1<?php
2/**
3 * A PHP diff engine for phpwiki. (Taken from phpwiki-1.3.3)
4 *
5 * Additions by Axel Boldt for MediaWiki
6 *
7 * @copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
8 * @license  You may copy this code freely under the conditions of the GPL.
9 */
10define('USE_ASSERTS', function_exists('assert'));
11
12class _DiffOp {
13    var $type;
14    var $orig;
15    var $closing;
16
17    /**
18     * @return _DiffOp
19     */
20    function reverse() {
21        throw new \RuntimeException("pure virtual");
22    }
23
24    function norig() {
25        return $this->orig ? count($this->orig) : 0;
26    }
27
28    function nclosing() {
29        return $this->closing ? count($this->closing) : 0;
30    }
31}
32
33class _DiffOp_Copy extends _DiffOp {
34    var $type = 'copy';
35
36    function __construct($orig, $closing = false) {
37        if (!is_array($closing))
38            $closing = $orig;
39        $this->orig = $orig;
40        $this->closing = $closing;
41    }
42
43    function reverse() {
44        return new _DiffOp_Copy($this->closing, $this->orig);
45    }
46}
47
48class _DiffOp_Delete extends _DiffOp {
49    var $type = 'delete';
50
51    function __construct($lines) {
52        $this->orig = $lines;
53        $this->closing = false;
54    }
55
56    function reverse() {
57        return new _DiffOp_Add($this->orig);
58    }
59}
60
61class _DiffOp_Add extends _DiffOp {
62    var $type = 'add';
63
64    function __construct($lines) {
65        $this->closing = $lines;
66        $this->orig = false;
67    }
68
69    function reverse() {
70        return new _DiffOp_Delete($this->closing);
71    }
72}
73
74class _DiffOp_Change extends _DiffOp {
75    var $type = 'change';
76
77    function __construct($orig, $closing) {
78        $this->orig = $orig;
79        $this->closing = $closing;
80    }
81
82    function reverse() {
83        return new _DiffOp_Change($this->closing, $this->orig);
84    }
85}
86
87
88/**
89 * Class used internally by Diff to actually compute the diffs.
90 *
91 * The algorithm used here is mostly lifted from the perl module
92 * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
93 *   http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
94 *
95 * More ideas are taken from:
96 *   http://www.ics.uci.edu/~eppstein/161/960229.html
97 *
98 * Some ideas are (and a bit of code) are from from analyze.c, from GNU
99 * diffutils-2.7, which can be found at:
100 *   ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
101 *
102 * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
103 * are my own.
104 *
105 * @author Geoffrey T. Dairiki
106 * @access private
107 */
108class _DiffEngine {
109
110    var $xchanged = array();
111    var $ychanged = array();
112    var $xv = array();
113    var $yv = array();
114    var $xind = array();
115    var $yind = array();
116    var $seq;
117    var $in_seq;
118    var $lcs;
119
120    /**
121     * @param array $from_lines
122     * @param array $to_lines
123     * @return _DiffOp[]
124     */
125    function diff($from_lines, $to_lines) {
126        $n_from = count($from_lines);
127        $n_to = count($to_lines);
128
129        $this->xchanged = $this->ychanged = array();
130        $this->xv = $this->yv = array();
131        $this->xind = $this->yind = array();
132        unset($this->seq);
133        unset($this->in_seq);
134        unset($this->lcs);
135
136        // Skip leading common lines.
137        for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
138            if ($from_lines[$skip] != $to_lines[$skip])
139                break;
140            $this->xchanged[$skip] = $this->ychanged[$skip] = false;
141        }
142        // Skip trailing common lines.
143        $xi = $n_from;
144        $yi = $n_to;
145        for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
146            if ($from_lines[$xi] != $to_lines[$yi])
147                break;
148            $this->xchanged[$xi] = $this->ychanged[$yi] = false;
149        }
150
151        // Ignore lines which do not exist in both files.
152        for ($xi = $skip; $xi < $n_from - $endskip; $xi++)
153            $xhash[$from_lines[$xi]] = 1;
154        for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
155            $line = $to_lines[$yi];
156            if (($this->ychanged[$yi] = empty($xhash[$line])))
157                continue;
158            $yhash[$line] = 1;
159            $this->yv[] = $line;
160            $this->yind[] = $yi;
161        }
162        for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
163            $line = $from_lines[$xi];
164            if (($this->xchanged[$xi] = empty($yhash[$line])))
165                continue;
166            $this->xv[] = $line;
167            $this->xind[] = $xi;
168        }
169
170        // Find the LCS.
171        $this->_compareseq(0, count($this->xv), 0, count($this->yv));
172
173        // Merge edits when possible
174        $this->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
175        $this->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);
176
177        // Compute the edit operations.
178        $edits = array();
179        $xi = $yi = 0;
180        while ($xi < $n_from || $yi < $n_to) {
181            USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
182            USE_ASSERTS && assert($xi < $n_from || $this->ychanged[$yi]);
183
184            // Skip matching "snake".
185            $copy = array();
186            while ($xi < $n_from && $yi < $n_to && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
187                $copy[] = $from_lines[$xi++];
188                ++$yi;
189            }
190            if ($copy)
191                $edits[] = new _DiffOp_Copy($copy);
192
193            // Find deletes & adds.
194            $delete = array();
195            while ($xi < $n_from && $this->xchanged[$xi])
196                $delete[] = $from_lines[$xi++];
197
198            $add = array();
199            while ($yi < $n_to && $this->ychanged[$yi])
200                $add[] = $to_lines[$yi++];
201
202            if ($delete && $add)
203                $edits[] = new _DiffOp_Change($delete, $add);
204            elseif ($delete)
205                $edits[] = new _DiffOp_Delete($delete);
206            elseif ($add)
207                $edits[] = new _DiffOp_Add($add);
208        }
209        return $edits;
210    }
211
212
213    /**
214     * Divide the Largest Common Subsequence (LCS) of the sequences
215     * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
216     * sized segments.
