includes/diff/DairikiDiff.php

   1 <?php
   2 /**
   3  * A PHP diff engine for phpwiki. (Taken from phpwiki-1.3.3)
   4  *
   5  * Copyright © 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
   6  * You may copy this code freely under the conditions of the GPL.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup DifferenceEngine
  25  * @defgroup DifferenceEngine DifferenceEngine
  26  */
  27
  28 /**
  29  * @todo document
  30  * @private
  31  * @ingroup DifferenceEngine
  32  */
  33 class _DiffOp {
  34         var $type;
  35         var $orig;
  36         var $closing;
  37
  38         function reverse() {
  39                 trigger_error( 'pure virtual', E_USER_ERROR );
  40         }
  41
  42         /**
  43          * @return int
  44          */
  45         function norig() {
  46                 return $this->orig ? count( $this->orig ) : 0;
  47         }
  48
  49         /**
  50          * @return int
  51          */
  52         function nclosing() {
  53                 return $this->closing ? count( $this->closing ) : 0;
  54         }
  55 }
  56
  57 /**
  58  * @todo document
  59  * @private
  60  * @ingroup DifferenceEngine
  61  */
  62 class _DiffOp_Copy extends _DiffOp {
  63         var $type = 'copy';
  64
  65         function __construct( $orig, $closing = false ) {
  66                 if ( !is_array( $closing ) ) {
  67                         $closing = $orig;
  68                 }
  69                 $this->orig = $orig;
  70                 $this->closing = $closing;
  71         }
  72
  73         /**
  74          * @return _DiffOp_Copy
  75          */
  76         function reverse() {
  77                 return new _DiffOp_Copy( $this->closing, $this->orig );
  78         }
  79 }
  80
  81 /**
  82  * @todo document
  83  * @private
  84  * @ingroup DifferenceEngine
  85  */
  86 class _DiffOp_Delete extends _DiffOp {
  87         var $type = 'delete';
  88
  89         function __construct( $lines ) {
  90                 $this->orig = $lines;
  91                 $this->closing = false;
  92         }
  93
  94         /**
  95          * @return _DiffOp_Add
  96          */
  97         function reverse() {
  98                 return new _DiffOp_Add( $this->orig );
  99         }
 100 }
 101
 102 /**
 103  * @todo document
 104  * @private
 105  * @ingroup DifferenceEngine
 106  */
 107 class _DiffOp_Add extends _DiffOp {
 108         var $type = 'add';
 109
 110         function __construct( $lines ) {
 111                 $this->closing = $lines;
 112                 $this->orig = false;
 113         }
 114
 115         /**
 116          * @return _DiffOp_Delete
 117          */
 118         function reverse() {
 119                 return new _DiffOp_Delete( $this->closing );
 120         }
 121 }
 122
 123 /**
 124  * @todo document
 125  * @private
 126  * @ingroup DifferenceEngine
 127  */
 128 class _DiffOp_Change extends _DiffOp {
 129         var $type = 'change';
 130
 131         function __construct( $orig, $closing ) {
 132                 $this->orig = $orig;
 133                 $this->closing = $closing;
 134         }
 135
 136         /**
 137          * @return _DiffOp_Change
 138          */
 139         function reverse() {
 140                 return new _DiffOp_Change( $this->closing, $this->orig );
 141         }
 142 }
 143
 144 /**
 145  * Class used internally by Diff to actually compute the diffs.
 146  *
 147  * The algorithm used here is mostly lifted from the perl module
 148  * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
 149  *       http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
 150  *
 151  * More ideas are taken from:
 152  *       http://www.ics.uci.edu/~eppstein/161/960229.html
 153  *
 154  * Some ideas are (and a bit of code) are from from analyze.c, from GNU
 155  * diffutils-2.7, which can be found at:
 156  *       ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
 157  *
 158  * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
 159  * are my own.
 160  *
 161  * Line length limits for robustness added by Tim Starling, 2005-08-31
 162  * Alternative implementation added by Guy Van den Broeck, 2008-07-30
 163  *
 164  * @author Geoffrey T. Dairiki, Tim Starling, Guy Van den Broeck
 165  * @private
 166  * @ingroup DifferenceEngine
 167  */
 168 class _DiffEngine {
 169
 170         const MAX_XREF_LENGTH = 10000;
 171
 172         protected $xchanged, $ychanged;
 173
 174         protected $xv = array(), $yv = array();
 175         protected $xind = array(), $yind = array();
 176
 177         protected $seq = array(), $in_seq = array();
 178
 179         protected $lcs = 0;
 180
 181         /**
 182          * @param $from_lines
 183          * @param $to_lines
 184          * @return array
 185          */
 186         function diff( $from_lines, $to_lines ) {
 187                 wfProfileIn( __METHOD__ );
 188
 189                 // Diff and store locally
 190                 $this->diff_local( $from_lines, $to_lines );
 191
 192                 // Merge edits when possible
 193                 $this->_shift_boundaries( $from_lines, $this->xchanged, $this->ychanged );
 194                 $this->_shift_boundaries( $to_lines, $this->ychanged, $this->xchanged );
 195
 196                 // Compute the edit operations.
 197                 $n_from = count( $from_lines );
 198                 $n_to = count( $to_lines );
 199
 200                 $edits = array();
 201                 $xi = $yi = 0;
 202                 while ( $xi < $n_from || $yi < $n_to ) {
 203                         assert( '$yi < $n_to || $this->xchanged[$xi]' );
 204                         assert( '$xi < $n_from || $this->ychanged[$yi]' );
 205
 206                         // Skip matching "snake".
 207                         $copy = array();
 208                         while ( $xi < $n_from && $yi < $n_to
 209                         && !$this->xchanged[$xi] && !$this->ychanged[$yi] ) {
 210                                 $copy[] = $from_lines[$xi++];
 211                                 ++$yi;
 212                         }
 213                         if ( $copy ) {
 214                                 $edits[] = new _DiffOp_Copy( $copy );
 215                         }
 216
 217                         // Find deletes & adds.
