<?php
/**
*
* This file is part of the phpBB Forum Software package.
*
* @copyright (c) phpBB Limited <https://www.phpbb.com>
* @license GNU General Public License, version 2 (GPL-2.0)
*
* For full copyright and license information, please see
* the docs/CREDITS.txt file.
*
*/
/**
* @ignore
*/
if (!defined('IN_PHPBB'))
{
exit;
}
/**
* 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/)
*
* @author Geoffrey T. Dairiki <dairiki@dairiki.org>
* @package diff
*
* @access private
*/
class diff_engine
{
/**
* If set to true we trim all lines before we compare them. This ensures that sole space/tab changes do not trigger diffs.
*/
var $skip_whitespace_changes = true;
function diff(&$from_lines, &$to_lines, $preserve_cr = true)
{
// Remove empty lines...
// If preserve_cr is true, we basically only change \r\n and bare \r to \n to get the same carriage returns for both files
// If it is false, we try to only use \n once per line and ommit all empty lines to be able to get a proper data diff
if (is_array($from_lines))
{
$from_lines = implode("\n", $from_lines);
}
if (is_array($to_lines))
{
$to_lines = implode("\n", $to_lines);
}
if ($preserve_cr)
{
$from_lines = explode("\n", str_replace("\r", "\n", str_replace("\r\n", "\n", $from_lines)));
$to_lines = explode("\n", str_replace("\r", "\n", str_replace("\r\n", "\n", $to_lines)));
}
else
{
$from_lines = explode("\n", preg_replace('#[\n\r]+#', "\n", $from_lines));
$to_lines = explode("\n", preg_replace('#[\n\r]+#', "\n", $to_lines));
}
$n_from = count($from_lines);
$n_to = count($to_lines);
$this->xchanged = $this->ychanged = $this->xv = $this->yv = $this->xind = $this->yind = array();
unset($this->seq, $this->in_seq, $this->lcs);
// Skip leading common lines.
for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++)
{
if (trim($from_lines[$skip]) !== trim($to_lines[$skip]))
{
break;
}
$this->xchanged[$skip] = $this->ychanged[$skip] = false;
}
// Skip trailing common lines.
$xi = $n_from;
$yi = $n_to;
for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++)
{
if (trim($from_lines[$xi]) !== trim($to_lines[$yi]))
{
break;
}
$this->xchanged[$xi] = $this->ychanged[$yi] = false;
}
// Ignore lines which do not exist in both files.
for ($xi = $skip; $xi < $n_from - $endskip; $xi++)
{
if ($this->skip_whitespace_changes) $xhash[trim($from_lines[$xi])] = 1; else $xhash[$from_lines[$xi]] = 1;
}
for ($yi = $skip; $yi < $n_to - $endskip; $yi++)
{
$line = ($this->skip_whitespace_changes) ? trim($to_lines[$yi]) : $to_lines[$yi];
if (($this->ychanged[$yi] = empty($xhash[$line])))
{
continue;
}
$yhash[$line] = 1;
$this->yv[] = $line;
$this->yind[] = $yi;
}
for ($xi = $skip; $xi < $n_from - $endskip; $xi++)
{
$line = ($this->skip_whitespace_changes) ? trim($from_lines[$xi]) : $from_lines[$xi];
if (($this->xchanged[$xi] = empty($yhash[$line])))
{
continue;
}
$this->xv[] = $line;
$this->xind[] = $xi;
}
// Find the LCS.
$this->_compareseq(0, count($this->xv), 0, count($this->yv));
// Merge edits when possible.
if ($this->skip_whitespace_changes)
{
$from_lines_clean = array_map('trim', $from_lines);
$to_lines_clean = array_map('trim', $to_lines);
$this->_shift_boundaries($from_lines_clean, $this->xchanged, $this->ychanged);
$this->_shift_boundaries($to_lines_clean, $this->ychanged, $this->xchanged);
unset($from_lines_clean, $to_lines_clean);
}
else
{
$this->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
$this->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);
}
// Compute the edit operations.
$edits = array();
$xi = $yi = 0;
while ($xi < $n_from || $yi < $n_to)
{
// Skip matching "snake".
