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  * @file
   9  * @ingroup DifferenceEngine
  10  * @defgroup DifferenceEngine DifferenceEngine
  11  */
  12
  13 /**
  14  * @todo document
  15  * @private
  16  * @ingroup DifferenceEngine
  17  */
  18 class _DiffOp { #FIXME: no longer private!
  19         var $type;
  20         var $orig;
  21         var $closing;
  22
  23         function reverse() {
  24                 trigger_error( 'pure virtual', E_USER_ERROR );
  25         }
  26
  27         /**
  28          * @return int
  29          */
  30         function norig() {
  31                 return $this->orig ? sizeof( $this->orig ) : 0;
  32         }
  33
  34         /**
  35          * @return int
  36          */
  37         function nclosing() {
  38                 return $this->closing ? sizeof( $this->closing ) : 0;
  39         }
  40 }
  41
  42 /**
  43  * @todo document
  44  * @private
  45  * @ingroup DifferenceEngine
  46  */
  47 class _DiffOp_Copy extends _DiffOp { #FIXME: no longer private!
  48         var $type = 'copy';
  49
  50         function __construct( $orig, $closing = false ) {
  51                 if ( !is_array( $closing ) ) {
  52                         $closing = $orig;
  53                 }
  54                 $this->orig = $orig;
  55                 $this->closing = $closing;
  56         }
  57
  58         /**
  59          * @return _DiffOp_Copy
  60          */
  61         function reverse() {
  62                 return new _DiffOp_Copy( $this->closing, $this->orig );
  63         }
  64 }
  65
  66 /**
  67  * @todo document
  68  * @private
  69  * @ingroup DifferenceEngine
  70  */
  71 class _DiffOp_Delete extends _DiffOp { #FIXME: no longer private!
  72         var $type = 'delete';
  73
  74         function __construct( $lines ) {
  75                 $this->orig = $lines;
  76                 $this->closing = false;
  77         }
  78
  79         /**
  80          * @return _DiffOp_Add
  81          */
  82         function reverse() {
  83                 return new _DiffOp_Add( $this->orig );
  84         }
  85 }
  86
  87 /**
  88  * @todo document
  89  * @private
  90  * @ingroup DifferenceEngine
  91  */
  92 class _DiffOp_Add extends _DiffOp { #FIXME: no longer private!
  93         var $type = 'add';
  94
  95         function __construct( $lines ) {
  96                 $this->closing = $lines;
  97                 $this->orig = false;
  98         }
  99
 100         /**
 101          * @return _DiffOp_Delete
 102          */
 103         function reverse() {
 104                 return new _DiffOp_Delete( $this->closing );
 105         }
 106 }
 107
 108 /**
 109  * @todo document
 110  * @private
 111  * @ingroup DifferenceEngine
 112  */
 113 class _DiffOp_Change extends _DiffOp { #FIXME: no longer private!
 114         var $type = 'change';
 115
 116         function __construct( $orig, $closing ) {
 117                 $this->orig = $orig;
 118                 $this->closing = $closing;
 119         }
 120
 121         /**
 122          * @return _DiffOp_Change
 123          */
 124         function reverse() {
 125                 return new _DiffOp_Change( $this->closing, $this->orig );
 126         }
 127 }
 128
 129 /**
 130  * Class used internally by Diff to actually compute the diffs.
 131  *
 132  * The algorithm used here is mostly lifted from the perl module
 133  * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
 134  *       http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
 135  *
 136  * More ideas are taken from:
 137  *       http://www.ics.uci.edu/~eppstein/161/960229.html
 138  *
 139  * Some ideas are (and a bit of code) are from from analyze.c, from GNU
 140  * diffutils-2.7, which can be found at:
 141  *       ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
 142  *
 143  * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
 144  * are my own.
 145  *
 146  * Line length limits for robustness added by Tim Starling, 2005-08-31
 147  * Alternative implementation added by Guy Van den Broeck, 2008-07-30
 148  *
 149  * @author Geoffrey T. Dairiki, Tim Starling, Guy Van den Broeck
 150  * @private
 151  * @ingroup DifferenceEngine
 152  */
 153 class _DiffEngine { #FIXME: no longer private!
 154
 155         const MAX_XREF_LENGTH =  10000;
 156
 157         protected $xchanged, $ychanged;
 158
 159         protected $xv = array(), $yv = array();
 160         protected $xind = array(), $yind = array();
 161
 162         protected $seq = array(), $in_seq = array();
 163
 164         protected $lcs = 0;
 165
 166         /**
 167          * @param $from_lines
 168          * @param $to_lines
 169          * @return array
 170          */
 171         function diff ( $from_lines, $to_lines ) {
 172                 wfProfileIn( __METHOD__ );
 173
 174                 // Diff and store locally
 175                 $this->diff_local( $from_lines, $to_lines );
 176
 177                 // Merge edits when possible
 178                 $this->_shift_boundaries( $from_lines, $this->xchanged, $this->ychanged );
 179                 $this->_shift_boundaries( $to_lines, $this->ychanged, $this->xchanged );
 180
 181                 // Compute the edit operations.
 182                 $n_from = sizeof( $from_lines );
 183                 $n_to = sizeof( $to_lines );
 184
 185                 $edits = array();
 186                 $xi = $yi = 0;
 187                 while ( $xi < $n_from || $yi < $n_to ) {
 188                         assert( '$yi < $n_to || $this->xchanged[$xi]' );
 189                         assert( '$xi < $n_from || $this->ychanged[$yi]' );
 190
 191                         // Skip matching "snake".
 192                         $copy = array();
 193                         while ( $xi < $n_from && $yi < $n_to
 194                         && !$this->xchanged[$xi] && !$this->ychanged[$yi] ) {
 195                                 $copy[] = $from_lines[$xi++];
 196                                 ++$yi;
 197                         }
 198                         if ( $copy ) {
 199                                 $edits[] = new _DiffOp_Copy( $copy );
 200                         }
 201
 202                         // Find deletes & adds.
