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
 784                 $prevtype = 'none';
 785                 foreach ( $this->edits as $edit ) {
 786                         if ( $prevtype == $edit->type ) {
 787                                 trigger_error( 'Edit sequence is non-optimal', E_USER_ERROR );
 788                         }
 789                         $prevtype = $edit->type;
 790                 }
 791
 792                 $lcs = $this->lcs();
 793                 trigger_error( 'Diff okay: LCS = ' . $lcs, E_USER_NOTICE );
 794                 wfProfileOut( __METHOD__ );
 795         }
 796 }
 797
 798 /**
 799  * @todo document, bad name.
 800  * @private
 801  * @ingroup DifferenceEngine
 802  */
 803 class MappedDiff extends Diff {
 804         /**
 805          * Constructor.
 806          *
 807          * Computes diff between sequences of strings.
 808          *
 809          * This can be used to compute things like
 810          * case-insensitve diffs, or diffs which ignore
 811          * changes in white-space.
 812          *
 813          * @param $from_lines array An array of strings.
 814          *      (Typically these are lines from a file.)
 815          *
 816          * @param $to_lines array An array of strings.
 817          *
 818          * @param $mapped_from_lines array This array should
 819          *      have the same size number of elements as $from_lines.
 820          *      The elements in $mapped_from_lines and
 821          *      $mapped_to_lines are what is actually compared
 822          *      when computing the diff.
 823          *
 824          * @param $mapped_to_lines array This array should
 825          *      have the same number of elements as $to_lines.
 826          */
 827         function __construct( $from_lines, $to_lines,
 828                 $mapped_from_lines, $mapped_to_lines ) {
 829                 wfProfileIn( __METHOD__ );
 830
 831                 assert( 'count( $from_lines ) == count( $mapped_from_lines )' );
 832                 assert( 'count( $to_lines ) == count( $mapped_to_lines )' );
 833
 834                 parent::__construct( $mapped_from_lines, $mapped_to_lines );
 835
 836                 $xi = $yi = 0;
 837                 for ( $i = 0; $i < count( $this->edits ); $i++ ) {
 838                         $orig = &$this->edits[$i]->orig;
 839                         if ( is_array( $orig ) ) {
 840                                 $orig = array_slice( $from_lines, $xi, count( $orig ) );
 841                                 $xi += count( $orig );
 842                         }
 843
 844                         $closing = &$this->edits[$i]->closing;
 845                         if ( is_array( $closing ) ) {
 846                                 $closing = array_slice( $to_lines, $yi, count( $closing ) );
 847                                 $yi += count( $closing );
 848                         }
 849                 }
 850                 wfProfileOut( __METHOD__ );
 851         }
 852 }
 853
 854 /**
 855  * A class to format Diffs
 856  *
 857  * This class formats the diff in classic diff format.
 858  * It is intended that this class be customized via inheritance,
 859  * to obtain fancier outputs.
 860  * @todo document
 861  * @private
 862  * @ingroup DifferenceEngine
 863  */
 864 class DiffFormatter {
 865         /**
 866          * Number of leading context "lines" to preserve.
 867          *
 868          * This should be left at zero for this class, but subclasses
 869          * may want to set this to other values.
 870          */
 871         var $leading_context_lines = 0;
 872
 873         /**
 874          * Number of trailing context "lines" to preserve.
 875          *
 876          * This should be left at zero for this class, but subclasses
 877          * may want to set this to other values.
 878          */
 879         var $trailing_context_lines = 0;
 880
 881         /**
 882          * Format a diff.
 883          *
 884          * @param $diff Diff A Diff object.
 885          * @return string The formatted output.
