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/includes/diff/ -> engine.php (summary)

This file is part of the phpBB Forum Software package.

Copyright: (c) phpBB Limited
License: GNU General Public License, version 2 (GPL-2.0)
File Size: 557 lines (14 kb)
Included or required:0 times
Referenced: 0 times
Includes or requires: 0 files

Defines 1 class

diff_engine:: (5 methods):
  diff()
  _diag()
  _lcs_pos()
  _compareseq()
  _shift_boundaries()


Class: diff_engine  - X-Ref

Code from pear.php.net, Text_Diff-1.1.0 package
http://pear.php.net/package/Text_Diff/ (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/)

diff(&$from_lines, &$to_lines, $preserve_cr = true)   X-Ref
If set to true we trim all lines before we compare them. This ensures that sole space/tab changes do not trigger diffs.


_diag($xoff, $xlim, $yoff, $ylim, $nchunks)   X-Ref
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.

_lcs_pos($ypos)   X-Ref
No description

_compareseq($xoff, $xlim, $yoff, $ylim)   X-Ref
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.

_shift_boundaries($lines, &$changed, $other_changed)   X-Ref
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).



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