 203                         $delete = array();
 204                         while ( $xi < $n_from && $this->xchanged[$xi] ) {
 205                                 $delete[] = $from_lines[$xi++];
 206                         }
 207
 208                         $add = array();
 209                         while ( $yi < $n_to && $this->ychanged[$yi] )  {
 210                                 $add[] = $to_lines[$yi++];
 211                         }
 212
 213                         if ( $delete && $add ) {
 214                                 $edits[] = new _DiffOp_Change( $delete, $add );
 215                         } elseif ( $delete ) {
 216                                 $edits[] = new _DiffOp_Delete( $delete );
 217                         } elseif ( $add ) {
 218                                 $edits[] = new _DiffOp_Add( $add );
 219                         }
 220                 }
 221                 wfProfileOut( __METHOD__ );
 222                 return $edits;
 223         }
 224
 225         /**
 226          * @param $from_lines
 227          * @param $to_lines
 228          */
 229         function diff_local ( $from_lines, $to_lines ) {
 230                 global $wgExternalDiffEngine;
 231                 wfProfileIn( __METHOD__ );
 232
 233                 if ( $wgExternalDiffEngine == 'wikidiff3' ) {
 234                         // wikidiff3
 235                         $wikidiff3 = new WikiDiff3();
 236                         $wikidiff3->diff( $from_lines, $to_lines );
 237                         $this->xchanged = $wikidiff3->removed;
 238                         $this->ychanged = $wikidiff3->added;
 239                         unset( $wikidiff3 );
 240                 } else {
 241                         // old diff
 242                         $n_from = sizeof( $from_lines );
 243                         $n_to = sizeof( $to_lines );
 244                         $this->xchanged = $this->ychanged = array();
 245                         $this->xv = $this->yv = array();
 246                         $this->xind = $this->yind = array();
 247                         unset( $this->seq );
 248                         unset( $this->in_seq );
 249                         unset( $this->lcs );
 250
 251                         // Skip leading common lines.
 252                         for ( $skip = 0; $skip < $n_from && $skip < $n_to; $skip++ ) {
 253                                 if ( $from_lines[$skip] !== $to_lines[$skip] ) {
 254                                         break;
 255                                 }
 256                                 $this->xchanged[$skip] = $this->ychanged[$skip] = false;
 257                         }
 258                         // Skip trailing common lines.
 259                         $xi = $n_from; $yi = $n_to;
 260                         for ( $endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++ ) {
 261                                 if ( $from_lines[$xi] !== $to_lines[$yi] ) {
 262                                         break;
 263                                 }
 264                                 $this->xchanged[$xi] = $this->ychanged[$yi] = false;
 265                         }
 266
 267                         // Ignore lines which do not exist in both files.
 268                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 269                                 $xhash[$this->_line_hash( $from_lines[$xi] )] = 1;
 270                         }
 271
 272                         for ( $yi = $skip; $yi < $n_to - $endskip; $yi++ ) {
 273                                 $line = $to_lines[$yi];
 274                                 if ( ( $this->ychanged[$yi] = empty( $xhash[$this->_line_hash( $line )] ) ) ) {
 275                                         continue;
 276                                 }
 277                                 $yhash[$this->_line_hash( $line )] = 1;
 278                                 $this->yv[] = $line;
 279                                 $this->yind[] = $yi;
 280                         }
 281                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 282                                 $line = $from_lines[$xi];
 283                                 if ( ( $this->xchanged[$xi] = empty( $yhash[$this->_line_hash( $line )] ) ) ) {
 284                                         continue;
 285                                 }
 286                                 $this->xv[] = $line;
 287                                 $this->xind[] = $xi;
 288                         }
 289
 290                         // Find the LCS.
 291                         $this->_compareseq( 0, sizeof( $this->xv ), 0, sizeof( $this->yv ) );
 292                 }
 293                 wfProfileOut( __METHOD__ );
 294         }
 295
 296         /**
 297          * Returns the whole line if it's small enough, or the MD5 hash otherwise
 298          * @param $line string
 299          * @return string
 300          */
 301         function _line_hash( $line ) {
 302                 if ( strlen( $line ) > self::MAX_XREF_LENGTH ) {
 303                         return md5( $line );
 304                 } else {
 305                         return $line;
 306                 }
 307         }
 308
 309         /**
 310          * Divide the Largest Common Subsequence (LCS) of the sequences
 311          * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
 312          * sized segments.
 313          *
 314          * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an
 315          * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
 316          * sub sequences.  The first sub-sequence is contained in [X0, X1),
 317          * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
 318          * that (X0, Y0) == (XOFF, YOFF) and
 319          * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
 320          *
 321          * This function assumes that the first lines of the specified portions
 322          * of the two files do not match, and likewise that the last lines do not
 323          * match.  The caller must trim matching lines from the beginning and end
 324          * of the portions it is going to specify.
 325          * @param $xoff
 326          * @param $xlim
 327          * @param $yoff
 328          * @param $ylim
 329          * @param $nchunks
 330          * @return array
 331          */
 332         function _diag( $xoff, $xlim, $yoff, $ylim, $nchunks ) {
 333                 $flip = false;
 334
 335                 if ( $xlim - $xoff > $ylim - $yoff ) {
 336                         // Things seems faster (I'm not sure I understand why)
 337                         // when the shortest sequence in X.
 338                         $flip = true;
 339                         list( $xoff, $xlim, $yoff, $ylim ) = array( $yoff, $ylim, $xoff, $xlim );
 340                 }
 341
 342                 if ( $flip ) {
 343                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 344                                 $ymatches[$this->xv[$i]][] = $i;
 345                         }
 346                 } else {
 347                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 348                                 $ymatches[$this->yv[$i]][] = $i;
 349                         }
 350                 }
 351
 352                 $this->lcs = 0;
 353                 $this->seq[0] = $yoff - 1;
 354                 $this->in_seq = array();
 355                 $ymids[0] = array();
 356
 357                 $numer = $xlim - $xoff + $nchunks - 1;
 358                 $x = $xoff;
 359                 for ( $chunk = 0; $chunk < $nchunks; $chunk++ ) {
 360                         if ( $chunk > 0 ) {
 361                                 for ( $i = 0; $i <= $this->lcs; $i++ ) {
 362                                         $ymids[$i][$chunk -1] = $this->seq[$i];
 363                                 }
 364                         }
 365
 366                         $x1 = $xoff + (int)( ( $numer + ( $xlim -$xoff ) * $chunk ) / $nchunks );
 367                         for ( ; $x < $x1; $x++ ) {
 368                                 $line = $flip ? $this->yv[$x] : $this->xv[$x];
 369                                 if ( empty( $ymatches[$line] ) ) {
 370                                         continue;
 371                                 }
 372                                 $matches = $ymatches[$line];
 373                                 reset( $matches );
 374                                 while ( list( , $y ) = each( $matches ) ) {
 375                                         if ( empty( $this->in_seq[$y] ) ) {
 376                                                 $k = $this->_lcs_pos( $y );
 377                                                 assert( '$k > 0' );
 378                                                 $ymids[$k] = $ymids[$k -1];
 379                                                 break;
 380                                         }
 381                                 }
 382                                 while ( list ( , $y ) = each( $matches ) ) {
 383                                         if ( $y > $this->seq[$k -1] ) {
 384                                                 assert( '$y < $this->seq[$k]' );
 385                                                 // Optimization: this is a common case:
 386                                                 //      next match is just replacing previous match.