 218                         $delete = array();
 219                         while ( $xi < $n_from && $this->xchanged[$xi] ) {
 220                                 $delete[] = $from_lines[$xi++];
 221                         }
 222
 223                         $add = array();
 224                         while ( $yi < $n_to && $this->ychanged[$yi] ) {
 225                                 $add[] = $to_lines[$yi++];
 226                         }
 227
 228                         if ( $delete && $add ) {
 229                                 $edits[] = new _DiffOp_Change( $delete, $add );
 230                         } elseif ( $delete ) {
 231                                 $edits[] = new _DiffOp_Delete( $delete );
 232                         } elseif ( $add ) {
 233                                 $edits[] = new _DiffOp_Add( $add );
 234                         }
 235                 }
 236                 wfProfileOut( __METHOD__ );
 237                 return $edits;
 238         }
 239
 240         /**
 241          * @param $from_lines
 242          * @param $to_lines
 243          */
 244         function diff_local( $from_lines, $to_lines ) {
 245                 global $wgExternalDiffEngine;
 246                 wfProfileIn( __METHOD__ );
 247
 248                 if ( $wgExternalDiffEngine == 'wikidiff3' ) {
 249                         // wikidiff3
 250                         $wikidiff3 = new WikiDiff3();
 251                         $wikidiff3->diff( $from_lines, $to_lines );
 252                         $this->xchanged = $wikidiff3->removed;
 253                         $this->ychanged = $wikidiff3->added;
 254                         unset( $wikidiff3 );
 255                 } else {
 256                         // old diff
 257                         $n_from = count( $from_lines );
 258                         $n_to = count( $to_lines );
 259                         $this->xchanged = $this->ychanged = array();
 260                         $this->xv = $this->yv = array();
 261                         $this->xind = $this->yind = array();
 262                         unset( $this->seq );
 263                         unset( $this->in_seq );
 264                         unset( $this->lcs );
 265
 266                         // Skip leading common lines.
 267                         for ( $skip = 0; $skip < $n_from && $skip < $n_to; $skip++ ) {
 268                                 if ( $from_lines[$skip] !== $to_lines[$skip] ) {
 269                                         break;
 270                                 }
 271                                 $this->xchanged[$skip] = $this->ychanged[$skip] = false;
 272                         }
 273                         // Skip trailing common lines.
 274                         $xi = $n_from; $yi = $n_to;
 275                         for ( $endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++ ) {
 276                                 if ( $from_lines[$xi] !== $to_lines[$yi] ) {
 277                                         break;
 278                                 }
 279                                 $this->xchanged[$xi] = $this->ychanged[$yi] = false;
 280                         }
 281
 282                         // Ignore lines which do not exist in both files.
 283                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 284                                 $xhash[$this->_line_hash( $from_lines[$xi] )] = 1;
 285                         }
 286
 287                         for ( $yi = $skip; $yi < $n_to - $endskip; $yi++ ) {
 288                                 $line = $to_lines[$yi];
 289                                 if ( ( $this->ychanged[$yi] = empty( $xhash[$this->_line_hash( $line )] ) ) ) {
 290                                         continue;
 291                                 }
 292                                 $yhash[$this->_line_hash( $line )] = 1;
 293                                 $this->yv[] = $line;
 294                                 $this->yind[] = $yi;
 295                         }
 296                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 297                                 $line = $from_lines[$xi];
 298                                 if ( ( $this->xchanged[$xi] = empty( $yhash[$this->_line_hash( $line )] ) ) ) {
 299                                         continue;
 300                                 }
 301                                 $this->xv[] = $line;
 302                                 $this->xind[] = $xi;
 303                         }
 304
 305                         // Find the LCS.
 306                         $this->_compareseq( 0, count( $this->xv ), 0, count( $this->yv ) );
 307                 }
 308                 wfProfileOut( __METHOD__ );
 309         }
 310
 311         /**
 312          * Returns the whole line if it's small enough, or the MD5 hash otherwise
 313          * @param $line string
 314          * @return string
 315          */
 316         function _line_hash( $line ) {
 317                 if ( strlen( $line ) > self::MAX_XREF_LENGTH ) {
 318                         return md5( $line );
 319                 } else {
 320                         return $line;
 321                 }
 322         }
 323
 324         /**
 325          * Divide the Largest Common Subsequence (LCS) of the sequences
 326          * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
 327          * sized segments.
 328          *
 329          * Returns (LCS, PTS). LCS is the length of the LCS. PTS is an
 330          * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
 331          * sub sequences.  The first sub-sequence is contained in [X0, X1),
 332          * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
 333          * that (X0, Y0) == (XOFF, YOFF) and
 334          * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
 335          *
 336          * This function assumes that the first lines of the specified portions
 337          * of the two files do not match, and likewise that the last lines do not
 338          * match.  The caller must trim matching lines from the beginning and end
 339          * of the portions it is going to specify.
 340          * @param $xoff
 341          * @param $xlim
 342          * @param $yoff
 343          * @param $ylim
 344          * @param $nchunks
 345          * @return array
 346          */
 347         function _diag( $xoff, $xlim, $yoff, $ylim, $nchunks ) {
 348                 $flip = false;
 349
 350                 if ( $xlim - $xoff > $ylim - $yoff ) {
 351                         // Things seems faster (I'm not sure I understand why)
 352                         // when the shortest sequence in X.
 353                         $flip = true;
 354                         list( $xoff, $xlim, $yoff, $ylim ) = array( $yoff, $ylim, $xoff, $xlim );
 355                 }
 356
 357                 if ( $flip ) {
 358                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 359                                 $ymatches[$this->xv[$i]][] = $i;
 360                         }
 361                 } else {
 362                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 363                                 $ymatches[$this->yv[$i]][] = $i;
 364                         }
 365                 }
 366
 367                 $this->lcs = 0;
 368                 $this->seq[0] = $yoff - 1;
 369                 $this->in_seq = array();
 370                 $ymids[0] = array();
 371
 372                 $numer = $xlim - $xoff + $nchunks - 1;
 373                 $x = $xoff;
 374                 for ( $chunk = 0; $chunk < $nchunks; $chunk++ ) {
 375                         if ( $chunk > 0 ) {
 376                                 for ( $i = 0; $i <= $this->lcs; $i++ ) {
 377                                         $ymids[$i][$chunk -1] = $this->seq[$i];
 378                                 }
 379                         }
 380
 381                         $x1 = $xoff + (int)( ( $numer + ( $xlim -$xoff ) * $chunk ) / $nchunks );
 382                         for ( ; $x < $x1; $x++ ) {
 383                                 $line = $flip ? $this->yv[$x] : $this->xv[$x];
 384                                 if ( empty( $ymatches[$line] ) ) {
 385                                         continue;
 386                                 }
 387                                 $matches = $ymatches[$line];
 388                                 reset( $matches );
 389                                 while ( list( , $y ) = each( $matches ) ) {
 390                                         if ( empty( $this->in_seq[$y] ) ) {
 391                                                 $k = $this->_lcs_pos( $y );
 392                                                 assert( '$k > 0' );
 393                                                 $ymids[$k] = $ymids[$k -1];
 394                                                 break;
 395                                         }
 396                                 }
 397                                 while ( list ( , $y ) = each( $matches ) ) {
 398                                         if ( $y > $this->seq[$k -1] ) {
 399                                                 assert( '$y < $this->seq[$k]' );
 400                                                 // Optimization: this is a common case:
 401                                                 //      next match is just replacing previous match.
