(\$line)
;#      jcode::convert(\$line, $ocode [, $icode [, $option]])
;#      jcode::xxx2yyy(\$line [, $option])
;#      &{$jcode::convf{'xxx', 'yyy'}}(\$line)
;#      jcode::to($ocode, $line [, $icode [, $option]])
;#      jcode::jis($line [, $icode [, $option]])
;#      jcode::euc($line [, $icode [, $option]])
;#      jcode::sjis($line [, $icode [, $option]])
;#      jcode::jis_inout($in, $out)
;#      jcode::get_inout($string)
;#      jcode::cache()
;#      jcode::nocache()
;#      jcode::flush()
;#      jcode::h2z_xxx(\$line)
;#      jcode::z2h_xxx(\$line)
;#      &{$jcode::z2hf{'xxx'}}(\$line)
;#      &{$jcode::h2zf{'xxx'}}(\$line)
;#      jcode::tr(\$line, $from, $to [, $option])
;#      jcode::trans($line, $from, $to [, $option)
;#      jcode::init()
;#
;######################################################################
;#
;# SAMPLES
;#
;# Convert any Kanji code to JIS and print each line with code name.
;#
;#      while (defined($s = <>)) {
;#          $code = &jcode'convert(*s, 'jis');
;#          print $code, "\t", $s;
;#      }
;#      
;# Convert all lines to JIS according to the first recognized line.
;#
;#      while (defined($s = <>)) {
;#          print, next unless $s =~ /[\033\200-\377]/;
;#          (*f, $icode) = &jcode'convert(*s, 'jis');
;#          print;
;#          defined(&f) || next;
;#          while (<>) { &f(*s); print; }
;#          last;
;#      }
;#
;# The safest way of JIS conversion.
;#
;#      while (defined($s = <>)) {
;#          ($matched, $icode) = &jcode'getcode(*s);
;#          if (@buf == 0 && $matched == 0) {
;#              print $s;
;#              next;
;#          }
;#          push(@buf, $s);
;#          next unless $icode;
;#          while (defined($s = shift(@buf))) {
;#              &jcode'convert(*s, 'jis', $icode);
;#              print $s;
;#          }
;#          while (defined($s = <>)) {
;#              &jcode'convert(*s, 'jis', $icode);
;#              print $s;
;#          }
;#          last;
;#      }
;#      print @buf if @buf;
;#              
;######################################################################

;#
;# Call initialize function if it is not called yet.  This may sound
;# strange but it makes easy to embed the jcode.pl at the end of
;# script.  Call &jcode'init at the beginning of the script in that
;# case.
;#
&init unless defined $version;

;#
;# Initialize variables.
;#
sub init {
    $version = $rcsid =~ /,v ([\d.]+)/ ? $1 : 'unknown';

    $re_bin  = '[\000-\006\177\377]';

    $re_jis0208_1978 = '\e\$\@';
    $re_jis0208_1983 = '\e\$B';
    $re_jis0208_1990 = '\e&\@\e\$B';
    $re_jis0208 = "$re_jis0208_1978|$re_jis0208_1983|$re_jis0208_1990";
    $re_jis0212 = '\e\$\(D';
    $re_jp      = "$re_jis0208|$re_jis0212";
    $re_asc     = '\e\([BJ]';
    $re_kana    = '\e\(I';

    $esc_0208 = "\e\$B";
    $esc_0212 = "\e\$(D";
    $esc_asc  = "\e(B";
    $esc_kana = "\e(I";

    $re_sjis_c    = '[\201-\237\340-\374][\100-\176\200-\374]';
    $re_sjis_kana = '[\241-\337]';

    $re_euc_c    = '[\241-\376][\241-\376]';
    $re_euc_kana = '\216[\241-\337]';
    $re_euc_0212 = '\217[\241-\376][\241-\376]';

    # Use `geta' for undefined character code
    $undef_sjis = "\x81\xac";

    $cache = 1;