 387                                                 $this->in_seq[$this->seq[$k]] = false;
 388                                                 $this->seq[$k] = $y;
 389                                                 $this->in_seq[$y] = 1;
 390                                         } elseif ( empty( $this->in_seq[$y] ) ) {
 391                                                 $k = $this->_lcs_pos( $y );
 392                                                 assert( '$k > 0' );
 393                                                 $ymids[$k] = $ymids[$k -1];
 394                                         }
 395                                 }
 396                         }
 397                 }
 398
 399                 $seps[] = $flip ? array( $yoff, $xoff ) : array( $xoff, $yoff );
 400                 $ymid = $ymids[$this->lcs];
 401                 for ( $n = 0; $n < $nchunks - 1; $n++ ) {
 402                         $x1 = $xoff + (int)( ( $numer + ( $xlim - $xoff ) * $n ) / $nchunks );
 403                         $y1 = $ymid[$n] + 1;
 404                         $seps[] = $flip ? array( $y1, $x1 ) : array( $x1, $y1 );
 405                 }
 406                 $seps[] = $flip ? array( $ylim, $xlim ) : array( $xlim, $ylim );
 407
 408                 return array( $this->lcs, $seps );
 409         }
 410
 411         /**
 412          * @param $ypos
 413          * @return int
 414          */
 415         function _lcs_pos( $ypos ) {
 416                 $end = $this->lcs;
 417                 if ( $end == 0 || $ypos > $this->seq[$end] ) {
 418                         $this->seq[++$this->lcs] = $ypos;
 419                         $this->in_seq[$ypos] = 1;
 420                         return $this->lcs;
 421                 }
 422
 423                 $beg = 1;
 424                 while ( $beg < $end ) {
 425                         $mid = (int)( ( $beg + $end ) / 2 );
 426                         if ( $ypos > $this->seq[$mid] ) {
 427                                 $beg = $mid + 1;
 428                         } else {
 429                                 $end = $mid;
 430                         }
 431                 }
 432
 433                 assert( '$ypos != $this->seq[$end]' );
 434
 435                 $this->in_seq[$this->seq[$end]] = false;
 436                 $this->seq[$end] = $ypos;
 437                 $this->in_seq[$ypos] = 1;
 438                 return $end;
 439         }
 440
 441         /**
 442          * Find LCS of two sequences.
 443          *
 444          * The results are recorded in the vectors $this->{x,y}changed[], by
 445          * storing a 1 in the element for each line that is an insertion
 446          * or deletion (ie. is not in the LCS).
 447          *
 448          * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
 449          *
 450          * Note that XLIM, YLIM are exclusive bounds.
 451          * All line numbers are origin-0 and discarded lines are not counted.
 452          * @param $xoff
 453          * @param $xlim
 454          * @param $yoff
 455          * @param $ylim
 456          */
 457         function _compareseq ( $xoff, $xlim, $yoff, $ylim ) {
 458                 // Slide down the bottom initial diagonal.
 459                 while ( $xoff < $xlim && $yoff < $ylim
 460                 && $this->xv[$xoff] == $this->yv[$yoff] ) {
 461                         ++$xoff;
 462                         ++$yoff;
 463                 }
 464
 465                 // Slide up the top initial diagonal.
 466                 while ( $xlim > $xoff && $ylim > $yoff
 467                 && $this->xv[$xlim - 1] == $this->yv[$ylim - 1] ) {
 468                         --$xlim;
 469                         --$ylim;
 470                 }
 471
 472                 if ( $xoff == $xlim || $yoff == $ylim ) {
 473                         $lcs = 0;
 474                 } else {
 475                         // This is ad hoc but seems to work well.
 476                         // $nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
 477                         // $nchunks = max(2,min(8,(int)$nchunks));
 478                         $nchunks = min( 7, $xlim - $xoff, $ylim - $yoff ) + 1;
 479                         list ( $lcs, $seps )
 480                         = $this->_diag( $xoff, $xlim, $yoff, $ylim, $nchunks );
 481                 }
 482
 483                 if ( $lcs == 0 ) {
 484                         // X and Y sequences have no common subsequence:
 485                         // mark all changed.
 486                         while ( $yoff < $ylim ) {
 487                                 $this->ychanged[$this->yind[$yoff++]] = 1;
 488                         }
 489                         while ( $xoff < $xlim ) {
 490                                 $this->xchanged[$this->xind[$xoff++]] = 1;
 491                         }
 492                 } else {
 493                         // Use the partitions to split this problem into subproblems.
 494                         reset( $seps );
 495                         $pt1 = $seps[0];
 496                         while ( $pt2 = next( $seps ) ) {
 497                                 $this->_compareseq ( $pt1[0], $pt2[0], $pt1[1], $pt2[1] );
 498                                 $pt1 = $pt2;
 499                         }
 500                 }
 501         }
 502
 503         /**
 504          * Adjust inserts/deletes of identical lines to join changes
 505          * as much as possible.
 506          *
 507          * We do something when a run of changed lines include a
 508          * line at one end and has an excluded, identical line at the other.
 509          * We are free to choose which identical line is included.
 510          * `compareseq' usually chooses the one at the beginning,
 511          * but usually it is cleaner to consider the following identical line
 512          * to be the "change".
 513          *
 514          * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
 515          */
 516         function _shift_boundaries( $lines, &$changed, $other_changed ) {
 517                 wfProfileIn( __METHOD__ );
 518                 $i = 0;
 519                 $j = 0;
 520
 521                 assert( 'sizeof($lines) == sizeof($changed)' );
 522                 $len = sizeof( $lines );
 523                 $other_len = sizeof( $other_changed );
 524
 525                 while ( 1 ) {
 526                         /*
 527                          * Scan forwards to find beginning of another run of changes.
