phpBB API Documentation
Class

diff_engine

class diff_engine

Code from pear.php.net, TextDiff-1.1.0 package http://pear.php.net/package/TextDiff/ (native engine)

Modified by phpBB Limited to meet our coding standards and being able to integrate into phpBB

Class used internally by Text_Diff to actually compute the diffs. This class is implemented using native PHP code.

The algorithm used here is mostly lifted from the perl module Algorithm::Diff (version 1.06) by Ned Konz, which is available at: http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip

More ideas are taken from: http://www.ics.uci.edu/~eppstein/161/960229.html

Some ideas (and a bit of code) are taken from analyze.c, of GNU diffutils-2.7, which can be found at: ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz

Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from Geoffrey T. Dairiki dairiki@dairiki.org. The original PHP version of this code was written by him, and is used/adapted with his permission.

Copyright 2004-2008 The Horde Project (http://www.horde.org/)

Properties

$skip_whitespace_changes If set to true we trim all lines before we compare them.

Methods

diff($from_lines, $to_lines, $preserve_cr = true)

_diag($xoff, $xlim, $yoff, $ylim, $nchunks)

Divides the Largest Common Subsequence (LCS) of the sequences (XOFF, XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized segments.

_lcs_pos($ypos)

_compareseq($xoff, $xlim, $yoff, $ylim)

Finds LCS of two sequences.

_shift_boundaries($lines, $changed, $other_changed)

Adjusts inserts/deletes of identical lines to join changes as much as possible.

Details

at line 60
public diff($from_lines, $to_lines, $preserve_cr = true)

Parameters

$from_lines
$to_lines
$preserve_cr

at line 232
public _diag($xoff, $xlim, $yoff, $ylim, $nchunks)

Divides the Largest Common Subsequence (LCS) of the sequences (XOFF, XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized segments.

Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of NCHUNKS+1 (X, Y) indexes giving the diving points between sub sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1), the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) == (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).

This function assumes that the first lines of the specified portions of the two files do not match, and likewise that the last lines do not match. The caller must trim matching lines from the beginning and end of the portions it is going to specify.

Parameters

$xoff
$xlim
$yoff
$ylim
$nchunks

at line 331
public _lcs_pos($ypos)

Parameters

$ypos

at line 375
public _compareseq($xoff, $xlim, $yoff, $ylim)

Finds LCS of two sequences.

The results are recorded in the vectors $this->{x,y}changed[], by storing a 1 in the element for each line that is an insertion or deletion (ie. is not in the LCS).

The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.

Note that XLIM, YLIM are exclusive bounds. All line numbers are origin-0 and discarded lines are not counted.

Parameters

$xoff
$xlim
$yoff
$ylim

at line 442
public _shift_boundaries($lines, $changed, $other_changed)

Adjusts inserts/deletes of identical lines to join changes as much as possible.

We do something when a run of changed lines include a line at one end and has an excluded, identical line at the other. We are free to choose which identical line is included. 'compareseq' usually chooses the one at the beginning, but usually it is cleaner to consider the following identical line to be the "change".

This is extracted verbatim from analyze.c (GNU diffutils-2.7).

Parameters

$lines
$changed
$other_changed