217     *
218     * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an
219     * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
220     * sub sequences.  The first sub-sequence is contained in [X0, X1),
221     * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
222     * that (X0, Y0) == (XOFF, YOFF) and
223     * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
224     *
225     * This function assumes that the first lines of the specified portions
226     * of the two files do not match, and likewise that the last lines do not
227     * match.  The caller must trim matching lines from the beginning and end
228     * of the portions it is going to specify.
229     *
230     * @param integer $xoff
231     * @param integer $xlim
232     * @param integer $yoff
233     * @param integer $ylim
234     * @param integer $nchunks
235     *
236     * @return array
237     */
238    function _diag($xoff, $xlim, $yoff, $ylim, $nchunks) {
239        $flip = false;
240
241        if ($xlim - $xoff > $ylim - $yoff) {
242            // Things seems faster (I'm not sure I understand why)
243            // when the shortest sequence in X.
244            $flip = true;
245            list ($xoff, $xlim, $yoff, $ylim) = array($yoff, $ylim, $xoff, $xlim);
246        }
247
248        if ($flip)
249            for ($i = $ylim - 1; $i >= $yoff; $i--)
250                $ymatches[$this->xv[$i]][] = $i;
251        else
252            for ($i = $ylim - 1; $i >= $yoff; $i--)
253                $ymatches[$this->yv[$i]][] = $i;
254
255        $this->lcs = 0;
256        $this->seq[0]= $yoff - 1;
257        $this->in_seq = array();
258        $ymids[0] = array();
259
260        $numer = $xlim - $xoff + $nchunks - 1;
261        $x = $xoff;
262        for ($chunk = 0; $chunk < $nchunks; $chunk++) {
263            if ($chunk > 0)
264                for ($i = 0; $i <= $this->lcs; $i++)
265                    $ymids[$i][$chunk-1] = $this->seq[$i];
266
267            $x1 = $xoff + (int)(($numer + ($xlim-$xoff)*$chunk) / $nchunks);
268            for ( ; $x < $x1; $x++) {
269                $line = $flip ? $this->yv[$x] : $this->xv[$x];
270                if (empty($ymatches[$line]))
271                    continue;
272                $matches = $ymatches[$line];
273                $switch = false;
274                foreach ($matches as $y) {
275                    if ($switch && $y > $this->seq[$k-1]) {
276                        USE_ASSERTS && assert($y < $this->seq[$k]);
277                        // Optimization: this is a common case:
278                        //  next match is just replacing previous match.
279                        $this->in_seq[$this->seq[$k]] = false;
280                        $this->seq[$k] = $y;
281                        $this->in_seq[$y] = 1;
282                    }
283                    else if (empty($this->in_seq[$y])) {
284                        $k = $this->_lcs_pos($y);
285                        USE_ASSERTS && assert($k > 0);
286                        $ymids[$k] = $ymids[$k-1];
287                        $switch = true;
288                    }
289                }
290            }
291        }
292
293        $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
294        $ymid = $ymids[$this->lcs];
295        for ($n = 0; $n < $nchunks - 1; $n++) {
296            $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
297            $y1 = $ymid[$n] + 1;
298            $seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
299        }
300        $seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
301
302        return array($this->lcs, $seps);
303    }
304
305    function _lcs_pos($ypos) {
306        $end = $this->lcs;
307        if ($end == 0 || $ypos > $this->seq[$end]) {
308            $this->seq[++$this->lcs] = $ypos;
309            $this->in_seq[$ypos] = 1;
310            return $this->lcs;
311        }
312
313        $beg = 1;
314        while ($beg < $end) {
315            $mid = (int)(($beg + $end) / 2);
316            if ($ypos > $this->seq[$mid])
317                $beg = $mid + 1;
318            else
319                $end = $mid;
320        }
321
322        USE_ASSERTS && assert($ypos != $this->seq[$end]);
323
324        $this->in_seq[$this->seq[$end]] = false;
325        $this->seq[$end] = $ypos;
326        $this->in_seq[$ypos] = 1;
327        return $end;
328    }
329
330    /**
331     * Find LCS of two sequences.
332     *
333     * The results are recorded in the vectors $this->{x,y}changed[], by
334     * storing a 1 in the element for each line that is an insertion
335     * or deletion (ie. is not in the LCS).
336     *
337     * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
338     *
339     * Note that XLIM, YLIM are exclusive bounds.
340     * All line numbers are origin-0 and discarded lines are not counted.
341     *
342     * @param integer $xoff
343     * @param integer $xlim
344     * @param integer $yoff
345     * @param integer $ylim
346     */
347    function _compareseq($xoff, $xlim, $yoff, $ylim) {
348        // Slide down the bottom initial diagonal.
349        while ($xoff < $xlim && $yoff < $ylim && $this->xv[$xoff] == $this->yv[$yoff]) {
350            ++$xoff;
351            ++$yoff;
352        }
353
354        // Slide up the top initial diagonal.
355        while ($xlim > $xoff && $ylim > $yoff && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
356            --$xlim;
357            --$ylim;
358        }
359
360        if ($xoff == $xlim || $yoff == $ylim)
361            $lcs = 0;
362        else {
363            // This is ad hoc but seems to work well.
364            //$nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
365            //$nchunks = max(2,min(8,(int)$nchunks));
366            $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
367            list ($lcs, $seps)
368                = $this->_diag($xoff,$xlim,$yoff, $ylim,$nchunks);
369        }
370
371        if ($lcs == 0) {
372            // X and Y sequences have no common subsequence:
373            // mark all changed.
374            while ($yoff < $ylim)
375                $this->ychanged[$this->yind[$yoff++]] = 1;
376            while ($xoff < $xlim)
377                $this->xchanged[$this->xind[$xoff++]] = 1;
378        }
379        else {
380            // Use the partitions to split this problem into subproblems.
381            reset($seps);
382            $pt1 = $seps[0];
383            while ($pt2 = next($seps)) {
384                $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
385                $pt1 = $pt2;
386            }
387        }
388    }
389
390    /**
391     * Adjust inserts/deletes of identical lines to join changes
392     * as much as possible.
393     *
394     * We do something when a run of changed lines include a
395     * line at one end and has an excluded, identical line at the other.
