includes/diff/DairikiDiff.php

   1 <?php
   2 /**
   3  * A PHP diff engine for phpwiki. (Taken from phpwiki-1.3.3)
   4  *
   5  * Copyright © 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
   6  * You may copy this code freely under the conditions of the GPL.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup DifferenceEngine
  25  * @defgroup DifferenceEngine DifferenceEngine
  26  */
  27
  28 /**
  29  * @todo document
  30  * @private
  31  * @ingroup DifferenceEngine
  32  */
  33 abstract class DiffOp {
  34
  35         /**
  36          * @var string
  37          */
  38         public $type;
  39
  40         /**
  41          * @var string[]
  42          */
  43         public $orig;
  44
  45         /**
  46          * @var string[]
  47          */
  48         public $closing;
  49
  50         /**
  51          * @return string
  52          */
  53         public function getType() {
  54                 return $this->type;
  55         }
  56
  57         /**
  58          * @return string[]
  59          */
  60         public function getOrig() {
  61                 return $this->orig;
  62         }
  63
  64         /**
  65          * @param int $i
  66          * @return string|null
  67          */
  68         public function getClosing( $i = null ) {
  69                 if ( $i === null ) {
  70                         return $this->closing;
  71                 }
  72                 if ( array_key_exists( $i, $this->closing ) ) {
  73                         return $this->closing[$i];
  74                 }
  75                 return null;
  76         }
  77
  78         abstract public function reverse();
  79
  80         /**
  81          * @return int
  82          */
  83         public function norig() {
  84                 return $this->orig ? count( $this->orig ) : 0;
  85         }
  86
  87         /**
  88          * @return int
  89          */
  90         public function nclosing() {
  91                 return $this->closing ? count( $this->closing ) : 0;
  92         }
  93 }
  94
  95 /**
  96  * @todo document
  97  * @private
  98  * @ingroup DifferenceEngine
  99  */
 100 class DiffOpCopy extends DiffOp {
 101         public $type = 'copy';
 102
 103         public function __construct( $orig, $closing = false ) {
 104                 if ( !is_array( $closing ) ) {
 105                         $closing = $orig;
 106                 }
 107                 $this->orig = $orig;
 108                 $this->closing = $closing;
 109         }
 110
 111         /**
 112          * @return DiffOpCopy
 113          */
 114         public function reverse() {
 115                 return new DiffOpCopy( $this->closing, $this->orig );
 116         }
 117 }
 118
 119 /**
 120  * @todo document
 121  * @private
 122  * @ingroup DifferenceEngine
 123  */
 124 class DiffOpDelete extends DiffOp {
 125         public $type = 'delete';
 126
 127         public function __construct( $lines ) {
 128                 $this->orig = $lines;
 129                 $this->closing = false;
 130         }
 131
 132         /**
 133          * @return DiffOpAdd
 134          */
 135         public function reverse() {
 136                 return new DiffOpAdd( $this->orig );
 137         }
 138 }
 139
 140 /**
 141  * @todo document
 142  * @private
 143  * @ingroup DifferenceEngine
 144  */
 145 class DiffOpAdd extends DiffOp {
 146         public $type = 'add';
 147
 148         public function __construct( $lines ) {
 149                 $this->closing = $lines;
 150                 $this->orig = false;
 151         }
 152
 153         /**
 154          * @return DiffOpDelete
 155          */
 156         public function reverse() {
 157                 return new DiffOpDelete( $this->closing );
 158         }
 159 }
 160
 161 /**
 162  * @todo document
 163  * @private
 164  * @ingroup DifferenceEngine
 165  */
 166 class DiffOpChange extends DiffOp {
 167         public $type = 'change';
 168
 169         public function __construct( $orig, $closing ) {
 170                 $this->orig = $orig;
 171                 $this->closing = $closing;
 172         }
 173
 174         /**
 175          * @return DiffOpChange
 176          */
 177         public function reverse() {
 178                 return new DiffOpChange( $this->closing, $this->orig );
 179         }
 180 }
 181
 182 /**
 183  * Class used internally by Diff to actually compute the diffs.
