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 ? sizeof( $this->orig ) : 0;
  47         }
  48
  49         /**
  50          * @return int
  51          */
  52         function nclosing() {
  53                 return $this->closing ? sizeof( $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 = sizeof( $from_lines );
 198                 $n_to = sizeof( $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 = sizeof( $from_lines );
 258                         $n_to = sizeof( $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, sizeof( $this->xv ), 0, sizeof( $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 )
 495                         = $this->_diag( $xoff, $xlim, $yoff, $ylim, $nchunks );
 496                 }
 497
 498                 if ( $lcs == 0 ) {
 499                         // X and Y sequences have no common subsequence:
 500                         // mark all changed.
 501                         while ( $yoff < $ylim ) {
 502                                 $this->ychanged[$this->yind[$yoff++]] = 1;
 503                         }
 504                         while ( $xoff < $xlim ) {
 505                                 $this->xchanged[$this->xind[$xoff++]] = 1;
 506                         }
 507                 } else {
 508                         // Use the partitions to split this problem into subproblems.
 509                         reset( $seps );
 510                         $pt1 = $seps[0];
 511                         while ( $pt2 = next( $seps ) ) {
 512                                 $this->_compareseq ( $pt1[0], $pt2[0], $pt1[1], $pt2[1] );
 513                                 $pt1 = $pt2;
 514                         }
 515                 }
 516         }
 517
 518         /**
 519          * Adjust inserts/deletes of identical lines to join changes
 520          * as much as possible.
 521          *
 522          * We do something when a run of changed lines include a
 523          * line at one end and has an excluded, identical line at the other.
 524          * We are free to choose which identical line is included.
 525          * `compareseq' usually chooses the one at the beginning,
 526          * but usually it is cleaner to consider the following identical line
 527          * to be the "change".
 528          *
 529          * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
 530          */
 531         function _shift_boundaries( $lines, &$changed, $other_changed ) {
 532                 wfProfileIn( __METHOD__ );
 533                 $i = 0;
 534                 $j = 0;
 535
 536                 assert( 'sizeof($lines) == sizeof($changed)' );
 537                 $len = sizeof( $lines );
 538                 $other_len = sizeof( $other_changed );
 539
 540                 while ( 1 ) {
 541                         /*
 542                          * Scan forwards to find beginning of another run of changes.
 543                          * Also keep track of the corresponding point in the other file.
 544                          *
 545                          * Throughout this code, $i and $j are adjusted together so that
 546                          * the first $i elements of $changed and the first $j elements
 547                          * of $other_changed both contain the same number of zeros
 548                          * (unchanged lines).
 549                          * Furthermore, $j is always kept so that $j == $other_len or
 550                          * $other_changed[$j] == false.
 551                          */
 552                         while ( $j < $other_len && $other_changed[$j] ) {
 553                                 $j++;
 554                         }
 555
 556                         while ( $i < $len && ! $changed[$i] ) {
 557                                 assert( '$j < $other_len && ! $other_changed[$j]' );
 558                                 $i++; $j++;
 559                                 while ( $j < $other_len && $other_changed[$j] )
 560                                 $j++;
 561                         }
 562
 563                         if ( $i == $len ) {
 564                                 break;
 565                         }
 566
 567                         $start = $i;
 568
 569                         // Find the end of this run of changes.
 570                         while ( ++$i < $len && $changed[$i] ) {
 571                                 continue;
 572                         }
 573
 574                         do {
 575                                 /*
 576                                  * Record the length of this run of changes, so that
 577                                  * we can later determine whether the run has grown.
 578                                  */
 579                                 $runlength = $i - $start;
 580
 581                                 /*
 582                                  * Move the changed region back, so long as the
 583                                  * previous unchanged line matches the last changed one.
 584                                  * This merges with previous changed regions.
 585                                  */
 586                                 while ( $start > 0 && $lines[$start - 1] == $lines[$i - 1] ) {
 587                                         $changed[--$start] = 1;
 588                                         $changed[--$i] = false;
 589                                         while ( $start > 0 && $changed[$start - 1] ) {
 590                                                 $start--;
 591                                         }
 592                                         assert( '$j > 0' );
 593                                         while ( $other_changed[--$j] ) {
 594                                                 continue;
 595                                         }
 596                                         assert( '$j >= 0 && !$other_changed[$j]' );
 597                                 }
 598
 599                                 /*
 600                                  * Set CORRESPONDING to the end of the changed run, at the last
 601                                  * point where it corresponds to a changed run in the other file.