396     * We are free to choose which identical line is included.
397     * `compareseq' usually chooses the one at the beginning,
398     * but usually it is cleaner to consider the following identical line
399     * to be the "change".
400     *
401     * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
402     *
403     * @param array $lines
404     * @param array $changed
405     * @param array $other_changed
406     */
407    function _shift_boundaries($lines, &$changed, $other_changed) {
408        $i = 0;
409        $j = 0;
410
411        USE_ASSERTS && assert(count($lines) == count($changed));
412        $len = count($lines);
413        $other_len = count($other_changed);
414
415        while (1) {
416            /*
417             * Scan forwards to find beginning of another run of changes.
418             * Also keep track of the corresponding point in the other file.
419             *
420             * Throughout this code, $i and $j are adjusted together so that
421             * the first $i elements of $changed and the first $j elements
422             * of $other_changed both contain the same number of zeros
423             * (unchanged lines).
424             * Furthermore, $j is always kept so that $j == $other_len or
425             * $other_changed[$j] == false.
426             */
427            while ($j < $other_len && $other_changed[$j])
428                $j++;
429
430            while ($i < $len && ! $changed[$i]) {
431                USE_ASSERTS && assert($j < $other_len && ! $other_changed[$j]);
432                $i++;
433                $j++;
434                while ($j < $other_len && $other_changed[$j])
435                    $j++;
436            }
437
438            if ($i == $len)
439                break;
440
441            $start = $i;
442
443            // Find the end of this run of changes.
444            while (++$i < $len && $changed[$i])
445                continue;
446
447            do {
448                /*
449                 * Record the length of this run of changes, so that
450                 * we can later determine whether the run has grown.
451                 */
452                $runlength = $i - $start;
453
454                /*
455                 * Move the changed region back, so long as the
456                 * previous unchanged line matches the last changed one.
457                 * This merges with previous changed regions.
458                 */
459                while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
460                    $changed[--$start] = 1;
461                    $changed[--$i] = false;
462                    while ($start > 0 && $changed[$start - 1])
463                        $start--;
464                    USE_ASSERTS && assert($j > 0);
465                    while ($other_changed[--$j])
466                        continue;
467                    USE_ASSERTS && assert($j >= 0 && !$other_changed[$j]);
468                }
469
470                /*
471                 * Set CORRESPONDING to the end of the changed run, at the last
472                 * point where it corresponds to a changed run in the other file.
473                 * CORRESPONDING == LEN means no such point has been found.
474                 */
475                $corresponding = $j < $other_len ? $i : $len;
476
477                /*
478                 * Move the changed region forward, so long as the
479                 * first changed line matches the following unchanged one.
480                 * This merges with following changed regions.
481                 * Do this second, so that if there are no merges,
482                 * the changed region is moved forward as far as possible.
483                 */
484                while ($i < $len && $lines[$start] == $lines[$i]) {
485                    $changed[$start++] = false;
486                    $changed[$i++] = 1;
487                    while ($i < $len && $changed[$i])
488                        $i++;
489
490                    USE_ASSERTS && assert($j < $other_len && ! $other_changed[$j]);
491                    $j++;
492                    if ($j < $other_len && $other_changed[$j]) {
493                        $corresponding = $i;
494                        while ($j < $other_len && $other_changed[$j])
495                            $j++;
496                    }
497                }
498            } while ($runlength != $i - $start);
499
500            /*
501             * If possible, move the fully-merged run of changes
502             * back to a corresponding run in the other file.
503             */
504            while ($corresponding < $i) {
505                $changed[--$start] = 1;
506                $changed[--$i] = 0;
507                USE_ASSERTS && assert($j > 0);
508                while ($other_changed[--$j])
509                    continue;
510                USE_ASSERTS && assert($j >= 0 && !$other_changed[$j]);
511            }
512        }
513    }
514}
515
516/**
517 * Class representing a 'diff' between two sequences of strings.
518 */
519class Diff {
520
521    var $edits;
522
523    /**
524     * Constructor.
525     * Computes diff between sequences of strings.
526     *
527     * @param array $from_lines An array of strings.
528     *                          (Typically these are lines from a file.)
529     * @param array $to_lines   An array of strings.
530     */
531    function __construct($from_lines, $to_lines) {
532        $eng = new _DiffEngine;
533        $this->edits = $eng->diff($from_lines, $to_lines);
534        //$this->_check($from_lines, $to_lines);
535    }
536
537    /**
538     * Compute reversed Diff.
539     *
540     * SYNOPSIS:
541     *
542     *  $diff = new Diff($lines1, $lines2);
543     *  $rev = $diff->reverse();
544     *
545     * @return Diff  A Diff object representing the inverse of the
546     *               original diff.
547     */
548    function reverse() {
549        $rev = $this;
550        $rev->edits = array();
551        foreach ($this->edits as $edit) {
552            $rev->edits[] = $edit->reverse();
553        }
554        return $rev;
555    }
556
557    /**
558     * Check for empty diff.
559     *
560     * @return bool True iff two sequences were identical.
561     */
562    function isEmpty() {
563        foreach ($this->edits as $edit) {
564            if ($edit->type != 'copy')
565                return false;
566        }
567        return true;
568    }
569
570    /**
571     * Compute the length of the Longest Common Subsequence (LCS).
572     *
573     * This is mostly for diagnostic purposed.
574     *
575     * @return int The length of the LCS.
576     */
577    function lcs() {
578        $lcs = 0;
579        foreach ($this->edits as $edit) {
580            if ($edit->type == 'copy')
581                $lcs += count($edit->orig);
582        }
583        return $lcs;
584    }
585
586    /**
587     * Get the original set of lines.
588     *
589     * This reconstructs the $from_lines parameter passed to the
590     * constructor.
591     *
592     * @return array The original sequence of strings.
593     */
594    function orig() {
595        $lines = array();
596
597        foreach ($this->edits as $edit) {
598            if ($edit->orig)
599                array_splice($lines, count($lines), 0, $edit->orig);
600        }
601        return $lines;
602    }
603
604    /**
605     * Get the closing set of lines.
