Text::Diff - Perform diffs on files and record sets

Text-Diff documentation Contained in the Text-Diff distribution.

Index

Code Index:

NAME

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Text::Diff - Perform diffs on files and record sets

SYNOPSIS

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    use Text::Diff;

    ## Mix and match filenames, strings, file handles, producer subs,
    ## or arrays of records; returns diff in a string.
    ## WARNING: can return B<large> diffs for large files.
    my $diff = diff "file1.txt", "file2.txt", { STYLE => "Context" };
    my $diff = diff \$string1,   \$string2,   \%options;
    my $diff = diff \*FH1,       \*FH2;
    my $diff = diff \&reader1,   \&reader2;
    my $diff = diff \@records1,  \@records2;

    ## May also mix input types:
    my $diff = diff \@records1,  "file_B.txt";

DESCRIPTION

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diff() provides a basic set of services akin to the GNU diff utility. It is not anywhere near as feature complete as GNU diff, but it is better integrated with Perl and available on all platforms. It is often faster than shelling out to a system's diff executable for small files, and generally slower on larger files.

Relies on Algorithm::Diff for, well, the algorithm. This may not produce the same exact diff as a system's local diff executable, but it will be a valid diff and comprehensible by patch. We haven't seen any differences between Algorithm::Diff's logic and GNU diff's, but we have not examined them to make sure they are indeed identical.

Note: If you don't want to import the diff function, do one of the following:

   use Text::Diff ();

   require Text::Diff;

That's a pretty rare occurence, so diff() is exported by default. =head1 OPTIONS

diff() takes two parameters from which to draw input and a set of options to control it's output. The options are:

FILENAME_A, MTIME_A, FILENAME_B, MTIME_B

The name of the file and the modification time "files"

These are filled in automatically for each file when diff() is passed a filename, unless a defined value is passed in.

If a filename is not passed in and FILENAME_A and FILENAME_B are not provided or undef, the header will not be printed.

Unused on OldStyle diffs.

OFFSET_A, OFFSET_B

The index of the first line / element. These default to 1 for all parameter types except ARRAY references, for which the default is 0. This is because ARRAY references are presumed to be data structures, while the others are line oriented text.

STYLE

"Unified", "Context", "OldStyle", or an object or class reference for a class providing file_header(), hunk_header(), hunk(), hunk_footer() and file_footer() methods. The two footer() methods are provided for overloading only; none of the formats provide them.

Defaults to "Unified" (unlike standard diff, but Unified is what's most often used in submitting patches and is the most human readable of the three.

If the package indicated by the STYLE has no hunk() method, c<diff()> will load it automatically (lazy loading). Since all such packages should inherit from Text::Diff::Base, this should be marvy.

Styles may be specified as class names (STYLE = "Foo"), in which case they will be new()ed with no parameters, or as objects (STYLE = Foo->new>).

CONTEXT

How many lines before and after each diff to display. Ignored on old-style diffs. Defaults to 3.

OUTPUT

Examples and their equivalent subroutines:

    OUTPUT   => \*FOOHANDLE,   # like: sub { print FOOHANDLE shift() }
    OUTPUT   => \$output,      # like: sub { $output .= shift }
    OUTPUT   => \@output,      # like: sub { push @output, shift }
    OUTPUT   => sub { $output .= shift },

If no OUTPUT is supplied, returns the diffs in a string. If OUTPUT is a CODE ref, it will be called once with the (optional) file header, and once for each hunk body with the text to emit. If OUTPUT is an IO::Handle, output will be emitted to that handle.

FILENAME_PREFIX_A, FILENAME_PREFIX_B

The string to print before the filename in the header. Unused on OldStyle diffs. Defaults are "---", "+++" for Unified and "***", "+++" for Context.

KEYGEN, KEYGEN_ARGS

These are passed to traverse_sequences in Algorithm::Diff.

Note: if neither FILENAME_ option is defined, the header will not be printed. If at one is present, the other and both MTIME_ options must be present or "Use of undefined variable" warnings will be generated (except on OldStyle diffs, which ignores these options).

Formatting Classes

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These functions implement the output formats. They are grouped in to classes so diff() can use class names to call the correct set of output routines and so that you may inherit from them easily. There are no constructors or instance methods for these classes, though subclasses may provide them if need be.

Each class has file_header(), hunk_header(), hunk(), and footer() methods identical to those documented in the Text::Diff::Unified section. header() is called before the hunk() is first called, footer() afterwards. The default footer function is an empty method provided for overloading:

    sub footer { return "End of patch\n" }

Some output formats are provided by external modules (which are loaded automatically), such as Text::Diff::Table. These are are documented here to keep the documentation simple.