 602                                  * CORRESPONDING == LEN means no such point has been found.
 603                                  */
 604                                 $corresponding = $j < $other_len ? $i : $len;
 605
 606                                 /*
 607                                  * Move the changed region forward, so long as the
 608                                  * first changed line matches the following unchanged one.
 609                                  * This merges with following changed regions.
 610                                  * Do this second, so that if there are no merges,
 611                                  * the changed region is moved forward as far as possible.
 612                                  */
 613                                 while ( $i < $len && $lines[$start] == $lines[$i] ) {
 614                                         $changed[$start++] = false;
 615                                         $changed[$i++] = 1;
 616                                         while ( $i < $len && $changed[$i] ) {
 617                                                 $i++;
 618                                         }
 619
 620                                         assert( '$j < $other_len && ! $other_changed[$j]' );
 621                                         $j++;
 622                                         if ( $j < $other_len && $other_changed[$j] ) {
 623                                                 $corresponding = $i;
 624                                                 while ( $j < $other_len && $other_changed[$j] ) {
 625                                                         $j++;
 626                                                 }
 627                                         }
 628                                 }
 629                         } while ( $runlength != $i - $start );
 630
 631                         /*
 632                          * If possible, move the fully-merged run of changes
 633                          * back to a corresponding run in the other file.
 634                          */
 635                         while ( $corresponding < $i ) {
 636                                 $changed[--$start] = 1;
 637                                 $changed[--$i] = 0;
 638                                 assert( '$j > 0' );
 639                                 while ( $other_changed[--$j] ) {
 640                                         continue;
 641                                 }
 642                                 assert( '$j >= 0 && !$other_changed[$j]' );
 643                         }
 644                 }
 645                 wfProfileOut( __METHOD__ );
 646         }
 647 }
 648
 649 /**
 650  * Class representing a 'diff' between two sequences of strings.
 651  * @todo document
 652  * @private
 653  * @ingroup DifferenceEngine
 654  */
 655 class Diff {
 656         var $edits;
 657
 658         /**
 659          * Constructor.
 660          * Computes diff between sequences of strings.
 661          *
 662          * @param $from_lines array An array of strings.
 663          *                (Typically these are lines from a file.)
 664          * @param $to_lines array An array of strings.
 665          */
 666         function __construct( $from_lines, $to_lines ) {
 667                 $eng = new _DiffEngine;
 668                 $this->edits = $eng->diff( $from_lines, $to_lines );
 669                 // $this->_check($from_lines, $to_lines);
 670         }
 671
 672         /**
 673          * Compute reversed Diff.
 674          *
 675          * SYNOPSIS:
 676          *
 677          *      $diff = new Diff($lines1, $lines2);
 678          *      $rev = $diff->reverse();
 679          * @return Object A Diff object representing the inverse of the
 680          *                                original diff.
 681          */
 682         function reverse() {
 683                 $rev = $this;
 684                 $rev->edits = array();
 685                 foreach ( $this->edits as $edit ) {
 686                         $rev->edits[] = $edit->reverse();
 687                 }
 688                 return $rev;
 689         }
 690
 691         /**
 692          * Check for empty diff.
 693          *
 694          * @return bool True iff two sequences were identical.
 695          */
 696         function isEmpty() {
 697                 foreach ( $this->edits as $edit ) {
 698                         if ( $edit->type != 'copy' ) {
 699                                 return false;
 700                         }
 701                 }
 702                 return true;
 703         }
 704
 705         /**
 706          * Compute the length of the Longest Common Subsequence (LCS).
 707          *
 708          * This is mostly for diagnostic purposed.
 709          *
 710          * @return int The length of the LCS.
 711          */
 712         function lcs() {
 713                 $lcs = 0;
 714                 foreach ( $this->edits as $edit ) {
 715                         if ( $edit->type == 'copy' ) {
 716                                 $lcs += sizeof( $edit->orig );
 717                         }
 718                 }
 719                 return $lcs;
 720         }
 721
 722         /**
 723          * Get the original set of lines.