606     *
607     * This reconstructs the $to_lines parameter passed to the
608     * constructor.
609     *
610     * @return array The sequence of strings.
611     */
612    function closing() {
613        $lines = array();
614
615        foreach ($this->edits as $edit) {
616            if ($edit->closing)
617                array_splice($lines, count($lines), 0, $edit->closing);
618        }
619        return $lines;
620    }
621
622    /**
623     * Check a Diff for validity.
624     *
625     * This is here only for debugging purposes.
626     *
627     * @param mixed $from_lines
628     * @param mixed $to_lines
629     */
630    function _check($from_lines, $to_lines) {
631        if (serialize($from_lines) != serialize($this->orig()))
632            throw new \RuntimeException("Reconstructed original doesn't match");
633        if (serialize($to_lines) != serialize($this->closing()))
634            throw new \RuntimeException("Reconstructed closing doesn't match");
635
636        $rev = $this->reverse();
637        if (serialize($to_lines) != serialize($rev->orig()))
638            throw new \RuntimeException("Reversed original doesn't match");
639        if (serialize($from_lines) != serialize($rev->closing()))
640            throw new \RuntimeException("Reversed closing doesn't match");
641
642        $prevtype = 'none';
643        foreach ($this->edits as $edit) {
644            if ($prevtype == $edit->type)
645                throw new \RuntimeException("Edit sequence is non-optimal");
646            $prevtype = $edit->type;
647        }
648
649        $lcs = $this->lcs();
650        trigger_error("Diff okay: LCS = $lcs", E_USER_NOTICE);
651    }
652}
653
654/**
655 * FIXME: bad name.
656 */
657class MappedDiff extends Diff {
658    /**
659     * Constructor.
660     *
661     * Computes diff between sequences of strings.
662     *
663     * This can be used to compute things like
664     * case-insensitve diffs, or diffs which ignore
665     * changes in white-space.
666     *
667     * @param string[] $from_lines         An array of strings.
668     *                                     (Typically these are lines from a file.)
669     *
670     * @param string[] $to_lines           An array of strings.
671     *
672     * @param string[] $mapped_from_lines  This array should
673     *                                     have the same size number of elements as $from_lines.
674     *                                     The elements in $mapped_from_lines and
675     *                                     $mapped_to_lines are what is actually compared
676     *                                     when computing the diff.
677     *
678     * @param string[] $mapped_to_lines    This array should
679     *                                     have the same number of elements as $to_lines.
680     */
681    function __construct($from_lines, $to_lines, $mapped_from_lines, $mapped_to_lines) {
682
683        assert(count($from_lines) == count($mapped_from_lines));
684        assert(count($to_lines) == count($mapped_to_lines));
685
686        parent::__construct($mapped_from_lines, $mapped_to_lines);
687
688        $xi = $yi = 0;
689        $ecnt = count($this->edits);
690        for ($i = 0; $i < $ecnt; $i++) {
691            $orig = &$this->edits[$i]->orig;
692            if (is_array($orig)) {
693                $orig = array_slice($from_lines, $xi, count($orig));
694                $xi += count($orig);
695            }
696
697            $closing = &$this->edits[$i]->closing;
698            if (is_array($closing)) {
699                $closing = array_slice($to_lines, $yi, count($closing));
700                $yi += count($closing);
701            }
702        }
703    }
704}
705
706/**
707 * A class to format Diffs
708 *
709 * This class formats the diff in classic diff format.
710 * It is intended that this class be customized via inheritance,
711 * to obtain fancier outputs.
712 */
713class DiffFormatter {
714    /**
715     * Number of leading context "lines" to preserve.
716     *
717     * This should be left at zero for this class, but subclasses
718     * may want to set this to other values.
719     */
720    var $leading_context_lines = 0;
721
722    /**
723     * Number of trailing context "lines" to preserve.
724     *
725     * This should be left at zero for this class, but subclasses
726     * may want to set this to other values.
727     */
728    var $trailing_context_lines = 0;
729
730    /**
731     * Format a diff.
732     *
733     * @param Diff $diff A Diff object.
734     * @return string The formatted output.
735     */
736    function format($diff) {
737
738        $xi = $yi = 1;
739        $x0 = $y0 = 0;
740        $block = false;
741        $context = array();
742
743        $nlead = $this->leading_context_lines;
744        $ntrail = $this->trailing_context_lines;
745
746        $this->_start_diff();
747
748        foreach ($diff->edits as $edit) {
749            if ($edit->type == 'copy') {
750                if (is_array($block)) {
751                    if (count($edit->orig) <= $nlead + $ntrail) {
752                        $block[] = $edit;
753                    }
754                    else{
755                        if ($ntrail) {
756                            $context = array_slice($edit->orig, 0, $ntrail);
757                            $block[] = new _DiffOp_Copy($context);
758                        }
759                        $this->_block($x0, $ntrail + $xi - $x0, $y0, $ntrail + $yi - $y0, $block);
760                        $block = false;
761                    }
762                }
763                $context = $edit->orig;
764            }
765            else {
766                if (! is_array($block)) {
767                    $context = array_slice($context, count($context) - $nlead);
768                    $x0 = $xi - count($context);
769                    $y0 = $yi - count($context);
770                    $block = array();
771                    if ($context)
772                        $block[] = new _DiffOp_Copy($context);
773                }
774                $block[] = $edit;
775            }
776
777            if ($edit->orig)
778                $xi += count($edit->orig);
779            if ($edit->closing)
780                $yi += count($edit->closing);
781        }
782
783        if (is_array($block))
784            $this->_block($x0, $xi - $x0, $y0, $yi - $y0, $block);
785
786        return $this->_end_diff();
787    }
788
789    /**
790     * @param int $xbeg
791     * @param int $xlen
792     * @param int $ybeg
793     * @param int $ylen
794     * @param array $edits
795     */
796    function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
797        $this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
798        foreach ($edits as $edit) {
799            if ($edit->type == 'copy')
800                $this->_context($edit->orig);
801            elseif ($edit->type == 'add')
802                $this->_added($edit->closing);
803            elseif ($edit->type == 'delete')
804                $this->_deleted($edit->orig);
805            elseif ($edit->type == 'change')
806                $this->_changed($edit->orig, $edit->closing);
807            else
808                throw new \RuntimeException("Unknown edit type");
809        }
810        $this->_end_block();
811    }
812
813    function _start_diff() {
814        ob_start();
815    }
816
817    function _end_diff() {
818        $val = ob_get_contents();
819        ob_end_clean();
820        return $val;
821    }
822
823    /**
824     * @param int $xbeg
825     * @param int $xlen
826     * @param int $ybeg
827     * @param int $ylen
828     * @return string
829     */
830    function _block_header($xbeg, $xlen, $ybeg, $ylen) {
831        if ($xlen > 1)
832            $xbeg .= "," . ($xbeg + $xlen - 1);
833        if ($ylen > 1)
834            $ybeg .= "," . ($ybeg + $ylen - 1);
835
836        return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
837    }
838
839    /**
840     * @param string $header
841     */
842    function _start_block($header) {
843        echo $header;
844    }
845
846    function _end_block() {
847    }
848
849    function _lines($lines, $prefix = ' ') {
850        foreach ($lines as $line)
851            echo "$prefix ".$this->_escape($line)."\n";
852    }
853
854    function _context($lines) {
855        $this->_lines($lines);
856    }
857
858    function _added($lines) {
859        $this->_lines($lines, ">");
860    }
861    function _deleted($lines) {
862        $this->_lines($lines, "<");
863    }
864
865    function _changed($orig, $closing) {
866        $this->_deleted($orig);
867        echo "---\n";
868        $this->_added($closing);
869    }
870
871    /**
872     * Escape string
873     *
874     * Override this method within other formatters if escaping required.
