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* @version $Id: engine.php,v 1.7 2007/10/05 14:36:33 acydburn Exp $
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* @copyright (c) 2006 phpBB Group
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* @license http://opensource.org/licenses/gpl-license.php GNU Public License
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if (!defined('IN_PHPBB'))
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* Code from pear.php.net, Text_Diff-0.2.1 (beta) package
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* http://pear.php.net/package/Text_Diff/
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* Modified by phpBB Group to meet our coding standards
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* and being able to integrate into phpBB
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* Class used internally by Diff to actually compute the diffs. This class is
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* implemented using native PHP code.
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* The algorithm used here is mostly lifted from the perl module
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* Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
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* http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
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* More ideas are taken from:
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* http://www.ics.uci.edu/~eppstein/161/960229.html
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* Some ideas (and a bit of code) are taken from analyze.c, of GNU
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* diffutils-2.7, which can be found at:
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* ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
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* Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
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* Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
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* code was written by him, and is used/adapted with his permission.
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* @author Geoffrey T. Dairiki <dairiki@dairiki.org>
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function diff(&$from_lines, &$to_lines, $preserve_cr = true)
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// Remove empty lines...
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// If preserve_cr is true, we basically only change \r\n and bare \r to \n to get the same carriage returns for both files
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// If it is false, we try to only use \n once per line and ommit all empty lines to be able to get a proper data diff
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if (is_array($from_lines))
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$from_lines = implode("\n", $from_lines);
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if (is_array($to_lines))
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$to_lines = implode("\n", $to_lines);
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$from_lines = explode("\n", str_replace("\r", "\n", str_replace("\r\n", "\n", $from_lines)));
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$to_lines = explode("\n", str_replace("\r", "\n", str_replace("\r\n", "\n", $to_lines)));
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$from_lines = explode("\n", preg_replace('#[\n\r]+#', "\n", $from_lines));
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$to_lines = explode("\n", preg_replace('#[\n\r]+#', "\n", $to_lines));
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$n_from = sizeof($from_lines);
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$n_to = sizeof($to_lines);
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$this->xchanged = $this->ychanged = $this->xv = $this->yv = $this->xind = $this->yind = array();
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unset($this->seq, $this->in_seq, $this->lcs);
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// Skip leading common lines.
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for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++)
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if ($from_lines[$skip] !== $to_lines[$skip])
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$this->xchanged[$skip] = $this->ychanged[$skip] = false;
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// Skip trailing common lines.
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for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++)
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if ($from_lines[$xi] !== $to_lines[$yi])
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$this->xchanged[$xi] = $this->ychanged[$yi] = false;
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// Ignore lines which do not exist in both files.
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for ($xi = $skip; $xi < $n_from - $endskip; $xi++)
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$xhash[$from_lines[$xi]] = 1;
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for ($yi = $skip; $yi < $n_to - $endskip; $yi++)
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$line = $to_lines[$yi];
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if (($this->ychanged[$yi] = empty($xhash[$line])))
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for ($xi = $skip; $xi < $n_from - $endskip; $xi++)
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$line = $from_lines[$xi];
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if (($this->xchanged[$xi] = empty($yhash[$line])))
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$this->_compareseq(0, sizeof($this->xv), 0, sizeof($this->yv));
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// Merge edits when possible.
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$this->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
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$this->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);
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// Compute the edit operations.
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while ($xi < $n_from || $yi < $n_to)
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// Skip matching "snake".
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while ($xi < $n_from && $yi < $n_to && !$this->xchanged[$xi] && !$this->ychanged[$yi])
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$copy[] = $from_lines[$xi++];
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$edits[] = &new diff_op_copy($copy);
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// Find deletes & adds.
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while ($xi < $n_from && $this->xchanged[$xi])
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$delete[] = $from_lines[$xi++];
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while ($yi < $n_to && $this->ychanged[$yi])
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$add[] = $to_lines[$yi++];
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$edits[] = &new diff_op_change($delete, $add);
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$edits[] = &new diff_op_delete($delete);
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$edits[] = &new diff_op_add($add);
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* Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
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* XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized segments.
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* Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of
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* NCHUNKS+1 (X, Y) indexes giving the diving points between sub
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* sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1),
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* the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) ==
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* (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
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* This function assumes that the first lines of the specified portions of
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* the two files do not match, and likewise that the last lines do not
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* match. The caller must trim matching lines from the beginning and end
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* of the portions it is going to specify.
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function _diag($xoff, $xlim, $yoff, $ylim, $nchunks)
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if ($xlim - $xoff > $ylim - $yoff)
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// Things seems faster (I'm not sure I understand why) when the shortest sequence is in X.
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list($xoff, $xlim, $yoff, $ylim) = array($yoff, $ylim, $xoff, $xlim);
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for ($i = $ylim - 1; $i >= $yoff; $i--)
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$ymatches[$this->xv[$i]][] = $i;
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for ($i = $ylim - 1; $i >= $yoff; $i--)
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$ymatches[$this->yv[$i]][] = $i;
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$this->seq[0]= $yoff - 1;
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$this->in_seq = array();
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$numer = $xlim - $xoff + $nchunks - 1;
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for ($chunk = 0; $chunk < $nchunks; $chunk++)
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for ($i = 0; $i <= $this->lcs; $i++)
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$ymids[$i][$chunk - 1] = $this->seq[$i];
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$x1 = $xoff + (int)(($numer + ($xlim-$xoff)*$chunk) / $nchunks);
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for (; $x < $x1; $x++)
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$line = $flip ? $this->yv[$x] : $this->xv[$x];
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if (empty($ymatches[$line]))
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$matches = $ymatches[$line];
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foreach ($matches as $y)
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if (empty($this->in_seq[$y]))
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$k = $this->_lcs_pos($y);
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$ymids[$k] = $ymids[$k - 1];
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while (list($junk, $y) = each($matches))
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if ($y > $this->seq[$k - 1])
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// Optimization: this is a common case: next match is just replacing previous match.
