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 {
  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         protected $xchanged, $ychanged;
 139
 140         protected $xv = array(), $yv = array();
 141         protected $xind = array(), $yind = array();
 142
 143         protected $seq = array(), $in_seq = array();
 144
 145         protected $lcs = 0;
 146
 147         function diff ( $from_lines, $to_lines ) {
 148                 wfProfileIn( __METHOD__ );
 149
 150                 // Diff and store locally
 151                 $this->diff_local( $from_lines, $to_lines );
 152
 153                 // Merge edits when possible
 154                 $this->_shift_boundaries( $from_lines, $this->xchanged, $this->ychanged );
 155                 $this->_shift_boundaries( $to_lines, $this->ychanged, $this->xchanged );
 156
 157                 // Compute the edit operations.
 158                 $n_from = sizeof( $from_lines );
 159                 $n_to = sizeof( $to_lines );
 160
 161                 $edits = array();
 162                 $xi = $yi = 0;
 163                 while ( $xi < $n_from || $yi < $n_to ) {
 164                         assert( $yi < $n_to || $this->xchanged[$xi] );
 165                         assert( $xi < $n_from || $this->ychanged[$yi] );
 166
 167                         // Skip matching "snake".
 168                         $copy = array();
 169                         while ( $xi < $n_from && $yi < $n_to
 170                         && !$this->xchanged[$xi] && !$this->ychanged[$yi] ) {
 171                                 $copy[] = $from_lines[$xi++];
 172                                 ++$yi;
 173                         }
 174                         if ( $copy ) {
 175                                 $edits[] = new _DiffOp_Copy( $copy );
 176                         }
 177
 178                         // Find deletes & adds.
 179                         $delete = array();
 180                         while ( $xi < $n_from && $this->xchanged[$xi] ) {
 181                                 $delete[] = $from_lines[$xi++];
 182                         }
 183
 184                         $add = array();
 185                         while ( $yi < $n_to && $this->ychanged[$yi] )  {
 186                                 $add[] = $to_lines[$yi++];
 187                         }
 188
 189                         if ( $delete && $add ) {
 190                                 $edits[] = new _DiffOp_Change( $delete, $add );
 191                         } elseif ( $delete ) {
 192                                 $edits[] = new _DiffOp_Delete( $delete );
 193                         } elseif ( $add ) {
 194                                 $edits[] = new _DiffOp_Add( $add );
 195                         }
 196                 }
 197                 wfProfileOut( __METHOD__ );
 198                 return $edits;
 199         }
 200
 201         function diff_local ( $from_lines, $to_lines ) {
 202                 global $wgExternalDiffEngine;
 203                 wfProfileIn( __METHOD__ );
 204
 205                 if ( $wgExternalDiffEngine == 'wikidiff3' ) {
 206                         // wikidiff3
 207                         $wikidiff3 = new WikiDiff3();
 208                         $wikidiff3->diff( $from_lines, $to_lines );
 209                         $this->xchanged = $wikidiff3->removed;
 210                         $this->ychanged = $wikidiff3->added;
 211                         unset( $wikidiff3 );
 212                 } else {
 213                         // old diff
 214                         $n_from = sizeof( $from_lines );
 215                         $n_to = sizeof( $to_lines );
 216                         $this->xchanged = $this->ychanged = array();
 217                         $this->xv = $this->yv = array();
 218                         $this->xind = $this->yind = array();
 219                         unset( $this->seq );
 220                         unset( $this->in_seq );
 221                         unset( $this->lcs );
 222
 223                         // Skip leading common lines.
 224                         for ( $skip = 0; $skip < $n_from && $skip < $n_to; $skip++ ) {
 225                                 if ( $from_lines[$skip] !== $to_lines[$skip] )
 226                                 break;
 227                                 $this->xchanged[$skip] = $this->ychanged[$skip] = false;
 228                         }
 229                         // Skip trailing common lines.
 230                         $xi = $n_from; $yi = $n_to;
 231                         for ( $endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++ ) {
 232                                 if ( $from_lines[$xi] !== $to_lines[$yi] )
 233                                 break;
 234                                 $this->xchanged[$xi] = $this->ychanged[$yi] = false;
 235                         }
 236
 237                         // Ignore lines which do not exist in both files.
 238                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 239                                 $xhash[$this->_line_hash( $from_lines[$xi] )] = 1;
 240                         }
 241
 242                         for ( $yi = $skip; $yi < $n_to - $endskip; $yi++ ) {
 243                                 $line = $to_lines[$yi];
 244                                 if ( ( $this->ychanged[$yi] = empty( $xhash[$this->_line_hash( $line )] ) ) )
 245                                 continue;
 246                                 $yhash[$this->_line_hash( $line )] = 1;
 247                                 $this->yv[] = $line;
 248                                 $this->yind[] = $yi;
 249                         }
 250                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 251                                 $line = $from_lines[$xi];
 252                                 if ( ( $this->xchanged[$xi] = empty( $yhash[$this->_line_hash( $line )] ) ) )
 253                                 continue;
 254                                 $this->xv[] = $line;
 255                                 $this->xind[] = $xi;
 256                         }
 257
 258                         // Find the LCS.