 528                          * Also keep track of the corresponding point in the other file.
 529                          *
 530                          * Throughout this code, $i and $j are adjusted together so that
 531                          * the first $i elements of $changed and the first $j elements
 532                          * of $other_changed both contain the same number of zeros
 533                          * (unchanged lines).
 534                          * Furthermore, $j is always kept so that $j == $other_len or
 535                          * $other_changed[$j] == false.
 536                          */
 537                         while ( $j < $other_len && $other_changed[$j] ) {
 538                                 $j++;
 539                         }
 540
 541                         while ( $i < $len && ! $changed[$i] ) {
 542                                 assert( '$j < $other_len && ! $other_changed[$j]' );
 543                                 $i++; $j++;
 544                                 while ( $j < $other_len && $other_changed[$j] )
 545                                 $j++;
 546                         }
 547
 548                         if ( $i == $len ) {
 549                                 break;
 550                         }
 551
 552                         $start = $i;
 553
 554                         // Find the end of this run of changes.
 555                         while ( ++$i < $len && $changed[$i] ) {
 556                                 continue;
 557                         }
 558
 559                         do {
 560                                 /*
 561                                  * Record the length of this run of changes, so that
 562                                  * we can later determine whether the run has grown.
 563                                  */
 564                                 $runlength = $i - $start;
 565
 566                                 /*
 567                                  * Move the changed region back, so long as the
 568                                  * previous unchanged line matches the last changed one.
 569                                  * This merges with previous changed regions.
 570                                  */
 571                                 while ( $start > 0 && $lines[$start - 1] == $lines[$i - 1] ) {
 572                                         $changed[--$start] = 1;
 573                                         $changed[--$i] = false;
 574                                         while ( $start > 0 && $changed[$start - 1] ) {
 575                                                 $start--;
 576                                         }
 577                                         assert( '$j > 0' );
 578                                         while ( $other_changed[--$j] ) {
 579                                                 continue;
 580                                         }
 581                                         assert( '$j >= 0 && !$other_changed[$j]' );
 582                                 }
 583
 584                                 /*
 585                                  * Set CORRESPONDING to the end of the changed run, at the last
 586                                  * point where it corresponds to a changed run in the other file.
 587                                  * CORRESPONDING == LEN means no such point has been found.
 588                                  */
 589                                 $corresponding = $j < $other_len ? $i : $len;
 590
 591                                 /*
 592                                  * Move the changed region forward, so long as the
 593                                  * first changed line matches the following unchanged one.
 594                                  * This merges with following changed regions.
 595                                  * Do this second, so that if there are no merges,
 596                                  * the changed region is moved forward as far as possible.
 597                                  */
 598                                 while ( $i < $len && $lines[$start] == $lines[$i] ) {
 599                                         $changed[$start++] = false;
 600                                         $changed[$i++] = 1;
 601                                         while ( $i < $len && $changed[$i] ) {
 602                                                 $i++;
 603                                         }
 604
 605                                         assert( '$j < $other_len && ! $other_changed[$j]' );
 606                                         $j++;
 607                                         if ( $j < $other_len && $other_changed[$j] ) {
 608                                                 $corresponding = $i;
 609                                                 while ( $j < $other_len && $other_changed[$j] ) {
 610                                                         $j++;
 611                                                 }
 612                                         }
 613                                 }
 614                         } while ( $runlength != $i - $start );
 615
 616                         /*
 617                          * If possible, move the fully-merged run of changes
 618                          * back to a corresponding run in the other file.
 619                          */
 620                         while ( $corresponding < $i ) {
 621                                 $changed[--$start] = 1;
 622                                 $changed[--$i] = 0;
 623                                 assert( '$j > 0' );
 624                                 while ( $other_changed[--$j] ) {
 625                                         continue;
 626                                 }
 627                                 assert( '$j >= 0 && !$other_changed[$j]' );
 628                         }
 629                 }
 630                 wfProfileOut( __METHOD__ );
 631         }
 632 }
 633
 634 /**
 635  * Class representing a 'diff' between two sequences of strings.
 636  * @todo document
 637  * @private
 638  * @ingroup DifferenceEngine
 639  */
 640 class Diff extends DiffResult {
 641         var $edits;
 642
 643         /**
 644          * Constructor.
 645          * Computes diff between sequences of strings.
 646          *
 647          * @param $from_lines array An array of strings.
 648          *                (Typically these are lines from a file.)
 649          * @param $to_lines array An array of strings.
 650          * @param $eng _DiffEngine|null The diff engine to use.
 651          */
 652         function __construct( $from_lines, $to_lines, $eng = null  ) {
 653                 if ( !$eng ) {
 654                         $eng = new _DiffEngine();
 655                 }
 656
 657                 $edits = $eng->diff( $from_lines, $to_lines );
 658
 659                 parent::__construct( $edits );
 660
 661                 //$this->_check( $from_lines, $to_lines );
 662         }
 663 }
 664
 665 /**
 666  * Class representing the result of 'diffin' two sequences of strings.
 667  * @todo document
 668  * @private
 669  * @ingroup DifferenceEngine
 670  */
 671 class DiffResult {
 672
 673         /**
 674          * Constructor.
 675          *
 676          * @param $edits array An array of Edit.
 677          */
 678         function __construct( $edits  ) {
 679                 $this->edits = $edits;
 680         }
 681
 682         /**
 683          * Compute reversed Diff.
 684          *
 685          * SYNOPSIS:
 686          *
 687          *      $diff = new Diff($lines1, $lines2);
 688          *      $rev = $diff->reverse();
 689          * @return Object A Diff object representing the inverse of the
 690          *                                original diff.
 691          */
 692         function reverse() {
 693                 $rev = $this;
 694                 $rev->edits = array();
 695                 foreach ( $this->edits as $edit ) {
 696                         $rev->edits[] = $edit->reverse();
 697                 }
 698                 return $rev;
 699         }
 700
 701         /**
 702          * Check for empty diff.
 703          *
 704          * @return bool True iff two sequences were identical.
 705          */
 706         function isEmpty() {
 707                 foreach ( $this->edits as $edit ) {
 708                         if ( $edit->type != 'copy' ) {
 709                                 return false;
 710                         }
 711                 }
 712                 return true;
 713         }
 714
 715         /**
 716          * Compute the length of the Longest Common Subsequence (LCS).
