package Text::Tabs;

require Exporter;

@ISA = (Exporter);
@EXPORT = qw(expand unexpand $tabstop);

use vars qw($VERSION $tabstop $debug);
$VERSION = 2009.0305;

use strict;

BEGIN {
$tabstop = 8;
$debug = 0;
}

sub expand {
my @l;
my $pad;
for ( @_ ) {
my $s = '';
for (split(/^/m, $_, -1)) {
my $offs = 0;
s{\t}{
$pad = $tabstop - (pos() + $offs) % $tabstop;
$offs += $pad - 1;
" " x $pad;
}eg;
$s .= $_;
}
push(@l, $s);
}
return @l if wantarray;
return $l[0];
}

sub unexpand
{
my (@l) = @_;
my @e;
my $x;
my $line;
my @lines;
my $lastbit;
my $ts_as_space = " "x$tabstop;
for $x (@l) {
@lines = split("\n", $x, -1);
for $line (@lines) {
$line = expand($line);
@e = split(/(.{$tabstop})/,$line,-1);
$lastbit = pop(@e);
$lastbit = ''
unless defined $lastbit;
$lastbit = "\t"
if $lastbit eq $ts_as_space;
for $_ (@e) {
if ($debug) {
my $x = $_;
$x =~ s/\t/^I\t/gs;
print "sub on '$x'\n";
}
s/ +$/\t/;
}
$line = join('',@e, $lastbit);
}
$x = join("\n", @lines);
}
return @l if wantarray;
return $l[0];
}

1;
__END__

sub expand
{
my (@l) = @_;
for $_ (@l) {
1 while s/(^|\n)([^\t\n]*)(\t+)/
$1. $2 . (" " x
($tabstop * length($3)
- (length($2) % $tabstop)))
/sex;
}
return @l if wantarray;
return $l[0];
}


=head1 NAME

Text::Tabs -- expand and unexpand tabs per the unix expand(1) and unexpand(1)

=head1 SYNOPSIS

use Text::Tabs;

$tabstop = 4; # default = 8
@lines_without_tabs = expand(@lines_with_tabs);
@lines_with_tabs = unexpand(@lines_without_tabs);

=head1 DESCRIPTION

Text::Tabs does about what the unix utilities expand(1) and unexpand(1)
do. Given a line with tabs in it, expand will replace the tabs with
the appropriate number of spaces. Given a line with or without tabs in
it, unexpand will add tabs when it can save bytes by doing so (just
like C<unexpand -a>). Invisible compression with plain ASCII!

=head1 EXAMPLE

#!perl
# unexpand -a
use Text::Tabs;

while (<>) {
print unexpand $_;
}

Instead of the C<expand> comand, use:

perl -MText::Tabs -n -e 'print expand $_'

Instead of the C<unexpand -a> command, use:

perl -MText::Tabs -n -e 'print unexpand $_'

=head1 LICENSE

Copyright (C) 1996-2002,2005,2006 David Muir Sharnoff.
Copyright (C) 2005 Aristotle Pagaltzis
This module may be modified, used, copied, and redistributed at your own risk.
Publicly redistributed modified versions must use a different name.