 259                         $this->_compareseq( 0, sizeof( $this->xv ), 0, sizeof( $this->yv ) );
 260                 }
 261                 wfProfileOut( __METHOD__ );
 262         }
 263
 264         /**
 265          * Returns the whole line if it's small enough, or the MD5 hash otherwise
 266          */
 267         function _line_hash( $line ) {
 268                 if ( strlen( $line ) > self::MAX_XREF_LENGTH ) {
 269                         return md5( $line );
 270                 } else {
 271                         return $line;
 272                 }
 273         }
 274
 275         /* Divide the Largest Common Subsequence (LCS) of the sequences
 276          * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
 277          * sized segments.
 278          *
 279          * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an
 280          * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
 281          * sub sequences.  The first sub-sequence is contained in [X0, X1),
 282          * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
 283          * that (X0, Y0) == (XOFF, YOFF) and
 284          * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
 285          *
 286          * This function assumes that the first lines of the specified portions
 287          * of the two files do not match, and likewise that the last lines do not
 288          * match.  The caller must trim matching lines from the beginning and end
 289          * of the portions it is going to specify.
 290          */
 291         function _diag ( $xoff, $xlim, $yoff, $ylim, $nchunks ) {
 292                 $flip = false;
 293
 294                 if ( $xlim - $xoff > $ylim - $yoff ) {
 295                         // Things seems faster (I'm not sure I understand why)
 296                         // when the shortest sequence in X.
 297                         $flip = true;
 298                         list ( $xoff, $xlim, $yoff, $ylim ) = array( $yoff, $ylim, $xoff, $xlim );
 299                 }
 300
 301                 if ( $flip ) {
 302                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 303                                 $ymatches[$this->xv[$i]][] = $i;
 304                         }
 305                 } else {
 306                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 307                                 $ymatches[$this->yv[$i]][] = $i;
 308                         }
 309                 }
 310
 311                 $this->lcs = 0;
 312                 $this->seq[0] = $yoff - 1;
 313                 $this->in_seq = array();
 314                 $ymids[0] = array();
 315
 316                 $numer = $xlim - $xoff + $nchunks - 1;
 317                 $x = $xoff;
 318                 for ( $chunk = 0; $chunk < $nchunks; $chunk++ ) {
 319                         if ( $chunk > 0 ) {
 320                                 for ( $i = 0; $i <= $this->lcs; $i++ ) {
 321                                         $ymids[$i][$chunk -1] = $this->seq[$i];
 322                                 }
 323                         }
 324
 325                         $x1 = $xoff + (int)( ( $numer + ( $xlim -$xoff ) * $chunk ) / $nchunks );
 326                         for ( ; $x < $x1; $x++ ) {
 327                                 $line = $flip ? $this->yv[$x] : $this->xv[$x];
 328                                 if ( empty( $ymatches[$line] ) ) {
 329                                         continue;
 330                                 }
 331                                 $matches = $ymatches[$line];
 332                                 reset( $matches );
 333                                 while ( list( , $y ) = each( $matches ) ) {
 334                                         if ( empty( $this->in_seq[$y] ) ) {
 335                                                 $k = $this->_lcs_pos( $y );
 336                                                 assert( $k > 0 );
 337                                                 $ymids[$k] = $ymids[$k -1];
 338                                                 break;
 339                                         }
 340                                 }
 341                                 while ( list ( , $y ) = each( $matches ) ) {
 342                                         if ( $y > $this->seq[$k -1] ) {
 343                                                 assert( $y < $this->seq[$k] );
 344                                                 // Optimization: this is a common case:
 345                                                 //      next match is just replacing previous match.
 346                                                 $this->in_seq[$this->seq[$k]] = false;
 347                                                 $this->seq[$k] = $y;
 348                                                 $this->in_seq[$y] = 1;
 349                                         } else if ( empty( $this->in_seq[$y] ) ) {
 350                                                 $k = $this->_lcs_pos( $y );
 351                                                 assert( $k > 0 );
 352                                                 $ymids[$k] = $ymids[$k -1];
 353                                         }
 354                                 }
 355                         }
 356                 }
 357
 358                 $seps[] = $flip ? array( $yoff, $xoff ) : array( $xoff, $yoff );
 359                 $ymid = $ymids[$this->lcs];
 360                 for ( $n = 0; $n < $nchunks - 1; $n++ ) {
 361                         $x1 = $xoff + (int)( ( $numer + ( $xlim - $xoff ) * $n ) / $nchunks );
 362                         $y1 = $ymid[$n] + 1;
 363                         $seps[] = $flip ? array( $y1, $x1 ) : array( $x1, $y1 );
 364                 }
 365                 $seps[] = $flip ? array( $ylim, $xlim ) : array( $xlim, $ylim );
 366
 367                 return array( $this->lcs, $seps );
 368         }
 369
 370         function _lcs_pos ( $ypos ) {
 371                 $end = $this->lcs;
 372                 if ( $end == 0 || $ypos > $this->seq[$end] ) {
 373                         $this->seq[++$this->lcs] = $ypos;
 374                         $this->in_seq[$ypos] = 1;
 375                         return $this->lcs;
 376                 }
 377
 378                 $beg = 1;
 379                 while ( $beg < $end ) {
 380                         $mid = (int)( ( $beg + $end ) / 2 );
 381                         if ( $ypos > $this->seq[$mid] )
 382                         $beg = $mid + 1;
 383                         else
 384                         $end = $mid;
 385                 }
 386
 387                 assert( $ypos != $this->seq[$end] );
 388
 389                 $this->in_seq[$this->seq[$end]] = false;
 390                 $this->seq[$end] = $ypos;
 391                 $this->in_seq[$ypos] = 1;
 392                 return $end;
 393         }
 394
 395         /* Find LCS of two sequences.