875     * Base class requires $str to be returned WITHOUT escaping.
876     *
877     * @param $str string Text string to escape
878     * @return string The escaped string.
879     */
880    function _escape($str){
881        return $str;
882    }
883}
884
885/**
886 * Utilityclass for styling HTML formatted diffs
887 *
888 * Depends on global var $DIFF_INLINESTYLES, if true some minimal predefined
889 * inline styles are used. Useful for HTML mails and RSS feeds
890 *
891 * @author Andreas Gohr <andi@splitbrain.org>
892 */
893class HTMLDiff {
894    /**
895     * Holds the style names and basic CSS
896     */
897    static public $styles = array(
898            'diff-addedline'    => 'background-color: #ddffdd;',
899            'diff-deletedline'  => 'background-color: #ffdddd;',
900            'diff-context'      => 'background-color: #f5f5f5;',
901            'diff-mark'         => 'color: #ff0000;',
902        );
903
904    /**
905     * Return a class or style parameter
906     *
907     * @param string $classname
908     *
909     * @return string
910     */
911    static function css($classname){
912        global $DIFF_INLINESTYLES;
913
914        if($DIFF_INLINESTYLES){
915            if(!isset(self::$styles[$classname])) return '';
916            return 'style="'.self::$styles[$classname].'"';
917        }else{
918            return 'class="'.$classname.'"';
919        }
920    }
921}
922
923/**
924 *  Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
925 *
926 */
927
928define('NBSP', "\xC2\xA0");     // utf-8 non-breaking space.
929
930class _HWLDF_WordAccumulator {
931
932    /** @var array */
933    protected $_lines;
934
935    /** @var string */
936    protected $_line;
937
938    /** @var string */
939    protected $_group;
940
941    /** @var string */
942    protected $_tag;
943
944    function __construct() {
945        $this->_lines = array();
946        $this->_line = '';
947        $this->_group = '';
948        $this->_tag = '';
949    }
950
951    function _flushGroup($new_tag) {
952        if ($this->_group !== '') {
953            if ($this->_tag == 'mark')
954                $this->_line .= '<strong '.HTMLDiff::css('diff-mark').'>'.$this->_escape($this->_group).'</strong>';
955            elseif ($this->_tag == 'add')
956                $this->_line .= '<span '.HTMLDiff::css('diff-addedline').'>'.$this->_escape($this->_group).'</span>';
957            elseif ($this->_tag == 'del')
958                $this->_line .= '<span '.HTMLDiff::css('diff-deletedline').'><del>'.$this->_escape($this->_group).'</del></span>';
959            else
960                $this->_line .= $this->_escape($this->_group);
961        }
962        $this->_group = '';
963        $this->_tag = $new_tag;
964    }
965
966    /**
967     * @param string $new_tag
968     */
969    function _flushLine($new_tag) {
970        $this->_flushGroup($new_tag);
971        if ($this->_line != '')
972            $this->_lines[] = $this->_line;
973        $this->_line = '';
974    }
975
976    function addWords($words, $tag = '') {
977        if ($tag != $this->_tag)
978            $this->_flushGroup($tag);
979
980        foreach ($words as $word) {
981            // new-line should only come as first char of word.