 724          *
 725          * This reconstructs the $from_lines parameter passed to the
 726          * constructor.
 727          *
 728          * @return array The original sequence of strings.
 729          */
 730         function orig() {
 731                 $lines = array();
 732
 733                 foreach ( $this->edits as $edit ) {
 734                         if ( $edit->orig ) {
 735                                 array_splice( $lines, sizeof( $lines ), 0, $edit->orig );
 736                         }
 737                 }
 738                 return $lines;
 739         }
 740
 741         /**
 742          * Get the closing set of lines.
 743          *
 744          * This reconstructs the $to_lines parameter passed to the
 745          * constructor.
 746          *
 747          * @return array The sequence of strings.
 748          */
 749         function closing() {
 750                 $lines = array();
 751
 752                 foreach ( $this->edits as $edit ) {
 753                         if ( $edit->closing ) {
 754                                 array_splice( $lines, sizeof( $lines ), 0, $edit->closing );
 755                         }
 756                 }
 757                 return $lines;
 758         }
 759
 760         /**
 761          * Check a Diff for validity.
 762          *
 763          * This is here only for debugging purposes.
 764          * @param $from_lines
 765          * @param $to_lines
 766          */
 767         function _check( $from_lines, $to_lines ) {
 768                 wfProfileIn( __METHOD__ );
 769                 if ( serialize( $from_lines ) != serialize( $this->orig() ) ) {
 770                         trigger_error( "Reconstructed original doesn't match", E_USER_ERROR );
 771                 }
 772                 if ( serialize( $to_lines ) != serialize( $this->closing() ) ) {
 773                         trigger_error( "Reconstructed closing doesn't match", E_USER_ERROR );
 774                 }
 775
 776                 $rev = $this->reverse();
 777                 if ( serialize( $to_lines ) != serialize( $rev->orig() ) ) {
 778                         trigger_error( "Reversed original doesn't match", E_USER_ERROR );
 779                 }
 780                 if ( serialize( $from_lines ) != serialize( $rev->closing() ) ) {
 781                         trigger_error( "Reversed closing doesn't match", E_USER_ERROR );
 782                 }
 783
 784
 785                 $prevtype = 'none';
 786                 foreach ( $this->edits as $edit ) {
 787                         if ( $prevtype == $edit->type ) {
 788                                 trigger_error( 'Edit sequence is non-optimal', E_USER_ERROR );
 789                         }
 790                         $prevtype = $edit->type;
 791                 }
 792
 793                 $lcs = $this->lcs();
 794                 trigger_error( 'Diff okay: LCS = ' . $lcs, E_USER_NOTICE );
 795                 wfProfileOut( __METHOD__ );
 796         }
 797 }
 798
 799 /**
 800  * @todo document, bad name.
 801  * @private
 802  * @ingroup DifferenceEngine
 803  */
 804 class MappedDiff extends Diff {
 805         /**
 806          * Constructor.
 807          *
 808          * Computes diff between sequences of strings.
 809          *
 810          * This can be used to compute things like
 811          * case-insensitve diffs, or diffs which ignore
 812          * changes in white-space.
 813          *
 814          * @param $from_lines array An array of strings.
 815          *      (Typically these are lines from a file.)
 816          *
 817          * @param $to_lines array An array of strings.
 818          *
 819          * @param $mapped_from_lines array This array should
 820          *      have the same size number of elements as $from_lines.
 821          *      The elements in $mapped_from_lines and
 822          *      $mapped_to_lines are what is actually compared
 823          *      when computing the diff.
 824          *
 825          * @param $mapped_to_lines array This array should
 826          *      have the same number of elements as $to_lines.
