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DiffOld.pm
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# This is a version of Algorithm::Diff that uses only a comparison function, # like versions <= 0.59 used to. # $Revision: 1.3 $ package Algorithm::DiffOld; use strict; use vars qw($VERSION @EXPORT_OK @ISA @EXPORT); use integer; # see below in _replaceNextLargerWith() for mod to make # if you don't use this require Exporter; @ISA = qw(Exporter); @EXPORT = qw(); @EXPORT_OK = qw(LCS diff traverse_sequences); $VERSION = 1.10; # manually tracking Algorithm::Diff # McIlroy-Hunt diff algorithm # Adapted from the Smalltalk code of Mario I. Wolczko, <mario@wolczko.com> # by Ned Konz, perl@bike-nomad.com =head1 NAME Algorithm::DiffOld - Compute `intelligent' differences between two files / lists but use the old (<=0.59) interface. =head1 NOTE This has been provided as part of the Algorithm::Diff package by Ned Konz. This particular module is B<ONLY> for people who B<HAVE> to have the old interface, which uses a comparison function rather than a key generating function. Because each of the lines in one array have to be compared with each of the lines in the other array, this does M*N comparisons. This can be very slow. I clocked it at taking 18 times as long as the stock version of Algorithm::Diff for a 4000-line file. It will get worse quadratically as array sizes increase. =head1 SYNOPSIS use Algorithm::DiffOld qw(diff LCS traverse_sequences); @lcs = LCS( \@seq1, \@seq2, $comparison_function ); $lcsref = LCS( \@seq1, \@seq2, $comparison_function ); @diffs = diff( \@seq1, \@seq2, $comparison_function ); traverse_sequences( \@seq1, \@seq2, { MATCH => $callback, DISCARD_A => $callback, DISCARD_B => $callback, }, $comparison_function ); =head1 COMPARISON FUNCTIONS Each of the main routines should be passed a comparison function. If you aren't passing one in, B<use Algorithm::Diff instead>. These functions should return a true value when two items should compare as equal. For instance, @lcs = LCS( \@seq1, \@seq2, sub { my ($a, $b) = @_; $a eq $b } ); but if that is all you're doing with your comparison function, just use Algorithm::Diff and let it do this (this is its default). Or: sub someFunkyComparisonFunction { my ($a, $b) = @_; $a =~ m{$b}; } @diffs = diff( \@lines, \@patterns, \&someFunkyComparisonFunction ); which would allow you to diff an array @lines which consists of text lines with an array @patterns which consists of regular expressions. This is actually the reason I wrote this version -- there is no way to do this with a key generation function as in the stock Algorithm::Diff. =cut # Find the place at which aValue would normally be inserted into the array. If # that place is already occupied by aValue, do nothing, and return undef. If # the place does not exist (i.e., it is off the end of the array), add it to # the end, otherwise replace the element at that point with aValue. # It is assumed that the array's values are numeric. # This is where the bulk (75%) of the time is spent in this module, so try to # make it fast! sub _replaceNextLargerWith { my ( $array, $aValue, $high ) = @_; $high ||= $#$array; # off the end? if ( $high == -1 || $aValue > $array->[ -1 ] ) { push( @$array, $aValue ); return $high + 1; } # binary search for insertion point... my $low = 0; my $index; my $found; while ( $low <= $high ) { $index = ( $high + $low ) / 2; # $index = int(( $high + $low ) / 2); # without 'use integer' $found = $array->[ $index ]; if ( $aValue == $found ) { return undef; } elsif ( $aValue > $found ) { $low = $index + 1; } else { $high = $index - 1; } } # now insertion point is in $low. $array->[ $low ] = $aValue; # overwrite next larger return $low; } # This method computes the longest common subsequence in $a and $b. # Result is array or ref, whose