982            if ($word == '')
983                continue;
984            if ($word[0] == "\n") {
985                $this->_group .= NBSP;
986                $this->_flushLine($tag);
987                $word = substr($word, 1);
988            }
989            assert(!strstr($word, "\n"));
990            $this->_group .= $word;
991        }
992    }
993
994    function getLines() {
995        $this->_flushLine('~done');
996        return $this->_lines;
997    }
998
999    function _escape($str){
1000        return hsc($str);
1001    }
1002}
1003
1004class WordLevelDiff extends MappedDiff {
1005
1006    function __construct($orig_lines, $closing_lines) {
1007        list ($orig_words, $orig_stripped) = $this->_split($orig_lines);
1008        list ($closing_words, $closing_stripped) = $this->_split($closing_lines);
1009
1010        parent::__construct($orig_words, $closing_words, $orig_stripped, $closing_stripped);
1011    }
1012
1013    function _split($lines) {
1014        if (!preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xsu',
1015             implode("\n", $lines), $m)) {
1016            return array(array(''), array(''));
1017        }
1018        return array($m[0], $m[1]);
1019    }
1020
1021    function orig() {
1022        $orig = new _HWLDF_WordAccumulator;
1023
1024        foreach ($this->edits as $edit) {
1025            if ($edit->type == 'copy')
1026                $orig->addWords($edit->orig);
1027            elseif ($edit->orig)
1028                $orig->addWords($edit->orig, 'mark');
1029        }
1030        return $orig->getLines();
1031    }
1032
1033    function closing() {
1034        $closing = new _HWLDF_WordAccumulator;
1035
1036        foreach ($this->edits as $edit) {
1037            if ($edit->type == 'copy')
1038                $closing->addWords($edit->closing);
1039            elseif ($edit->closing)
1040                $closing->addWords($edit->closing, 'mark');
1041        }
1042        return $closing->getLines();
1043    }
1044}
1045
1046class InlineWordLevelDiff extends MappedDiff {
1047
1048    function __construct($orig_lines, $closing_lines) {
1049        list ($orig_words, $orig_stripped) = $this->_split($orig_lines);
1050        list ($closing_words, $closing_stripped) = $this->_split($closing_lines);
1051
1052        parent::__construct($orig_words, $closing_words, $orig_stripped, $closing_stripped);
1053    }
1054
1055    function _split($lines) {
1056        if (!preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xsu',
1057             implode("\n", $lines), $m)) {
1058            return array(array(''), array(''));
1059        }
1060        return array($m[0], $m[1]);
1061    }
1062
1063    function inline() {
1064        $orig = new _HWLDF_WordAccumulator;
1065        foreach ($this->edits as $edit) {
1066            if ($edit->type == 'copy')
1067                $orig->addWords($edit->closing);
1068            elseif ($edit->type == 'change'){
1069                $orig->addWords($edit->orig, 'del');
1070                $orig->addWords($edit->closing, 'add');
1071            } elseif ($edit->type == 'delete')
1072                $orig->addWords($edit->orig, 'del');
1073            elseif ($edit->type == 'add')
1074                $orig->addWords($edit->closing, 'add');
1075            elseif ($edit->orig)
1076                $orig->addWords($edit->orig, 'del');
1077        }
1078        return $orig->getLines();
1079    }
1080}
1081
1082/**
1083 * "Unified" diff formatter.
1084 *
1085 * This class formats the diff in classic "unified diff" format.
1086 *
1087 * NOTE: output is plain text and unsafe for use in HTML without escaping.
1088 */
1089class UnifiedDiffFormatter extends DiffFormatter {
1090
1091    function __construct($context_lines = 4) {
1092        $this->leading_context_lines = $context_lines;
1093        $this->trailing_context_lines = $context_lines;
1094    }
1095
1096    function _block_header($xbeg, $xlen, $ybeg, $ylen) {
1097        if ($xlen != 1)
1098            $xbeg .= "," . $xlen;
1099        if ($ylen != 1)
1100            $ybeg .= "," . $ylen;
1101        return "@@ -$xbeg +$ybeg @@\n";
1102    }
1103
1104    function _added($lines) {
1105        $this->_lines($lines, "+");
1106    }
1107    function _deleted($lines) {
1108        $this->_lines($lines, "-");
1109    }
1110    function _changed($orig, $final) {
1111        $this->_deleted($orig);
1112        $this->_added($final);
1113    }
1114}
1115
1116/**
1117 *  Wikipedia Table style diff formatter.
1118 *
1119 */
1120class TableDiffFormatter extends DiffFormatter {
1121    var $colspan = 2;
1122
1123    function __construct() {
1124        $this->leading_context_lines = 2;
1125        $this->trailing_context_lines = 2;
1126    }
1127
1128    /**
1129     * @param Diff $diff
1130     * @return string
1131     */
1132    function format($diff) {
1133        // Preserve whitespaces by converting some to non-breaking spaces.
1134        // Do not convert all of them to allow word-wrap.
1135        $val = parent::format($diff);
1136        $val = str_replace('  ','&#160; ', $val);
1137        $val = preg_replace('/ (?=<)|(?<=[ >]) /', '&#160;', $val);
1138        return $val;
1139    }
1140
1141    function _pre($text){
1142        $text = htmlspecialchars($text);
1143        return $text;
1144    }
1145
1146    function _block_header($xbeg, $xlen, $ybeg, $ylen) {
1147        global $lang;
1148        $l1 = $lang['line'].' '.$xbeg;
1149        $l2 = $lang['line'].' '.$ybeg;
1150        $r = '<tr><td '.HTMLDiff::css('diff-blockheader').' colspan="'.$this->colspan.'">'.$l1.":</td>\n".
1151             '<td '.HTMLDiff::css('diff-blockheader').' colspan="'.$this->colspan.'">'.$l2.":</td>\n".
1152             "</tr>\n";
1153        return $r;
1154    }
1155
1156    function _start_block($header) {
1157        print($header);
1158    }
1159
1160    function _end_block() {
1161    }
1162
1163    function _lines($lines, $prefix=' ', $color="white") {
1164    }
1165
1166    function addedLine($line,$escaped=false) {
1167        if (!$escaped){
1168            $line = $this->_escape($line);
1169        }
1170        return '<td '.HTMLDiff::css('diff-lineheader').'>+</td>'.
1171               '<td '.HTMLDiff::css('diff-addedline').'>' .  $line.'</td>';
1172    }
1173
1174    function deletedLine($line,$escaped=false) {
1175        if (!$escaped){
1176            $line = $this->_escape($line);
1177        }
1178        return '<td '.HTMLDiff::css('diff-lineheader').'>-</td>'.
1179               '<td '.HTMLDiff::css('diff-deletedline').'>' .  $line.'</td>';
1180    }
1181
1182    function emptyLine() {
1183        return '<td colspan="'.$this->colspan.'">&#160;</td>';
1184    }
1185
1186    function contextLine($line) {
1187        return '<td '.HTMLDiff::css('diff-lineheader').'>&#160;</td>'.
