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darcs-hash:20050112202454-9977f-60936f24fe2092a30223627e0683de2df61d0c4a.gz

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diff --git a/inc/DifferenceEngine.php b/inc/DifferenceEngine.php
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+<?php
+
+// A PHP diff engine for phpwiki. (Taken from phpwiki-1.3.3)
+//
+// Copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
+// You may copy this code freely under the conditions of the GPL.
+//
+
+define('USE_ASSERTS', function_exists('assert'));
+
+class _DiffOp {
+	var $type;
+	var $orig;
+	var $closing;
+	
+	function reverse() {
+		trigger_error("pure virtual", E_USER_ERROR);
+	}
+
+	function norig() {
+		return $this->orig ? sizeof($this->orig) : 0;
+	}
+
+	function nclosing() {
+		return $this->closing ? sizeof($this->closing) : 0;
+	}
+}
+
+class _DiffOp_Copy extends _DiffOp {
+	var $type = 'copy';
+	
+	function _DiffOp_Copy ($orig, $closing = false) {
+		if (!is_array($closing))
+			$closing = $orig;
+		$this->orig = $orig;
+		$this->closing = $closing;
+	}
+
+	function reverse() {
+		return new _DiffOp_Copy($this->closing, $this->orig);
+	}
+}
+
+class _DiffOp_Delete extends _DiffOp {
+	var $type = 'delete';
+	
+	function _DiffOp_Delete ($lines) {
+		$this->orig = $lines;
+		$this->closing = false;
+	}
+
+	function reverse() {
+		return new _DiffOp_Add($this->orig);
+	}
+}
+
+class _DiffOp_Add extends _DiffOp {
+	var $type = 'add';
+	
+	function _DiffOp_Add ($lines) {
+		$this->closing = $lines;
+		$this->orig = false;
+	}
+
+	function reverse() {
+		return new _DiffOp_Delete($this->closing);
+	}
+}
+
+class _DiffOp_Change extends _DiffOp {
+	var $type = 'change';
+	
+	function _DiffOp_Change ($orig, $closing) {
+		$this->orig = $orig;
+		$this->closing = $closing;
+	}
+
+	function reverse() {
+		return new _DiffOp_Change($this->closing, $this->orig);
+	}
+}
+		
+	  
+/**
+ * Class used internally by Diff to actually compute the diffs.
+ *
+ * The algorithm used here is mostly lifted from the perl module
+ * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
+ *	 http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
+ *
+ * More ideas are taken from:
+ *	 http://www.ics.uci.edu/~eppstein/161/960229.html
+ *
+ * Some ideas are (and a bit of code) are from from analyze.c, from GNU
+ * diffutils-2.7, which can be found at:
+ *	 ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
+ *
+ * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
+ * are my own.
+ *
+ * @author Geoffrey T. Dairiki
+ * @access private
+ */
+class _DiffEngine
+{
+	function diff ($from_lines, $to_lines) {
+		$n_from = sizeof($from_lines);
+		$n_to = sizeof($to_lines);
+
+		$this->xchanged = $this->ychanged = array();
+		$this->xv = $this->yv = array();
+		$this->xind = $this->yind = array();
+		unset($this->seq);
+		unset($this->in_seq);
+		unset($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 < $n_to) {
+			USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
+			USE_ASSERTS && assert($xi < $n_from || $this->ychanged[$yi]);
+
+			// 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)
+				$edits[] = new _DiffOp_Copy($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)
+				$edits[] = new _DiffOp_Change($delete, $add);
+			elseif ($delete)
+				$edits[] = new _DiffOp_Delete($delete);
+			elseif ($add)
+				$edits[] = new _DiffOp_Add($add);
+		}
+		return $edits;
+	}
+	
+
+	/* Divide the Largest Common Subsequence (LCS) of the sequences
+	 * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
+	 * sized segments.
