/**

*

* @package diff

* @version $Id: engine.php 8765 2008-08-16 22:18:25Z aptx $

* @copyright (c) 2006 phpBB Group

* @license http://opensource.org/licenses/gpl-license.php GNU Public License

*

*/

/**

* @ignore

*/

if (!defined('IN_PHPBB'))

{

	exit;

}

/**

* Code from pear.php.net, Text_Diff-1.0.0 package

* http://pear.php.net/package/Text_Diff/ (native engine)

*

* Modified by phpBB Group 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

{

	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));

		}

		$n_from = sizeof($from_lines);

		$n_to = sizeof($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 ($from_lines[$skip] !== $to_lines[$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 ($from_lines[$xi] !== $to_lines[$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++)

		{

			$xhash[$from_lines[$xi]] = 1;

		}

		for ($yi = $skip; $yi < $n_to - $endskip; $yi++)

		{

			$line = $to_lines[$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 = $from_lines[$xi];

			if (($this->xchanged[$xi] = empty($yhash[$line])))

			{

				continue;

			}

			$this->xv[] = $line;

			$this->xind[] = $xi;

		}

		// Find the LCS.

		$this->_compareseq(0, sizeof($this->xv), 0, sizeof($this->yv));

		// Merge edits when possible.

		$this->_shift_boundaries($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 (list(, $y) = each($matches))

				{

					if (empty($this->in_seq[$y]))

					{

						$k = $this->_lcs_pos($y);

						$ymids[$k] = $ymids[$k - 1];

						break;

					}

				}

				// no reset() here

				while (list(, $y) = each($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;

		$len = sizeof($lines);

		$other_len = sizeof($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;

				}

			}

		}

	}

}

?>