    # X0201 -> X0208 KANA conversion table.  Looks weird?  Not that
    # much.  This is simply JIS text without escape sequences.
    ($h2z_high = $h2z = <<'__TABLE_END__') =~ tr/\041-\176/\241-\376/;
!       !#      $       !"      %       !&      "       !V      #       !W
^       !+      _       !,      0       !<
'       %!      (       %#      )       %%      *       %'      +       %)
,       %c      -       %e      .       %g      /       %C
1       %"      2       %$      3       %&      4       %(      5       %*
6       %+      7       %-      8       %/      9       %1      :       %3
6^      %,      7^      %.      8^      %0      9^      %2      :^      %4
;       %5      <       %7      =       %9      >       %;      ?       %=
;^      %6      <^      %8      =^      %:      >^      %<      ?^      %>
@       %?      A       %A      B       %D      C       %F      D       %H
@^      %@      A^      %B      B^      %E      C^      %G      D^      %I
E       %J      F       %K      G       %L      H       %M      I       %N
J       %O      K       %R      L       %U      M       %X      N       %[
J^      %P      K^      %S      L^      %V      M^      %Y      N^      %\
J_      %Q      K_      %T      L_      %W      M_      %Z      N_      %]
O       %^      P       %_      Q       %`      R       %a      S       %b
T       %d                      U       %f                      V       %h
W       %i      X       %j      Y       %k      Z       %l      [       %m
\       %o      ]       %s      &       %r      3^      %t
__TABLE_END__
    %h2z = split(/\s+/, $h2z . $h2z_high);
    %z2h = reverse %h2z;

    $convf{'jis'  , 'jis' } = *jis2jis;
    $convf{'jis'  , 'sjis'} = *jis2sjis;
    $convf{'jis'  , 'euc' } = *jis2euc;
    $convf{'euc'  , 'jis' } = *euc2jis;
    $convf{'euc'  , 'sjis'} = *euc2sjis;
    $convf{'euc'  , 'euc' } = *euc2euc;
    $convf{'sjis' , 'jis' } = *sjis2jis;
    $convf{'sjis' , 'sjis'} = *sjis2sjis;
    $convf{'sjis' , 'euc' } = *sjis2euc;
    $h2zf{'jis' } = *h2z_jis;
    $z2hf{'jis' } = *z2h_jis;
    $h2zf{'euc' } = *h2z_euc;
    $z2hf{'euc' } = *z2h_euc;
    $h2zf{'sjis'} = *h2z_sjis;
    $z2hf{'sjis'} = *z2h_sjis;
}

;#
;# Set escape sequences which should be put before and after Japanese
;# (JIS X0208) string.
;#
sub jis_inout {
    $esc_0208 = shift || $esc_0208;
    $esc_0208 = "\e\$$esc_0208" if length($esc_0208) == 1;
    $esc_asc = shift || $esc_asc;
    $esc_asc = "\e\($esc_asc" if length($esc_asc) == 1;
    ($esc_0208, $esc_asc);
}

;#
;# Get JIS in and out sequences from the string.
;#
sub get_inout {
    local($esc_0208, $esc_asc);
    $_[$[] =~ /($re_jis0208)/o && ($esc_0208 = $1);
    $_[$[] =~ /($re_asc)/o && ($esc_asc = $1);
    ($esc_0208, $esc_asc);
}

;#
;# Recognize character code.
;#
sub getcode {
    local(*s) = @_;
    local($matched, $code);

    if ($s !~ /[\e\200-\377]/) {        # not Japanese
        $matched = 0;
        $code = undef;
    }                                   # 'jis'
    elsif ($s =~ /$re_jp|$re_asc|$re_kana/o) {
        $matched = 1;
        $code = 'jis';
    }
    elsif ($s =~ /$re_bin/o) {          # 'binary'
        $matched = 0;
        $code = 'binary';
    }
    else {                              # should be 'euc' or 'sjis'
        local($sjis, $euc) = (0, 0);

        while ($s =~ /(($re_sjis_c)+)/go) {
            $sjis += length($1);
        }
        while ($s =~ /(($re_euc_c|$re_euc_kana|$re_euc_0212)+)/go) {
            $euc  += length($1);
        }
        $matched = &max($sjis, $euc);
        $code = ('euc', undef, 'sjis')[($sjis<=>$euc) + $[ + 1];
    }
    wantarray ? ($matched, $code) : $code;
}
sub max { $_[ $[ + ($_[ $[ ] < $_[ $[ + 1 ]) ]; }

;#
;# Convert any code to specified code.
;#
sub convert {
    local(*s, $ocode, $icode, $opt) = @_;
    return (undef, undef) unless $icode = $icode || &getcode(*s);
    return (undef, $icode) if $icode eq 'binary';
    $ocode = 'jis' unless $ocode;
    $ocode = $icode if $ocode eq 'noconv';
    local(*f) = $convf{$icode, $ocode};
    &f(*s, $opt);
    wantarray ? (*f, $icode) : $icode;
}