Text::Diff::Base

Returns "" for all methods (other than new()).

Text::Diff::Unified

  --- A   Mon Nov 12 23:49:30 2001
  +++ B   Mon Nov 12 23:49:30 2001
  @@ -2,13 +2,13 @@
   2
   3
   4
  -5d
  +5a
   6
   7
   8
   9
  +9a
   10
   11
  -11d
   12
   13
file_header
  $s = Text::Diff::Unified->file_header( $options );

Returns a string containing a unified header. The sole parameter is the options hash passed in to diff(), containing at least:

  FILENAME_A  => $fn1,
  MTIME_A     => $mtime1,
  FILENAME_B  => $fn2,
  MTIME_B     => $mtime2

May also contain

  FILENAME_PREFIX_A    => "---",
  FILENAME_PREFIX_B    => "+++",

to override the default prefixes (default values shown).

hunk_header
  Text::Diff::Unified->hunk_header( \@ops, $options );

Returns a string containing the output of one hunk of unified diff.

Text::Diff::Unified::hunk
  Text::Diff::Unified->hunk( \@seq_a, \@seq_b, \@ops, $options );

Returns a string containing the output of one hunk of unified diff.

Text::Diff::Table

  +--+----------------------------------+--+------------------------------+
  |  |../Test-Differences-0.2/MANIFEST  |  |../Test-Differences/MANIFEST  |
  |  |Thu Dec 13 15:38:49 2001          |  |Sat Dec 15 02:09:44 2001      |
  +--+----------------------------------+--+------------------------------+
  |  |                                  * 1|Changes                       *
  | 1|Differences.pm                    | 2|Differences.pm                |
  | 2|MANIFEST                          | 3|MANIFEST                      |
  |  |                                  * 4|MANIFEST.SKIP                 *
  | 3|Makefile.PL                       | 5|Makefile.PL                   |
  |  |                                  * 6|t/00escape.t                  *
  | 4|t/00flatten.t                     | 7|t/00flatten.t                 |
  | 5|t/01text_vs_data.t                | 8|t/01text_vs_data.t            |
  | 6|t/10test.t                        | 9|t/10test.t                    |
  +--+----------------------------------+--+------------------------------+

This format also goes to some pains to highlight "invisible" characters on differing elements by selectively escaping whitespace:

  +--+--------------------------+--------------------------+
  |  |demo_ws_A.txt             |demo_ws_B.txt             |
  |  |Fri Dec 21 08:36:32 2001  |Fri Dec 21 08:36:50 2001  |
  +--+--------------------------+--------------------------+
  | 1|identical                 |identical                 |
  * 2|        spaced in         |        also spaced in    *
  * 3|embedded space            |embedded        tab       *
  | 4|identical                 |identical                 |
  * 5|        spaced in         |\ttabbed in               *
  * 6|trailing spaces\s\s\n     |trailing tabs\t\t\n       *
  | 7|identical                 |identical                 |
  * 8|lf line\n                 |crlf line\r\n             *
  * 9|embedded ws               |embedded\tws              *
  +--+--------------------------+--------------------------+

See Text::Diff::Table for more details, including how the whitespace escaping works.

Text::Diff::Context

    *** A   Mon Nov 12 23:49:30 2001
    --- B   Mon Nov 12 23:49:30 2001
    ***************
    *** 2,14 ****
      2
      3
      4
    ! 5d
      6
      7
      8
      9
      10
      11
    - 11d
      12
      13
    --- 2,14 ----
      2
      3
      4
    ! 5a
      6
      7
      8
      9
    + 9a
      10
      11
      12
      13

Note: hunk_header() returns only "***************\n".

Text::Diff::OldStyle

    5c5
    < 5d
    ---
    > 5a
    9a10
    > 9a
    12d12
    < 11d

Note: no file_header().

LIMITATIONS

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Must suck both input files entirely in to memory and store them with a normal amount of Perlish overhead (one array location) per record. This is implied by the implementation of Algorithm::Diff, which takes two arrays. If Algorithm::Diff ever offers an incremental mode, this can be changed (contact the maintainers of Algorithm::Diff and Text::Diff if you need this; it shouldn't be too terribly hard to tie arrays in this fashion).

Does not provide most of the more refined GNU diff options: recursive directory tree scanning, ignoring blank lines / whitespace, etc., etc. These can all be added as time permits and need arises, many are rather easy; patches quite welcome.