1188               '<td '.HTMLDiff::css('diff-context').'>'.$this->_escape($line).'</td>';
1189    }
1190
1191    function _added($lines) {
1192        $this->_addedLines($lines,false);
1193    }
1194
1195    function _addedLines($lines,$escaped=false){
1196        foreach ($lines as $line) {
1197            print('<tr>' . $this->emptyLine() . $this->addedLine($line,$escaped) . "</tr>\n");
1198        }
1199    }
1200
1201    function _deleted($lines) {
1202        foreach ($lines as $line) {
1203            print('<tr>' . $this->deletedLine($line) . $this->emptyLine() . "</tr>\n");
1204        }
1205    }
1206
1207    function _context($lines) {
1208        foreach ($lines as $line) {
1209            print('<tr>' . $this->contextLine($line) .  $this->contextLine($line) . "</tr>\n");
1210        }
1211    }
1212
1213    function _changed($orig, $closing) {
1214        $diff = new WordLevelDiff($orig, $closing);  // this escapes the diff data
1215        $del = $diff->orig();
1216        $add = $diff->closing();
1217
1218        while ($line = array_shift($del)) {
1219            $aline = array_shift($add);
1220            print('<tr>' . $this->deletedLine($line,true) . $this->addedLine($aline,true) . "</tr>\n");
1221        }
1222        $this->_addedLines($add,true); # If any leftovers
1223    }
1224
1225    function _escape($str) {
1226        return hsc($str);
1227    }
1228}
1229
1230/**
1231 *  Inline style diff formatter.
1232 *
1233 */
1234class InlineDiffFormatter extends DiffFormatter {
1235    var $colspan = 2;
1236
1237    function __construct() {
1238        $this->leading_context_lines = 2;
1239        $this->trailing_context_lines = 2;
1240    }
1241
1242    /**
1243     * @param Diff $diff
1244     * @return string
1245     */
1246    function format($diff) {
1247        // Preserve whitespaces by converting some to non-breaking spaces.
1248        // Do not convert all of them to allow word-wrap.
1249        $val = parent::format($diff);
1250        $val = str_replace('  ','&#160; ', $val);
1251        $val = preg_replace('/ (?=<)|(?<=[ >]) /', '&#160;', $val);
1252        return $val;
1253    }
1254
1255    function _pre($text){
1256        $text = htmlspecialchars($text);
1257        return $text;
1258    }
1259
1260    function _block_header($xbeg, $xlen, $ybeg, $ylen) {
1261        global $lang;
1262        if ($xlen != 1)
1263            $xbeg .= "," . $xlen;
1264        if ($ylen != 1)
1265            $ybeg .= "," . $ylen;
1266        $r = '<tr><td colspan="'.$this->colspan.'" '.HTMLDiff::css('diff-blockheader').'>@@ '.$lang['line']." -$xbeg +$ybeg @@";
1267        $r .= ' <span '.HTMLDiff::css('diff-deletedline').'><del>'.$lang['deleted'].'</del></span>';
1268        $r .= ' <span '.HTMLDiff::css('diff-addedline').'>'.$lang['created'].'</span>';
1269        $r .= "</td></tr>\n";
1270        return $r;
1271    }
1272
1273    function _start_block($header) {
1274        print($header."\n");
1275    }
1276
1277    function _end_block() {
1278    }
1279
1280    function _lines($lines, $prefix=' ', $color="white") {
1281    }
1282
1283    function _added($lines) {
1284        foreach ($lines as $line) {
1285            print('<tr><td '.HTMLDiff::css('diff-lineheader').'>&#160;</td><td '.HTMLDiff::css('diff-addedline').'>'. $this->_escape($line) . "</td></tr>\n");
1286        }
1287    }
1288
1289    function _deleted($lines) {
1290        foreach ($lines as $line) {
1291            print('<tr><td '.HTMLDiff::css('diff-lineheader').'>&#160;</td><td '.HTMLDiff::css('diff-deletedline').'><del>' . $this->_escape($line) . "</del></td></tr>\n");
1292        }
1293    }
1294
1295    function _context($lines) {
1296        foreach ($lines as $line) {
1297            print('<tr><td '.HTMLDiff::css('diff-lineheader').'>&#160;</td><td '.HTMLDiff::css('diff-context').'>'. $this->_escape($line) ."</td></tr>\n");
1298        }
1299    }
1300
1301    function _changed($orig, $closing) {
1302        $diff = new InlineWordLevelDiff($orig, $closing);  // this escapes the diff data
1303        $add = $diff->inline();
1304
1305        foreach ($add as $line)
1306            print('<tr><td '.HTMLDiff::css('diff-lineheader').'>&#160;</td><td>'.$line."</td></tr>\n");
1307    }
1308
1309    function _escape($str) {
1310        return hsc($str);
1311    }
1312}
1313
1314/**
1315 * A class for computing three way diffs.
1316 *
1317 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
1318 */
1319class Diff3 extends Diff {
1320
1321    /**
1322     * Conflict counter.
1323     *
1324     * @var integer
1325     */
1326    var $_conflictingBlocks = 0;
1327
1328    /**
1329     * Computes diff between 3 sequences of strings.
1330     *
1331     * @param array $orig    The original lines to use.
1332     * @param array $final1  The first version to compare to.
1333     * @param array $final2  The second version to compare to.