 886          */
 887         function format( $diff ) {
 888                 wfProfileIn( __METHOD__ );
 889
 890                 $xi = $yi = 1;
 891                 $block = false;
 892                 $context = array();
 893
 894                 $nlead = $this->leading_context_lines;
 895                 $ntrail = $this->trailing_context_lines;
 896
 897                 $this->_start_diff();
 898
 899                 foreach ( $diff->edits as $edit ) {
 900                         if ( $edit->type == 'copy' ) {
 901                                 if ( is_array( $block ) ) {
 902                                         if ( count( $edit->orig ) <= $nlead + $ntrail ) {
 903                                                 $block[] = $edit;
 904                                         } else {
 905                                                 if ( $ntrail ) {
 906                                                         $context = array_slice( $edit->orig, 0, $ntrail );
 907                                                         $block[] = new _DiffOp_Copy( $context );
 908                                                 }
 909                                                 $this->_block( $x0, $ntrail + $xi - $x0,
 910                                                         $y0, $ntrail + $yi - $y0,
 911                                                         $block );
 912                                                 $block = false;
 913                                         }
 914                                 }
 915                                 $context = $edit->orig;
 916                         } else {
 917                                 if ( !is_array( $block ) ) {
 918                                         $context = array_slice( $context, count( $context ) - $nlead );
 919                                         $x0 = $xi - count( $context );
 920                                         $y0 = $yi - count( $context );
 921                                         $block = array();
 922                                         if ( $context ) {
 923                                                 $block[] = new _DiffOp_Copy( $context );
 924                                         }
 925                                 }
 926                                 $block[] = $edit;
 927                         }
 928
 929                         if ( $edit->orig ) {
 930                                 $xi += count( $edit->orig );
 931                         }
 932                         if ( $edit->closing ) {
 933                                 $yi += count( $edit->closing );
 934                         }
 935                 }
 936
 937                 if ( is_array( $block ) ) {
 938                         $this->_block( $x0, $xi - $x0,
 939                                 $y0, $yi - $y0,
 940                                 $block );
 941                 }
 942
 943                 $end = $this->_end_diff();
 944                 wfProfileOut( __METHOD__ );
 945                 return $end;
 946         }
 947
 948         /**
 949          * @param $xbeg
 950          * @param $xlen
 951          * @param $ybeg
 952          * @param $ylen
 953          * @param $edits
 954          */
 955         function _block( $xbeg, $xlen, $ybeg, $ylen, &$edits ) {
 956                 wfProfileIn( __METHOD__ );
 957                 $this->_start_block( $this->_block_header( $xbeg, $xlen, $ybeg, $ylen ) );
 958                 foreach ( $edits as $edit ) {
 959                         if ( $edit->type == 'copy' ) {
 960                                 $this->_context( $edit->orig );
 961                         } elseif ( $edit->type == 'add' ) {
 962                                 $this->_added( $edit->closing );
 963                         } elseif ( $edit->type == 'delete' ) {
 964                                 $this->_deleted( $edit->orig );
 965                         } elseif ( $edit->type == 'change' ) {
 966                                 $this->_changed( $edit->orig, $edit->closing );
 967                         } else {
 968                                 trigger_error( 'Unknown edit type', E_USER_ERROR );
 969                         }
 970                 }
 971                 $this->_end_block();
 972                 wfProfileOut( __METHOD__ );
 973         }
 974
 975         function _start_diff() {
 976                 ob_start();
 977         }
 978
 979         /**
 980          * @return string
 981          */
 982         function _end_diff() {
 983                 $val = ob_get_contents();
 984                 ob_end_clean();
 985                 return $val;
 986         }
 987
 988         /**
 989          * @param $xbeg
 990          * @param $xlen
 991          * @param $ybeg
 992          * @param $ylen
 993          * @return string
 994          */
 995         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
 996                 if ( $xlen > 1 ) {
 997                         $xbeg .= ',' . ( $xbeg + $xlen - 1 );
 998                 }
 999                 if ( $ylen > 1 ) {
1000                         $ybeg .= ',' . ( $ybeg + $ylen - 1 );
1001                 }
1002
1003                 return $xbeg . ( $xlen ? ( $ylen ? 'c' : 'd' ) : 'a' ) . $ybeg;
1004         }
1005
1006         function _start_block( $header ) {
1007                 echo $header . "\n";
1008         }
1009
1010         function _end_block() {
1011         }
1012
1013         /**
1014          * @param $lines
1015          * @param $prefix string
1016          */
1017         function _lines( $lines, $prefix = ' ' ) {
1018                 foreach ( $lines as $line ) {
1019                         echo "$prefix $line\n";
1020                 }
1021         }
1022
1023         /**
1024          * @param $lines
1025          */
1026         function _context( $lines ) {
1027                 $this->_lines( $lines );
1028         }
1029
1030         /**
1031          * @param $lines
1032          */
1033         function _added( $lines ) {
1034                 $this->_lines( $lines, '>' );
1035         }
1036
1037         /**
1038          * @param $lines
1039          */
1040         function _deleted( $lines ) {
1041                 $this->_lines( $lines, '<' );
1042         }
1043
1044         /**
1045          * @param $orig
1046          * @param $closing
1047          */
1048         function _changed( $orig, $closing ) {
1049                 $this->_deleted( $orig );
1050                 echo "---\n";