 827          */
 828         function __construct( $from_lines, $to_lines,
 829                 $mapped_from_lines, $mapped_to_lines ) {
 830                 wfProfileIn( __METHOD__ );
 831
 832                 assert( 'sizeof( $from_lines ) == sizeof( $mapped_from_lines )' );
 833                 assert( 'sizeof( $to_lines ) == sizeof( $mapped_to_lines )' );
 834
 835                 parent::__construct( $mapped_from_lines, $mapped_to_lines );
 836
 837                 $xi = $yi = 0;
 838                 for ( $i = 0; $i < sizeof( $this->edits ); $i++ ) {
 839                         $orig = &$this->edits[$i]->orig;
 840                         if ( is_array( $orig ) ) {
 841                                 $orig = array_slice( $from_lines, $xi, sizeof( $orig ) );
 842                                 $xi += sizeof( $orig );
 843                         }
 844
 845                         $closing = &$this->edits[$i]->closing;
 846                         if ( is_array( $closing ) ) {
 847                                 $closing = array_slice( $to_lines, $yi, sizeof( $closing ) );
 848                                 $yi += sizeof( $closing );
 849                         }
 850                 }
 851                 wfProfileOut( __METHOD__ );
 852         }
 853 }
 854
 855 /**
 856  * A class to format Diffs
 857  *
 858  * This class formats the diff in classic diff format.
 859  * It is intended that this class be customized via inheritance,
 860  * to obtain fancier outputs.
 861  * @todo document
 862  * @private
 863  * @ingroup DifferenceEngine
 864  */
 865 class DiffFormatter {
 866         /**
 867          * Number of leading context "lines" to preserve.
 868          *
 869          * This should be left at zero for this class, but subclasses
 870          * may want to set this to other values.
 871          */
 872         var $leading_context_lines = 0;
 873
 874         /**
 875          * Number of trailing context "lines" to preserve.
 876          *
 877          * This should be left at zero for this class, but subclasses
 878          * may want to set this to other values.
 879          */
 880         var $trailing_context_lines = 0;
 881
 882         /**
 883          * Format a diff.
 884          *
 885          * @param $diff Diff A Diff object.
 886          * @return string The formatted output.
 887          */
 888         function format( $diff ) {
 889                 wfProfileIn( __METHOD__ );
 890
 891                 $xi = $yi = 1;
 892                 $block = false;
 893                 $context = array();
 894
 895                 $nlead = $this->leading_context_lines;
 896                 $ntrail = $this->trailing_context_lines;
 897
 898                 $this->_start_diff();
 899
 900                 foreach ( $diff->edits as $edit ) {
 901                         if ( $edit->type == 'copy' ) {
 902                                 if ( is_array( $block ) ) {
 903                                         if ( sizeof( $edit->orig ) <= $nlead + $ntrail ) {
 904                                                 $block[] = $edit;
 905                                         } else {
 906                                                 if ( $ntrail ) {
 907                                                         $context = array_slice( $edit->orig, 0, $ntrail );
 908                                                         $block[] = new _DiffOp_Copy( $context );
 909                                                 }
 910                                                 $this->_block( $x0, $ntrail + $xi - $x0,
 911                                                         $y0, $ntrail + $yi - $y0,
 912                                                         $block );
 913                                                 $block = false;
 914                                         }
 915                                 }
 916                                 $context = $edit->orig;
 917                         } else {
 918                                 if ( !is_array( $block ) ) {
 919                                         $context = array_slice( $context, sizeof( $context ) - $nlead );
 920                                         $x0 = $xi - sizeof( $context );
 921                                         $y0 = $yi - sizeof( $context );
 922                                         $block = array();
 923                                         if ( $context ) {
 924                                                 $block[] = new _DiffOp_Copy( $context );
 925                                         }
 926                                 }
 927                                 $block[] = $edit;
 928                         }
 929
 930                         if ( $edit->orig ) {
 931                                 $xi += sizeof( $edit->orig );
 932                         }
 933                         if ( $edit->closing ) {
 934                                 $yi += sizeof( $edit->closing );
 935                         }
 936                 }
 937
 938                 if ( is_array( $block ) ) {
 939                         $this->_block( $x0, $xi - $x0,