 717          *
 718          * This is mostly for diagnostic purposed.
 719          *
 720          * @return int The length of the LCS.
 721          */
 722         function lcs() {
 723                 $lcs = 0;
 724                 foreach ( $this->edits as $edit ) {
 725                         if ( $edit->type == 'copy' ) {
 726                                 $lcs += sizeof( $edit->orig );
 727                         }
 728                 }
 729                 return $lcs;
 730         }
 731
 732         /**
 733          * Get the original set of lines.
 734          *
 735          * This reconstructs the $from_lines parameter passed to the
 736          * constructor.
 737          *
 738          * @return array The original sequence of strings.
 739          */
 740         function orig() {
 741                 $lines = array();
 742
 743                 foreach ( $this->edits as $edit ) {
 744                         if ( $edit->orig ) {
 745                                 array_splice( $lines, sizeof( $lines ), 0, $edit->orig );
 746                         }
 747                 }
 748                 return $lines;
 749         }
 750
 751         /**
 752          * Get the closing set of lines.
 753          *
 754          * @return array The sequence of strings.
 755          */
 756         function closing() {
 757                 $lines = array();
 758
 759                 foreach ( $this->edits as $edit ) {
 760                         if ( $edit->closing ) {
 761                                 array_splice( $lines, sizeof( $lines ), 0, $edit->closing );
 762                         }
 763                 }
 764                 return $lines;
 765         }
 766
 767         /**
 768          * Check a Diff for validity.
 769          *
 770          * This is here only for debugging purposes.
 771          * @param $from_lines
 772          * @param $to_lines
 773          */
 774         function _check( $from_lines, $to_lines ) {
 775                 wfProfileIn( __METHOD__ );
 776                 if ( serialize( $from_lines ) != serialize( $this->orig() ) ) {
 777                         trigger_error( "Reconstructed original doesn't match", E_USER_ERROR );
 778                 }
 779                 if ( serialize( $to_lines ) != serialize( $this->closing() ) ) {
 780                         trigger_error( "Reconstructed closing doesn't match", E_USER_ERROR );
 781                 }
 782
 783                 $rev = $this->reverse();
 784                 if ( serialize( $to_lines ) != serialize( $rev->orig() ) ) {
 785                         trigger_error( "Reversed original doesn't match", E_USER_ERROR );
 786                 }
 787                 if ( serialize( $from_lines ) != serialize( $rev->closing() ) ) {
 788                         trigger_error( "Reversed closing doesn't match", E_USER_ERROR );
 789                 }
 790
 791
 792                 $prevtype = 'none';
 793                 foreach ( $this->edits as $edit ) {
 794                         if ( $prevtype == $edit->type ) {
 795                                 trigger_error( 'Edit sequence is non-optimal', E_USER_ERROR );
 796                         }
 797                         $prevtype = $edit->type;
 798                 }
 799
 800                 $lcs = $this->lcs();
 801                 trigger_error( 'Diff okay: LCS = ' . $lcs, E_USER_NOTICE );
 802                 wfProfileOut( __METHOD__ );
 803         }
 804 }
 805
 806 /**
 807  * @todo document, bad name.
 808  * @private
 809  * @ingroup DifferenceEngine
 810  */
 811 class MappedDiff extends Diff {
 812         /**
 813          * Constructor.
 814          *
 815          * Computes diff between sequences of strings.
 816          *
 817          * This can be used to compute things like
 818          * case-insensitve diffs, or diffs which ignore
 819          * changes in white-space.
 820          *
 821          * @param $from_lines array An array of strings.
 822          *      (Typically these are lines from a file.)
 823          *
 824          * @param $to_lines array An array of strings.
 825          *
 826          * @param $mapped_from_lines array This array should
 827          *      have the same size number of elements as $from_lines.
 828          *      The elements in $mapped_from_lines and
 829          *      $mapped_to_lines are what is actually compared
 830          *      when computing the diff.
 831          *
 832          * @param $mapped_to_lines array This array should
 833          *      have the same number of elements as $to_lines.
 834          */
 835         function __construct( $from_lines, $to_lines,
 836                 $mapped_from_lines, $mapped_to_lines ) {
 837                 wfProfileIn( __METHOD__ );
 838
 839                 assert( 'sizeof( $from_lines ) == sizeof( $mapped_from_lines )' );
 840                 assert( 'sizeof( $to_lines ) == sizeof( $mapped_to_lines )' );
 841
 842                 parent::__construct( $mapped_from_lines, $mapped_to_lines );
 843
 844                 $xi = $yi = 0;
 845                 for ( $i = 0; $i < sizeof( $this->edits ); $i++ ) {
 846                         $orig = &$this->edits[$i]->orig;
 847                         if ( is_array( $orig ) ) {
 848                                 $orig = array_slice( $from_lines, $xi, sizeof( $orig ) );
 849                                 $xi += sizeof( $orig );
 850                         }
 851
 852                         $closing = &$this->edits[$i]->closing;
 853                         if ( is_array( $closing ) ) {
 854                                 $closing = array_slice( $to_lines, $yi, sizeof( $closing ) );
 855                                 $yi += sizeof( $closing );
 856                         }
 857                 }
 858                 wfProfileOut( __METHOD__ );
 859         }
 860 }
 861
 862 /**
 863  * A class to format Diffs
 864  *
 865  * This class formats the diff in classic diff format.
 866  * It is intended that this class be customized via inheritance,
 867  * to obtain fancier outputs.
 868  * @todo document
 869  * @private
 870  * @ingroup DifferenceEngine
 871  */
 872 class DiffFormatter {
 873         /**
 874          * Number of leading 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 $leading_context_lines = 0;
 880
 881         /**
 882          * Number of trailing context "lines" to preserve.
 883          *
 884          * This should be left at zero for this class, but subclasses
 885          * may want to set this to other values.
 886          */
 887         var $trailing_context_lines = 0;
 888
 889         /**
 890          * Format a diff.
 891          *
 892          * @param $diff Diff A Diff object.
 893          * @return string The formatted output.