1051                 $this->_added( $closing );
1052         }
1053 }
1054
1055 /**
1056  * A formatter that outputs unified diffs
1057  * @ingroup DifferenceEngine
1058  */
1059 class UnifiedDiffFormatter extends DiffFormatter {
1060         var $leading_context_lines = 2;
1061         var $trailing_context_lines = 2;
1062
1063         /**
1064          * @param $lines
1065          */
1066         function _added( $lines ) {
1067                 $this->_lines( $lines, '+' );
1068         }
1069
1070         /**
1071          * @param $lines
1072          */
1073         function _deleted( $lines ) {
1074                 $this->_lines( $lines, '-' );
1075         }
1076
1077         /**
1078          * @param $orig
1079          * @param $closing
1080          */
1081         function _changed( $orig, $closing ) {
1082                 $this->_deleted( $orig );
1083                 $this->_added( $closing );
1084         }
1085
1086         /**
1087          * @param $xbeg
1088          * @param $xlen
1089          * @param $ybeg
1090          * @param $ylen
1091          * @return string
1092          */
1093         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1094                 return "@@ -$xbeg,$xlen +$ybeg,$ylen @@";
1095         }
1096 }
1097
1098 /**
1099  * A pseudo-formatter that just passes along the Diff::$edits array
1100  * @ingroup DifferenceEngine
1101  */
1102 class ArrayDiffFormatter extends DiffFormatter {
1103
1104         /**
1105          * @param $diff
1106          * @return array
1107          */
1108         function format( $diff ) {
1109                 $oldline = 1;
1110                 $newline = 1;
1111                 $retval = array();
1112                 foreach ( $diff->edits as $edit ) {
1113                         switch( $edit->type ) {
1114                                 case 'add':
1115                                         foreach ( $edit->closing as $l ) {
1116                                                 $retval[] = array(
1117                                                         'action' => 'add',
1118                                                         'new' => $l,
1119                                                         'newline' => $newline++
1120                                                 );
1121                                         }
1122                                         break;
1123                                 case 'delete':
1124                                         foreach ( $edit->orig as $l ) {
1125                                                 $retval[] = array(
1126                                                         'action' => 'delete',
1127                                                         'old' => $l,
1128                                                         'oldline' => $oldline++,
1129                                                 );
1130                                         }
1131                                         break;
1132                                 case 'change':
1133                                         foreach ( $edit->orig as $i => $l ) {
1134                                                 $retval[] = array(
1135                                                         'action' => 'change',
1136                                                         'old' => $l,
1137                                                         'new' => isset( $edit->closing[$i] ) ? $edit->closing[$i] : null,
1138                                                         'oldline' => $oldline++,
1139                                                         'newline' => $newline++,
1140                                                 );
1141                                         }
1142                                         break;
1143                                 case 'copy':
1144                                         $oldline += count( $edit->orig );
1145                                         $newline += count( $edit->orig );
1146                         }
1147                 }
1148                 return $retval;
1149         }
1150 }
1151
1152 /**
1153  * Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
1154  */
1155
1156 define( 'NBSP', '&#160;' ); // iso-8859-x non-breaking space.
1157
1158 /**
1159  * @todo document
1160  * @private
1161  * @ingroup DifferenceEngine
1162  */
1163 class _HWLDF_WordAccumulator {
1164         function __construct() {
1165                 $this->_lines = array();
1166                 $this->_line = '';
1167                 $this->_group = '';
1168                 $this->_tag = '';
1169         }
1170
1171         /**
1172          * @param $new_tag
1173          */
1174         function _flushGroup( $new_tag ) {
1175                 if ( $this->_group !== '' ) {
1176                         if ( $this->_tag == 'ins' ) {
1177                                 $this->_line .= '<ins class="diffchange diffchange-inline">' .
1178                                                 htmlspecialchars( $this->_group ) . '</ins>';
1179                         } elseif ( $this->_tag == 'del' ) {
1180                                 $this->_line .= '<del class="diffchange diffchange-inline">' .
1181                                                 htmlspecialchars( $this->_group ) . '</del>';
1182                         } else {
1183                                 $this->_line .= htmlspecialchars( $this->_group );
1184                         }
1185                 }
1186                 $this->_group = '';
1187                 $this->_tag = $new_tag;
1188         }
1189
1190         /**
1191          * @param $new_tag
1192          */
1193         function _flushLine( $new_tag ) {
1194                 $this->_flushGroup( $new_tag );
1195                 if ( $this->_line != '' ) {
1196                         array_push( $this->_lines, $this->_line );
1197                 } else {
1198                         # make empty lines visible by inserting an NBSP
1199                         array_push( $this->_lines, NBSP );
1200                 }
1201                 $this->_line = '';
1202         }
1203
1204         /**
1205          * @param $words
1206          * @param $tag string
1207          */
1208         function addWords ( $words, $tag = '' ) {
1209                 if ( $tag != $this->_tag ) {
1210                         $this->_flushGroup( $tag );
1211                 }
1212
1213                 foreach ( $words as $word ) {
1214                         // new-line should only come as first char of word.