 940                                 $y0, $yi - $y0,
 941                                 $block );
 942                 }
 943
 944                 $end = $this->_end_diff();
 945                 wfProfileOut( __METHOD__ );
 946                 return $end;
 947         }
 948
 949         /**
 950          * @param $xbeg
 951          * @param $xlen
 952          * @param $ybeg
 953          * @param $ylen
 954          * @param $edits
 955          */
 956         function _block( $xbeg, $xlen, $ybeg, $ylen, &$edits ) {
 957                 wfProfileIn( __METHOD__ );
 958                 $this->_start_block( $this->_block_header( $xbeg, $xlen, $ybeg, $ylen ) );
 959                 foreach ( $edits as $edit ) {
 960                         if ( $edit->type == 'copy' ) {
 961                                 $this->_context( $edit->orig );
 962                         } elseif ( $edit->type == 'add' ) {
 963                                 $this->_added( $edit->closing );
 964                         } elseif ( $edit->type == 'delete' ) {
 965                                 $this->_deleted( $edit->orig );
 966                         } elseif ( $edit->type == 'change' ) {
 967                                 $this->_changed( $edit->orig, $edit->closing );
 968                         } else {
 969                                 trigger_error( 'Unknown edit type', E_USER_ERROR );
 970                         }
 971                 }
 972                 $this->_end_block();
 973                 wfProfileOut( __METHOD__ );
 974         }
 975
 976         function _start_diff() {
 977                 ob_start();
 978         }
 979
 980         /**
 981          * @return string
 982          */
 983         function _end_diff() {
 984                 $val = ob_get_contents();
 985                 ob_end_clean();
 986                 return $val;
 987         }
 988
 989         /**
 990          * @param $xbeg
 991          * @param $xlen
 992          * @param $ybeg
 993          * @param $ylen
 994          * @return string
 995          */
 996         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
 997                 if ( $xlen > 1 ) {
 998                         $xbeg .= ',' . ( $xbeg + $xlen - 1 );
 999                 }
1000                 if ( $ylen > 1 ) {
1001                         $ybeg .= ',' . ( $ybeg + $ylen - 1 );
1002                 }
1003
1004                 return $xbeg . ( $xlen ? ( $ylen ? 'c' : 'd' ) : 'a' ) . $ybeg;
1005         }
1006
1007         function _start_block( $header ) {
1008                 echo $header . "\n";
1009         }
1010
1011         function _end_block() {
1012         }
1013
1014         /**
1015          * @param $lines
1016          * @param $prefix string
1017          */
1018         function _lines( $lines, $prefix = ' ' ) {
1019                 foreach ( $lines as $line ) {
1020                         echo "$prefix $line\n";
1021                 }
1022         }
1023
1024         /**
1025          * @param $lines
1026          */
1027         function _context( $lines ) {
1028                 $this->_lines( $lines );
1029         }
1030
1031         /**
1032          * @param $lines
1033          */
1034         function _added( $lines ) {
1035                 $this->_lines( $lines, '>' );
1036         }
1037
1038         /**
1039          * @param $lines
1040          */
1041         function _deleted( $lines ) {
1042                 $this->_lines( $lines, '<' );
1043         }
1044
1045         /**
1046          * @param $orig
1047          * @param $closing
1048          */
1049         function _changed( $orig, $closing ) {
1050                 $this->_deleted( $orig );
1051                 echo "---\n";
1052                 $this->_added( $closing );
1053         }
1054 }
1055
1056 /**
1057  * A formatter that outputs unified diffs
1058  * @ingroup DifferenceEngine
1059  */
1060 class UnifiedDiffFormatter extends DiffFormatter {
1061         var $leading_context_lines = 2;
1062         var $trailing_context_lines = 2;
1063
1064         /**
1065          * @param $lines
1066          */
1067         function _added( $lines ) {
1068                 $this->_lines( $lines, '+' );
1069         }
1070
1071         /**
1072          * @param $lines
1073          */
1074         function _deleted( $lines ) {
1075                 $this->_lines( $lines, '-' );
1076         }
1077
1078         /**
1079          * @param $orig
1080          * @param $closing
1081          */
1082         function _changed( $orig, $closing ) {
1083                 $this->_deleted( $orig );
1084                 $this->_added( $closing );
1085         }
1086
1087         /**
1088          * @param $xbeg
1089          * @param $xlen
1090          * @param $ybeg
1091          * @param $ylen
1092          * @return string
1093          */
1094         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1095                 return "@@ -$xbeg,$xlen +$ybeg,$ylen @@";
1096         }
1097 }
1098
1099 /**
1100  * A pseudo-formatter that just passes along the Diff::$edits array
1101  * @ingroup DifferenceEngine
1102  */