 402                                                 $this->in_seq[$this->seq[$k]] = false;
 403                                                 $this->seq[$k] = $y;
 404                                                 $this->in_seq[$y] = 1;
 405                                         } elseif ( empty( $this->in_seq[$y] ) ) {
 406                                                 $k = $this->_lcs_pos( $y );
 407                                                 assert( '$k > 0' );
 408                                                 $ymids[$k] = $ymids[$k -1];
 409                                         }
 410                                 }
 411                         }
 412                 }
 413
 414                 $seps[] = $flip ? array( $yoff, $xoff ) : array( $xoff, $yoff );
 415                 $ymid = $ymids[$this->lcs];
 416                 for ( $n = 0; $n < $nchunks - 1; $n++ ) {
 417                         $x1 = $xoff + (int)( ( $numer + ( $xlim - $xoff ) * $n ) / $nchunks );
 418                         $y1 = $ymid[$n] + 1;
 419                         $seps[] = $flip ? array( $y1, $x1 ) : array( $x1, $y1 );
 420                 }
 421                 $seps[] = $flip ? array( $ylim, $xlim ) : array( $xlim, $ylim );
 422
 423                 return array( $this->lcs, $seps );
 424         }
 425
 426         /**
 427          * @param $ypos
 428          * @return int
 429          */
 430         function _lcs_pos( $ypos ) {
 431                 $end = $this->lcs;
 432                 if ( $end == 0 || $ypos > $this->seq[$end] ) {
 433                         $this->seq[++$this->lcs] = $ypos;
 434                         $this->in_seq[$ypos] = 1;
 435                         return $this->lcs;
 436                 }
 437
 438                 $beg = 1;
 439                 while ( $beg < $end ) {
 440                         $mid = (int)( ( $beg + $end ) / 2 );
 441                         if ( $ypos > $this->seq[$mid] ) {
 442                                 $beg = $mid + 1;
 443                         } else {
 444                                 $end = $mid;
 445                         }
 446                 }
 447
 448                 assert( '$ypos != $this->seq[$end]' );
 449
 450                 $this->in_seq[$this->seq[$end]] = false;
 451                 $this->seq[$end] = $ypos;
 452                 $this->in_seq[$ypos] = 1;
 453                 return $end;
 454         }
 455
 456         /**
 457          * Find LCS of two sequences.
 458          *
 459          * The results are recorded in the vectors $this->{x,y}changed[], by
 460          * storing a 1 in the element for each line that is an insertion
 461          * or deletion (ie. is not in the LCS).
 462          *
 463          * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
 464          *
 465          * Note that XLIM, YLIM are exclusive bounds.
 466          * All line numbers are origin-0 and discarded lines are not counted.
 467          * @param $xoff
 468          * @param $xlim
 469          * @param $yoff
 470          * @param $ylim
 471          */
 472         function _compareseq( $xoff, $xlim, $yoff, $ylim ) {
 473                 // Slide down the bottom initial diagonal.
 474                 while ( $xoff < $xlim && $yoff < $ylim
 475                 && $this->xv[$xoff] == $this->yv[$yoff] ) {
 476                         ++$xoff;
 477                         ++$yoff;
 478                 }
 479
 480                 // Slide up the top initial diagonal.
 481                 while ( $xlim > $xoff && $ylim > $yoff
 482                 && $this->xv[$xlim - 1] == $this->yv[$ylim - 1] ) {
 483                         --$xlim;
 484                         --$ylim;
 485                 }
 486
 487                 if ( $xoff == $xlim || $yoff == $ylim ) {
 488                         $lcs = 0;
 489                 } else {
 490                         // This is ad hoc but seems to work well.
 491                         // $nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
 492                         // $nchunks = max(2,min(8,(int)$nchunks));
 493                         $nchunks = min( 7, $xlim - $xoff, $ylim - $yoff ) + 1;
 494                         list ( $lcs, $seps ) = $this->_diag( $xoff, $xlim, $yoff, $ylim, $nchunks );
 495                 }
 496
 497                 if ( $lcs == 0 ) {
 498                         // X and Y sequences have no common subsequence:
 499                         // mark all changed.
 500                         while ( $yoff < $ylim ) {
 501                                 $this->ychanged[$this->yind[$yoff++]] = 1;
 502                         }
 503                         while ( $xoff < $xlim ) {
 504                                 $this->xchanged[$this->xind[$xoff++]] = 1;
 505                         }
 506                 } else {
 507                         // Use the partitions to split this problem into subproblems.
 508                         reset( $seps );
 509                         $pt1 = $seps[0];
 510                         while ( $pt2 = next( $seps ) ) {
 511                                 $this->_compareseq( $pt1[0], $pt2[0], $pt1[1], $pt2[1] );
 512                                 $pt1 = $pt2;
 513                         }
 514                 }
 515         }
 516
 517         /**
 518          * Adjust inserts/deletes of identical lines to join changes
 519          * as much as possible.
 520          *
 521          * We do something when a run of changed lines include a
 522          * line at one end and has an excluded, identical line at the other.
 523          * We are free to choose which identical line is included.
 524          * `compareseq' usually chooses the one at the beginning,
 525          * but usually it is cleaner to consider the following identical line
 526          * to be the "change".