1215                         if ( $word == '' ) {
1216                                 continue;
1217                         }
1218                         if ( $word[0] == "\n" ) {
1219                                 $this->_flushLine( $tag );
1220                                 $word = substr( $word, 1 );
1221                         }
1222                         assert( '!strstr( $word, "\n" )' );
1223                         $this->_group .= $word;
1224                 }
1225         }
1226
1227         /**
1228          * @return array
1229          */
1230         function getLines() {
1231                 $this->_flushLine( '~done' );
1232                 return $this->_lines;
1233         }
1234 }
1235
1236 /**
1237  * @todo document
1238  * @private
1239  * @ingroup DifferenceEngine
1240  */
1241 class WordLevelDiff extends MappedDiff {
1242         const MAX_LINE_LENGTH = 10000;
1243
1244         /**
1245          * @param $orig_lines
1246          * @param $closing_lines
1247          */
1248         function __construct ( $orig_lines, $closing_lines ) {
1249                 wfProfileIn( __METHOD__ );
1250
1251                 list( $orig_words, $orig_stripped ) = $this->_split( $orig_lines );
1252                 list( $closing_words, $closing_stripped ) = $this->_split( $closing_lines );
1253
1254                 parent::__construct( $orig_words, $closing_words,
1255                 $orig_stripped, $closing_stripped );
1256                 wfProfileOut( __METHOD__ );
1257         }
1258
1259         /**
1260          * @param $lines
1261          * @return array
1262          */
1263         function _split( $lines ) {
1264                 wfProfileIn( __METHOD__ );
1265
1266                 $words = array();
1267                 $stripped = array();
1268                 $first = true;
1269                 foreach ( $lines as $line ) {
1270                         # If the line is too long, just pretend the entire line is one big word
1271                         # This prevents resource exhaustion problems
1272                         if ( $first ) {
1273                                 $first = false;
1274                         } else {
1275                                 $words[] = "\n";
1276                                 $stripped[] = "\n";
1277                         }
1278                         if ( strlen( $line ) > self::MAX_LINE_LENGTH ) {
1279                                 $words[] = $line;
1280                                 $stripped[] = $line;
1281                         } else {
1282                                 $m = array();
1283                                 if ( preg_match_all( '/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
1284                                         $line, $m ) )
1285                                 {
1286                                         $words = array_merge( $words, $m[0] );
1287                                         $stripped = array_merge( $stripped, $m[1] );
1288                                 }
1289                         }
1290                 }
1291                 wfProfileOut( __METHOD__ );
1292                 return array( $words, $stripped );
1293         }
1294
1295         /**
1296          * @return array
1297          */
1298         function orig() {
1299                 wfProfileIn( __METHOD__ );
1300                 $orig = new _HWLDF_WordAccumulator;
1301
1302                 foreach ( $this->edits as $edit ) {
1303                         if ( $edit->type == 'copy' ) {
1304                                 $orig->addWords( $edit->orig );
1305                         } elseif ( $edit->orig ) {
1306                                 $orig->addWords( $edit->orig, 'del' );
1307                         }
1308                 }
1309                 $lines = $orig->getLines();
1310                 wfProfileOut( __METHOD__ );
1311                 return $lines;
1312         }
1313
1314         /**
1315          * @return array
1316          */
1317         function closing() {
1318                 wfProfileIn( __METHOD__ );
1319                 $closing = new _HWLDF_WordAccumulator;
1320
1321                 foreach ( $this->edits as $edit ) {
1322                         if ( $edit->type == 'copy' ) {
1323                                 $closing->addWords( $edit->closing );
1324                         } elseif ( $edit->closing ) {
1325                                 $closing->addWords( $edit->closing, 'ins' );
1326                         }
1327                 }
1328                 $lines = $closing->getLines();
1329                 wfProfileOut( __METHOD__ );
1330                 return $lines;
1331         }
1332 }
1333
1334 /**
1335  * Wikipedia Table style diff formatter.