;#
;# Easy return-by-value interfaces.
;#
sub jis  { &to('jis',  @_); }
sub euc  { &to('euc',  @_); }
sub sjis { &to('sjis', @_); }
sub to {
    local($ocode, $s, $icode, $opt) = @_;
    &convert(*s, $ocode, $icode, $opt);
    $s;
}
sub what {
    local($s) = @_;
    &getcode(*s);
}
sub trans {
    local($s) = shift;
    &tr(*s, @_);
    $s;
}

;#
;# SJIS to JIS
;#
sub sjis2jis {
    local(*s, $opt, $n) = @_;
    &sjis2sjis(*s, $opt) if $opt;
    $s =~ s/(($re_sjis_c|$re_sjis_kana)+)/&_sjis2jis($1) . $esc_asc/geo;
    $n;
}
sub _sjis2jis {
    local($s) = shift;
    $s =~ s/(($re_sjis_c)+|($re_sjis_kana)+)/&__sjis2jis($1)/geo;
    $s;
}
sub __sjis2jis {
    local($s) = shift;
    if ($s =~ /^$re_sjis_kana/o) {
        $n += $s =~ tr/\241-\337/\041-\137/;
        $esc_kana . $s;
    } else {
        $n += $s =~ s/($re_sjis_c)/$s2e{$1}||&s2e($1)/geo;
        $s =~ tr/\241-\376/\041-\176/;
        $esc_0208 . $s;
    }
}

;#
;# EUC to JIS
;#
sub euc2jis {
    local(*s, $opt, $n) = @_;
    &euc2euc(*s, $opt) if $opt;
    $s =~ s/(($re_euc_c|$re_euc_kana|$re_euc_0212)+)/
        &_euc2jis($1) . $esc_asc
    /geo;
    $n;
}
sub _euc2jis {
    local($s) = shift;
    $s =~ s/(($re_euc_c)+|($re_euc_kana)+|($re_euc_0212)+)/&__euc2jis($1)/geo;
    $s;
}
sub __euc2jis {
    local($s) = shift;
    local($esc);

    if ($s =~ tr/\216//d) {
        $esc = $esc_kana;
    } elsif ($s =~ tr/\217//d) {
        $esc = $esc_0212;
    } else {
        $esc = $esc_0208;
    }

    $n += $s =~ tr/\241-\376/\041-\176/;
    $esc . $s;
}

;#
;# JIS to EUC
;#
sub jis2euc {
    local(*s, $opt, $n) = @_;
    $s =~ s/($re_jp|$re_asc|$re_kana)([^\e]*)/&_jis2euc($1,$2)/geo;
    &euc2euc(*s, $opt) if $opt;
    $n;
}
sub _jis2euc {
    local($esc, $s) = @_;
    if ($esc !~ /^$re_asc/o) {
        $n += $s =~ tr/\041-\176/\241-\376/;
        if ($esc =~ /^$re_kana/o) {
            $s =~ s/([\241-\337])/\216$1/g;
        }
        elsif ($esc =~ /^$re_jis0212/o) {
            $s =~ s/([\241-\376][\241-\376])/\217$1/g;
        }
    }
    $s;
}

;#
;# JIS to SJIS
;#
sub jis2sjis {
    local(*s, $opt, $n) = @_;
    &jis2jis(*s, $opt) if $opt;
    $s =~ s/($re_jp|$re_asc|$re_kana)([^\e]*)/&_jis2sjis($1,$2)/geo;
    $n;
}
sub _jis2sjis {
    local($esc, $s) = @_;
    if ($esc =~ /^$re_jis0212/o) {
        $s =~ s/../$undef_sjis/g;
        $n = length;
    }
    elsif ($esc !~ /^$re_asc/o) {
        $n += $s =~ tr/\041-\176/\241-\376/;
        if ($esc =~ /^$re_jp/o) {
            $s =~ s/($re_euc_c)/$e2s{$1}||&e2s($1)/geo;
        }
    }
    $s;
}