 894          */
 895         function format( $diff ) {
 896                 wfProfileIn( __METHOD__ );
 897
 898                 $xi = $yi = 1;
 899                 $block = false;
 900                 $context = array();
 901
 902                 $nlead = $this->leading_context_lines;
 903                 $ntrail = $this->trailing_context_lines;
 904
 905                 $this->_start_diff();
 906
 907                 foreach ( $diff->edits as $edit ) {
 908                         if ( $edit->type == 'copy' ) {
 909                                 if ( is_array( $block ) ) {
 910                                         if ( sizeof( $edit->orig ) <= $nlead + $ntrail ) {
 911                                                 $block[] = $edit;
 912                                         } else {
 913                                                 if ( $ntrail ) {
 914                                                         $context = array_slice( $edit->orig, 0, $ntrail );
 915                                                         $block[] = new _DiffOp_Copy( $context );
 916                                                 }
 917                                                 $this->_block( $x0, $ntrail + $xi - $x0,
 918                                                         $y0, $ntrail + $yi - $y0,
 919                                                         $block );
 920                                                 $block = false;
 921                                         }
 922                                 }
 923                                 $context = $edit->orig;
 924                         } else {
 925                                 if ( !is_array( $block ) ) {
 926                                         $context = array_slice( $context, sizeof( $context ) - $nlead );
 927                                         $x0 = $xi - sizeof( $context );
 928                                         $y0 = $yi - sizeof( $context );
 929                                         $block = array();
 930                                         if ( $context ) {
 931                                                 $block[] = new _DiffOp_Copy( $context );
 932                                         }
 933                                 }
 934                                 $block[] = $edit;
 935                         }
 936
 937                         if ( $edit->orig ) {
 938                                 $xi += sizeof( $edit->orig );
 939                         }
 940                         if ( $edit->closing ) {
 941                                 $yi += sizeof( $edit->closing );
 942                         }
 943                 }
 944
 945                 if ( is_array( $block ) ) {
 946                         $this->_block( $x0, $xi - $x0,
 947                                 $y0, $yi - $y0,
 948                                 $block );
 949                 }
 950
 951                 $end = $this->_end_diff();
 952                 wfProfileOut( __METHOD__ );
 953                 return $end;
 954         }
 955
 956         /**
 957          * @param $xbeg
 958          * @param $xlen
 959          * @param $ybeg
 960          * @param $ylen
 961          * @param $edits
 962          */
 963         function _block( $xbeg, $xlen, $ybeg, $ylen, &$edits ) {
 964                 wfProfileIn( __METHOD__ );
 965                 $this->_start_block( $this->_block_header( $xbeg, $xlen, $ybeg, $ylen ) );
 966                 foreach ( $edits as $edit ) {
 967                         if ( $edit->type == 'copy' ) {
 968                                 $this->_context( $edit->orig );
 969                         } elseif ( $edit->type == 'add' ) {
 970                                 $this->_added( $edit->closing );
 971                         } elseif ( $edit->type == 'delete' ) {
 972                                 $this->_deleted( $edit->orig );
 973                         } elseif ( $edit->type == 'change' ) {
 974                                 $this->_changed( $edit->orig, $edit->closing );
 975                         } else {
 976                                 trigger_error( 'Unknown edit type', E_USER_ERROR );
 977                         }
 978                 }
 979                 $this->_end_block();
 980                 wfProfileOut( __METHOD__ );
 981         }
 982
 983         function _start_diff() {
 984                 ob_start();
 985         }
 986
 987         /**
 988          * @return string
 989          */
 990         function _end_diff() {
 991                 $val = ob_get_contents();
 992                 ob_end_clean();
 993                 return $val;
 994         }
 995
 996         /**
 997          * @param $xbeg
 998          * @param $xlen
 999          * @param $ybeg
1000          * @param $ylen
1001          * @return string
1002          */
1003         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1004                 if ( $xlen > 1 ) {
1005                         $xbeg .= ',' . ( $xbeg + $xlen - 1 );
1006                 }
1007                 if ( $ylen > 1 ) {
1008                         $ybeg .= ',' . ( $ybeg + $ylen - 1 );
1009                 }
1010
1011                 return $xbeg . ( $xlen ? ( $ylen ? 'c' : 'd' ) : 'a' ) . $ybeg;
1012         }
1013
1014         function _start_block( $header ) {
1015                 echo $header . "\n";
1016         }
1017
1018         function _end_block() {
1019         }
1020
1021         /**
1022          * @param $lines
1023          * @param $prefix string
1024          */
1025         function _lines( $lines, $prefix = ' ' ) {
1026                 foreach ( $lines as $line ) {
1027                         echo "$prefix $line\n";
1028                 }
1029         }
1030
1031         /**
1032          * @param $lines
1033          */
1034         function _context( $lines ) {
1035                 $this->_lines( $lines );
1036         }
1037
1038         /**
1039          * @param $lines
1040          */
1041         function _added( $lines ) {
1042                 $this->_lines( $lines, '>' );
1043         }
1044
1045         /**
1046          * @param $lines
1047          */
1048         function _deleted( $lines ) {
1049                 $this->_lines( $lines, '<' );
1050         }
1051
1052         /**
1053          * @param $orig
1054          * @param $closing
1055          */
1056         function _changed( $orig, $closing ) {
1057                 $this->_deleted( $orig );
1058                 echo "---\n";
1059                 $this->_added( $closing );
1060         }
1061 }
1062
1063 /**
1064  * A formatter that outputs unified diffs
1065  * @ingroup DifferenceEngine
1066  */
1067 class UnifiedDiffFormatter extends DiffFormatter {
1068         var $leading_context_lines = 2;
1069         var $trailing_context_lines = 2;
1070
1071         /**
1072          * @param $lines
1073          */
1074         function _added( $lines ) {
1075                 $this->_lines( $lines, '+' );
1076         }
1077
1078         /**
1079          * @param $lines
1080          */
1081         function _deleted( $lines ) {
1082                 $this->_lines( $lines, '-' );
1083         }
1084
1085         /**
1086          * @param $orig
1087          * @param $closing
1088          */
1089         function _changed( $orig, $closing ) {
1090                 $this->_deleted( $orig );
1091                 $this->_added( $closing );
1092         }
1093
1094         /**
1095          * @param $xbeg
1096          * @param $xlen
1097          * @param $ybeg
1098          * @param $ylen
1099          * @return string
1100          */
1101         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1102                 return "@@ -$xbeg,$xlen +$ybeg,$ylen @@";
1103         }
1104 }
1105
1106 /**
1107  * A pseudo-formatter that just passes along the Diff::$edits array
1108  * @ingroup DifferenceEngine
1109  */
1110 class ArrayDiffFormatter extends DiffFormatter {
1111
1112         /**
1113          * @param $diff
1114          * @return array
1115          */
1116         function format( $diff ) {
1117                 $oldline = 1;
1118                 $newline = 1;
1119                 $retval = array();
1120                 foreach ( $diff->edits as $edit ) {
1121                         switch( $edit->type ) {
1122                                 case 'add':
1123                                         foreach ( $edit->closing as $l ) {
1124                                                 $retval[] = array(
1125                                                         'action' => 'add',
1126                                                         'new' => $l,
1127                                                         'newline' => $newline++
1128                                                 );
1129                                         }
1130                                         break;
1131                                 case 'delete':
1132                                         foreach ( $edit->orig as $l ) {
1133                                                 $retval[] = array(
1134                                                         'action' => 'delete',
1135                                                         'old' => $l,
1136                                                         'oldline' => $oldline++,
1137                                                 );
1138                                         }
1139                                         break;
1140                                 case 'change':
1141                                         foreach ( $edit->orig as $i => $l ) {
1142                                                 $retval[] = array(
1143                                                         'action' => 'change',
1144                                                         'old' => $l,
1145                                                         'new' => isset( $edit->closing[$i] ) ? $edit->closing[$i] : null,
1146                                                         'oldline' => $oldline++,
1147                                                         'newline' => $newline++,
1148                                                 );
1149                                         }
1150                                         break;
1151                                 case 'copy':
1152                                         $oldline += count( $edit->orig );
1153                                         $newline += count( $edit->orig );
1154                         }
1155                 }
1156                 return $retval;
1157         }
1158 }
1159
1160 /**
1161  * Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
1162  */
1163
1164 define( 'NBSP', '&#160;' ); // iso-8859-x non-breaking space.