$copy = array();
while ($xi < $n_from && $yi < $n_to && !$this->xchanged[$xi] && !$this->ychanged[$yi])
{
$copy[] = $from_lines[$xi++];
$yi++;
}
if ($copy)
{
$edits[] = new diff_op_copy($copy);
}
// Find deletes & adds.
$delete = array();
while ($xi < $n_from && $this->xchanged[$xi])
{
$delete[] = $from_lines[$xi++];
}
$add = array();
while ($yi < $n_to && $this->ychanged[$yi])
{
$add[] = $to_lines[$yi++];
}
if ($delete && $add)
{
$edits[] = new diff_op_change($delete, $add);
}
else if ($delete)
{
$edits[] = new diff_op_delete($delete);
}
else if ($add)
{
$edits[] = new diff_op_add($add);
}
}
return $edits;
}
/**
* Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
* XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized segments.
*
* Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of
* NCHUNKS+1 (X, Y) indexes giving the diving points between sub
* sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1),
* the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) ==
* (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
*
* This function assumes that the first lines of the specified portions of
* the two files do not match, and likewise that the last lines do not
* match. The caller must trim matching lines from the beginning and end
* of the portions it is going to specify.
*/
function _diag($xoff, $xlim, $yoff, $ylim, $nchunks)
{
$flip = false;
if ($xlim - $xoff > $ylim - $yoff)
{
// Things seems faster (I'm not sure I understand why) when the shortest sequence is in X.
$flip = true;
list($xoff, $xlim, $yoff, $ylim) = array($yoff, $ylim, $xoff, $xlim);
}
if ($flip)
{
for ($i = $ylim - 1; $i >= $yoff; $i--)
{
$ymatches[$this->xv[$i]][] = $i;
}
}
else
{
for ($i = $ylim - 1; $i >= $yoff; $i--)
{
$ymatches[$this->yv[$i]][] = $i;
}
}
$this->lcs = 0;
$this->seq[0]= $yoff - 1;
$this->in_seq = array();
$ymids[0] = array();
$numer = $xlim - $xoff + $nchunks - 1;
$x = $xoff;
for ($chunk = 0; $chunk < $nchunks; $chunk++)
{
if ($chunk > 0)
{
for ($i = 0; $i <= $this->lcs; $i++)
{
$ymids[$i][$chunk - 1] = $this->seq[$i];
}
}
$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $chunk) / $nchunks);
for (; $x < $x1; $x++)
{
$line = $flip ? $this->yv[$x] : $this->xv[$x];
if (empty($ymatches[$line]))
{
continue;
}
$matches = $ymatches[$line];
reset($matches);
while ($y = current($matches))
{
next($matches);
if (empty($this->in_seq[$y]))
{
$k = $this->_lcs_pos($y);
$ymids[$k] = $ymids[$k - 1];
break;
}
}
// no reset() here
while ($y = current($matches))
{
next($matches);
if ($y > $this->seq[$k - 1])
{
// Optimization: this is a common case: next match is just replacing previous match.
$this->in_seq[$this->seq[$k]] = false;
$this->seq[$k] = $y;
$this->in_seq[$y] = 1;
}
else if (empty($this->in_seq[$y]))
{
$k = $this->_lcs_pos($y);
$ymids[$k] = $ymids[$k - 1];
}
}
}
}
$seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
$ymid = $ymids[$this->lcs];
for ($n = 0; $n < $nchunks - 1; $n++)
{
$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
$y1 = $ymid[$n] + 1;
$seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
}
$seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
return array($this->lcs, $seps);
}
function _lcs_pos($ypos)
{
$end = $this->lcs;
if ($end == 0 || $ypos > $this->seq[$end])
{
$this->seq[++$this->lcs] = $ypos;
$this->in_seq[$ypos] = 1;
return $this->lcs;
}
$beg = 1;
while ($beg < $end)
{
$mid = (int)(($beg + $end) / 2);
if ($ypos > $this->seq[$mid])
{
$beg = $mid + 1;
}
else
{
$end = $mid;
}
}
$this->in_seq[$this->seq[$end]] = false;
$this->seq[$end] = $ypos;
$this->in_seq[$ypos] = 1;
return $end;
}
/**
* Finds LCS of two sequences.
*
* The results are recorded in the vectors $this->{x,y}changed[], by
* storing a 1 in the element for each line that is an insertion or
* deletion (ie. is not in the LCS).