1103 class ArrayDiffFormatter extends DiffFormatter {
1104
1105         /**
1106          * @param $diff
1107          * @return array
1108          */
1109         function format( $diff ) {
1110                 $oldline = 1;
1111                 $newline = 1;
1112                 $retval = array();
1113                 foreach ( $diff->edits as $edit ) {
1114                         switch( $edit->type ) {
1115                                 case 'add':
1116                                         foreach ( $edit->closing as $l ) {
1117                                                 $retval[] = array(
1118                                                         'action' => 'add',
1119                                                         'new' => $l,
1120                                                         'newline' => $newline++
1121                                                 );
1122                                         }
1123                                         break;
1124                                 case 'delete':
1125                                         foreach ( $edit->orig as $l ) {
1126                                                 $retval[] = array(
1127                                                         'action' => 'delete',
1128                                                         'old' => $l,
1129                                                         'oldline' => $oldline++,
1130                                                 );
1131                                         }
1132                                         break;
1133                                 case 'change':
1134                                         foreach ( $edit->orig as $i => $l ) {
1135                                                 $retval[] = array(
1136                                                         'action' => 'change',
1137                                                         'old' => $l,
1138                                                         'new' => isset( $edit->closing[$i] ) ? $edit->closing[$i] : null,
1139                                                         'oldline' => $oldline++,
1140                                                         'newline' => $newline++,
1141                                                 );
1142                                         }
1143                                         break;
1144                                 case 'copy':
1145                                         $oldline += count( $edit->orig );
1146                                         $newline += count( $edit->orig );
1147                         }
1148                 }
1149                 return $retval;
1150         }
1151 }
1152
1153 /**
1154  * Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
1155  */
1156
1157 define( 'NBSP', '&#160;' ); // iso-8859-x non-breaking space.
1158
1159 /**
1160  * @todo document
1161  * @private
1162  * @ingroup DifferenceEngine
1163  */
1164 class _HWLDF_WordAccumulator {
1165         function __construct() {
1166                 $this->_lines = array();
1167                 $this->_line = '';
1168                 $this->_group = '';
1169                 $this->_tag = '';
1170         }
1171
1172         /**
1173          * @param $new_tag
1174          */
1175         function _flushGroup( $new_tag ) {
1176                 if ( $this->_group !== '' ) {
1177                         if ( $this->_tag == 'ins' ) {
1178                                 $this->_line .= '<ins class="diffchange diffchange-inline">' .
1179                                                 htmlspecialchars( $this->_group ) . '</ins>';
1180                         } elseif ( $this->_tag == 'del' ) {
1181                                 $this->_line .= '<del class="diffchange diffchange-inline">' .
1182                                                 htmlspecialchars( $this->_group ) . '</del>';
1183                         } else {
1184                                 $this->_line .= htmlspecialchars( $this->_group );
1185                         }
1186                 }
1187                 $this->_group = '';
1188                 $this->_tag = $new_tag;
1189         }
1190
1191         /**
1192          * @param $new_tag
1193          */
1194         function _flushLine( $new_tag ) {
1195                 $this->_flushGroup( $new_tag );
1196                 if ( $this->_line != '' ) {
1197                         array_push( $this->_lines, $this->_line );
1198                 } else {
1199                         # make empty lines visible by inserting an NBSP
1200                         array_push( $this->_lines, NBSP );
1201                 }
1202                 $this->_line = '';
1203         }
1204
1205         /**
1206          * @param $words
1207          * @param $tag string
1208          */
1209         function addWords ( $words, $tag = '' ) {
1210                 if ( $tag != $this->_tag ) {
1211                         $this->_flushGroup( $tag );
1212                 }
1213
1214                 foreach ( $words as $word ) {
1215                         // new-line should only come as first char of word.