 527          *
 528          * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
 529          */
 530         function _shift_boundaries( $lines, &$changed, $other_changed ) {
 531                 wfProfileIn( __METHOD__ );
 532                 $i = 0;
 533                 $j = 0;
 534
 535                 assert( 'count($lines) == count($changed)' );
 536                 $len = count( $lines );
 537                 $other_len = count( $other_changed );
 538
 539                 while ( 1 ) {
 540                         /*
 541                          * Scan forwards to find beginning of another run of changes.
 542                          * Also keep track of the corresponding point in the other file.
 543                          *
 544                          * Throughout this code, $i and $j are adjusted together so that
 545                          * the first $i elements of $changed and the first $j elements
 546                          * of $other_changed both contain the same number of zeros
 547                          * (unchanged lines).
 548                          * Furthermore, $j is always kept so that $j == $other_len or
 549                          * $other_changed[$j] == false.
 550                          */
 551                         while ( $j < $other_len && $other_changed[$j] ) {
 552                                 $j++;
 553                         }
 554
 555                         while ( $i < $len && ! $changed[$i] ) {
 556                                 assert( '$j < $other_len && ! $other_changed[$j]' );
 557                                 $i++; $j++;
 558                                 while ( $j < $other_len && $other_changed[$j] )
 559                                 $j++;
 560                         }
 561
 562                         if ( $i == $len ) {
 563                                 break;
 564                         }
 565
 566                         $start = $i;
 567
 568                         // Find the end of this run of changes.
 569                         while ( ++$i < $len && $changed[$i] ) {
 570                                 continue;
 571                         }
 572
 573                         do {
 574                                 /*
 575                                  * Record the length of this run of changes, so that
 576                                  * we can later determine whether the run has grown.
 577                                  */
 578                                 $runlength = $i - $start;
 579
 580                                 /*
 581                                  * Move the changed region back, so long as the
 582                                  * previous unchanged line matches the last changed one.
 583                                  * This merges with previous changed regions.
 584                                  */
 585                                 while ( $start > 0 && $lines[$start - 1] == $lines[$i - 1] ) {
 586                                         $changed[--$start] = 1;
 587                                         $changed[--$i] = false;
 588                                         while ( $start > 0 && $changed[$start - 1] ) {
 589                                                 $start--;
 590                                         }
 591                                         assert( '$j > 0' );
 592                                         while ( $other_changed[--$j] ) {
 593                                                 continue;
 594                                         }
 595                                         assert( '$j >= 0 && !$other_changed[$j]' );
 596                                 }
 597
 598                                 /*
 599                                  * Set CORRESPONDING to the end of the changed run, at the last
 600                                  * point where it corresponds to a changed run in the other file.
 601                                  * CORRESPONDING == LEN means no such point has been found.
 602                                  */
 603                                 $corresponding = $j < $other_len ? $i : $len;
 604
 605                                 /*
 606                                  * Move the changed region forward, so long as the
 607                                  * first changed line matches the following unchanged one.
 608                                  * This merges with following changed regions.
 609                                  * Do this second, so that if there are no merges,
 610                                  * the changed region is moved forward as far as possible.
 611                                  */
 612                                 while ( $i < $len && $lines[$start] == $lines[$i] ) {
 613                                         $changed[$start++] = false;
 614                                         $changed[$i++] = 1;
 615                                         while ( $i < $len && $changed[$i] ) {
 616                                                 $i++;
 617                                         }
 618
 619                                         assert( '$j < $other_len && ! $other_changed[$j]' );
 620                                         $j++;
 621                                         if ( $j < $other_len && $other_changed[$j] ) {
 622                                                 $corresponding = $i;
 623                                                 while ( $j < $other_len && $other_changed[$j] ) {
 624                                                         $j++;
 625                                                 }
 626                                         }
 627                                 }
 628                         } while ( $runlength != $i - $start );
 629
 630                         /*
 631                          * If possible, move the fully-merged run of changes
 632                          * back to a corresponding run in the other file.
 633                          */
 634                         while ( $corresponding < $i ) {
 635                                 $changed[--$start] = 1;
 636                                 $changed[--$i] = 0;
 637                                 assert( '$j > 0' );
 638                                 while ( $other_changed[--$j] ) {
 639                                         continue;
 640                                 }
 641                                 assert( '$j >= 0 && !$other_changed[$j]' );
 642                         }
 643                 }
 644                 wfProfileOut( __METHOD__ );
 645         }
 646 }
 647
 648 /**
 649  * Class representing a 'diff' between two sequences of strings.
 650  * @todo document
 651  * @private
 652  * @ingroup DifferenceEngine
 653  */
 654 class Diff {
 655         var $edits;
 656
 657         /**
 658          * Constructor.
 659          * Computes diff between sequences of strings.
 660          *
 661          * @param $from_lines array An array of strings.
 662          *                (Typically these are lines from a file.)
 663          * @param $to_lines array An array of strings.
 664          */
 665         function __construct( $from_lines, $to_lines ) {
 666                 $eng = new _DiffEngine;
 667                 $this->edits = $eng->diff( $from_lines, $to_lines );
 668                 // $this->_check($from_lines, $to_lines);
 669         }
 670
 671         /**
 672          * Compute reversed Diff.
 673          *
 674          * SYNOPSIS:
 675          *
 676          *      $diff = new Diff($lines1, $lines2);
 677          *      $rev = $diff->reverse();
 678          * @return Object A Diff object representing the inverse of the
 679          *                                original diff.
 680          */
 681         function reverse() {
 682                 $rev = $this;
 683                 $rev->edits = array();
 684                 foreach ( $this->edits as $edit ) {
 685                         $rev->edits[] = $edit->reverse();
 686                 }
 687                 return $rev;
 688         }
 689
 690         /**
 691          * Check for empty diff.
 692          *
 693          * @return bool True iff two sequences were identical.
 694          */
 695         function isEmpty() {
 696                 foreach ( $this->edits as $edit ) {
 697                         if ( $edit->type != 'copy' ) {
 698                                 return false;
 699                         }
 700                 }
 701                 return true;
 702         }
 703
 704         /**
 705          * Compute the length of the Longest Common Subsequence (LCS).
 706          *
 707          * This is mostly for diagnostic purposed.
 708          *
 709          * @return int The length of the LCS.
 710          */
 711         function lcs() {
 712                 $lcs = 0;
 713                 foreach ( $this->edits as $edit ) {
 714                         if ( $edit->type == 'copy' ) {
 715                                 $lcs += count( $edit->orig );
 716                         }
 717                 }
 718                 return $lcs;
 719         }
 720
 721         /**
 722          * Get the original set of lines.