 396          *
 397          * The results are recorded in the vectors $this->{x,y}changed[], by
 398          * storing a 1 in the element for each line that is an insertion
 399          * or deletion (ie. is not in the LCS).
 400          *
 401          * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
 402          *
 403          * Note that XLIM, YLIM are exclusive bounds.
 404          * All line numbers are origin-0 and discarded lines are not counted.
 405          */
 406         function _compareseq ( $xoff, $xlim, $yoff, $ylim ) {
 407                 // Slide down the bottom initial diagonal.
 408                 while ( $xoff < $xlim && $yoff < $ylim
 409                 && $this->xv[$xoff] == $this->yv[$yoff] ) {
 410                         ++$xoff;
 411                         ++$yoff;
 412                 }
 413
 414                 // Slide up the top initial diagonal.
 415                 while ( $xlim > $xoff && $ylim > $yoff
 416                 && $this->xv[$xlim - 1] == $this->yv[$ylim - 1] ) {
 417                         --$xlim;
 418                         --$ylim;
 419                 }
 420
 421                 if ( $xoff == $xlim || $yoff == $ylim ) {
 422                         $lcs = 0;
 423                 } else {
 424                         // This is ad hoc but seems to work well.
 425                         // $nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
 426                         // $nchunks = max(2,min(8,(int)$nchunks));
 427                         $nchunks = min( 7, $xlim - $xoff, $ylim - $yoff ) + 1;
 428                         list ( $lcs, $seps )
 429                         = $this->_diag( $xoff, $xlim, $yoff, $ylim, $nchunks );
 430                 }
 431
 432                 if ( $lcs == 0 ) {
 433                         // X and Y sequences have no common subsequence:
 434                         // mark all changed.
 435                         while ( $yoff < $ylim ) {
 436                                 $this->ychanged[$this->yind[$yoff++]] = 1;
 437                         }
 438                         while ( $xoff < $xlim ) {
 439                                 $this->xchanged[$this->xind[$xoff++]] = 1;
 440                         }
 441                 } else {
 442                         // Use the partitions to split this problem into subproblems.
 443                         reset( $seps );
 444                         $pt1 = $seps[0];
 445                         while ( $pt2 = next( $seps ) ) {
 446                                 $this->_compareseq ( $pt1[0], $pt2[0], $pt1[1], $pt2[1] );
 447                                 $pt1 = $pt2;
 448                         }
 449                 }
 450         }
 451
 452         /* Adjust inserts/deletes of identical lines to join changes
 453          * as much as possible.
 454          *
 455          * We do something when a run of changed lines include a
 456          * line at one end and has an excluded, identical line at the other.
 457          * We are free to choose which identical line is included.
 458          * `compareseq' usually chooses the one at the beginning,
 459          * but usually it is cleaner to consider the following identical line
 460          * to be the "change".
 461          *
 462          * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
 463          */
 464         function _shift_boundaries ( $lines, &$changed, $other_changed ) {
 465                 wfProfileIn( __METHOD__ );
 466                 $i = 0;
 467                 $j = 0;
 468
 469                 assert( 'sizeof($lines) == sizeof($changed)' );
 470                 $len = sizeof( $lines );
 471                 $other_len = sizeof( $other_changed );
 472
 473                 while ( 1 ) {
 474                         /*
 475                          * Scan forwards to find beginning of another run of changes.
 476                          * Also keep track of the corresponding point in the other file.
 477                          *
 478                          * Throughout this code, $i and $j are adjusted together so that
 479                          * the first $i elements of $changed and the first $j elements
 480                          * of $other_changed both contain the same number of zeros
 481                          * (unchanged lines).
 482                          * Furthermore, $j is always kept so that $j == $other_len or
 483                          * $other_changed[$j] == false.
 484                          */
 485                         while ( $j < $other_len && $other_changed[$j] ) {
 486                                 $j++;
 487                         }
 488
 489                         while ( $i < $len && ! $changed[$i] ) {
 490                                 assert( '$j < $other_len && ! $other_changed[$j]' );
 491                                 $i++; $j++;
 492                                 while ( $j < $other_len && $other_changed[$j] )
 493                                 $j++;
 494                         }
 495
 496                         if ( $i == $len ) {
 497                                 break;
 498                         }
 499
 500                         $start = $i;
 501
 502                         // Find the end of this run of changes.
 503                         while ( ++$i < $len && $changed[$i] ) {
 504                                 continue;
 505                         }
 506
 507                         do {
 508                                 /*
 509                                  * Record the length of this run of changes, so that
 510                                  * we can later determine whether the run has grown.
 511                                  */
 512                                 $runlength = $i - $start;
 513
 514                                 /*
 515                                  * Move the changed region back, so long as the
 516                                  * previous unchanged line matches the last changed one.
 517                                  * This merges with previous changed regions.
 518                                  */
 519                                 while ( $start > 0 && $lines[$start - 1] == $lines[$i - 1] ) {
 520                                         $changed[--$start] = 1;
 521                                         $changed[--$i] = false;
 522                                         while ( $start > 0 && $changed[$start - 1] ) {
 523                                                 $start--;
 524                                         }
 525                                         assert( '$j > 0' );
 526                                         while ( $other_changed[--$j] ) {
 527                                                 continue;
 528                                         }
 529                                         assert( '$j >= 0 && !$other_changed[$j]' );
 530                                 }
 531
 532                                 /*
 533                                  * Set CORRESPONDING to the end of the changed run, at the last
 534                                  * point where it corresponds to a changed run in the other file.