+	 *
+	 * Returns (LCS, PTS).	LCS is the length of the LCS. PTS is an
+	 * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
+	 * sub sequences.  The first sub-sequence is contained in [X0, X1),
+	 * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
+	 * that (X0, Y0) == (XOFF, YOFF) and
+	 * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
+	 *
+	 * This function assumes that the first lines of the specified portions
+	 * of the two files do not match, and likewise that the last lines do not
+	 * match.  The caller must trim matching lines from the beginning and end
+	 * of the portions it is going to specify.
+	 */
+	function _diag ($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 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($matches);
+		while (list ($junk, $y) = each($matches))
+			if (empty($this->in_seq[$y])) {
+			$k = $this->_lcs_pos($y);
+			USE_ASSERTS && assert($k > 0);
+			$ymids[$k] = $ymids[$k-1];
+			break;
+					}
+		while (list ($junk, $y) = each($matches)) {
+			if ($y > $this->seq[$k-1]) {
+			USE_ASSERTS && assert($y < $this->seq[$k]);
+			// 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);
+			USE_ASSERTS && assert($k > 0);
+			$ymids[$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 = $mid;
+		}
+
+	USE_ASSERTS && assert($ypos != $this->seq[$end]);
+
+	$this->in_seq[$this->seq[$end]] = false;
+	$this->seq[$end] = $ypos;
+	$this->in_seq[$ypos] = 1;
+	return $end;
+	}
+
+	/* Find 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 = $pt2;
+			}
+		}
+	}
+
+	/* Adjust inserts/deletes of identical lines to join changes
+	 * as much as possible.
+	 *
+	 * We do something when a run of changed lines include a
+	 * line at one end and has an excluded, identical line at the other.
+	 * We are free to choose which identical line is included.
+	 * `compareseq' usually chooses the one at the beginning,
+	 * but usually it is cleaner to consider the following identical line
+	 * to be the "change".
+	 *
+	 * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
+	 */
+	function _shift_boundaries ($lines, &$changed, $other_changed) {
+	$i = 0;
+	$j = 0;
+
+	USE_ASSERTS && assert('sizeof($lines) == sizeof($changed)');
+	$len = sizeof($lines);
+	$other_len = sizeof($other_changed);
+
+	while (1) {
+		/*
+		 * Scan forwards to find 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]) {
+		USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
+		$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])
+			$start--;
+			USE_ASSERTS && assert('$j > 0');
+			while ($other_changed[--$j])
+			continue;
+			USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+				}
+
+		/*
+		 * 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])
+			$i++;
+
+			USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
+			$j++;
+			if ($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;
+		USE_ASSERTS && assert('$j > 0');
+		while ($other_changed[--$j])
+			continue;
+		USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+			}
+		}
+	}
+}
+
+/**
+ * Class representing a 'diff' between two sequences of strings.
+ */
+class Diff 
+{
+	var $edits;
+
+	/**
+	 * Constructor.
+	 * Computes diff between sequences of strings.
+	 *
+	 * @param $from_lines array An array of strings.
+	 *		  (Typically these are lines from a file.)
+	 * @param $to_lines array An array of strings.
+	 */
+	function Diff($from_lines, $to_lines) {
+		$eng = new _DiffEngine;
+		$this->edits = $eng->diff($from_lines, $to_lines);
+		//$this->_check($from_lines, $to_lines);
+	}
+
+	/**
+	 * Compute reversed Diff.
+	 *
+	 * SYNOPSIS:
+	 *
+	 *	$diff = new Diff($lines1, $lines2);
+	 *	$rev = $diff->reverse();
+	 * @return object A Diff object representing the inverse of the
+	 *				  original diff.
+	 */
+	function reverse () {
+	$rev = $this;
+		$rev->edits = array();
+		foreach ($this->edits as $edit) {
+			$rev->edits[] = $edit->reverse();
+		}
+	return $rev;
+	}
+
+	/**
+	 * Check for empty diff.
+	 *
+	 * @return bool True iff two sequences were identical.