 723          *
 724          * This reconstructs the $from_lines parameter passed to the
 725          * constructor.
 726          *
 727          * @return array The original sequence of strings.
 728          */
 729         function orig() {
 730                 $lines = array();
 731
 732                 foreach ( $this->edits as $edit ) {
 733                         if ( $edit->orig ) {
 734                                 array_splice( $lines, count( $lines ), 0, $edit->orig );
 735                         }
 736                 }
 737                 return $lines;
 738         }
 739
 740         /**
 741          * Get the closing set of lines.
 742          *
 743          * This reconstructs the $to_lines parameter passed to the
 744          * constructor.
 745          *
 746          * @return array The sequence of strings.
 747          */
 748         function closing() {
 749                 $lines = array();
 750
 751                 foreach ( $this->edits as $edit ) {
 752                         if ( $edit->closing ) {
 753                                 array_splice( $lines, count( $lines ), 0, $edit->closing );
 754                         }
 755                 }
 756                 return $lines;
 757         }
 758
 759         /**
 760          * Check a Diff for validity.
 761          *
 762          * This is here only for debugging purposes.
 763          * @param $from_lines
 764          * @param $to_lines
 765          */
 766         function _check( $from_lines, $to_lines ) {
 767                 wfProfileIn( __METHOD__ );
 768                 if ( serialize( $from_lines ) != serialize( $this->orig() ) ) {
 769                         trigger_error( "Reconstructed original doesn't match", E_USER_ERROR );
 770                 }
 771                 if ( serialize( $to_lines ) != serialize( $this->closing() ) ) {
 772                         trigger_error( "Reconstructed closing doesn't match", E_USER_ERROR );
 773                 }
 774
 775                 $rev = $this->reverse();
 776                 if ( serialize( $to_lines ) != serialize( $rev->orig() ) ) {
 777                         trigger_error( "Reversed original doesn't match", E_USER_ERROR );
 778                 }
 779                 if ( serialize( $from_lines ) != serialize( $rev->closing() ) ) {
 780                         trigger_error( "Reversed closing doesn't match", E_USER_ERROR );
 781                 }
 782
 783                 $prevtype = 'none';
 784                 foreach ( $this->edits as $edit ) {
 785                         if ( $prevtype == $edit->type ) {
 786                                 trigger_error( 'Edit sequence is non-optimal', E_USER_ERROR );
 787                         }
 788                         $prevtype = $edit->type;
 789                 }
 790
 791                 $lcs = $this->lcs();
 792                 trigger_error( 'Diff okay: LCS = ' . $lcs, E_USER_NOTICE );
 793                 wfProfileOut( __METHOD__ );
 794         }
 795 }
 796
 797 /**
 798  * @todo document, bad name.
 799  * @private
 800  * @ingroup DifferenceEngine
 801  */
 802 class MappedDiff extends Diff {
 803         /**
 804          * Constructor.
 805          *
 806          * Computes diff between sequences of strings.
 807          *
 808          * This can be used to compute things like
 809          * case-insensitve diffs, or diffs which ignore
 810          * changes in white-space.
 811          *
 812          * @param $from_lines array An array of strings.
 813          *      (Typically these are lines from a file.)
 814          *
 815          * @param $to_lines array An array of strings.
 816          *
 817          * @param $mapped_from_lines array This array should
 818          *      have the same size number of elements as $from_lines.
 819          *      The elements in $mapped_from_lines and
 820          *      $mapped_to_lines are what is actually compared
 821          *      when computing the diff.
 822          *
 823          * @param $mapped_to_lines array This array should
 824          *      have the same number of elements as $to_lines.
 825          */
 826         function __construct( $from_lines, $to_lines,
 827                 $mapped_from_lines, $mapped_to_lines ) {
 828                 wfProfileIn( __METHOD__ );
 829
 830                 assert( 'count( $from_lines ) == count( $mapped_from_lines )' );
 831                 assert( 'count( $to_lines ) == count( $mapped_to_lines )' );
 832
 833                 parent::__construct( $mapped_from_lines, $mapped_to_lines );
 834
 835                 $xi = $yi = 0;
 836                 for ( $i = 0; $i < count( $this->edits ); $i++ ) {
 837                         $orig = &$this->edits[$i]->orig;
 838                         if ( is_array( $orig ) ) {
 839                                 $orig = array_slice( $from_lines, $xi, count( $orig ) );
 840                                 $xi += count( $orig );
 841                         }
 842
 843                         $closing = &$this->edits[$i]->closing;
 844                         if ( is_array( $closing ) ) {
 845                                 $closing = array_slice( $to_lines, $yi, count( $closing ) );
 846                                 $yi += count( $closing );
 847                         }
 848                 }
 849                 wfProfileOut( __METHOD__ );
 850         }
 851 }
 852
 853 /**
 854  * A class to format Diffs
 855  *
 856  * This class formats the diff in classic diff format.
 857  * It is intended that this class be customized via inheritance,
 858  * to obtain fancier outputs.
 859  * @todo document
 860  * @private
 861  * @ingroup DifferenceEngine
 862  */
 863 class DiffFormatter {
 864         /**
 865          * Number of leading context "lines" to preserve.
 866          *
 867          * This should be left at zero for this class, but subclasses
 868          * may want to set this to other values.
 869          */
 870         var $leading_context_lines = 0;
 871
 872         /**
 873          * Number of trailing context "lines" to preserve.
 874          *
 875          * This should be left at zero for this class, but subclasses
 876          * may want to set this to other values.
 877          */
 878         var $trailing_context_lines = 0;
 879
 880         /**
 881          * Format a diff.
 882          *
 883          * @param $diff Diff A Diff object.
 884          * @return string The formatted output.