 184  *
 185  * The algorithm used here is mostly lifted from the perl module
 186  * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
 187  *     http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
 188  *
 189  * More ideas are taken from:
 190  *     http://www.ics.uci.edu/~eppstein/161/960229.html
 191  *
 192  * Some ideas are (and a bit of code) are from from analyze.c, from GNU
 193  * diffutils-2.7, which can be found at:
 194  *     ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
 195  *
 196  * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
 197  * are my own.
 198  *
 199  * Line length limits for robustness added by Tim Starling, 2005-08-31
 200  * Alternative implementation added by Guy Van den Broeck, 2008-07-30
 201  *
 202  * @author Geoffrey T. Dairiki, Tim Starling, Guy Van den Broeck
 203  * @private
 204  * @ingroup DifferenceEngine
 205  */
 206 class DiffEngine {
 207         const MAX_XREF_LENGTH = 10000;
 208
 209         protected $xchanged, $ychanged;
 210
 211         protected $xv = array(), $yv = array();
 212         protected $xind = array(), $yind = array();
 213
 214         protected $seq = array(), $in_seq = array();
 215
 216         protected $lcs = 0;
 217
 218         /**
 219          * @param string[] $from_lines
 220          * @param string[] $to_lines
 221          *
 222          * @return DiffOp[]
 223          */
 224         public function diff( $from_lines, $to_lines ) {
 225                 wfProfileIn( __METHOD__ );
 226
 227                 // Diff and store locally
 228                 $this->diffLocal( $from_lines, $to_lines );
 229
 230                 // Merge edits when possible
 231                 $this->shiftBoundaries( $from_lines, $this->xchanged, $this->ychanged );
 232                 $this->shiftBoundaries( $to_lines, $this->ychanged, $this->xchanged );
 233
 234                 // Compute the edit operations.
 235                 $n_from = count( $from_lines );
 236                 $n_to = count( $to_lines );
 237
 238                 $edits = array();
 239                 $xi = $yi = 0;
 240                 while ( $xi < $n_from || $yi < $n_to ) {
 241                         assert( '$yi < $n_to || $this->xchanged[$xi]' );
 242                         assert( '$xi < $n_from || $this->ychanged[$yi]' );
 243
 244                         // Skip matching "snake".
 245                         $copy = array();
 246                         while ( $xi < $n_from && $yi < $n_to
 247                                 && !$this->xchanged[$xi] && !$this->ychanged[$yi]
 248                         ) {
 249                                 $copy[] = $from_lines[$xi++];
 250                                 ++$yi;
 251                         }
 252                         if ( $copy ) {
 253                                 $edits[] = new DiffOpCopy( $copy );
 254                         }
 255
 256                         // Find deletes & adds.
 257                         $delete = array();
 258                         while ( $xi < $n_from && $this->xchanged[$xi] ) {
 259                                 $delete[] = $from_lines[$xi++];
 260                         }
 261
 262                         $add = array();
 263                         while ( $yi < $n_to && $this->ychanged[$yi] ) {
 264                                 $add[] = $to_lines[$yi++];
 265                         }
 266
 267                         if ( $delete && $add ) {
 268                                 $edits[] = new DiffOpChange( $delete, $add );
 269                         } elseif ( $delete ) {
 270                                 $edits[] = new DiffOpDelete( $delete );
 271                         } elseif ( $add ) {
 272                                 $edits[] = new DiffOpAdd( $add );
 273                         }
 274                 }
 275                 wfProfileOut( __METHOD__ );
 276
 277                 return $edits;
 278         }
 279
 280         /**
 281          * @param string[] $from_lines
 282          * @param string[] $to_lines
 283          */
 284         private function diffLocal( $from_lines, $to_lines ) {
 285                 global $wgExternalDiffEngine;
 286                 wfProfileIn( __METHOD__ );
 287
 288                 if ( $wgExternalDiffEngine == 'wikidiff3' ) {
 289                         // wikidiff3
 290                         $wikidiff3 = new WikiDiff3();
 291                         $wikidiff3->diff( $from_lines, $to_lines );
 292                         $this->xchanged = $wikidiff3->removed;
 293                         $this->ychanged = $wikidiff3->added;
 294                         unset( $wikidiff3 );
 295                 } else {
 296                         // old diff
 297                         $n_from = count( $from_lines );
 298                         $n_to = count( $to_lines );
 299                         $this->xchanged = $this->ychanged = array();
 300                         $this->xv = $this->yv = array();
 301                         $this->xind = $this->yind = array();
 302                         unset( $this->seq );
 303                         unset( $this->in_seq );
 304                         unset( $this->lcs );
 305
 306                         // Skip leading common lines.