;#
;# SJIS to EUC
;#
sub sjis2euc {
    local(*s, $opt,$n) = @_;
    $n = $s =~ s/($re_sjis_c|$re_sjis_kana)/$s2e{$1}||&s2e($1)/geo;
    &euc2euc(*s, $opt) if $opt;
    $n;
}
sub s2e {
    local($c1, $c2, $code);
    ($c1, $c2) = unpack('CC', $code = shift);

    if (0xa1 <= $c1 && $c1 <= 0xdf) {
        $c2 = $c1;
        $c1 = 0x8e;
    } elsif (0x9f <= $c2) {
        $c1 = $c1 * 2 - ($c1 >= 0xe0 ? 0xe0 : 0x60);
        $c2 += 2;
    } else {
        $c1 = $c1 * 2 - ($c1 >= 0xe0 ? 0xe1 : 0x61);
        $c2 += 0x60 + ($c2 < 0x7f);
    }
    if ($cache) {
        $s2e{$code} = pack('CC', $c1, $c2);
    } else {
        pack('CC', $c1, $c2);
    }
}

;#
;# EUC to SJIS
;#
sub euc2sjis {
    local(*s, $opt,$n) = @_;
    &euc2euc(*s, $opt) if $opt;
    $n = $s =~ s/($re_euc_c|$re_euc_kana|$re_euc_0212)/$e2s{$1}||&e2s($1)/geo;
}
sub e2s {
    local($c1, $c2, $code);
    ($c1, $c2) = unpack('CC', $code = shift);

    if ($c1 == 0x8e) {          # SS2
        return substr($code, 1, 1);
    } elsif ($c1 == 0x8f) {     # SS3
        return $undef_sjis;
    } elsif ($c1 % 2) {
        $c1 = ($c1>>1) + ($c1 < 0xdf ? 0x31 : 0x71);
        $c2 -= 0x60 + ($c2 < 0xe0);
    } else {
        $c1 = ($c1>>1) + ($c1 < 0xdf ? 0x30 : 0x70);
        $c2 -= 2;
    }
    if ($cache) {
        $e2s{$code} = pack('CC', $c1, $c2);
    } else {
        pack('CC', $c1, $c2);
    }
}

;#
;# JIS to JIS, SJIS to SJIS, EUC to EUC
;#
sub jis2jis {
    local(*s, $opt) = @_;
    $s =~ s/$re_jis0208/$esc_0208/go;
    $s =~ s/$re_asc/$esc_asc/go;
    &h2z_jis(*s) if $opt =~ /z/;
    &z2h_jis(*s) if $opt =~ /h/;
}
sub sjis2sjis {
    local(*s, $opt) = @_;
    &h2z_sjis(*s) if $opt =~ /z/;
    &z2h_sjis(*s) if $opt =~ /h/;
}
sub euc2euc {
    local(*s, $opt) = @_;
    &h2z_euc(*s) if $opt =~ /z/;
    &z2h_euc(*s) if $opt =~ /h/;
}

;#
;# Cache control functions
;#
sub cache {
    ($cache, $cache = 1)[$[];
}
sub nocache {
    ($cache, $cache = 0)[$[];
}
sub flushcache {
    undef %e2s;
    undef %s2e;
}

;#
;# X0201 -> X0208 KANA conversion routine
;#
sub h2z_jis {
    local(*s, $n) = @_;
    if ($s =~ s/$re_kana([^\e]*)/$esc_0208 . &_h2z_jis($1)/geo) {
        1 while $s =~ s/(($re_jis0208)[^\e]*)($re_jis0208)/$1/o;
    }
    $n;
}
sub _h2z_jis {
    local($s) = @_;
    $n += $s =~ s/(([\041-\137])([\136\137])?)/
        $h2z{$1} || $h2z{$2} . $h2z{$3}
    /ge;
    $s;
}

sub h2z_euc {
    local(*s) = @_;
    $s =~ s/\216([\241-\337])(\216([\336\337]))?/
        $h2z{"$1$3"} || $h2z{$1} . $h2z{$3}
    /ge;
}

sub h2z_sjis {
    local(*s, $n) = @_;
    $s =~ s/(($re_sjis_c)+)|(([\241-\337])([\336\337])?)/
        $1 || ($n++, $h2z{$3} ? $e2s{$h2z{$3}} || &e2s($h2z{$3})
                              : &e2s($h2z{$4}) . ($5 && &e2s($h2z{$5})))
    /geo;
    $n;
}