Uses closures internally, this may lead to leaks on perl versions 5.6.1 and prior if used many times over a process' life time.

AUTHOR

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Adam Kennedy <adamk@cpan.org>

Barrie Slaymaker <barries@slaysys.com>

COPYRIGHT

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Some parts copyright 2009 Adam Kennedy.

Copyright 2001 Barrie Slaymaker. All Rights Reserved.

You may use this under the terms of either the Artistic License or GNU Public License v 2.0 or greater.

Text-Diff documentation Contained in the Text-Diff distribution. 
package Text::Diff;

use 5.00503;
use strict;
use Carp;
use Exporter        ();
use Algorithm::Diff ();
use vars qw{$VERSION @ISA @EXPORT};
BEGIN {
	$VERSION = '1.41';
	@ISA     = 'Exporter';
	@EXPORT  = 'diff';
};

## Hunks are made of ops.  An op is the starting index for each
## sequence and the opcode:
use constant A       => 0;   # Array index before match/discard
use constant B       => 1;
use constant OPCODE  => 2;   # "-", " ", "+"
use constant FLAG    => 3;   # What to display if not OPCODE "!"

my %internal_styles = (
    Unified  => undef,
    Context  => undef,
    OldStyle => undef,
    Table    => undef,   ## "internal", but in another module
);

sub diff {
    my @seqs    = ( shift, shift );
    my $options = shift || {};

    for my $i ( 0 .. 1 ) {
        my $seq = $seqs[$i];
	my $type = ref $seq;

        while ( $type eq "CODE" ) {
	    $seqs[$i] = $seq = $seq->( $options );
	    $type = ref $seq;
	}

	my $AorB = !$i ? "A" : "B";

        if ( $type eq "ARRAY" ) {
            ## This is most efficient :)
            $options->{"OFFSET_$AorB"} = 0
                unless defined $options->{"OFFSET_$AorB"};
        }
        elsif ( $type eq "SCALAR" ) {
            $seqs[$i] = [split( /^/m, $$seq )];
            $options->{"OFFSET_$AorB"} = 1
                unless defined $options->{"OFFSET_$AorB"};
        }
        elsif ( ! $type ) {
            $options->{"OFFSET_$AorB"} = 1
                unless defined $options->{"OFFSET_$AorB"};
	    $options->{"FILENAME_$AorB"} = $seq
	        unless defined $options->{"FILENAME_$AorB"};
	    $options->{"MTIME_$AorB"} = (stat($seq))[9]
	        unless defined $options->{"MTIME_$AorB"};

            local $/ = "\n";
            open F, "<$seq" or carp "$!: $seq";
            $seqs[$i] = [<F>];
            close F;

        }
        elsif ( $type eq "GLOB" || UNIVERSAL::isa( $seq, "IO::Handle" ) ) {
            $options->{"OFFSET_$AorB"} = 1
                unless defined $options->{"OFFSET_$AorB"};
            local $/ = "\n";
            $seqs[$i] = [<$seq>];
        }
        else {
            confess "Can't handle input of type ", ref;
        }
    }

    ## Config vars
    my $output;
    my $output_handler = $options->{OUTPUT};
    my $type = ref $output_handler ;
    if ( ! defined $output_handler ) {
        $output = "";
        $output_handler = sub { $output .= shift };
    }
    elsif ( $type eq "CODE" ) {
        ## No problems, mate.
    }
    elsif ( $type eq "SCALAR" ) {
        my $out_ref = $output_handler;
        $output_handler = sub { $$out_ref .= shift };
    }
    elsif ( $type eq "ARRAY" ) {
        my $out_ref = $output_handler;
        $output_handler = sub { push @$out_ref, shift };
    }
    elsif ( $type eq "GLOB" || UNIVERSAL::isa $output_handler, "IO::Handle" ) {
        my $output_handle = $output_handler;
        $output_handler = sub { print $output_handle shift };
    }
    else {
        croak "Unrecognized output type: $type";
    }

    my $style  = $options->{STYLE};
    $style = "Unified" unless defined $options->{STYLE};
    $style = "Text::Diff::$style" if exists $internal_styles{$style};

    if ( ! $style->can( "hunk" ) ) {
	eval "require $style; 1" or die $@;
    }

    $style = $style->new
	if ! ref $style && $style->can( "new" );

    my $ctx_lines = $options->{CONTEXT};
    $ctx_lines = 3 unless defined $ctx_lines;
    $ctx_lines = 0 if $style->isa( "Text::Diff::OldStyle" );

    my @keygen_args = $options->{KEYGEN_ARGS}
        ? @{$options->{KEYGEN_ARGS}}
        : ();

