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