1216                         if ( $word == '' ) {
1217                                 continue;
1218                         }
1219                         if ( $word[0] == "\n" ) {
1220                                 $this->_flushLine( $tag );
1221                                 $word = substr( $word, 1 );
1222                         }
1223                         assert( '!strstr( $word, "\n" )' );
1224                         $this->_group .= $word;
1225                 }
1226         }
1227
1228         /**
1229          * @return array
1230          */
1231         function getLines() {
1232                 $this->_flushLine( '~done' );
1233                 return $this->_lines;
1234         }
1235 }
1236
1237 /**
1238  * @todo document
1239  * @private
1240  * @ingroup DifferenceEngine
1241  */
1242 class WordLevelDiff extends MappedDiff {
1243         const MAX_LINE_LENGTH = 10000;
1244
1245         /**
1246          * @param $orig_lines
1247          * @param $closing_lines
1248          */
1249         function __construct ( $orig_lines, $closing_lines ) {
1250                 wfProfileIn( __METHOD__ );
1251
1252                 list( $orig_words, $orig_stripped ) = $this->_split( $orig_lines );
1253                 list( $closing_words, $closing_stripped ) = $this->_split( $closing_lines );
1254
1255                 parent::__construct( $orig_words, $closing_words,
1256                 $orig_stripped, $closing_stripped );
1257                 wfProfileOut( __METHOD__ );
1258         }
1259
1260         /**
1261          * @param $lines
1262          * @return array
1263          */
1264         function _split( $lines ) {
1265                 wfProfileIn( __METHOD__ );
1266
1267                 $words = array();
1268                 $stripped = array();
1269                 $first = true;
1270                 foreach ( $lines as $line ) {
1271                         # If the line is too long, just pretend the entire line is one big word
1272                         # This prevents resource exhaustion problems
1273                         if ( $first ) {
1274                                 $first = false;
1275                         } else {
1276                                 $words[] = "\n";
1277                                 $stripped[] = "\n";
1278                         }
1279                         if ( strlen( $line ) > self::MAX_LINE_LENGTH ) {
1280                                 $words[] = $line;
1281                                 $stripped[] = $line;
1282                         } else {
1283                                 $m = array();
1284                                 if ( preg_match_all( '/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
1285                                         $line, $m ) )
1286                                 {
1287                                         $words = array_merge( $words, $m[0] );
1288                                         $stripped = array_merge( $stripped, $m[1] );
1289                                 }
1290                         }
1291                 }
1292                 wfProfileOut( __METHOD__ );
1293                 return array( $words, $stripped );
1294         }
1295
1296         /**
1297          * @return array
1298          */
1299         function orig() {
1300                 wfProfileIn( __METHOD__ );
1301                 $orig = new _HWLDF_WordAccumulator;
1302
1303                 foreach ( $this->edits as $edit ) {
1304                         if ( $edit->type == 'copy' ) {
1305                                 $orig->addWords( $edit->orig );
1306                         } elseif ( $edit->orig ) {
1307                                 $orig->addWords( $edit->orig, 'del' );
1308                         }
1309                 }
1310                 $lines = $orig->getLines();
1311                 wfProfileOut( __METHOD__ );
1312                 return $lines;
1313         }
1314
1315         /**
1316          * @return array
1317          */
1318         function closing() {
1319                 wfProfileIn( __METHOD__ );
1320                 $closing = new _HWLDF_WordAccumulator;
1321
1322                 foreach ( $this->edits as $edit ) {
1323                         if ( $edit->type == 'copy' ) {
1324                                 $closing->addWords( $edit->closing );
1325                         } elseif ( $edit->closing ) {
1326                                 $closing->addWords( $edit->closing, 'ins' );
1327                         }
1328                 }
1329                 $lines = $closing->getLines();
1330                 wfProfileOut( __METHOD__ );
1331                 return $lines;
1332         }
1333 }
1334
1335 /**
1336  * Wikipedia Table style diff formatter.
1337  * @todo document
1338  * @private
1339  * @ingroup DifferenceEngine
1340  */
1341 class TableDiffFormatter extends DiffFormatter {
1342         function __construct() {
1343                 $this->leading_context_lines = 2;
1344                 $this->trailing_context_lines = 2;
1345         }
1346
1347         /**
1348          * @static
1349          * @param $msg
1350          * @return mixed
1351          */
1352         public static function escapeWhiteSpace( $msg ) {
1353                 $msg = preg_replace( '/^ /m', '&#160; ', $msg );
1354                 $msg = preg_replace( '/ $/m', ' &#160;', $msg );
1355                 $msg = preg_replace( '/  /', '&#160; ', $msg );
1356                 return $msg;
1357         }
1358
1359         /**
1360          * @param $xbeg
1361          * @param $xlen
1362          * @param $ybeg
1363          * @param $ylen
1364          * @return string
1365          */
1366         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1367                 $r = '<tr><td colspan="2" class="diff-lineno"><!--LINE ' . $xbeg . "--></td>\n" .