 307                         for ( $skip = 0; $skip < $n_from && $skip < $n_to; $skip++ ) {
 308                                 if ( $from_lines[$skip] !== $to_lines[$skip] ) {
 309                                         break;
 310                                 }
 311                                 $this->xchanged[$skip] = $this->ychanged[$skip] = false;
 312                         }
 313                         // Skip trailing common lines.
 314                         $xi = $n_from;
 315                         $yi = $n_to;
 316                         for ( $endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++ ) {
 317                                 if ( $from_lines[$xi] !== $to_lines[$yi] ) {
 318                                         break;
 319                                 }
 320                                 $this->xchanged[$xi] = $this->ychanged[$yi] = false;
 321                         }
 322
 323                         // Ignore lines which do not exist in both files.
 324                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 325                                 $xhash[$this->lineHash( $from_lines[$xi] )] = 1;
 326                         }
 327
 328                         for ( $yi = $skip; $yi < $n_to - $endskip; $yi++ ) {
 329                                 $line = $to_lines[$yi];
 330                                 if ( ( $this->ychanged[$yi] = empty( $xhash[$this->lineHash( $line )] ) ) ) {
 331                                         continue;
 332                                 }
 333                                 $yhash[$this->lineHash( $line )] = 1;
 334                                 $this->yv[] = $line;
 335                                 $this->yind[] = $yi;
 336                         }
 337                         for ( $xi = $skip; $xi < $n_from - $endskip; $xi++ ) {
 338                                 $line = $from_lines[$xi];
 339                                 if ( ( $this->xchanged[$xi] = empty( $yhash[$this->lineHash( $line )] ) ) ) {
 340                                         continue;
 341                                 }
 342                                 $this->xv[] = $line;
 343                                 $this->xind[] = $xi;
 344                         }
 345
 346                         // Find the LCS.
 347                         $this->compareSeq( 0, count( $this->xv ), 0, count( $this->yv ) );
 348                 }
 349                 wfProfileOut( __METHOD__ );
 350         }
 351
 352         /**
 353          * Returns the whole line if it's small enough, or the MD5 hash otherwise
 354          *
 355          * @param string $line
 356          *
 357          * @return string
 358          */
 359         private function lineHash( $line ) {
 360                 if ( strlen( $line ) > self::MAX_XREF_LENGTH ) {
 361                         return md5( $line );
 362                 } else {
 363                         return $line;
 364                 }
 365         }
 366
 367         /**
 368          * Divide the Largest Common Subsequence (LCS) of the sequences
 369          * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
 370          * sized segments.
 371          *
 372          * Returns (LCS, PTS). LCS is the length of the LCS. PTS is an
 373          * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
 374          * sub sequences.  The first sub-sequence is contained in [X0, X1),
 375          * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
 376          * that (X0, Y0) == (XOFF, YOFF) and
 377          * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
 378          *
 379          * This function assumes that the first lines of the specified portions
 380          * of the two files do not match, and likewise that the last lines do not
 381          * match.  The caller must trim matching lines from the beginning and end
 382          * of the portions it is going to specify.