1165
1166 /**
1167  * @todo document
1168  * @private
1169  * @ingroup DifferenceEngine
1170  */
1171 class _HWLDF_WordAccumulator {
1172         function __construct() {
1173                 $this->_lines = array();
1174                 $this->_line = '';
1175                 $this->_group = '';
1176                 $this->_tag = '';
1177         }
1178
1179         /**
1180          * @param $new_tag
1181          */
1182         function _flushGroup( $new_tag ) {
1183                 if ( $this->_group !== '' ) {
1184                         if ( $this->_tag == 'ins' ) {
1185                                 $this->_line .= '<ins class="diffchange diffchange-inline">' .
1186                                                 htmlspecialchars( $this->_group ) . '</ins>';
1187                         } elseif ( $this->_tag == 'del' ) {
1188                                 $this->_line .= '<del class="diffchange diffchange-inline">' .
1189                                                 htmlspecialchars( $this->_group ) . '</del>';
1190                         } else {
1191                                 $this->_line .= htmlspecialchars( $this->_group );
1192                         }
1193                 }
1194                 $this->_group = '';
1195                 $this->_tag = $new_tag;
1196         }
1197
1198         /**
1199          * @param $new_tag
1200          */
1201         function _flushLine( $new_tag ) {
1202                 $this->_flushGroup( $new_tag );
1203                 if ( $this->_line != '' ) {
1204                         array_push( $this->_lines, $this->_line );
1205                 } else {
1206                         # make empty lines visible by inserting an NBSP
1207                         array_push( $this->_lines, NBSP );
1208                 }
1209                 $this->_line = '';
1210         }
1211
1212         /**
1213          * @param $words
1214          * @param $tag string
1215          */
1216         function addWords ( $words, $tag = '' ) {
1217                 if ( $tag != $this->_tag ) {
1218                         $this->_flushGroup( $tag );
1219                 }
1220
1221                 foreach ( $words as $word ) {
1222                         // new-line should only come as first char of word.
1223                         if ( $word == '' ) {
1224                                 continue;
1225                         }
1226                         if ( $word[0] == "\n" ) {
1227                                 $this->_flushLine( $tag );
1228                                 $word = substr( $word, 1 );
1229                         }
1230                         assert( '!strstr( $word, "\n" )' );
1231                         $this->_group .= $word;
1232                 }
1233         }
1234
1235         /**
1236          * @return array
1237          */
1238         function getLines() {
1239                 $this->_flushLine( '~done' );
1240                 return $this->_lines;
1241         }
1242 }
1243
1244 /**
1245  * @todo document
1246  * @private
1247  * @ingroup DifferenceEngine
1248  */
1249 class WordLevelDiff extends MappedDiff {
1250         const MAX_LINE_LENGTH = 10000;
1251
1252         /**
1253          * @param $orig_lines
1254          * @param $closing_lines
1255          */
1256         function __construct ( $orig_lines, $closing_lines ) {
1257                 wfProfileIn( __METHOD__ );
1258
1259                 list( $orig_words, $orig_stripped ) = $this->_split( $orig_lines );
1260                 list( $closing_words, $closing_stripped ) = $this->_split( $closing_lines );
1261
1262                 parent::__construct( $orig_words, $closing_words,
1263                 $orig_stripped, $closing_stripped );
1264                 wfProfileOut( __METHOD__ );
1265         }
1266
1267         /**
1268          * @param $lines
1269          * @return array
1270          */
1271         function _split( $lines ) {
1272                 wfProfileIn( __METHOD__ );
1273
1274                 $words = array();
1275                 $stripped = array();
1276                 $first = true;
1277                 foreach ( $lines as $line ) {
1278                         # If the line is too long, just pretend the entire line is one big word
1279                         # This prevents resource exhaustion problems
1280                         if ( $first ) {
1281                                 $first = false;
1282                         } else {
1283                                 $words[] = "\n";
1284                                 $stripped[] = "\n";
1285                         }
1286                         if ( strlen( $line ) > self::MAX_LINE_LENGTH ) {
1287                                 $words[] = $line;
1288                                 $stripped[] = $line;
1289                         } else {
1290                                 $m = array();
1291                                 if ( preg_match_all( '/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
1292                                         $line, $m ) )
1293                                 {
1294                                         $words = array_merge( $words, $m[0] );
1295                                         $stripped = array_merge( $stripped, $m[1] );
1296                                 }
1297                         }
1298                 }
1299                 wfProfileOut( __METHOD__ );
1300                 return array( $words, $stripped );
1301         }
1302
1303         /**
1304          * @return array
1305          */
1306         function orig() {
1307                 wfProfileIn( __METHOD__ );
1308                 $orig = new _HWLDF_WordAccumulator;
1309
1310                 foreach ( $this->edits as $edit ) {
1311                         if ( $edit->type == 'copy' ) {
1312                                 $orig->addWords( $edit->orig );
1313                         } elseif ( $edit->orig ) {
1314                                 $orig->addWords( $edit->orig, 'del' );
1315                         }
1316                 }
1317                 $lines = $orig->getLines();
1318                 wfProfileOut( __METHOD__ );
1319                 return $lines;
1320         }
1321
1322         /**
1323          * @return array
1324          */
1325         function closing() {
1326                 wfProfileIn( __METHOD__ );
1327                 $closing = new _HWLDF_WordAccumulator;
1328
1329                 foreach ( $this->edits as $edit ) {
1330                         if ( $edit->type == 'copy' ) {
1331                                 $closing->addWords( $edit->closing );
1332                         } elseif ( $edit->closing ) {
1333                                 $closing->addWords( $edit->closing, 'ins' );
1334                         }
1335                 }
1336                 $lines = $closing->getLines();
1337                 wfProfileOut( __METHOD__ );
1338                 return $lines;
1339         }
1340 }
1341
1342 /**
1343  * Wikipedia Table style diff formatter.