    ## State vars
    my $diffs = 0; ## Number of discards this hunk
    my $ctx   = 0; ## Number of " " (ctx_lines) ops pushed after last diff.
    my @ops;       ## ops (" ", +, -) in this hunk
    my $hunks = 0; ## Number of hunks

    my $emit_ops = sub {
        $output_handler->( $style->file_header( @seqs,     $options ) )
	    unless $hunks++;
        $output_handler->( $style->hunk_header( @seqs, @_, $options ) );
        $output_handler->( $style->hunk       ( @seqs, @_, $options ) );
        $output_handler->( $style->hunk_footer( @seqs, @_, $options ) );
    };

    ## We keep 2*ctx_lines so that if a diff occurs
    ## at 2*ctx_lines we continue to grow the hunk instead
    ## of emitting diffs and context as we go. We
    ## need to know the total length of both of the two
    ## subsequences so the line count can be printed in the
    ## header.
    my $dis_a = sub {push @ops, [@_[0,1],"-"]; ++$diffs ; $ctx = 0 };
    my $dis_b = sub {push @ops, [@_[0,1],"+"]; ++$diffs ; $ctx = 0 };

    Algorithm::Diff::traverse_sequences(
        @seqs,
        {
            MATCH => sub {
                push @ops, [@_[0,1]," "];

                if ( $diffs && ++$ctx > $ctx_lines * 2 ) {
        	   $emit_ops->( [ splice @ops, 0, $#ops - $ctx_lines ] );
        	   $ctx = $diffs = 0;
                }

                ## throw away context lines that aren't needed any more
                shift @ops if ! $diffs && @ops > $ctx_lines;
            },
            DISCARD_A => $dis_a,
            DISCARD_B => $dis_b,
        },
        $options->{KEYGEN},  # pass in user arguments for key gen function
        @keygen_args,
    );

    if ( $diffs ) {
        $#ops -= $ctx - $ctx_lines if $ctx > $ctx_lines;
        $emit_ops->( \@ops );
    }

    $output_handler->( $style->file_footer( @seqs, $options ) ) if $hunks;

    return defined $output ? $output : $hunks;
}

sub _header {
    my ( $h ) = @_;
    my ( $p1, $fn1, $t1, $p2, $fn2, $t2 ) = @{$h}{
        "FILENAME_PREFIX_A",
        "FILENAME_A",
        "MTIME_A",
        "FILENAME_PREFIX_B",
        "FILENAME_B",
        "MTIME_B"
    };

    ## remember to change Text::Diff::Table if this logic is tweaked.
    return "" unless defined $fn1 && defined $fn2;

    return join( "",
        $p1, " ", $fn1, defined $t1 ? "\t" . localtime $t1 : (), "\n",
        $p2, " ", $fn2, defined $t2 ? "\t" . localtime $t2 : (), "\n",
    );
}

## _range encapsulates the building of, well, ranges.  Turns out there are
## a few nuances.
sub _range {
    my ( $ops, $a_or_b, $format ) = @_;

    my $start = $ops->[ 0]->[$a_or_b];
    my $after = $ops->[-1]->[$a_or_b];

    ## The sequence indexes in the lines are from *before* the OPCODE is
    ## executed, so we bump the last index up unless the OP indicates
    ## it didn't change.
    ++$after
        unless $ops->[-1]->[OPCODE] eq ( $a_or_b == A ? "+" : "-" );

    ## convert from 0..n index to 1..(n+1) line number.  The unless modifier
    ## handles diffs with no context, where only one file is affected.  In this
    ## case $start == $after indicates an empty range, and the $start must
    ## not be incremented.
    my $empty_range = $start == $after;
    ++$start unless $empty_range;

    return
        $start == $after
            ? $format eq "unified" && $empty_range
                ? "$start,0"
                : $start
            : $format eq "unified"
                ? "$start,".($after-$start+1)
                : "$start,$after";
}

sub _op_to_line {
    my ( $seqs, $op, $a_or_b, $op_prefixes ) = @_;

    my $opcode = $op->[OPCODE];
    return () unless defined $op_prefixes->{$opcode};

    my $op_sym = defined $op->[FLAG] ? $op->[FLAG] : $opcode;
    $op_sym = $op_prefixes->{$op_sym};
    return () unless defined $op_sym;

