aboutsummaryrefslogtreecommitdiff
path: root/lib/dokuwiki/inc/DifferenceEngine.php
blob: e28826c1f14ae146f4b3235e82a5c54ee56d1736 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
<?php
/**
 * A PHP diff engine for phpwiki. (Taken from phpwiki-1.3.3)
 *
 * Additions by Axel Boldt for MediaWiki
 *
 * @copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
 * @license  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', "\xC2\xA0");     // utf-8 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')
      $this->_line .= '<strong>'.$this->_group.'</strong>';
    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);
    if($text{0} == ' ') $text = '&nbsp;'.substr($text,1);
    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);
    if($line{0} == ' ') $line = '&nbsp;'.substr($line,1);
    return '<td>+</td><td class="diff-addedline">' .
      $line.'</td>';
  }

  function deletedLine( $line ) {
    $line = str_replace('  ',' &nbsp;',$line);
    if($line{0} == ' ') $line = '&nbsp;'.substr($line,1);
    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);
    if($line{0} == ' ') $line = '&nbsp;'.substr($line,1);
    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
  }
}


//Setup VIM: ex: et ts=2 enc=utf-8 :