 535                                  * CORRESPONDING == LEN means no such point has been found.
 536                                  */
 537                                 $corresponding = $j < $other_len ? $i : $len;
 538
 539                                 /*
 540                                  * Move the changed region forward, so long as the
 541                                  * first changed line matches the following unchanged one.
 542                                  * This merges with following changed regions.
 543                                  * Do this second, so that if there are no merges,
 544                                  * the changed region is moved forward as far as possible.
 545                                  */
 546                                 while ( $i < $len && $lines[$start] == $lines[$i] ) {
 547                                         $changed[$start++] = false;
 548                                         $changed[$i++] = 1;
 549                                         while ( $i < $len && $changed[$i] ) {
 550                                                 $i++;
 551                                         }
 552
 553                                         assert( '$j < $other_len && ! $other_changed[$j]' );
 554                                         $j++;
 555                                         if ( $j < $other_len && $other_changed[$j] ) {
 556                                                 $corresponding = $i;
 557                                                 while ( $j < $other_len && $other_changed[$j] ) {
 558                                                         $j++;
 559                                                 }
 560                                         }
 561                                 }
 562                         } while ( $runlength != $i - $start );
 563
 564                         /*
 565                          * If possible, move the fully-merged run of changes
 566                          * back to a corresponding run in the other file.
 567                          */
 568                         while ( $corresponding < $i ) {
 569                                 $changed[--$start] = 1;
 570                                 $changed[--$i] = 0;
 571                                 assert( '$j > 0' );
 572                                 while ( $other_changed[--$j] ) {
 573                                         continue;
 574                                 }
 575                                 assert( '$j >= 0 && !$other_changed[$j]' );
 576                         }
 577                 }
 578                 wfProfileOut( __METHOD__ );
 579         }
 580 }
 581
 582 /**
 583  * Class representing a 'diff' between two sequences of strings.
 584  * @todo document
 585  * @private
 586  * @ingroup DifferenceEngine
 587  */
 588 class Diff
 589 {
 590         var $edits;
 591
 592         /**
 593          * Constructor.
 594          * Computes diff between sequences of strings.
 595          *
 596          * @param $from_lines array An array of strings.
 597          *                (Typically these are lines from a file.)
 598          * @param $to_lines array An array of strings.
 599          */
 600         function __construct( $from_lines, $to_lines ) {
 601                 $eng = new _DiffEngine;
 602                 $this->edits = $eng->diff( $from_lines, $to_lines );
 603                 // $this->_check($from_lines, $to_lines);
 604         }
 605
 606         /**
 607          * Compute reversed Diff.
 608          *
 609          * SYNOPSIS:
 610          *
 611          *      $diff = new Diff($lines1, $lines2);
 612          *      $rev = $diff->reverse();
 613          * @return object A Diff object representing the inverse of the
 614          *                                original diff.
 615          */
 616         function reverse () {
 617                 $rev = $this;
 618                 $rev->edits = array();
 619                 foreach ( $this->edits as $edit ) {
 620                         $rev->edits[] = $edit->reverse();
 621                 }
 622                 return $rev;
 623         }
 624
 625         /**
 626          * Check for empty diff.
 627          *
 628          * @return bool True iff two sequences were identical.
 629          */
 630         function isEmpty () {
 631                 foreach ( $this->edits as $edit ) {
 632                         if ( $edit->type != 'copy' ) {
 633                                 return false;
 634                         }
 635                 }
 636                 return true;
 637         }
 638
 639         /**
 640          * Compute the length of the Longest Common Subsequence (LCS).
 641          *
 642          * This is mostly for diagnostic purposed.
 643          *
 644          * @return int The length of the LCS.
 645          */
 646         function lcs () {
 647                 $lcs = 0;
 648                 foreach ( $this->edits as $edit ) {
 649                         if ( $edit->type == 'copy' ) {
 650                                 $lcs += sizeof( $edit->orig );
 651                         }
 652                 }
 653                 return $lcs;
 654         }
 655
 656         /**
 657          * Get the original set of lines.
 658          *
 659          * This reconstructs the $from_lines parameter passed to the
 660          * constructor.
 661          *
 662          * @return array The original sequence of strings.
 663          */
 664         function orig() {
 665                 $lines = array();
 666
 667                 foreach ( $this->edits as $edit ) {
 668                         if ( $edit->orig ) {
 669                                 array_splice( $lines, sizeof( $lines ), 0, $edit->orig );
 670                         }
 671                 }
 672                 return $lines;
 673         }
 674
 675         /**
 676          * Get the closing set of lines.
 677          *
 678          * This reconstructs the $to_lines parameter passed to the
 679          * constructor.
 680          *
 681          * @return array The sequence of strings.
 682          */
 683         function closing() {
 684                 $lines = array();
 685
 686                 foreach ( $this->edits as $edit ) {
 687                         if ( $edit->closing ) {
 688                                 array_splice( $lines, sizeof( $lines ), 0, $edit->closing );
 689                         }
 690                 }
 691                 return $lines;
 692         }
 693
 694         /**
 695          * Check a Diff for validity.
 696          *
 697          * This is here only for debugging purposes.