1368                   '<td colspan="2" class="diff-lineno"><!--LINE ' . $ybeg . "--></td></tr>\n";
1369                 return $r;
1370         }
1371
1372         /**
1373          * @param $header
1374          */
1375         function _start_block( $header ) {
1376                 echo $header;
1377         }
1378
1379         function _end_block() {
1380         }
1381
1382         function _lines( $lines, $prefix = ' ', $color = 'white' ) {
1383         }
1384
1385         /**
1386          * HTML-escape parameter before calling this
1387          * @param $line
1388          * @return string
1389          */
1390         function addedLine( $line ) {
1391                 return $this->wrapLine( '+', 'diff-addedline', $line );
1392         }
1393
1394         /**
1395          * HTML-escape parameter before calling this
1396          * @param $line
1397          * @return string
1398          */
1399         function deletedLine( $line ) {
1400                 return $this->wrapLine( '−', 'diff-deletedline', $line );
1401         }
1402
1403         /**
1404          * HTML-escape parameter before calling this
1405          * @param $line
1406          * @return string
1407          */
1408         function contextLine( $line ) {
1409                 return $this->wrapLine( '&#160;', 'diff-context', $line );
1410         }
1411
1412         /**
1413          * @param $marker
1414          * @param $class
1415          * @param $line
1416          * @return string
1417          */
1418         private function wrapLine( $marker, $class, $line ) {
1419                 if ( $line !== '' ) {
1420                         // The <div> wrapper is needed for 'overflow: auto' style to scroll properly
1421                         $line = Xml::tags( 'div', null, $this->escapeWhiteSpace( $line ) );
1422                 }
1423                 return "<td class='diff-marker'>$marker</td><td class='$class'>$line</td>";
1424         }
1425
1426         /**
1427          * @return string
1428          */
1429         function emptyLine() {
1430                 return '<td colspan="2">&#160;</td>';
1431         }
1432
1433         /**
1434          * @param $lines array
1435          */
1436         function _added( $lines ) {
1437                 foreach ( $lines as $line ) {
1438                         echo '<tr>' . $this->emptyLine() .
1439                         $this->addedLine( '<ins class="diffchange">' .
1440                         htmlspecialchars( $line ) . '</ins>' ) . "</tr>\n";
1441                 }
1442         }
1443
1444         /**
1445          * @param $lines
1446          */
1447         function _deleted( $lines ) {
1448                 foreach ( $lines as $line ) {
1449                         echo '<tr>' . $this->deletedLine( '<del class="diffchange">' .
1450                         htmlspecialchars( $line ) . '</del>' ) .
1451                         $this->emptyLine() . "</tr>\n";
1452                 }
1453         }
1454
1455         /**
1456          * @param $lines
1457          */
1458         function _context( $lines ) {
1459                 foreach ( $lines as $line ) {
1460                         echo '<tr>' .
1461                         $this->contextLine( htmlspecialchars( $line ) ) .
1462                         $this->contextLine( htmlspecialchars( $line ) ) . "</tr>\n";
1463                 }
1464         }
1465
1466         /**
1467          * @param $orig
1468          * @param $closing
1469          */
1470         function _changed( $orig, $closing ) {
1471                 wfProfileIn( __METHOD__ );
1472
1473                 $diff = new WordLevelDiff( $orig, $closing );
1474                 $del = $diff->orig();
1475                 $add = $diff->closing();
1476
1477                 # Notice that WordLevelDiff returns HTML-escaped output.
1478                 # Hence, we will be calling addedLine/deletedLine without HTML-escaping.
1479
1480                 while ( $line = array_shift( $del ) ) {
1481                         $aline = array_shift( $add );
1482                         echo '<tr>' . $this->deletedLine( $line ) .
1483                         $this->addedLine( $aline ) . "</tr>\n";
1484                 }
1485                 foreach ( $add as $line ) {     # If any leftovers
1486                         echo '<tr>' . $this->emptyLine() .
1487                         $this->addedLine( $line ) . "</tr>\n";
1488                 }
1489                 wfProfileOut( __METHOD__ );
1490         }
1491 }