1334     */
1335    function __construct($orig, $final1, $final2) {
1336        $engine = new _DiffEngine();
1337
1338        $this->_edits = $this->_diff3($engine->diff($orig, $final1),
1339                                      $engine->diff($orig, $final2));
1340    }
1341
1342    /**
1343     * Returns the merged lines
1344     *
1345     * @param string $label1  label for first version
1346     * @param string $label2  label for second version
1347     * @param string $label3  separator between versions
1348     * @return array          lines of the merged text
1349     */
1350    function mergedOutput($label1='<<<<<<<',$label2='>>>>>>>',$label3='=======') {
1351        $lines = array();
1352        foreach ($this->_edits as $edit) {
1353            if ($edit->isConflict()) {
1354                /* FIXME: this should probably be moved somewhere else. */
1355                $lines = array_merge($lines,
1356                                     array($label1),
1357                                     $edit->final1,
1358                                     array($label3),
1359                                     $edit->final2,
1360                                     array($label2));
1361                $this->_conflictingBlocks++;
1362            } else {
1363                $lines = array_merge($lines, $edit->merged());
1364            }
1365        }
1366
1367        return $lines;
1368    }
1369
1370    /**
1371     * @access private
1372     *
1373     * @param array $edits1
1374     * @param array $edits2
1375     *
1376     * @return array
1377     */
1378    function _diff3($edits1, $edits2) {
1379        $edits = array();
1380        $bb = new _Diff3_BlockBuilder();
1381
1382        $e1 = current($edits1);
1383        $e2 = current($edits2);
1384        while ($e1 || $e2) {
1385            if ($e1 && $e2 && is_a($e1, '_DiffOp_copy') && is_a($e2, '_DiffOp_copy')) {
1386                /* We have copy blocks from both diffs. This is the (only)
1387                 * time we want to emit a diff3 copy block.  Flush current
1388                 * diff3 diff block, if any. */
1389                if ($edit = $bb->finish()) {
1390                    $edits[] = $edit;
1391                }
1392
1393                $ncopy = min($e1->norig(), $e2->norig());
1394                assert($ncopy > 0);
1395                $edits[] = new _Diff3_Op_copy(array_slice($e1->orig, 0, $ncopy));
1396
1397                if ($e1->norig() > $ncopy) {
1398                    array_splice($e1->orig, 0, $ncopy);
1399                    array_splice($e1->closing, 0, $ncopy);
1400                } else {
1401                    $e1 = next($edits1);
1402                }
1403
1404                if ($e2->norig() > $ncopy) {
1405                    array_splice($e2->orig, 0, $ncopy);
1406                    array_splice($e2->closing, 0, $ncopy);
1407                } else {
1408                    $e2 = next($edits2);
1409                }
1410            } else {
1411                if ($e1 && $e2) {
1412                    if ($e1->orig && $e2->orig) {
1413                        $norig = min($e1->norig(), $e2->norig());
1414                        $orig = array_splice($e1->orig, 0, $norig);
1415                        array_splice($e2->orig, 0, $norig);
1416                        $bb->input($orig);
1417                    }
1418
1419                    if (is_a($e1, '_DiffOp_copy')) {
1420                        $bb->out1(array_splice($e1->closing, 0, $norig));
1421                    }
1422
1423                    if (is_a($e2, '_DiffOp_copy')) {
1424                        $bb->out2(array_splice($e2->closing, 0, $norig));
1425                    }
1426                }
1427
1428                if ($e1 && ! $e1->orig) {
1429                    $bb->out1($e1->closing);
1430                    $e1 = next($edits1);
1431                }
1432                if ($e2 && ! $e2->orig) {
1433                    $bb->out2($e2->closing);
1434                    $e2 = next($edits2);
1435                }
1436            }
1437        }
1438
1439        if ($edit = $bb->finish()) {
1440            $edits[] = $edit;
1441        }
1442
1443        return $edits;
1444    }
1445}
1446
1447/**
1448 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
1449 *
1450 * @access private
1451 */
1452class _Diff3_Op {
1453
1454    /** @var array|mixed */
1455    protected $orig;
1456
1457    /** @var array|mixed */
1458    protected $final1;
1459
1460    /** @var array|mixed */
1461    protected $final2;
1462
1463    /** @var array|mixed|false */
1464    protected $_merged;
1465
1466    function __construct($orig = false, $final1 = false, $final2 = false) {
1467        $this->orig = $orig ? $orig : array();
1468        $this->final1 = $final1 ? $final1 : array();
1469        $this->final2 = $final2 ? $final2 : array();
1470    }
1471
1472    function merged() {
1473        if (!isset($this->_merged)) {
1474            if ($this->final1 === $this->final2) {
1475                $this->_merged = &$this->final1;
1476            } elseif ($this->final1 === $this->orig) {
1477                $this->_merged = &$this->final2;
1478            } elseif ($this->final2 === $this->orig) {
1479                $this->_merged = &$this->final1;
1480            } else {
1481                $this->_merged = false;
1482            }
1483        }
1484
1485        return $this->_merged;
1486    }
1487
1488    function isConflict() {
1489        return $this->merged() === false;
1490    }
1491
1492}
1493
1494/**
1495 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
1496 *
1497 * @access private
1498 */
1499class _Diff3_Op_copy extends _Diff3_Op {
1500
1501    function __construct($lines = false) {
1502        $this->orig = $lines ? $lines : array();
1503        $this->final1 = &$this->orig;
1504        $this->final2 = &$this->orig;
1505    }
1506
1507    function merged() {
1508        return $this->orig;
1509    }
1510
1511    function isConflict() {
1512        return false;
1513    }
1514}
1515
1516/**
1517 * @author  Geoffrey T. Dairiki <dairiki@dairiki.org>
1518 *
1519 * @access private
1520 */
1521class _Diff3_BlockBuilder {
1522
1523    function __construct() {
1524        $this->_init();
1525    }
1526
1527    function input($lines) {
1528        if ($lines) {
1529            $this->_append($this->orig, $lines);
1530        }
1531    }
1532
1533    function out1($lines) {
1534        if ($lines) {
1535            $this->_append($this->final1, $lines);
1536        }
1537    }
1538
1539    function out2($lines) {
1540        if ($lines) {
1541            $this->_append($this->final2, $lines);
1542        }
1543    }
1544
1545    function isEmpty() {
1546        return !$this->orig && !$this->final1 && !$this->final2;
1547    }
1548
1549    function finish() {
1550        if ($this->isEmpty()) {
1551            return false;
1552        } else {
1553            $edit = new _Diff3_Op($this->orig, $this->final1, $this->final2);
1554            $this->_init();
1555            return $edit;
1556        }
1557    }
1558
1559    function _init() {
1560        $this->orig = $this->final1 = $this->final2 = array();
1561    }
1562
1563    function _append(&$array, $lines) {
1564        array_splice($array, sizeof($array), 0, $lines);
1565    }
1566}
1567
1568//Setup VIM: ex: et ts=4 :
1569