 698          */
 699         function _check ( $from_lines, $to_lines ) {
 700                 wfProfileIn( __METHOD__ );
 701                 if ( serialize( $from_lines ) != serialize( $this->orig() ) ) {
 702                         trigger_error( "Reconstructed original doesn't match", E_USER_ERROR );
 703                 }
 704                 if ( serialize( $to_lines ) != serialize( $this->closing() ) ) {
 705                         trigger_error( "Reconstructed closing doesn't match", E_USER_ERROR );
 706                 }
 707
 708                 $rev = $this->reverse();
 709                 if ( serialize( $to_lines ) != serialize( $rev->orig() ) ) {
 710                         trigger_error( "Reversed original doesn't match", E_USER_ERROR );
 711                 }
 712                 if ( serialize( $from_lines ) != serialize( $rev->closing() ) ) {
 713                         trigger_error( "Reversed closing doesn't match", E_USER_ERROR );
 714                 }
 715
 716
 717                 $prevtype = 'none';
 718                 foreach ( $this->edits as $edit ) {
 719                         if ( $prevtype == $edit->type ) {
 720                                 trigger_error( "Edit sequence is non-optimal", E_USER_ERROR );
 721                         }
 722                         $prevtype = $edit->type;
 723                 }
 724
 725                 $lcs = $this->lcs();
 726                 trigger_error( 'Diff okay: LCS = ' . $lcs, E_USER_NOTICE );
 727                 wfProfileOut( __METHOD__ );
 728         }
 729 }
 730
 731 /**
 732  * @todo document, bad name.
 733  * @private
 734  * @ingroup DifferenceEngine
 735  */
 736 class MappedDiff extends Diff
 737 {
 738         /**
 739          * Constructor.
 740          *
 741          * Computes diff between sequences of strings.
 742          *
 743          * This can be used to compute things like
 744          * case-insensitve diffs, or diffs which ignore
 745          * changes in white-space.
 746          *
 747          * @param $from_lines array An array of strings.
 748          *      (Typically these are lines from a file.)
 749          *
 750          * @param $to_lines array An array of strings.
 751          *
 752          * @param $mapped_from_lines array This array should
 753          *      have the same size number of elements as $from_lines.
 754          *      The elements in $mapped_from_lines and
 755          *      $mapped_to_lines are what is actually compared
 756          *      when computing the diff.
 757          *
 758          * @param $mapped_to_lines array This array should
 759          *      have the same number of elements as $to_lines.
 760          */
 761         function __construct( $from_lines, $to_lines,
 762                 $mapped_from_lines, $mapped_to_lines ) {
 763                 wfProfileIn( __METHOD__ );
 764
 765                 assert( sizeof( $from_lines ) == sizeof( $mapped_from_lines ) );
 766                 assert( sizeof( $to_lines ) == sizeof( $mapped_to_lines ) );
 767
 768                 parent::__construct( $mapped_from_lines, $mapped_to_lines );
 769
 770                 $xi = $yi = 0;
 771                 for ( $i = 0; $i < sizeof( $this->edits ); $i++ ) {
 772                         $orig = &$this->edits[$i]->orig;
 773                         if ( is_array( $orig ) ) {
 774                                 $orig = array_slice( $from_lines, $xi, sizeof( $orig ) );
 775                                 $xi += sizeof( $orig );
 776                         }
 777
 778                         $closing = &$this->edits[$i]->closing;
 779                         if ( is_array( $closing ) ) {
 780                                 $closing = array_slice( $to_lines, $yi, sizeof( $closing ) );
 781                                 $yi += sizeof( $closing );
 782                         }
 783                 }
 784                 wfProfileOut( __METHOD__ );
 785         }
 786 }
 787
 788 /**
 789  * A class to format Diffs
 790  *
 791  * This class formats the diff in classic diff format.
 792  * It is intended that this class be customized via inheritance,
 793  * to obtain fancier outputs.
 794  * @todo document
 795  * @private
 796  * @ingroup DifferenceEngine
 797  */
 798 class DiffFormatter {
 799         /**
 800          * Number of leading context "lines" to preserve.
 801          *
 802          * This should be left at zero for this class, but subclasses
 803          * may want to set this to other values.
 804          */
 805         var $leading_context_lines = 0;
 806
 807         /**
 808          * Number of trailing context "lines" to preserve.
 809          *
 810          * This should be left at zero for this class, but subclasses
 811          * may want to set this to other values.
 812          */
 813         var $trailing_context_lines = 0;
 814
 815         /**
 816          * Format a diff.
 817          *
 818          * @param $diff Diff A Diff object.
 819          * @return string The formatted output.