1336  * @todo document
1337  * @private
1338  * @ingroup DifferenceEngine
1339  */
1340 class TableDiffFormatter extends DiffFormatter {
1341         function __construct() {
1342                 $this->leading_context_lines = 2;
1343                 $this->trailing_context_lines = 2;
1344         }
1345
1346         /**
1347          * @static
1348          * @param $msg
1349          * @return mixed
1350          */
1351         public static function escapeWhiteSpace( $msg ) {
1352                 $msg = preg_replace( '/^ /m', '&#160; ', $msg );
1353                 $msg = preg_replace( '/ $/m', ' &#160;', $msg );
1354                 $msg = preg_replace( '/  /', '&#160; ', $msg );
1355                 return $msg;
1356         }
1357
1358         /**
1359          * @param $xbeg
1360          * @param $xlen
1361          * @param $ybeg
1362          * @param $ylen
1363          * @return string
1364          */
1365         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1366                 $r = '<tr><td colspan="2" class="diff-lineno"><!--LINE ' . $xbeg . "--></td>\n" .
1367                         '<td colspan="2" class="diff-lineno"><!--LINE ' . $ybeg . "--></td></tr>\n";
1368                 return $r;
1369         }
1370
1371         /**
1372          * @param $header
1373          */
1374         function _start_block( $header ) {
1375                 echo $header;
1376         }
1377
1378         function _end_block() {
1379         }
1380
1381         function _lines( $lines, $prefix = ' ', $color = 'white' ) {
1382         }
1383
1384         /**
1385          * HTML-escape parameter before calling this
1386          * @param $line
1387          * @return string
1388          */
1389         function addedLine( $line ) {
1390                 return $this->wrapLine( '+', 'diff-addedline', $line );
1391         }
1392
1393         /**
1394          * HTML-escape parameter before calling this
1395          * @param $line
1396          * @return string
1397          */
1398         function deletedLine( $line ) {
1399                 return $this->wrapLine( '−', 'diff-deletedline', $line );
1400         }
1401
1402         /**
1403          * HTML-escape parameter before calling this
1404          * @param $line
1405          * @return string
1406          */
1407         function contextLine( $line ) {
1408                 return $this->wrapLine( '&#160;', 'diff-context', $line );
1409         }
1410
1411         /**
1412          * @param $marker
1413          * @param $class
1414          * @param $line
1415          * @return string
1416          */
1417         private function wrapLine( $marker, $class, $line ) {
1418                 if ( $line !== '' ) {
1419                         // The <div> wrapper is needed for 'overflow: auto' style to scroll properly
1420                         $line = Xml::tags( 'div', null, $this->escapeWhiteSpace( $line ) );
1421                 }
1422                 return "<td class='diff-marker'>$marker</td><td class='$class'>$line</td>";
1423         }
1424
1425         /**
1426          * @return string
1427          */
1428         function emptyLine() {
1429                 return '<td colspan="2">&#160;</td>';
1430         }
1431
1432         /**
1433          * @param $lines array
1434          */
1435         function _added( $lines ) {
1436                 foreach ( $lines as $line ) {
1437                         echo '<tr>' . $this->emptyLine() .
1438                         $this->addedLine( '<ins class="diffchange">' .
1439                         htmlspecialchars( $line ) . '</ins>' ) . "</tr>\n";
1440                 }
1441         }
1442
1443         /**
1444          * @param $lines
1445          */
1446         function _deleted( $lines ) {
1447                 foreach ( $lines as $line ) {
1448                         echo '<tr>' . $this->deletedLine( '<del class="diffchange">' .
1449                         htmlspecialchars( $line ) . '</del>' ) .
1450                         $this->emptyLine() . "</tr>\n";
1451                 }
1452         }
1453
1454         /**
1455          * @param $lines
1456          */
1457         function _context( $lines ) {
1458                 foreach ( $lines as $line ) {
1459                         echo '<tr>' .
1460                         $this->contextLine( htmlspecialchars( $line ) ) .
1461                         $this->contextLine( htmlspecialchars( $line ) ) . "</tr>\n";
1462                 }
1463         }
1464
1465         /**
1466          * @param $orig
1467          * @param $closing
1468          */
1469         function _changed( $orig, $closing ) {
1470                 wfProfileIn( __METHOD__ );
1471
1472                 $diff = new WordLevelDiff( $orig, $closing );
1473                 $del = $diff->orig();
1474                 $add = $diff->closing();
1475
1476                 # Notice that WordLevelDiff returns HTML-escaped output.
1477                 # Hence, we will be calling addedLine/deletedLine without HTML-escaping.
1478
1479                 while ( $line = array_shift( $del ) ) {
1480                         $aline = array_shift( $add );
1481                         echo '<tr>' . $this->deletedLine( $line ) .
1482                         $this->addedLine( $aline ) . "</tr>\n";
1483                 }
1484                 foreach ( $add as $line ) {     # If any leftovers
1485                         echo '<tr>' . $this->emptyLine() .
1486                         $this->addedLine( $line ) . "</tr>\n";
1487                 }
1488                 wfProfileOut( __METHOD__ );
1489         }
1490 }