 885          */
 886         function format( $diff ) {
 887                 wfProfileIn( __METHOD__ );
 888
 889                 $xi = $yi = 1;
 890                 $block = false;
 891                 $context = array();
 892
 893                 $nlead = $this->leading_context_lines;
 894                 $ntrail = $this->trailing_context_lines;
 895
 896                 $this->_start_diff();
 897
 898                 foreach ( $diff->edits as $edit ) {
 899                         if ( $edit->type == 'copy' ) {
 900                                 if ( is_array( $block ) ) {
 901                                         if ( count( $edit->orig ) <= $nlead + $ntrail ) {
 902                                                 $block[] = $edit;
 903                                         } else {
 904                                                 if ( $ntrail ) {
 905                                                         $context = array_slice( $edit->orig, 0, $ntrail );
 906                                                         $block[] = new _DiffOp_Copy( $context );
 907                                                 }
 908                                                 $this->_block( $x0, $ntrail + $xi - $x0,
 909                                                         $y0, $ntrail + $yi - $y0,
 910                                                         $block );
 911                                                 $block = false;
 912                                         }
 913                                 }
 914                                 $context = $edit->orig;
 915                         } else {
 916                                 if ( !is_array( $block ) ) {
 917                                         $context = array_slice( $context, count( $context ) - $nlead );
 918                                         $x0 = $xi - count( $context );
 919                                         $y0 = $yi - count( $context );
 920                                         $block = array();
 921                                         if ( $context ) {
 922                                                 $block[] = new _DiffOp_Copy( $context );
 923                                         }
 924                                 }
 925                                 $block[] = $edit;
 926                         }
 927
 928                         if ( $edit->orig ) {
 929                                 $xi += count( $edit->orig );
 930                         }
 931                         if ( $edit->closing ) {
 932                                 $yi += count( $edit->closing );
 933                         }
 934                 }
 935
 936                 if ( is_array( $block ) ) {
 937                         $this->_block( $x0, $xi - $x0,
 938                                 $y0, $yi - $y0,
 939                                 $block );
 940                 }
 941
 942                 $end = $this->_end_diff();
 943                 wfProfileOut( __METHOD__ );
 944                 return $end;
 945         }
 946
 947         /**
 948          * @param $xbeg
 949          * @param $xlen
 950          * @param $ybeg
 951          * @param $ylen
 952          * @param $edits
 953          */
 954         function _block( $xbeg, $xlen, $ybeg, $ylen, &$edits ) {
 955                 wfProfileIn( __METHOD__ );
 956                 $this->_start_block( $this->_block_header( $xbeg, $xlen, $ybeg, $ylen ) );
 957                 foreach ( $edits as $edit ) {
 958                         if ( $edit->type == 'copy' ) {
 959                                 $this->_context( $edit->orig );
 960                         } elseif ( $edit->type == 'add' ) {
 961                                 $this->_added( $edit->closing );
 962                         } elseif ( $edit->type == 'delete' ) {
 963                                 $this->_deleted( $edit->orig );
 964                         } elseif ( $edit->type == 'change' ) {
 965                                 $this->_changed( $edit->orig, $edit->closing );
 966                         } else {
 967                                 trigger_error( 'Unknown edit type', E_USER_ERROR );
 968                         }
 969                 }
 970                 $this->_end_block();
 971                 wfProfileOut( __METHOD__ );
 972         }
 973
 974         function _start_diff() {
 975                 ob_start();
 976         }
 977
 978         /**
 979          * @return string
 980          */
 981         function _end_diff() {
 982                 $val = ob_get_contents();
 983                 ob_end_clean();
 984                 return $val;
 985         }
 986
 987         /**
 988          * @param $xbeg
 989          * @param $xlen
 990          * @param $ybeg
 991          * @param $ylen
 992          * @return string
 993          */
 994         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
 995                 if ( $xlen > 1 ) {
 996                         $xbeg .= ',' . ( $xbeg + $xlen - 1 );
 997                 }
 998                 if ( $ylen > 1 ) {
 999                         $ybeg .= ',' . ( $ybeg + $ylen - 1 );
1000                 }
1001
1002                 return $xbeg . ( $xlen ? ( $ylen ? 'c' : 'd' ) : 'a' ) . $ybeg;
1003         }
1004
1005         function _start_block( $header ) {
1006                 echo $header . "\n";
1007         }
1008
1009         function _end_block() {
1010         }
1011
1012         /**
1013          * @param $lines
1014          * @param $prefix string
1015          */
1016         function _lines( $lines, $prefix = ' ' ) {
1017                 foreach ( $lines as $line ) {
1018                         echo "$prefix $line\n";
1019                 }
1020         }
1021
1022         /**
1023          * @param $lines
1024          */
1025         function _context( $lines ) {
1026                 $this->_lines( $lines );
1027         }
1028
1029         /**
1030          * @param $lines
1031          */
1032         function _added( $lines ) {
1033                 $this->_lines( $lines, '>' );
1034         }
1035
1036         /**
1037          * @param $lines
1038          */
1039         function _deleted( $lines ) {
1040                 $this->_lines( $lines, '<' );
1041         }
1042
1043         /**
1044          * @param $orig
1045          * @param $closing
1046          */
1047         function _changed( $orig, $closing ) {
1048                 $this->_deleted( $orig );
1049                 echo "---\n";
1050                 $this->_added( $closing );
1051         }
1052 }
1053
1054 /**
1055  * A formatter that outputs unified diffs
1056  * @ingroup DifferenceEngine
1057  */
1058 class UnifiedDiffFormatter extends DiffFormatter {
1059         var $leading_context_lines = 2;
1060         var $trailing_context_lines = 2;
1061
1062         /**
1063          * @param $lines
1064          */
1065         function _added( $lines ) {
1066                 $this->_lines( $lines, '+' );
1067         }
1068
1069         /**
1070          * @param $lines
1071          */
1072         function _deleted( $lines ) {
1073                 $this->_lines( $lines, '-' );
1074         }
1075
1076         /**
1077          * @param $orig
1078          * @param $closing
1079          */
1080         function _changed( $orig, $closing ) {
1081                 $this->_deleted( $orig );
1082                 $this->_added( $closing );
1083         }
1084
1085         /**
1086          * @param $xbeg
1087          * @param $xlen
1088          * @param $ybeg
1089          * @param $ylen
1090          * @return string
1091          */
1092         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1093                 return "@@ -$xbeg,$xlen +$ybeg,$ylen @@";
1094         }
1095 }
1096
1097 /**
1098  * A pseudo-formatter that just passes along the Diff::$edits array
1099  * @ingroup DifferenceEngine
1100  */
1101 class ArrayDiffFormatter extends DiffFormatter {
1102
1103         /**
1104          * @param $diff
1105          * @return array
1106          */
1107         function format( $diff ) {
1108                 $oldline = 1;
1109                 $newline = 1;
1110                 $retval = array();
1111                 foreach ( $diff->edits as $edit ) {
1112                         switch( $edit->type ) {
1113                                 case 'add':
1114                                         foreach ( $edit->closing as $l ) {
1115                                                 $retval[] = array(
1116                                                         'action' => 'add',
1117                                                         'new' => $l,
1118                                                         'newline' => $newline++
1119                                                 );
1120                                         }
1121                                         break;
1122                                 case 'delete':
1123                                         foreach ( $edit->orig as $l ) {
1124                                                 $retval[] = array(
1125                                                         'action' => 'delete',
1126                                                         'old' => $l,
1127                                                         'oldline' => $oldline++,
1128                                                 );
1129                                         }
1130                                         break;
1131                                 case 'change':
1132                                         foreach ( $edit->orig as $i => $l ) {
1133                                                 $retval[] = array(
1134                                                         'action' => 'change',
1135                                                         'old' => $l,
1136                                                         'new' => isset( $edit->closing[$i] ) ? $edit->closing[$i] : null,
1137                                                         'oldline' => $oldline++,
1138                                                         'newline' => $newline++,
1139                                                 );
1140                                         }
1141                                         break;
1142                                 case 'copy':
1143                                         $oldline += count( $edit->orig );
1144                                         $newline += count( $edit->orig );
1145                         }
1146                 }
1147                 return $retval;
1148         }
1149 }
1150
1151 /**
1152  * Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
1153  */
1154
1155 define( 'NBSP', '&#160;' ); // iso-8859-x non-breaking space.