 820          */
 821         function format( $diff ) {
 822                 wfProfileIn( __METHOD__ );
 823
 824                 $xi = $yi = 1;
 825                 $block = false;
 826                 $context = array();
 827
 828                 $nlead = $this->leading_context_lines;
 829                 $ntrail = $this->trailing_context_lines;
 830
 831                 $this->_start_diff();
 832
 833                 foreach ( $diff->edits as $edit ) {
 834                         if ( $edit->type == 'copy' ) {
 835                                 if ( is_array( $block ) ) {
 836                                         if ( sizeof( $edit->orig ) <= $nlead + $ntrail ) {
 837                                                 $block[] = $edit;
 838                                         }
 839                                         else {
 840                                                 if ( $ntrail ) {
 841                                                         $context = array_slice( $edit->orig, 0, $ntrail );
 842                                                         $block[] = new _DiffOp_Copy( $context );
 843                                                 }
 844                                                 $this->_block( $x0, $ntrail + $xi - $x0,
 845                                                         $y0, $ntrail + $yi - $y0,
 846                                                         $block );
 847                                                 $block = false;
 848                                         }
 849                                 }
 850                                 $context = $edit->orig;
 851                         } else {
 852                                 if ( ! is_array( $block ) ) {
 853                                         $context = array_slice( $context, sizeof( $context ) - $nlead );
 854                                         $x0 = $xi - sizeof( $context );
 855                                         $y0 = $yi - sizeof( $context );
 856                                         $block = array();
 857                                         if ( $context ) {
 858                                                 $block[] = new _DiffOp_Copy( $context );
 859                                         }
 860                                 }
 861                                 $block[] = $edit;
 862                         }
 863
 864                         if ( $edit->orig ) {
 865                                 $xi += sizeof( $edit->orig );
 866                         }
 867                         if ( $edit->closing ) {
 868                                 $yi += sizeof( $edit->closing );
 869                         }
 870                 }
 871
 872                 if ( is_array( $block ) ) {
 873                         $this->_block( $x0, $xi - $x0,
 874                                 $y0, $yi - $y0,
 875                                 $block );
 876                 }
 877
 878                 $end = $this->_end_diff();
 879                 wfProfileOut( __METHOD__ );
 880                 return $end;
 881         }
 882
 883         function _block( $xbeg, $xlen, $ybeg, $ylen, &$edits ) {
 884                 wfProfileIn( __METHOD__ );
 885                 $this->_start_block( $this->_block_header( $xbeg, $xlen, $ybeg, $ylen ) );
 886                 foreach ( $edits as $edit ) {
 887                         if ( $edit->type == 'copy' ) {
 888                                 $this->_context( $edit->orig );
 889                         } elseif ( $edit->type == 'add' ) {
 890                                 $this->_added( $edit->closing );
 891                         } elseif ( $edit->type == 'delete' ) {
 892                                 $this->_deleted( $edit->orig );
 893                         } elseif ( $edit->type == 'change' ) {
 894                                 $this->_changed( $edit->orig, $edit->closing );
 895                         } else {
 896                                 trigger_error( 'Unknown edit type', E_USER_ERROR );
 897                         }
 898                 }
 899                 $this->_end_block();
 900                 wfProfileOut( __METHOD__ );
 901         }
 902
 903         function _start_diff() {
 904                 ob_start();
 905         }
 906
 907         function _end_diff() {
 908                 $val = ob_get_contents();
 909                 ob_end_clean();
 910                 return $val;
 911         }
 912
 913         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
 914                 if ( $xlen > 1 ) {
 915                         $xbeg .= "," . ( $xbeg + $xlen - 1 );
 916                 }
 917                 if ( $ylen > 1 ) {
 918                         $ybeg .= "," . ( $ybeg + $ylen - 1 );
 919                 }
 920
 921                 return $xbeg . ( $xlen ? ( $ylen ? 'c' : 'd' ) : 'a' ) . $ybeg;
 922         }
 923
 924         function _start_block( $header ) {
 925                 echo $header . "\n";
 926         }
 927
 928         function _end_block() {
 929         }
 930
 931         function _lines( $lines, $prefix = ' ' ) {
 932                 foreach ( $lines as $line ) {
 933                         echo "$prefix $line\n";
 934                 }
 935         }
 936
 937         function _context( $lines ) {
 938                 $this->_lines( $lines );
 939         }
 940
 941         function _added( $lines ) {
 942                 $this->_lines( $lines, '>' );
 943         }
 944         function _deleted( $lines ) {
 945                 $this->_lines( $lines, '<' );
 946         }
 947
 948         function _changed( $orig, $closing ) {
 949                 $this->_deleted( $orig );
 950                 echo "---\n";
 951                 $this->_added( $closing );
 952         }
 953 }
 954
 955 /**
 956  * A formatter that outputs unified diffs
 957  * @ingroup DifferenceEngine
 958  */
 959
 960 class UnifiedDiffFormatter extends DiffFormatter {
 961         var $leading_context_lines = 2;
 962         var $trailing_context_lines = 2;
 963
 964         function _added( $lines ) {
 965                 $this->_lines( $lines, '+' );
 966         }
 967         function _deleted( $lines ) {
 968                 $this->_lines( $lines, '-' );
 969         }
 970         function _changed( $orig, $closing ) {
 971                 $this->_deleted( $orig );
 972                 $this->_added( $closing );
 973         }
 974         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
 975                 return "@@ -$xbeg,$xlen +$ybeg,$ylen @@";
 976         }
 977 }
 978
 979 /**
 980  * A pseudo-formatter that just passes along the Diff::$edits array
 981  * @ingroup DifferenceEngine
 982  */
 983 class ArrayDiffFormatter extends DiffFormatter {
 984         function format( $diff ) {
 985                 $oldline = 1;
 986                 $newline = 1;
 987                 $retval = array();
 988                 foreach ( $diff->edits as $edit ) {
 989                         switch( $edit->type ) {
 990                                 case 'add':
 991                                         foreach ( $edit->closing as $l ) {
 992                                                 $retval[] = array(
 993                                                                 'action' => 'add',
 994                                                                 'new' => $l,
 995                                                                 'newline' => $newline++
 996                                                 );
 997                                         }
 998                                         break;
 999                                 case 'delete':
1000                                         foreach ( $edit->orig as $l ) {
1001                                                 $retval[] = array(
1002                                                                 'action' => 'delete',
1003                                                                 'old' => $l,
1004                                                                 'oldline' => $oldline++,
1005                                                 );
1006                                         }
1007                                         break;
1008                                 case 'change':
1009                                         foreach ( $edit->orig as $i => $l ) {
1010                                                 $retval[] = array(
1011                                                                 'action' => 'change',
1012                                                                 'old' => $l,
1013                                                                 'new' => @$edit->closing[$i],
1014                                                                 'oldline' => $oldline++,
1015                                                                 'newline' => $newline++,
1016                                                 );
1017                                         }
1018                                         break;
1019                                 case 'copy':
1020                                         $oldline += count( $edit->orig );
1021                                         $newline += count( $edit->orig );
1022                         }
1023                 }
1024                 return $retval;
1025         }
1026 }
1027
1028 /**
1029  *      Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
1030  *
1031  */
1032
1033 define( 'NBSP', '&#160;' ); // iso-8859-x non-breaking space.