 383          *
 384          * @param int $xoff
 385          * @param int $xlim
 386          * @param int $yoff
 387          * @param int $ylim
 388          * @param int $nchunks
 389          *
 390          * @return array List of two elements, integer and array[].
 391          */
 392         private function diag( $xoff, $xlim, $yoff, $ylim, $nchunks ) {
 393                 $flip = false;
 394
 395                 if ( $xlim - $xoff > $ylim - $yoff ) {
 396                         // Things seems faster (I'm not sure I understand why)
 397                         // when the shortest sequence in X.
 398                         $flip = true;
 399                         list( $xoff, $xlim, $yoff, $ylim ) = array( $yoff, $ylim, $xoff, $xlim );
 400                 }
 401
 402                 if ( $flip ) {
 403                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 404                                 $ymatches[$this->xv[$i]][] = $i;
 405                         }
 406                 } else {
 407                         for ( $i = $ylim - 1; $i >= $yoff; $i-- ) {
 408                                 $ymatches[$this->yv[$i]][] = $i;
 409                         }
 410                 }
 411
 412                 $this->lcs = 0;
 413                 $this->seq[0] = $yoff - 1;
 414                 $this->in_seq = array();
 415                 $ymids[0] = array();
 416
 417                 $numer = $xlim - $xoff + $nchunks - 1;
 418                 $x = $xoff;
 419                 for ( $chunk = 0; $chunk < $nchunks; $chunk++ ) {
 420                         if ( $chunk > 0 ) {
 421                                 for ( $i = 0; $i <= $this->lcs; $i++ ) {
 422                                         $ymids[$i][$chunk - 1] = $this->seq[$i];
 423                                 }
 424                         }
 425
 426                         $x1 = $xoff + (int)( ( $numer + ( $xlim - $xoff ) * $chunk ) / $nchunks );
 427                         // @codingStandardsIgnoreFile Ignore Squiz.WhiteSpace.SemicolonSpacing.Incorrect
 428                         for ( ; $x < $x1; $x++ ) {
 429                                 // @codingStandardsIgnoreEnd
 430                                 $line = $flip ? $this->yv[$x] : $this->xv[$x];
 431                                 if ( empty( $ymatches[$line] ) ) {
 432                                         continue;
 433                                 }
 434
 435                                 $k = 0;
 436                                 $matches = $ymatches[$line];
 437                                 reset( $matches );
 438                                 while ( list( , $y ) = each( $matches ) ) {
 439                                         if ( empty( $this->in_seq[$y] ) ) {
 440                                                 $k = $this->lcsPos( $y );
 441                                                 assert( '$k > 0' );
 442                                                 $ymids[$k] = $ymids[$k - 1];
 443                                                 break;
 444                                         }
 445                                 }
 446
 447                                 while ( list( , $y ) = each( $matches ) ) {
 448                                         if ( $y > $this->seq[$k - 1] ) {
 449                                                 assert( '$y < $this->seq[$k]' );
 450                                                 // Optimization: this is a common case:
 451                                                 //      next match is just replacing previous match.