+	 */
+	function isEmpty () {
+		foreach ($this->edits as $edit) {
+			if ($edit->type != 'copy')
+				return false;
+		}
+		return true;
+	}
+  
+	/**
+	 * Compute the length of the Longest Common Subsequence (LCS).
+	 *
+	 * This is mostly for diagnostic purposed.
+	 *
+	 * @return int The length of the LCS.
+	 */
+	function lcs () {
+	$lcs = 0;
+		foreach ($this->edits as $edit) {
+			if ($edit->type == 'copy')
+				$lcs += sizeof($edit->orig);
+		}
+	return $lcs;
+	}
+
+	/**
+	 * Get the original set of lines.
+	 *
+	 * This reconstructs the $from_lines parameter passed to the
+	 * constructor.
+	 *
+	 * @return array The original sequence of strings.
+	 */
+	function orig() {
+		$lines = array();
+		
+		foreach ($this->edits as $edit) {
+			if ($edit->orig)
+				array_splice($lines, sizeof($lines), 0, $edit->orig);
+		}
+		return $lines;
+	}
+
+	/**
+	 * Get the closing set of lines.
+	 *
+	 * This reconstructs the $to_lines parameter passed to the
+	 * constructor.
+	 *
+	 * @return array The sequence of strings.
+	 */
+	function closing() {
+		$lines = array();
+		
+		foreach ($this->edits as $edit) {
+			if ($edit->closing)
+				array_splice($lines, sizeof($lines), 0, $edit->closing);
+		}
+		return $lines;
+	}
+
+	/**
+	 * Check a Diff for validity. 
+	 *
+	 * This is here only for debugging purposes.
+	 */
+	function _check ($from_lines, $to_lines) {
+		if (serialize($from_lines) != serialize($this->orig()))
+			trigger_error("Reconstructed original doesn't match", E_USER_ERROR);
+		if (serialize($to_lines) != serialize($this->closing()))
+			trigger_error("Reconstructed closing doesn't match", E_USER_ERROR);
+
+		$rev = $this->reverse();
+		if (serialize($to_lines) != serialize($rev->orig()))
+			trigger_error("Reversed original doesn't match", E_USER_ERROR);
+		if (serialize($from_lines) != serialize($rev->closing()))
+			trigger_error("Reversed closing doesn't match", E_USER_ERROR);
+
+
+		$prevtype = 'none';
+		foreach ($this->edits as $edit) {
+			if ( $prevtype == $edit->type )
+				trigger_error("Edit sequence is non-optimal", E_USER_ERROR);
+			$prevtype = $edit->type;
+		}
+
+		$lcs = $this->lcs();
+		trigger_error("Diff okay: LCS = $lcs", E_USER_NOTICE);
+	}
+}
+			
+/**
+ * FIXME: bad name.
+ */
+class MappedDiff
+extends Diff
+{
+	/**
+	 * Constructor.
+	 *
+	 * Computes diff between sequences of strings.
+	 *
+	 * This can be used to compute things like
+	 * case-insensitve diffs, or diffs which ignore
+	 * changes in white-space.
+	 *
+	 * @param $from_lines array An array of strings.
+	 *	(Typically these are lines from a file.)
+	 *
+	 * @param $to_lines array An array of strings.
+	 *
+	 * @param $mapped_from_lines array This array should
+	 *	have the same size number of elements as $from_lines.
+	 *	The elements in $mapped_from_lines and
+	 *	$mapped_to_lines are what is actually compared
+	 *	when computing the diff.
+	 *
+	 * @param $mapped_to_lines array This array should
+	 *	have the same number of elements as $to_lines.