1156
1157 /**
1158  * @todo document
1159  * @private
1160  * @ingroup DifferenceEngine
1161  */
1162 class _HWLDF_WordAccumulator {
1163         function __construct() {
1164                 $this->_lines = array();
1165                 $this->_line = '';
1166                 $this->_group = '';
1167                 $this->_tag = '';
1168         }
1169
1170         /**
1171          * @param $new_tag
1172          */
1173         function _flushGroup( $new_tag ) {
1174                 if ( $this->_group !== '' ) {
1175                         if ( $this->_tag == 'ins' ) {
1176                                 $this->_line .= '<ins class="diffchange diffchange-inline">' .
1177                                                 htmlspecialchars( $this->_group ) . '</ins>';
1178                         } elseif ( $this->_tag == 'del' ) {
1179                                 $this->_line .= '<del class="diffchange diffchange-inline">' .
1180                                                 htmlspecialchars( $this->_group ) . '</del>';
1181                         } else {
1182                                 $this->_line .= htmlspecialchars( $this->_group );
1183                         }
1184                 }
1185                 $this->_group = '';
1186                 $this->_tag = $new_tag;
1187         }
1188
1189         /**
1190          * @param $new_tag
1191          */
1192         function _flushLine( $new_tag ) {
1193                 $this->_flushGroup( $new_tag );
1194                 if ( $this->_line != '' ) {
1195                         array_push( $this->_lines, $this->_line );
1196                 } else {
1197                         # make empty lines visible by inserting an NBSP
1198                         array_push( $this->_lines, NBSP );
1199                 }
1200                 $this->_line = '';
1201         }
1202
1203         /**
1204          * @param $words
1205          * @param $tag string
1206          */
1207         function addWords( $words, $tag = '' ) {
1208                 if ( $tag != $this->_tag ) {
1209                         $this->_flushGroup( $tag );
1210                 }
1211
1212                 foreach ( $words as $word ) {
1213                         // new-line should only come as first char of word.
1214                         if ( $word == '' ) {
1215                                 continue;
1216                         }
1217                         if ( $word[0] == "\n" ) {
1218                                 $this->_flushLine( $tag );
1219                                 $word = substr( $word, 1 );
1220                         }
1221                         assert( '!strstr( $word, "\n" )' );
1222                         $this->_group .= $word;
1223                 }
1224         }
1225
1226         /**
1227          * @return array
1228          */
1229         function getLines() {
1230                 $this->_flushLine( '~done' );
1231                 return $this->_lines;
1232         }
1233 }
1234
1235 /**
1236  * @todo document
1237  * @private
1238  * @ingroup DifferenceEngine
1239  */
1240 class WordLevelDiff extends MappedDiff {
1241         const MAX_LINE_LENGTH = 10000;
1242
1243         /**
1244          * @param $orig_lines
1245          * @param $closing_lines
1246          */
1247         function __construct( $orig_lines, $closing_lines ) {
1248                 wfProfileIn( __METHOD__ );
1249
1250                 list( $orig_words, $orig_stripped ) = $this->_split( $orig_lines );
1251                 list( $closing_words, $closing_stripped ) = $this->_split( $closing_lines );
1252
1253                 parent::__construct( $orig_words, $closing_words,
1254                 $orig_stripped, $closing_stripped );
1255                 wfProfileOut( __METHOD__ );
1256         }
1257
1258         /**
1259          * @param $lines
1260          * @return array
1261          */
1262         function _split( $lines ) {
1263                 wfProfileIn( __METHOD__ );
1264
1265                 $words = array();
1266                 $stripped = array();
1267                 $first = true;
1268                 foreach ( $lines as $line ) {
1269                         # If the line is too long, just pretend the entire line is one big word
1270                         # This prevents resource exhaustion problems
1271                         if ( $first ) {
1272                                 $first = false;
1273                         } else {
1274                                 $words[] = "\n";
1275                                 $stripped[] = "\n";
1276                         }
1277                         if ( strlen( $line ) > self::MAX_LINE_LENGTH ) {
1278                                 $words[] = $line;
1279                                 $stripped[] = $line;
1280                         } else {
1281                                 $m = array();
1282                                 if ( preg_match_all( '/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
1283                                         $line, $m ) )
1284                                 {
1285                                         $words = array_merge( $words, $m[0] );
1286                                         $stripped = array_merge( $stripped, $m[1] );
1287                                 }
1288                         }
1289                 }
1290                 wfProfileOut( __METHOD__ );
1291                 return array( $words, $stripped );
1292         }
1293
1294         /**
1295          * @return array
1296          */
1297         function orig() {
1298                 wfProfileIn( __METHOD__ );
1299                 $orig = new _HWLDF_WordAccumulator;
1300
1301                 foreach ( $this->edits as $edit ) {
1302                         if ( $edit->type == 'copy' ) {
1303                                 $orig->addWords( $edit->orig );
1304                         } elseif ( $edit->orig ) {
1305                                 $orig->addWords( $edit->orig, 'del' );
1306                         }
1307                 }
1308                 $lines = $orig->getLines();
1309                 wfProfileOut( __METHOD__ );
1310                 return $lines;
1311         }
1312
1313         /**
1314          * @return array
1315          */
1316         function closing() {
1317                 wfProfileIn( __METHOD__ );
1318                 $closing = new _HWLDF_WordAccumulator;
1319
1320                 foreach ( $this->edits as $edit ) {
1321                         if ( $edit->type == 'copy' ) {
1322                                 $closing->addWords( $edit->closing );
1323                         } elseif ( $edit->closing ) {
1324                                 $closing->addWords( $edit->closing, 'ins' );
1325                         }
1326                 }
1327                 $lines = $closing->getLines();
1328                 wfProfileOut( __METHOD__ );
1329                 return $lines;
1330         }
1331 }
1332
1333 /**
1334  * Wikipedia Table style diff formatter.