contents is such that # $a->[ $i ] == $b->[ $result[ $i ] ] # foreach $i in ( 0 .. $#result ) if $result[ $i ] is defined. # An additional argument may be passed; this is a CODE ref to a comparison # routine. By default, comparisons will use "eq" . # Note that this routine will be called as many as M*N times, so make it fast! # Additional parameters, if any, will be passed to the key generation routine. sub _longestCommonSubsequence { my $a = shift; # array ref my $b = shift; # array ref my $compare = shift || sub { my $a = shift; my $b = shift; $a eq $b }; my $aStart = 0; my $aFinish = $#$a; my $bStart = 0; my $bFinish = $#$b; my $matchVector = []; # First we prune off any common elements at the beginning while ( $aStart <= $aFinish and $bStart <= $bFinish and &$compare( $a->[ $aStart ], $b->[ $bStart ], @_ ) ) { $matchVector->[ $aStart++ ] = $bStart++; } # now the end while ( $aStart <= $aFinish and $bStart <= $bFinish and &$compare( $a->[ $aFinish ], $b->[ $bFinish ], @_ ) ) { $matchVector->[ $aFinish-- ] = $bFinish--; } my $thresh = []; my $links = []; my ( $i, $ai, $j, $k ); for ( $i = $aStart; $i <= $aFinish; $i++ ) { $k = 0; # look for each element of @b between $bStart and $bFinish # that matches $a->[ $i ], in reverse order for ($j = $bFinish; $j >= $bStart; $j--) { next if ! &$compare( $a->[$i], $b->[$j], @_ ); # optimization: most of the time this will be true if ( $k and $thresh->[ $k ] > $j and $thresh->[ $k - 1 ] < $j ) { $thresh->[ $k ] = $j; } else { $k = _replaceNextLargerWith( $thresh, $j, $k ); } # oddly, it's faster to always test this (CPU cache?). if ( defined( $k ) ) { $links->[ $k ] = [ ( $k ? $links->[ $k - 1 ] : undef ), $i, $j ]; } } } if ( @$thresh ) { for ( my $link = $links->[ $#$thresh ]; $link; $link = $link->[ 0 ] ) { $matchVector->[ $link->[ 1 ] ] = $link->[ 2 ]; } } return wantarray ? @$matchVector : $matchVector; } sub traverse_sequences { my $a = shift; # array ref my $b = shift; # array ref my $callbacks = shift || { }; my $compare = shift; my $matchCallback = $callbacks->{'MATCH'} || sub { }; my $discardACallback = $callbacks->{'DISCARD_A'} || sub { }; my $finishedACallback = $callbacks->{'A_FINISHED'}; my $discardBCallback = $callbacks->{'DISCARD_B'} || sub { }; my $finishedBCallback = $callbacks->{'B_FINISHED'}; my $matchVector = _longestCommonSubsequence( $a, $b, $compare, @_ ); # Process all the lines in match vector my $lastA = $#$a; my $lastB = $#$b; my $bi = 0; my $ai; for ( $ai = 0; $ai <= $#$matchVector; $ai++ ) { my $bLine = $matchVector->[ $ai ]; if ( defined( $bLine ) ) # matched { &$discardBCallback( $ai, $bi++, @_ ) while $bi < $bLine; &$matchCallback( $ai, $bi++, @_ ); } else { &$discardACallback( $ai, $bi, @_ ); } } # the last entry (if any) processed was a match. if ( defined( $finishedBCallback ) && $ai <= $lastA ) { &$finishedBCallback( $bi, @_ ); } else { &$discardACallback( $ai++, $bi, @_ ) while ( $ai <= $lastA ); } if ( defined( $finishedACallback ) && $bi <= $lastB ) { &$finishedACallback( $ai, @_ ); } else { &$discardBCallback( $ai, $bi++, @_ ) while ( $bi <= $lastB ); } return 1; } sub LCS { my $a = shift; # array ref my $matchVector = _longestCommonSubsequence( $a, @_ ); my @retval; my $i; for ( $i = 0; $i <= $#$matchVector; $i++ ) { if ( defined( $matchVector->[ $i ] ) ) { push( @retval, $a->[ $i ] ); } } return wantarray ? @retval : \@retval; } sub diff { my $a = shift; # array ref my $b = shift; # array ref my $retval = []; my $hunk = []; my $discard = sub { push( @$hunk, [ '-', $_[ 0 ], $a->[ $_[ 0 ] ] ] ) }; my $add = sub { push( @$hunk, [ '+', $_[ 1 ], $b->[ $_[ 1 ] ] ] ) }; my $match = sub { push( @$retval, $hunk ) if scalar(@$hunk); $hunk = [] }; traverse_sequences( $a, $b, { MATCH => $match, DISCARD_A => $discard, DISCARD_B => $add }, @_ ); &$match(); return wantarray ? @$retval : $retval; } 1;