1034
1035 /**
1036  * @todo document
1037  * @private
1038  * @ingroup DifferenceEngine
1039  */
1040 class _HWLDF_WordAccumulator {
1041         function __construct () {
1042                 $this->_lines = array();
1043                 $this->_line = '';
1044                 $this->_group = '';
1045                 $this->_tag = '';
1046         }
1047
1048         function _flushGroup ( $new_tag ) {
1049                 if ( $this->_group !== '' ) {
1050                         if ( $this->_tag == 'ins' ) {
1051                                 $this->_line .= '<ins class="diffchange diffchange-inline">' .
1052                                                 htmlspecialchars ( $this->_group ) . '</ins>';
1053                         } elseif ( $this->_tag == 'del' ) {
1054                                 $this->_line .= '<del class="diffchange diffchange-inline">' .
1055                                                 htmlspecialchars ( $this->_group ) . '</del>';
1056                         } else {
1057                                 $this->_line .= htmlspecialchars ( $this->_group );
1058                         }
1059                 }
1060                 $this->_group = '';
1061                 $this->_tag = $new_tag;
1062         }
1063
1064         function _flushLine ( $new_tag ) {
1065                 $this->_flushGroup( $new_tag );
1066                 if ( $this->_line != '' ) {
1067                         array_push ( $this->_lines, $this->_line );
1068                 } else {
1069                         # make empty lines visible by inserting an NBSP
1070                         array_push ( $this->_lines, NBSP );
1071                 }
1072                 $this->_line = '';
1073         }
1074
1075         function addWords ( $words, $tag = '' ) {
1076                 if ( $tag != $this->_tag ) {
1077                         $this->_flushGroup( $tag );
1078                 }
1079
1080                 foreach ( $words as $word ) {
1081                         // new-line should only come as first char of word.
1082                         if ( $word == '' ) {
1083                                 continue;
1084                         }
1085                         if ( $word[0] == "\n" ) {
1086                                 $this->_flushLine( $tag );
1087                                 $word = substr( $word, 1 );
1088                         }
1089                         assert( !strstr( $word, "\n" ) );
1090                         $this->_group .= $word;
1091                 }
1092         }
1093
1094         function getLines() {
1095                 $this->_flushLine( '~done' );
1096                 return $this->_lines;
1097         }
1098 }
1099
1100 /**
1101  * @todo document
1102  * @private
1103  * @ingroup DifferenceEngine
1104  */
1105 class WordLevelDiff extends MappedDiff {
1106         const MAX_LINE_LENGTH = 10000;
1107
1108         function __construct ( $orig_lines, $closing_lines ) {
1109                 wfProfileIn( __METHOD__ );
1110
1111                 list ( $orig_words, $orig_stripped ) = $this->_split( $orig_lines );
1112                 list ( $closing_words, $closing_stripped ) = $this->_split( $closing_lines );
1113
1114                 parent::__construct( $orig_words, $closing_words,
1115                 $orig_stripped, $closing_stripped );
1116                 wfProfileOut( __METHOD__ );
1117         }
1118
1119         function _split( $lines ) {
1120                 wfProfileIn( __METHOD__ );
1121
1122                 $words = array();
1123                 $stripped = array();
1124                 $first = true;
1125                 foreach ( $lines as $line ) {
1126                         # If the line is too long, just pretend the entire line is one big word
1127                         # This prevents resource exhaustion problems
1128                         if ( $first ) {
1129                                 $first = false;
1130                         } else {
1131                                 $words[] = "\n";
1132                                 $stripped[] = "\n";
1133                         }
1134                         if ( strlen( $line ) > self::MAX_LINE_LENGTH ) {
1135                                 $words[] = $line;
1136                                 $stripped[] = $line;
1137                         } else {
1138                                 $m = array();
1139                                 if ( preg_match_all( '/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
1140                                         $line, $m ) )
1141                                 {
1142                                         $words = array_merge( $words, $m[0] );
1143                                         $stripped = array_merge( $stripped, $m[1] );
1144                                 }
1145                         }
1146                 }
1147                 wfProfileOut( __METHOD__ );
1148                 return array( $words, $stripped );
1149         }
1150
1151         function orig () {
1152                 wfProfileIn( __METHOD__ );
1153                 $orig = new _HWLDF_WordAccumulator;
1154
1155                 foreach ( $this->edits as $edit ) {
1156                         if ( $edit->type == 'copy' ) {
1157                                 $orig->addWords( $edit->orig );
1158                         } elseif ( $edit->orig ) {
1159                                 $orig->addWords( $edit->orig, 'del' );
1160                         }
1161                 }
1162                 $lines = $orig->getLines();
1163                 wfProfileOut( __METHOD__ );
1164                 return $lines;
1165         }
1166
1167         function closing () {
1168                 wfProfileIn( __METHOD__ );
1169                 $closing = new _HWLDF_WordAccumulator;
1170
1171                 foreach ( $this->edits as $edit ) {
1172                         if ( $edit->type == 'copy' ) {
1173                                 $closing->addWords( $edit->closing );
1174                         } elseif ( $edit->closing ) {
1175                                 $closing->addWords( $edit->closing, 'ins' );
1176                         }
1177                 }
1178                 $lines = $closing->getLines();
1179                 wfProfileOut( __METHOD__ );
1180                 return $lines;
1181         }
1182 }
1183
1184 /**
1185  * Wikipedia Table style diff formatter.
