1package Text::Tabs;
2
3require Exporter;
4
5@ISA = (Exporter);
6@EXPORT = qw(expand unexpand $tabstop);
7
8use vars qw($VERSION $SUBVERSION $tabstop $debug);
9$VERSION = 2013.0523;
10$SUBVERSION = 'modern';
11
12use strict;
13
14use 5.010_000;
15
16BEGIN	{
17	$tabstop = 8;
18	$debug = 0;
19}
20
21my $CHUNK = qr/\X/;
22
23sub _xlen (_) { scalar(() = $_[0] =~ /$CHUNK/g) }
24sub _xpos (_) { _xlen( substr( $_[0], 0, pos($_[0]) ) ) }
25
26sub expand {
27	my @l;
28	my $pad;
29	for ( @_ ) {
30		my $s = '';
31		for (split(/^/m, $_, -1)) {
32			my $offs = 0;
33			s{\t}{
34			    # this works on both 5.10 and 5.11
35				$pad = $tabstop - (_xlen(${^PREMATCH}) + $offs) % $tabstop;
36			    # this works on 5.11, but fails on 5.10
37				#XXX# $pad = $tabstop - (_xpos() + $offs) % $tabstop;
38				$offs += $pad - 1;
39				" " x $pad;
40			}peg;
41			$s .= $_;
42		}
43		push(@l, $s);
44	}
45	return @l if wantarray;
46	return $l[0];
47}
48
49sub unexpand
50{
51	my (@l) = @_;
52	my @e;
53	my $x;
54	my $line;
55	my @lines;
56	my $lastbit;
57	my $ts_as_space = " " x $tabstop;
58	for $x (@l) {
59		@lines = split("\n", $x, -1);
60		for $line (@lines) {
61			$line = expand($line);
62			@e = split(/(${CHUNK}{$tabstop})/,$line,-1);
63			$lastbit = pop(@e);
64			$lastbit = ''
65				unless defined $lastbit;
66			$lastbit = "\t"
67				if $lastbit eq $ts_as_space;
68			for $_ (@e) {
69				if ($debug) {
70					my $x = $_;
71					$x =~ s/\t/^I\t/gs;
72					print "sub on '$x'\n";
73				}
74				s/  +$/\t/;
75			}
76			$line = join('',@e, $lastbit);
77		}
78		$x = join("\n", @lines);
79	}
80	return @l if wantarray;
81	return $l[0];
82}
83
841;
85__END__
86
87sub expand
88{
89	my (@l) = @_;
90	for $_ (@l) {
91		1 while s/(^|\n)([^\t\n]*)(\t+)/
92			$1. $2 . (" " x
93				($tabstop * length($3)
94				- (length($2) % $tabstop)))
95			/sex;
96	}
97	return @l if wantarray;
98	return $l[0];
99}
100
101
102=head1 NAME
103
104Text::Tabs - expand and unexpand tabs like unix expand(1) and unexpand(1)
105
106=head1 SYNOPSIS
107
108  use Text::Tabs;
109
110  $tabstop = 4;  # default = 8
111  @lines_without_tabs = expand(@lines_with_tabs);
112  @lines_with_tabs = unexpand(@lines_without_tabs);
113
114=head1 DESCRIPTION
115
116Text::Tabs does most of what the unix utilities expand(1) and unexpand(1)
117do.  Given a line with tabs in it, C<expand> replaces those tabs with
118the appropriate number of spaces.  Given a line with or without tabs in
119it, C<unexpand> adds tabs when it can save bytes by doing so,
120like the C<unexpand -a> command.
121
122Unlike the old unix utilities, this module correctly accounts for
123any Unicode combining characters (such as diacriticals) that may occur
124in each line for both expansion and unexpansion.  These are overstrike
125characters that do not increment the logical position.  Make sure
126you have the appropriate Unicode settings enabled.
127
128=head1 EXPORTS
129
130The following are exported:
131
132=over 4
133
134=item expand
135
136=item unexpand
137
138=item $tabstop
139
140The C<$tabstop> variable controls how many column positions apart each
141tabstop is.  The default is 8.
142
143Please note that C<local($tabstop)> doesn't do the right thing and if you want
144to use C<local> to override C<$tabstop>, you need to use
145C<local($Text::Tabs::tabstop)>.
146
147=back
148
149=head1 EXAMPLE
150
151  #!perl
152  # unexpand -a
153  use Text::Tabs;
154
155  while (<>) {
156    print unexpand $_;
157  }
158
159Instead of the shell's C<expand> command, use:
160
161  perl -MText::Tabs -n -e 'print expand $_'
162
163Instead of the shell's C<unexpand -a> command, use:
164
165  perl -MText::Tabs -n -e 'print unexpand $_'
166
167=head1 SUBVERSION
168
169This module comes in two flavors: one for modern perls (5.10 and above)
170and one for ancient obsolete perls.  The version for modern perls has
171support for Unicode.  The version for old perls does not.  You can tell
172which version you have installed by looking at C<$Text::Tabs::SUBVERSION>:
173it is C<old> for obsolete perls and C<modern> for current perls.
174
175This man page is for the version for modern perls and so that's probably
176what you've got.
177
178=head1 BUGS
179
180Text::Tabs handles only tabs (C<"\t">) and combining characters (C</\pM/>).  It doesn't
181count backwards for backspaces (C<"\t">), omit other non-printing control characters (C</\pC/>),
182or otherwise deal with any other zero-, half-, and full-width characters.
183
184=head1 LICENSE
185
186Copyright (C) 1996-2002,2005,2006 David Muir Sharnoff.
187Copyright (C) 2005 Aristotle Pagaltzis
188Copyright (C) 2012-2013 Google, Inc.
189This module may be modified, used, copied, and redistributed at your own risk.
190Although allowed by the preceding license, please do not publicly
191redistribute modified versions of this code with the name "Text::Tabs"
192unless it passes the unmodified Text::Tabs test suite.
193