+	 */
+	function MappedDiff($from_lines, $to_lines,
+						$mapped_from_lines, $mapped_to_lines) {
+
+		assert(sizeof($from_lines) == sizeof($mapped_from_lines));
+		assert(sizeof($to_lines) == sizeof($mapped_to_lines));
+		
+		$this->Diff($mapped_from_lines, $mapped_to_lines);
+
+		$xi = $yi = 0;
+		for ($i = 0; $i < sizeof($this->edits); $i++) {
+			$orig = &$this->edits[$i]->orig;
+			if (is_array($orig)) {
+				$orig = array_slice($from_lines, $xi, sizeof($orig));
+				$xi += sizeof($orig);
+			}
+			
+			$closing = &$this->edits[$i]->closing;
+			if (is_array($closing)) {
+				$closing = array_slice($to_lines, $yi, sizeof($closing));
+				$yi += sizeof($closing);
+			}
+		}
+	}
+}
+
+/**
+ * A class to format Diffs
+ *
+ * This class formats the diff in classic diff format.
+ * It is intended that this class be customized via inheritance,
+ * to obtain fancier outputs.
+ */
+class DiffFormatter
+{
+	/**
+	 * Number of leading context "lines" to preserve.
+	 *
+	 * This should be left at zero for this class, but subclasses
+	 * may want to set this to other values.
+	 */
+	var $leading_context_lines = 0;
+
+	/**
+	 * Number of trailing context "lines" to preserve.
+	 *
+	 * This should be left at zero for this class, but subclasses
+	 * may want to set this to other values.
+	 */
+	var $trailing_context_lines = 0;
+
+	/**
+	 * Format a diff.
+	 *
+	 * @param $diff object A Diff object.
+	 * @return string The formatted output.
+	 */
+	function format($diff) {
+
+		$xi = $yi = 1;
+		$block = false;
+		$context = array();
+
+		$nlead = $this->leading_context_lines;
+		$ntrail = $this->trailing_context_lines;
+
+		$this->_start_diff();
+
+		foreach ($diff->edits as $edit) {
+			if ($edit->type == 'copy') {
+				if (is_array($block)) {
+					if (sizeof($edit->orig) <= $nlead + $ntrail) {
+						$block[] = $edit;
+					}
+					else{
+						if ($ntrail) {
+							$context = array_slice($edit->orig, 0, $ntrail);
+							$block[] = new _DiffOp_Copy($context);
+						}
+						$this->_block($x0, $ntrail + $xi - $x0,
+									  $y0, $ntrail + $yi - $y0,
+									  $block);
+						$block = false;
+					}
+				}
+				$context = $edit->orig;
+			}
+			else {
+				if (! is_array($block)) {
+					$context = array_slice($context, sizeof($context) - $nlead);
+					$x0 = $xi - sizeof($context);
+					$y0 = $yi - sizeof($context);
+					$block = array();
+					if ($context)
+						$block[] = new _DiffOp_Copy($context);
+				}
+				$block[] = $edit;
+			}
+
+			if ($edit->orig)
+				$xi += sizeof($edit->orig);
+			if ($edit->closing)
+				$yi += sizeof($edit->closing);
+		}
+
+		if (is_array($block))
+			$this->_block($x0, $xi - $x0,
+						  $y0, $yi - $y0,
+						  $block);
+
+		return $this->_end_diff();
+	}
+
+	function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
+		$this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
+		foreach ($edits as $edit) {
+			if ($edit->type == 'copy')
+				$this->_context($edit->orig);
+			elseif ($edit->type == 'add')
+				$this->_added($edit->closing);
+			elseif ($edit->type == 'delete')
+				$this->_deleted($edit->orig);
+			elseif ($edit->type == 'change')
+				$this->_changed($edit->orig, $edit->closing);
+			else
+				trigger_error("Unknown edit type", E_USER_ERROR);
+		}
+		$this->_end_block();
+	}
+
+	function _start_diff() {
+		ob_start();
+	}
+
+	function _end_diff() {
+		$val = ob_get_contents();
+		ob_end_clean();
+		return $val;
+	}
+
+	function _block_header($xbeg, $xlen, $ybeg, $ylen) {
+		if ($xlen > 1)
+			$xbeg .= "," . ($xbeg + $xlen - 1);
+		if ($ylen > 1)
+			$ybeg .= "," . ($ybeg + $ylen - 1);
+
+		return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
+	}
+	
+	function _start_block($header) {
+		echo $header;
+	}
+	
+	function _end_block() {
+	}
+
+	function _lines($lines, $prefix = ' ') {
+		foreach ($lines as $line)
+			echo "$prefix $line\n";
+	}
+	
+	function _context($lines) {
+		$this->_lines($lines);
+	}
+
+	function _added($lines) {
+		$this->_lines($lines, ">");
+	}
+	function _deleted($lines) {
+		$this->_lines($lines, "<");
+	}
+
+	function _changed($orig, $closing) {
+		$this->_deleted($orig);
+		echo "---\n";
+		$this->_added($closing);
+	}
+}
+
+
+/**
+ *	Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
+ * 
+ */
+
+define('NBSP', "\xA0");			// iso-8859-x non-breaking space.