 452                                                 $this->in_seq[$this->seq[$k]] = false;
 453                                                 $this->seq[$k] = $y;
 454                                                 $this->in_seq[$y] = 1;
 455                                         } elseif ( empty( $this->in_seq[$y] ) ) {
 456                                                 $k = $this->lcsPos( $y );
 457                                                 assert( '$k > 0' );
 458                                                 $ymids[$k] = $ymids[$k - 1];
 459                                         }
 460                                 }
 461                         }
 462                 }
 463
 464                 $seps[] = $flip ? array( $yoff, $xoff ) : array( $xoff, $yoff );
 465                 $ymid = $ymids[$this->lcs];
 466                 for ( $n = 0; $n < $nchunks - 1; $n++ ) {
 467                         $x1 = $xoff + (int)( ( $numer + ( $xlim - $xoff ) * $n ) / $nchunks );
 468                         $y1 = $ymid[$n] + 1;
 469                         $seps[] = $flip ? array( $y1, $x1 ) : array( $x1, $y1 );
 470                 }
 471                 $seps[] = $flip ? array( $ylim, $xlim ) : array( $xlim, $ylim );
 472
 473                 return array( $this->lcs, $seps );
 474         }
 475
 476         /**
 477          * @param int $ypos
 478          *
 479          * @return int
 480          */
 481         private function lcsPos( $ypos ) {
 482                 $end = $this->lcs;
 483                 if ( $end == 0 || $ypos > $this->seq[$end] ) {
 484                         $this->seq[++$this->lcs] = $ypos;
 485                         $this->in_seq[$ypos] = 1;
 486
 487                         return $this->lcs;
 488                 }
 489
 490                 $beg = 1;
 491                 while ( $beg < $end ) {
 492                         $mid = (int)( ( $beg + $end ) / 2 );
 493                         if ( $ypos > $this->seq[$mid] ) {
 494                                 $beg = $mid + 1;
 495                         } else {
 496                                 $end = $mid;
 497                         }
 498                 }
 499
 500                 assert( '$ypos != $this->seq[$end]' );
 501
 502                 $this->in_seq[$this->seq[$end]] = false;
 503                 $this->seq[$end] = $ypos;
 504                 $this->in_seq[$ypos] = 1;
 505
 506                 return $end;
 507         }
 508
 509         /**
 510          * Find LCS of two sequences.
 511          *
 512          * The results are recorded in the vectors $this->{x,y}changed[], by
 513          * storing a 1 in the element for each line that is an insertion
 514          * or deletion (ie. is not in the LCS).
 515          *
 516          * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
 517          *
 518          * Note that XLIM, YLIM are exclusive bounds.
 519          * All line numbers are origin-0 and discarded lines are not counted.
 520          *
 521          * @param int $xoff
 522          * @param int $xlim
 523          * @param int $yoff
 524          * @param int $ylim
 525          */
 526         private function compareSeq( $xoff, $xlim, $yoff, $ylim ) {
 527                 // Slide down the bottom initial diagonal.
 528                 while ( $xoff < $xlim && $yoff < $ylim && $this->xv[$xoff] == $this->yv[$yoff] ) {
 529                         ++$xoff;
 530                         ++$yoff;
 531                 }
 532
 533                 // Slide up the top initial diagonal.
 534                 while ( $xlim > $xoff && $ylim > $yoff
 535                         && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]
 536                 ) {
 537                         --$xlim;
 538                         --$ylim;
 539                 }
 540
 541                 if ( $xoff == $xlim || $yoff == $ylim ) {
 542                         $lcs = 0;
 543                 } else {
 544                         // This is ad hoc but seems to work well.
 545                         // $nchunks = sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5);
 546                         // $nchunks = max(2,min(8,(int)$nchunks));
 547                         $nchunks = min( 7, $xlim - $xoff, $ylim - $yoff ) + 1;
 548                         list( $lcs, $seps ) = $this->diag( $xoff, $xlim, $yoff, $ylim, $nchunks );
 549                 }
 550
 551                 if ( $lcs == 0 ) {
 552                         // X and Y sequences have no common subsequence:
 553                         // mark all changed.
 554                         while ( $yoff < $ylim ) {
 555                                 $this->ychanged[$this->yind[$yoff++]] = 1;
 556                         }
 557                         while ( $xoff < $xlim ) {
 558                                 $this->xchanged[$this->xind[$xoff++]] = 1;
 559                         }
 560                 } else {
 561                         // Use the partitions to split this problem into subproblems.
 562                         reset( $seps );
 563                         $pt1 = $seps[0];
 564                         while ( $pt2 = next( $seps ) ) {
 565                                 $this->compareSeq( $pt1[0], $pt2[0], $pt1[1], $pt2[1] );
 566                                 $pt1 = $pt2;
 567                         }
 568                 }
 569         }
 570
 571         /**
 572          * Adjust inserts/deletes of identical lines to join changes
 573          * as much as possible.