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$this->in_seq[$this->seq[$k]] = false;
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$this->in_seq[$y] = 1;
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else if (empty($this->in_seq[$y]))
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$k = $this->_lcs_pos($y);
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$ymids[$k] = $ymids[$k - 1];
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$seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
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$ymid = $ymids[$this->lcs];
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for ($n = 0; $n < $nchunks - 1; $n++)
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$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
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$seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
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$seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
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return array($this->lcs, $seps);
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function _lcs_pos($ypos)
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if ($end == 0 || $ypos > $this->seq[$end])
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$this->seq[++$this->lcs] = $ypos;
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$this->in_seq[$ypos] = 1;
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$mid = (int)(($beg + $end) / 2);
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if ($ypos > $this->seq[$mid])
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$this->in_seq[$this->seq[$end]] = false;
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$this->seq[$end] = $ypos;
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$this->in_seq[$ypos] = 1;
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* Finds LCS of two sequences.
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* The results are recorded in the vectors $this->{x,y}changed[], by
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* storing a 1 in the element for each line that is an insertion or
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* deletion (ie. is not in the LCS).
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* The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
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* Note that XLIM, YLIM are exclusive bounds. All line numbers are
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* origin-0 and discarded lines are not counted.
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function _compareseq($xoff, $xlim, $yoff, $ylim)
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// Slide down the bottom initial diagonal.
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while ($xoff < $xlim && $yoff < $ylim && $this->xv[$xoff] == $this->yv[$yoff])
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// Slide up the top initial diagonal.
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while ($xlim > $xoff && $ylim > $yoff && $this->xv[$xlim - 1] == $this->yv[$ylim - 1])
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if ($xoff == $xlim || $yoff == $ylim)
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// This is ad hoc but seems to work well.
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// $nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
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// $nchunks = max(2,min(8,(int)$nchunks));
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$nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
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list($lcs, $seps) = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
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// X and Y sequences have no common subsequence: mark all changed.
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while ($yoff < $ylim)
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$this->ychanged[$this->yind[$yoff++]] = 1;
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while ($xoff < $xlim)
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$this->xchanged[$this->xind[$xoff++]] = 1;
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// Use the partitions to split this problem into subproblems.
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while ($pt2 = next($seps))
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$this->_compareseq($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
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* Adjusts inserts/deletes of identical lines to join changes as much as possible.
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* We do something when a run of changed lines include a line at one end
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* and has an excluded, identical line at the other. We are free to
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* choose which identical line is included. 'compareseq' usually chooses
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* the one at the beginning, but usually it is cleaner to consider the
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* following identical line to be the "change".
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* This is extracted verbatim from analyze.c (GNU diffutils-2.7).
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function _shift_boundaries($lines, &$changed, $other_changed)
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$len = sizeof($lines);
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$other_len = sizeof($other_changed);
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// Scan forward to find the beginning of another run of
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// changes. Also keep track of the corresponding point in the other file.
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// Throughout this code, $i and $j are adjusted together so that
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// the first $i elements of $changed and the first $j elements of
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// $other_changed both contain the same number of zeros (unchanged lines).
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// Furthermore, $j is always kept so that $j == $other_len or $other_changed[$j] == false.
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while ($j < $other_len && $other_changed[$j])
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while ($i < $len && ! $changed[$i])
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while ($j < $other_len && $other_changed[$j])
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// Find the end of this run of changes.
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while (++$i < $len && $changed[$i])
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// Record the length of this run of changes, so that we can later determine whether the run has grown.
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$runlength = $i - $start;
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// Move the changed region back, so long as the previous unchanged line matches the last changed one.
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// This merges with previous changed regions.
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while ($start > 0 && $lines[$start - 1] == $lines[$i - 1])
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$changed[--$start] = 1;
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$changed[--$i] = false;
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while ($start > 0 && $changed[$start - 1])
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while ($other_changed[--$j])
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// Set CORRESPONDING to the end of the changed run, at the last point where it corresponds to a changed run in the
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// other file. CORRESPONDING == LEN means no such point has been found.
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$corresponding = $j < $other_len ? $i : $len;
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// Move the changed region forward, so long as the first changed line matches the following unchanged one.
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// This merges with following changed regions.
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// Do this second, so that if there are no merges, the changed region is moved forward as far as possible.
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while ($i < $len && $lines[$start] == $lines[$i])
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$changed[$start++] = false;
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while ($i < $len && $changed[$i])
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if ($j < $other_len && $other_changed[$j])
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while ($j < $other_len && $other_changed[$j])
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while ($runlength != $i - $start);
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// If possible, move the fully-merged run of changes back to a corresponding run in the other file.
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while ($corresponding < $i)
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$changed[--$start] = 1;
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while ($other_changed[--$j])
b'\\ No newline at end of file'
added
removed
www/php/phpBB3/includes/diff/engine.php