;#
;# X0208 -> X0201 KANA conversion routine
;#
sub z2h_jis {
    local(*s, $n) = @_;
    $s =~ s/($re_jis0208)([^\e]+)/&_z2h_jis($2)/geo;
    $n;
}
sub _z2h_jis {
    local($s) = @_;
    $s =~ s/((\%[!-~]|![\#\"&VW+,<])+|([^!%][!-~]|![^\#\"&VW+,<])+)/
        &__z2h_jis($1)
    /ge;
    $s;
}
sub __z2h_jis {
    local($s) = @_;
    return $esc_0208 . $s unless $s =~ /^%/ || $s =~ /^![\#\"&VW+,<]/;
    $n += length($s) / 2;
    $s =~ s/(..)/$z2h{$1}/g;
    $esc_kana . $s;
}

sub z2h_euc {
    local(*s, $n) = @_;
    &init_z2h_euc unless defined %z2h_euc;
    $s =~ s/($re_euc_c|$re_euc_kana)/
        $z2h_euc{$1} ? ($n++, $z2h_euc{$1}) : $1
    /geo;
    $n;
}

sub z2h_sjis {
    local(*s, $n) = @_;
    &init_z2h_sjis unless defined %z2h_sjis;
    $s =~ s/($re_sjis_c)/$z2h_sjis{$1} ? ($n++, $z2h_sjis{$1}) : $1/geo;
    $n;
}

;#
;# Initializing JIS X0208 to X0201 KANA table for EUC and SJIS.  This
;# can be done in &init but it's not worth doing.  Similarly,
;# precalculated table is not worth to occupy the file space and
;# reduce the readability.  The author personnaly discourages to use
;# X0201 Kana character in the any situation.
;#
sub init_z2h_euc {
    local($k, $s);
    while (($k, $s) = each %z2h) {
        $s =~ s/([\241-\337])/\216$1/g && ($z2h_euc{$k} = $s);
    }
}
sub init_z2h_sjis {
    local($s, $v);
    while (($s, $v) = each %z2h) {
        $s =~ /[\200-\377]/ && ($z2h_sjis{&e2s($s)} = $v);
    }
}

;#
;# TR function for 2-byte code
;#
sub tr {
    # $prev_from, $prev_to, %table are persistent variables
    local(*s, $from, $to, $opt) = @_;
    local(@from, @to);
    local($jis, $n) = (0, 0);
    
    $jis++, &jis2euc(*s) if $s =~ /$re_jp|$re_asc|$re_kana/o;
    $jis++ if $to =~ /$re_jp|$re_asc|$re_kana/o;

    if (!defined($prev_from) || $from ne $prev_from || $to ne $prev_to) {
        ($prev_from, $prev_to) = ($from, $to);
        undef %table;
        &_maketable;
    }

    $s =~ s/([\200-\377][\000-\377]|[\000-\377])/
        defined($table{$1}) && ++$n ? $table{$1} : $1
    /ge;

    &euc2jis(*s) if $jis;

    $n;
}

sub _maketable {
    local($ascii) = '(\\\\[\\-\\\\]|[\0-\133\135-\177])';

    &jis2euc(*to) if $to =~ /$re_jp|$re_asc|$re_kana/o;
    &jis2euc(*from) if $from =~ /$re_jp|$re_asc|$re_kana/o;

    grep(s/(([\200-\377])[\200-\377]-\2[\200-\377])/&_expnd2($1)/ge,
         $from, $to);
    grep(s/($ascii-$ascii)/&_expnd1($1)/geo,
         $from, $to);

    @to   = $to   =~ /[\200-\377][\000-\377]|[\000-\377]/g;
    @from = $from =~ /[\200-\377][\000-\377]|[\000-\377]/g;
    push(@to, ($opt =~ /d/ ? '' : $to[$#to]) x (@from - @to)) if @to < @from;
    @table{@from} = @to;
}

sub _expnd1 {
    local($s) = @_;
    $s =~ s/\\(.)/$1/g;
    local($c1, $c2) = unpack('CxC', $s);
    if ($c1 <= $c2) {
        for ($s = ''; $c1 <= $c2; $c1++) {
            $s .= pack('C', $c1);
        }
    }
    $s;
}

sub _expnd2 {
    local($s) = @_;
    local($c1, $c2, $c3, $c4) = unpack('CCxCC', $s);
    if ($c1 == $c3 && $c2 <= $c4) {
        for ($s = ''; $c2 <= $c4; $c2++) {
            $s .= pack('CC', $c1, $c2);
        }
    }
    $s;
}

1;