+
+class _HWLDF_WordAccumulator {
+	function _HWLDF_WordAccumulator () {
+		$this->_lines = array();
+		$this->_line = '';
+		$this->_group = '';
+		$this->_tag = '';
+	}
+
+	function _flushGroup ($new_tag) {
+		if ($this->_group !== '') {
+	  if ($this->_tag == 'mark') 
+			$this->_line .= '<span class="diffchange">'.$this->_group.'</span>';
+	  else
+		$this->_line .= $this->_group;
+	}
+		$this->_group = '';
+		$this->_tag = $new_tag;
+	}
+	
+	function _flushLine ($new_tag) {
+		$this->_flushGroup($new_tag);
+		if ($this->_line != '')
+			$this->_lines[] = $this->_line;
+		$this->_line = '';
+	}
+				
+	function addWords ($words, $tag = '') {
+		if ($tag != $this->_tag)
+			$this->_flushGroup($tag);
+
+		foreach ($words as $word) {
+			// new-line should only come as first char of word.
+			if ($word == '')
+				continue;
+			if ($word[0] == "\n") {
+				$this->_group .= NBSP;
+				$this->_flushLine($tag);
+				$word = substr($word, 1);
+			}
+			assert(!strstr($word, "\n"));
+			$this->_group .= $word;
+		}
+	}
+
+	function getLines() {
+		$this->_flushLine('~done');
+		return $this->_lines;
+	}
+}
+
+class WordLevelDiff extends MappedDiff
+{
+	function WordLevelDiff ($orig_lines, $closing_lines) {
+		list ($orig_words, $orig_stripped) = $this->_split($orig_lines);
+		list ($closing_words, $closing_stripped) = $this->_split($closing_lines);
+
+		
+		$this->MappedDiff($orig_words, $closing_words,
+						  $orig_stripped, $closing_stripped);
+	}
+
+	function _split($lines) {
+		// FIXME: fix POSIX char class.
+#		 if (!preg_match_all('/ ( [^\S\n]+ | [[:alnum:]]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
+		if (!preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
+							implode("\n", $lines),
+							$m)) {
+			return array(array(''), array(''));
+		}
+		return array($m[0], $m[1]);
+	}
+
+	function orig () {
+		$orig = new _HWLDF_WordAccumulator;
+		
+		foreach ($this->edits as $edit) {
+			if ($edit->type == 'copy')
+				$orig->addWords($edit->orig);
+			elseif ($edit->orig)
+				$orig->addWords($edit->orig, 'mark');
+		}
+		return $orig->getLines();
+	}
+
+	function closing () {
+		$closing = new _HWLDF_WordAccumulator;
+		
+		foreach ($this->edits as $edit) {
+			if ($edit->type == 'copy')
+				$closing->addWords($edit->closing);
+			elseif ($edit->closing)
+				$closing->addWords($edit->closing, 'mark');
+		}
+		return $closing->getLines();
+	}
+}
+
+/**
+ * "Unified" diff formatter.