 574          *
 575          * We do something when a run of changed lines include a
 576          * line at one end and has an excluded, identical line at the other.
 577          * We are free to choose which identical line is included.
 578          * `compareseq' usually chooses the one at the beginning,
 579          * but usually it is cleaner to consider the following identical line
 580          * to be the "change".
 581          *
 582          * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
 583          */
 584         private function shiftBoundaries( $lines, &$changed, $other_changed ) {
 585                 wfProfileIn( __METHOD__ );
 586                 $i = 0;
 587                 $j = 0;
 588
 589                 assert( 'count($lines) == count($changed)' );
 590                 $len = count( $lines );
 591                 $other_len = count( $other_changed );
 592
 593                 while ( 1 ) {
 594                         /*
 595                          * Scan forwards to find beginning of another run of changes.
 596                          * Also keep track of the corresponding point in the other file.
 597                          *
 598                          * Throughout this code, $i and $j are adjusted together so that
 599                          * the first $i elements of $changed and the first $j elements
 600                          * of $other_changed both contain the same number of zeros
 601                          * (unchanged lines).
 602                          * Furthermore, $j is always kept so that $j == $other_len or
 603                          * $other_changed[$j] == false.
 604                          */
 605                         while ( $j < $other_len && $other_changed[$j] ) {
 606                                 $j++;
 607                         }
 608
 609                         while ( $i < $len && !$changed[$i] ) {
 610                                 assert( '$j < $other_len && ! $other_changed[$j]' );
 611                                 $i++;
 612                                 $j++;
 613                                 while ( $j < $other_len && $other_changed[$j] ) {
 614                                         $j++;
 615                                 }
 616                         }
 617
 618                         if ( $i == $len ) {
 619                                 break;
 620                         }
 621
 622                         $start = $i;
 623
 624                         // Find the end of this run of changes.
 625                         while ( ++$i < $len && $changed[$i] ) {
 626                                 continue;
 627                         }
 628
 629                         do {
 630                                 /*
 631                                  * Record the length of this run of changes, so that
 632                                  * we can later determine whether the run has grown.
 633                                  */
 634                                 $runlength = $i - $start;
 635
 636                                 /*
 637                                  * Move the changed region back, so long as the
 638                                  * previous unchanged line matches the last changed one.
 639                                  * This merges with previous changed regions.
 640                                  */
 641                                 while ( $start > 0 && $lines[$start - 1] == $lines[$i - 1] ) {
 642                                         $changed[--$start] = 1;
 643                                         $changed[--$i] = false;
 644                                         while ( $start > 0 && $changed[$start - 1] ) {
 645                                                 $start--;
 646                                         }
 647                                         assert( '$j > 0' );
 648                                         while ( $other_changed[--$j] ) {
 649                                                 continue;
 650                                         }
 651                                         assert( '$j >= 0 && !$other_changed[$j]' );
 652                                 }
 653
 654                                 /*
 655                                  * Set CORRESPONDING to the end of the changed run, at the last
 656                                  * point where it corresponds to a changed run in the other file.
 657                                  * CORRESPONDING == LEN means no such point has been found.
 658                                  */
 659                                 $corresponding = $j < $other_len ? $i : $len;
 660
 661                                 /*
 662                                  * Move the changed region forward, so long as the
 663                                  * first changed line matches the following unchanged one.
 664                                  * This merges with following changed regions.
 665                                  * Do this second, so that if there are no merges,
 666                                  * the changed region is moved forward as far as possible.