1344  * @todo document
1345  * @private
1346  * @ingroup DifferenceEngine
1347  */
1348 class TableDiffFormatter extends DiffFormatter {
1349         function __construct() {
1350                 $this->leading_context_lines = 2;
1351                 $this->trailing_context_lines = 2;
1352         }
1353
1354         /**
1355          * @static
1356          * @param $msg
1357          * @return mixed
1358          */
1359         public static function escapeWhiteSpace( $msg ) {
1360                 $msg = preg_replace( '/^ /m', '&#160; ', $msg );
1361                 $msg = preg_replace( '/ $/m', ' &#160;', $msg );
1362                 $msg = preg_replace( '/  /', '&#160; ', $msg );
1363                 return $msg;
1364         }
1365
1366         /**
1367          * @param $xbeg
1368          * @param $xlen
1369          * @param $ybeg
1370          * @param $ylen
1371          * @return string
1372          */
1373         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1374                 $r = '<tr><td colspan="2" class="diff-lineno"><!--LINE ' . $xbeg . "--></td>\n" .
1375                   '<td colspan="2" class="diff-lineno"><!--LINE ' . $ybeg . "--></td></tr>\n";
1376                 return $r;
1377         }
1378
1379         /**
1380          * @param $header
1381          */
1382         function _start_block( $header ) {
1383                 echo $header;
1384         }
1385
1386         function _end_block() {
1387         }
1388
1389         function _lines( $lines, $prefix = ' ', $color = 'white' ) {
1390         }
1391
1392         /**
1393          * HTML-escape parameter before calling this
1394          * @param $line
1395          * @return string
1396          */
1397         function addedLine( $line ) {
1398                 return $this->wrapLine( '+', 'diff-addedline', $line );
1399         }
1400
1401         /**
1402          * HTML-escape parameter before calling this
1403          * @param $line
1404          * @return string
1405          */
1406         function deletedLine( $line ) {
1407                 return $this->wrapLine( '−', 'diff-deletedline', $line );
1408         }
1409
1410         /**
1411          * HTML-escape parameter before calling this
1412          * @param $line
1413          * @return string
1414          */
1415         function contextLine( $line ) {
1416                 return $this->wrapLine( '&#160;', 'diff-context', $line );
1417         }
1418
1419         /**
1420          * @param $marker
1421          * @param $class
1422          * @param $line
1423          * @return string
1424          */
1425         private function wrapLine( $marker, $class, $line ) {
1426                 if ( $line !== '' ) {
1427                         // The <div> wrapper is needed for 'overflow: auto' style to scroll properly
1428                         $line = Xml::tags( 'div', null, $this->escapeWhiteSpace( $line ) );
1429                 }
1430                 return "<td class='diff-marker'>$marker</td><td class='$class'>$line</td>";
1431         }
1432
1433         /**
1434          * @return string
1435          */
1436         function emptyLine() {
1437                 return '<td colspan="2">&#160;</td>';
1438         }
1439
1440         /**
1441          * @param $lines array
1442          */
1443         function _added( $lines ) {
1444                 foreach ( $lines as $line ) {
1445                         echo '<tr>' . $this->emptyLine() .
1446                         $this->addedLine( '<ins class="diffchange">' .
1447                         htmlspecialchars( $line ) . '</ins>' ) . "</tr>\n";
1448                 }
1449         }
1450
1451         /**
1452          * @param $lines
1453          */
1454         function _deleted( $lines ) {
1455                 foreach ( $lines as $line ) {
1456                         echo '<tr>' . $this->deletedLine( '<del class="diffchange">' .
1457                         htmlspecialchars( $line ) . '</del>' ) .
1458                         $this->emptyLine() . "</tr>\n";
1459                 }
1460         }
1461
1462         /**
1463          * @param $lines
1464          */
1465         function _context( $lines ) {
1466                 foreach ( $lines as $line ) {
1467                         echo '<tr>' .
1468                         $this->contextLine( htmlspecialchars( $line ) ) .
1469                         $this->contextLine( htmlspecialchars( $line ) ) . "</tr>\n";
1470                 }
1471         }
1472
1473         /**
1474          * @param $orig
1475          * @param $closing
1476          */
1477         function _changed( $orig, $closing ) {
1478                 wfProfileIn( __METHOD__ );
1479
1480                 $diff = new WordLevelDiff( $orig, $closing );
1481                 $del = $diff->orig();
1482                 $add = $diff->closing();
1483
1484                 # Notice that WordLevelDiff returns HTML-escaped output.
1485                 # Hence, we will be calling addedLine/deletedLine without HTML-escaping.
1486
1487                 while ( $line = array_shift( $del ) ) {
1488                         $aline = array_shift( $add );
1489                         echo '<tr>' . $this->deletedLine( $line ) .
1490                         $this->addedLine( $aline ) . "</tr>\n";
1491                 }
1492                 foreach ( $add as $line ) {     # If any leftovers
1493                         echo '<tr>' . $this->emptyLine() .
1494                         $this->addedLine( $line ) . "</tr>\n";
1495                 }
1496                 wfProfileOut( __METHOD__ );
1497         }
1498 }