    $a_or_b = $op->[OPCODE] ne "+" ? 0 : 1 unless defined $a_or_b;
    return ( $op_sym, $seqs->[$a_or_b][$op->[$a_or_b]] );
}

SCOPE: {
    package Text::Diff::Base;

    sub new         {
        my $proto = shift;
	return bless { @_ }, ref $proto || $proto;
    }

    sub file_header { return "" }

    sub hunk_header { return "" }

    sub hunk        { return "" }

    sub hunk_footer { return "" }

    sub file_footer { return "" }
}

@Text::Diff::Unified::ISA = qw( Text::Diff::Base );

sub Text::Diff::Unified::file_header {
    shift; ## No instance data
    my $options = pop ;

    _header(
        { FILENAME_PREFIX_A => "---", FILENAME_PREFIX_B => "+++", %$options }
    );
}

sub Text::Diff::Unified::hunk_header {
    shift; ## No instance data
    pop; ## Ignore options
    my $ops = pop;

    return join( "",
        "@@ -",
        _range( $ops, A, "unified" ),
        " +",
        _range( $ops, B, "unified" ),
        " @@\n",
    );
}

sub Text::Diff::Unified::hunk {
    shift; ## No instance data
    pop; ## Ignore options
    my $ops = pop;

    my $prefixes = { "+" => "+", " " => " ", "-" => "-" };

    return join "", map _op_to_line( \@_, $_, undef, $prefixes ), @$ops
}

@Text::Diff::Context::ISA = qw( Text::Diff::Base );

sub Text::Diff::Context::file_header {
    _header { FILENAME_PREFIX_A=>"***", FILENAME_PREFIX_B=>"---", %{$_[-1]} };
}

sub Text::Diff::Context::hunk_header {
    return "***************\n";
}

sub Text::Diff::Context::hunk {
    shift; ## No instance data
    pop; ## Ignore options
    my $ops = pop;
    ## Leave the sequences in @_[0,1]

    my $a_range = _range( $ops, A, "" );
    my $b_range = _range( $ops, B, "" );

    ## Sigh.  Gotta make sure that differences that aren't adds/deletions
    ## get prefixed with "!", and that the old opcodes are removed.
    my $after;
    for ( my $start = 0; $start <= $#$ops ; $start = $after ) {
        ## Scan until next difference
        $after = $start + 1;
        my $opcode = $ops->[$start]->[OPCODE];
        next if $opcode eq " ";

        my $bang_it;
        while ( $after <= $#$ops && $ops->[$after]->[OPCODE] ne " " ) {
            $bang_it ||= $ops->[$after]->[OPCODE] ne $opcode;
            ++$after;
        }

        if ( $bang_it ) {
            for my $i ( $start..($after-1) ) {
                $ops->[$i]->[FLAG] = "!";
            }
        }
    }

    my $b_prefixes = { "+" => "+ ",  " " => "  ", "-" => undef, "!" => "! " };
    my $a_prefixes = { "+" => undef, " " => "  ", "-" => "- ",  "!" => "! " };

    return join( "",
        "*** ", $a_range, " ****\n",
        map( _op_to_line( \@_, $_, A, $a_prefixes ), @$ops ),
        "--- ", $b_range, " ----\n",
        map( _op_to_line( \@_, $_, B, $b_prefixes ), @$ops ),
    );
}

@Text::Diff::OldStyle::ISA = qw( Text::Diff::Base );

sub _op {
    my $ops = shift;
    my $op = $ops->[0]->[OPCODE];
    $op = "c" if grep $_->[OPCODE] ne $op, @$ops;
    $op = "a" if $op eq "+";
    $op = "d" if $op eq "-";
    return $op;
}

sub Text::Diff::OldStyle::hunk_header {
    shift; ## No instance data
    pop; ## ignore options
    my $ops = pop;

    my $op = _op $ops;

    return join "", _range( $ops, A, "" ), $op, _range( $ops, B, "" ), "\n";
}

sub Text::Diff::OldStyle::hunk {
    shift; ## No instance data
    pop; ## ignore options
    my $ops = pop;
    ## Leave the sequences in @_[0,1]

    my $a_prefixes = { "+" => undef,  " " => undef, "-" => "< "  };
    my $b_prefixes = { "+" => "> ",   " " => undef, "-" => undef };

    my $op = _op $ops;

    return join( "",
        map( _op_to_line( \@_, $_, A, $a_prefixes ), @$ops ),
        $op eq "c" ? "---\n" : (),
        map( _op_to_line( \@_, $_, B, $b_prefixes ), @$ops ),
    );
}

1;

__END__


1;