*
* The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
*
* Note that XLIM, YLIM are exclusive bounds. All line numbers are
* origin-0 and discarded lines are not counted.
*/
function _compareseq($xoff, $xlim, $yoff, $ylim)
{
// Slide down the bottom initial diagonal.
while ($xoff < $xlim && $yoff < $ylim && $this->xv[$xoff] == $this->yv[$yoff])
{
++$xoff;
++$yoff;
}
// Slide up the top initial diagonal.
while ($xlim > $xoff && $ylim > $yoff && $this->xv[$xlim - 1] == $this->yv[$ylim - 1])
{
--$xlim;
--$ylim;
}
if ($xoff == $xlim || $yoff == $ylim)
{
$lcs = 0;
}
else
{
// This is ad hoc but seems to work well.
// $nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
// $nchunks = max(2,min(8,(int)$nchunks));
$nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
list($lcs, $seps) = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
}
if ($lcs == 0)
{
// X and Y sequences have no common subsequence: mark all changed.
while ($yoff < $ylim)
{
$this->ychanged[$this->yind[$yoff++]] = 1;
}
while ($xoff < $xlim)
{
$this->xchanged[$this->xind[$xoff++]] = 1;
}
}
else
{
// Use the partitions to split this problem into subproblems.
reset($seps);
$pt1 = $seps[0];
while ($pt2 = next($seps))
{
$this->_compareseq($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
$pt1 = $pt2;
}
}
}
/**
* Adjusts inserts/deletes of identical lines to join changes as much as possible.
*
* We do something when a run of changed lines include a line at one end
* and has an excluded, identical line at the other. We are free to
* choose which identical line is included. 'compareseq' usually chooses
* the one at the beginning, but usually it is cleaner to consider the
* following identical line to be the "change".
*
* This is extracted verbatim from analyze.c (GNU diffutils-2.7).
*/
function _shift_boundaries($lines, &$changed, $other_changed)
{
$i = 0;
$j = 0;
$len = count($lines);
$other_len = count($other_changed);
while (1)
{
// Scan forward to find the beginning of another run of
// changes. Also keep track of the corresponding point in the other file.
//
// Throughout this code, $i and $j are adjusted together so that
// the first $i elements of $changed and the first $j elements of
// $other_changed both contain the same number of zeros (unchanged lines).
//
// Furthermore, $j is always kept so that $j == $other_len or $other_changed[$j] == false.
while ($j < $other_len && $other_changed[$j])
{
$j++;
}
while ($i < $len && ! $changed[$i])
{
$i++;
$j++;
while ($j < $other_len && $other_changed[$j])
{
$j++;
}
}
if ($i == $len)
{
break;
}
$start = $i;
// Find the end of this run of changes.
while (++$i < $len && $changed[$i])
{
continue;
}
do
{
// Record the length of this run of changes, so that we can later determine whether the run has grown.
$runlength = $i - $start;
// Move the changed region back, so long as the previous unchanged line matches the last changed one.
// This merges with previous changed regions.
while ($start > 0 && $lines[$start - 1] == $lines[$i - 1])
{
$changed[--$start] = 1;
$changed[--$i] = false;
while ($start > 0 && $changed[$start - 1])
{
$start--;
}
while ($other_changed[--$j])
{
continue;
}
}
// Set CORRESPONDING to the end of the changed run, at the last point where it corresponds to a changed run in the
// other file. CORRESPONDING == LEN means no such point has been found.
$corresponding = $j < $other_len ? $i : $len;
// Move the changed region forward, so long as the first changed line matches the following unchanged one.
// This merges with following changed regions.
// Do this second, so that if there are no merges, the changed region is moved forward as far as possible.
while ($i < $len && $lines[$start] == $lines[$i])
{
$changed[$start++] = false;
$changed[$i++] = 1;
while ($i < $len && $changed[$i])
{
$i++;
}
$j++;
if ($j < $other_len && $other_changed[$j])
{
$corresponding = $i;
while ($j < $other_len && $other_changed[$j])
{
$j++;
}
}
}
}
while ($runlength != $i - $start);
// If possible, move the fully-merged run of changes back to a corresponding run in the other file.
while ($corresponding < $i)
{
$changed[--$start] = 1;
$changed[--$i] = 0;
while ($other_changed[--$j])
{
continue;
}
}
}
}
}