1335  * @todo document
1336  * @private
1337  * @ingroup DifferenceEngine
1338  */
1339 class TableDiffFormatter extends DiffFormatter {
1340         function __construct() {
1341                 $this->leading_context_lines = 2;
1342                 $this->trailing_context_lines = 2;
1343         }
1344
1345         /**
1346          * @static
1347          * @param $msg
1348          * @return mixed
1349          */
1350         public static function escapeWhiteSpace( $msg ) {
1351                 $msg = preg_replace( '/^ /m', '&#160; ', $msg );
1352                 $msg = preg_replace( '/ $/m', ' &#160;', $msg );
1353                 $msg = preg_replace( '/  /', '&#160; ', $msg );
1354                 return $msg;
1355         }
1356
1357         /**
1358          * @param $xbeg
1359          * @param $xlen
1360          * @param $ybeg
1361          * @param $ylen
1362          * @return string
1363          */
1364         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1365                 $r = '<tr><td colspan="2" class="diff-lineno"><!--LINE ' . $xbeg . "--></td>\n" .
1366                         '<td colspan="2" class="diff-lineno"><!--LINE ' . $ybeg . "--></td></tr>\n";
1367                 return $r;
1368         }
1369
1370         /**
1371          * @param $header
1372          */
1373         function _start_block( $header ) {
1374                 echo $header;
1375         }
1376
1377         function _end_block() {
1378         }
1379
1380         function _lines( $lines, $prefix = ' ', $color = 'white' ) {
1381         }
1382
1383         /**
1384          * HTML-escape parameter before calling this
1385          * @param $line
1386          * @return string
1387          */
1388         function addedLine( $line ) {
1389                 return $this->wrapLine( '+', 'diff-addedline', $line );
1390         }
1391
1392         /**
1393          * HTML-escape parameter before calling this
1394          * @param $line
1395          * @return string
1396          */
1397         function deletedLine( $line ) {
1398                 return $this->wrapLine( '−', 'diff-deletedline', $line );
1399         }
1400
1401         /**
1402          * HTML-escape parameter before calling this
1403          * @param $line
1404          * @return string
1405          */
1406         function contextLine( $line ) {
1407                 return $this->wrapLine( '&#160;', 'diff-context', $line );
1408         }
1409
1410         /**
1411          * @param $marker
1412          * @param $class
1413          * @param $line
1414          * @return string
1415          */
1416         private function wrapLine( $marker, $class, $line ) {
1417                 if ( $line !== '' ) {
1418                         // The <div> wrapper is needed for 'overflow: auto' style to scroll properly
1419                         $line = Xml::tags( 'div', null, $this->escapeWhiteSpace( $line ) );
1420                 }
1421                 return "<td class='diff-marker'>$marker</td><td class='$class'>$line</td>";
1422         }
1423
1424         /**
1425          * @return string
1426          */
1427         function emptyLine() {
1428                 return '<td colspan="2">&#160;</td>';
1429         }
1430
1431         /**
1432          * @param $lines array
1433          */
1434         function _added( $lines ) {
1435                 foreach ( $lines as $line ) {
1436                         echo '<tr>' . $this->emptyLine() .
1437                         $this->addedLine( '<ins class="diffchange">' .
1438                         htmlspecialchars( $line ) . '</ins>' ) . "</tr>\n";
1439                 }
1440         }
1441
1442         /**
1443          * @param $lines
1444          */
1445         function _deleted( $lines ) {
1446                 foreach ( $lines as $line ) {
1447                         echo '<tr>' . $this->deletedLine( '<del class="diffchange">' .
1448                         htmlspecialchars( $line ) . '</del>' ) .
1449                         $this->emptyLine() . "</tr>\n";
1450                 }
1451         }
1452
1453         /**
1454          * @param $lines
1455          */
1456         function _context( $lines ) {
1457                 foreach ( $lines as $line ) {
1458                         echo '<tr>' .
1459                         $this->contextLine( htmlspecialchars( $line ) ) .
1460                         $this->contextLine( htmlspecialchars( $line ) ) . "</tr>\n";
1461                 }
1462         }
1463
1464         /**
1465          * @param $orig
1466          * @param $closing
1467          */
1468         function _changed( $orig, $closing ) {
1469                 wfProfileIn( __METHOD__ );
1470
1471                 $diff = new WordLevelDiff( $orig, $closing );
1472                 $del = $diff->orig();
1473                 $add = $diff->closing();
1474
1475                 # Notice that WordLevelDiff returns HTML-escaped output.
1476                 # Hence, we will be calling addedLine/deletedLine without HTML-escaping.
1477
1478                 while ( $line = array_shift( $del ) ) {
1479                         $aline = array_shift( $add );
1480                         echo '<tr>' . $this->deletedLine( $line ) .
1481                         $this->addedLine( $aline ) . "</tr>\n";
1482                 }
1483                 foreach ( $add as $line ) {     # If any leftovers
1484                         echo '<tr>' . $this->emptyLine() .
1485                         $this->addedLine( $line ) . "</tr>\n";
1486                 }
1487                 wfProfileOut( __METHOD__ );
1488         }
1489 }