1186  * @todo document
1187  * @private
1188  * @ingroup DifferenceEngine
1189  */
1190 class TableDiffFormatter extends DiffFormatter {
1191         function __construct() {
1192                 $this->leading_context_lines = 2;
1193                 $this->trailing_context_lines = 2;
1194         }
1195
1196         public static function escapeWhiteSpace( $msg ) {
1197                 $msg = preg_replace( '/^ /m', '&#160; ', $msg );
1198                 $msg = preg_replace( '/ $/m', ' &#160;', $msg );
1199                 $msg = preg_replace( '/  /', '&#160; ', $msg );
1200                 return $msg;
1201         }
1202
1203         function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
1204                 $r = '<tr><td colspan="2" class="diff-lineno"><!--LINE ' . $xbeg . "--></td>\n" .
1205                   '<td colspan="2" class="diff-lineno"><!--LINE ' . $ybeg . "--></td></tr>\n";
1206                 return $r;
1207         }
1208
1209         function _start_block( $header ) {
1210                 echo $header;
1211         }
1212
1213         function _end_block() {
1214         }
1215
1216         function _lines( $lines, $prefix = ' ', $color = 'white' ) {
1217         }
1218
1219         # HTML-escape parameter before calling this
1220         function addedLine( $line ) {
1221                 return $this->wrapLine( '+', 'diff-addedline', $line );
1222         }
1223
1224         # HTML-escape parameter before calling this
1225         function deletedLine( $line ) {
1226                 return $this->wrapLine( '−', 'diff-deletedline', $line );
1227         }
1228
1229         # HTML-escape parameter before calling this
1230         function contextLine( $line ) {
1231                 return $this->wrapLine( '&#160;', 'diff-context', $line );
1232         }
1233
1234         private function wrapLine( $marker, $class, $line ) {
1235                 if ( $line !== '' ) {
1236                         // The <div> wrapper is needed for 'overflow: auto' style to scroll properly
1237                         $line = Xml::tags( 'div', null, $this->escapeWhiteSpace( $line ) );
1238                 }
1239                 return "<td class='diff-marker'>$marker</td><td class='$class'>$line</td>";
1240         }
1241
1242         function emptyLine() {
1243                 return '<td colspan="2">&#160;</td>';
1244         }
1245
1246         function _added( $lines ) {
1247                 foreach ( $lines as $line ) {
1248                         echo '<tr>' . $this->emptyLine() .
1249                         $this->addedLine( '<ins class="diffchange">' .
1250                         htmlspecialchars ( $line ) . '</ins>' ) . "</tr>\n";
1251                 }
1252         }
1253
1254         function _deleted( $lines ) {
1255                 foreach ( $lines as $line ) {
1256                         echo '<tr>' . $this->deletedLine( '<del class="diffchange">' .
1257                         htmlspecialchars ( $line ) . '</del>' ) .
1258                         $this->emptyLine() . "</tr>\n";
1259                 }
1260         }
1261
1262         function _context( $lines ) {
1263                 foreach ( $lines as $line ) {
1264                         echo '<tr>' .
1265                         $this->contextLine( htmlspecialchars ( $line ) ) .
1266                         $this->contextLine( htmlspecialchars ( $line ) ) . "</tr>\n";
1267                 }
1268         }
1269
1270         function _changed( $orig, $closing ) {
1271                 wfProfileIn( __METHOD__ );
1272
1273                 $diff = new WordLevelDiff( $orig, $closing );
1274                 $del = $diff->orig();
1275                 $add = $diff->closing();
1276
1277                 # Notice that WordLevelDiff returns HTML-escaped output.
1278                 # Hence, we will be calling addedLine/deletedLine without HTML-escaping.
1279
1280                 while ( $line = array_shift( $del ) ) {
1281                         $aline = array_shift( $add );
1282                         echo '<tr>' . $this->deletedLine( $line ) .
1283                         $this->addedLine( $aline ) . "</tr>\n";
1284                 }
1285                 foreach ( $add as $line ) {     # If any leftovers
1286                         echo '<tr>' . $this->emptyLine() .
1287                         $this->addedLine( $line ) . "</tr>\n";
1288                 }
1289                 wfProfileOut( __METHOD__ );
1290         }
1291 }