+ *
+ * This class formats the diff in classic "unified diff" format.
+ */
+class UnifiedDiffFormatter extends DiffFormatter
+{
+    function UnifiedDiffFormatter($context_lines = 4) {
+        $this->leading_context_lines = $context_lines;
+        $this->trailing_context_lines = $context_lines;
+    }
+
+    function _block_header($xbeg, $xlen, $ybeg, $ylen) {
+        if ($xlen != 1)
+            $xbeg .= "," . $xlen;
+        if ($ylen != 1)
+            $ybeg .= "," . $ylen;
+        return "@@ -$xbeg +$ybeg @@\n";
+    }
+
+    function _added($lines) {
+        $this->_lines($lines, "+");
+    }
+    function _deleted($lines) {
+        $this->_lines($lines, "-");
+    }
+    function _changed($orig, $final) {
+        $this->_deleted($orig);
+        $this->_added($final);
+    }
+}
+
+/**
+ *	Wikipedia Table style diff formatter.
+ * 
+ */
+class TableDiffFormatter extends DiffFormatter
+{
+	function TableDiffFormatter() {
+		$this->leading_context_lines = 2;
+		$this->trailing_context_lines = 2;
+	}
+	
+  function _pre($text){
+    $text = htmlspecialchars($text);
+    $text = str_replace('  ',' &nbsp;',$text);
+    return $text;
+  }
+
+  function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
+    global $lang;
+    $l1 = $lang['line'].' '.$xbeg;
+    $l2 = $lang['line'].' '.$ybeg;
+		$r = '<tr><td class="diff-blockheader" colspan="2">'.$l1.":</td>\n" .
+		  '<td class="diff-blockheader" colspan="2">'.$l2.":</td></tr>\n";
+		return $r;
+	}
+
+	function _start_block( $header ) {
+		print( $header );
+	}
+
+	function _end_block() {
+	}
+
+	function _lines( $lines, $prefix=' ', $color="white" ) {
+	}
+
+	function addedLine( $line ) {
+    $line = str_replace('  ','&nbsp; ',$line);
+		return '<td>+</td><td class="diff-addedline">' .
+		  $line.'</td>';
+	}
+
+	function deletedLine( $line ) {
+    $line = str_replace('  ','&nbsp; ',$line);
+		return '<td>-</td><td class="diff-deletedline">' .
+		  $line.'</td>';
+	}
+
+	function emptyLine() {
+    $line = str_replace('  ','&nbsp; ',$line);
+		return '<td colspan="2">&nbsp;</td>';
+	}
+
+	function contextLine( $line ) {
+    $line = str_replace('  ','&nbsp; ',$line);
+		return '<td> </td><td class="diff-context">'.$line.'</td>';
+	}
+	
+	function _added($lines) {
+		foreach ($lines as $line) {
+			print( '<tr>' . $this->emptyLine() .
+			  $this->addedLine( $line ) . "</tr>\n" );
+		}
+	}
+
+	function _deleted($lines) {
+		foreach ($lines as $line) {
+			print( '<tr>' . $this->deletedLine( $line ) .
+			  $this->emptyLine() . "</tr>\n" );
+		}
+	}
+
+	function _context( $lines ) {
+		foreach ($lines as $line) {
+			print( '<tr>' . $this->contextLine( $line ) .
+			  $this->contextLine( $line ) . "</tr>\n" );
+		}
+	}
+
+	function _changed( $orig, $closing ) {
+		$diff = new WordLevelDiff( $orig, $closing );
+		$del = $diff->orig();
+		$add = $diff->closing();
+
+		while ( $line = array_shift( $del ) ) {
+			$aline = array_shift( $add );
+			print( '<tr>' . $this->deletedLine( $line ) .
+			  $this->addedLine( $aline ) . "</tr>\n" );
+		}
+		$this->_added( $add ); # If any leftovers
+	}
+}
+
+?>