 667                                  */
 668                                 while ( $i < $len && $lines[$start] == $lines[$i] ) {
 669                                         $changed[$start++] = false;
 670                                         $changed[$i++] = 1;
 671                                         while ( $i < $len && $changed[$i] ) {
 672                                                 $i++;
 673                                         }
 674
 675                                         assert( '$j < $other_len && ! $other_changed[$j]' );
 676                                         $j++;
 677                                         if ( $j < $other_len && $other_changed[$j] ) {
 678                                                 $corresponding = $i;
 679                                                 while ( $j < $other_len && $other_changed[$j] ) {
 680                                                         $j++;
 681                                                 }
 682                                         }
 683                                 }
 684                         } while ( $runlength != $i - $start );
 685
 686                         /*
 687                          * If possible, move the fully-merged run of changes
 688                          * back to a corresponding run in the other file.
 689                          */
 690                         while ( $corresponding < $i ) {
 691                                 $changed[--$start] = 1;
 692                                 $changed[--$i] = 0;
 693                                 assert( '$j > 0' );
 694                                 while ( $other_changed[--$j] ) {
 695                                         continue;
 696                                 }
 697                                 assert( '$j >= 0 && !$other_changed[$j]' );
 698                         }
 699                 }
 700                 wfProfileOut( __METHOD__ );
 701         }
 702 }
 703
 704 /**
 705  * Class representing a 'diff' between two sequences of strings.
 706  * @todo document
 707  * @private
 708  * @ingroup DifferenceEngine
 709  */
 710 class Diff {
 711
 712         /**
 713          * @var DiffOp[]
 714          */
 715         public $edits;
 716
 717         /**
 718          * Constructor.
 719          * Computes diff between sequences of strings.
 720          *
 721          * @param string[] $from_lines An array of strings.
 722          *   Typically these are lines from a file.
 723          * @param string[] $to_lines An array of strings.
 724          */
 725         public function __construct( $from_lines, $to_lines ) {
 726                 $eng = new DiffEngine;
 727                 $this->edits = $eng->diff( $from_lines, $to_lines );
 728         }
 729
 730         /**
 731          * @return DiffOp[]
 732          */
 733         public function getEdits() {
 734                 return $this->edits;
 735         }
 736
 737         /**
 738          * Compute reversed Diff.
 739          *
 740          * SYNOPSIS:
 741          *
 742          *    $diff = new Diff($lines1, $lines2);
 743          *    $rev = $diff->reverse();
 744          *
 745          * @return Object A Diff object representing the inverse of the
 746          *   original diff.
 747          */
 748         public function reverse() {
 749                 $rev = $this;
 750                 $rev->edits = array();
 751                 /** @var DiffOp $edit */
 752                 foreach ( $this->edits as $edit ) {
 753                         $rev->edits[] = $edit->reverse();
 754                 }
 755
 756                 return $rev;
 757         }
 758
 759         /**
 760          * Check for empty diff.
 761          *
 762          * @return bool True if two sequences were identical.
 763          */
 764         public function isEmpty() {
 765                 foreach ( $this->edits as $edit ) {
 766                         if ( $edit->type != 'copy' ) {
 767                                 return false;
 768                         }
 769                 }
 770
 771                 return true;
 772         }
 773
 774         /**
 775          * Compute the length of the Longest Common Subsequence (LCS).
 776          *
 777          * This is mostly for diagnostic purposed.
 778          *
 779          * @return int The length of the LCS.
 780          */
 781         public function lcs() {
 782                 $lcs = 0;
 783                 foreach ( $this->edits as $edit ) {
 784                         if ( $edit->type == 'copy' ) {
 785                                 $lcs += count( $edit->orig );
 786                         }
 787                 }
 788
 789                 return $lcs;
 790         }
 791
 792         /**
 793          * Get the original set of lines.
 794          *
 795          * This reconstructs the $from_lines parameter passed to the
 796          * constructor.
 797          *
 798          * @return string[] The original sequence of strings.
 799          */
 800         public function orig() {
 801                 $lines = array();
 802
 803                 foreach ( $this->edits as $edit ) {
 804                         if ( $edit->orig ) {
 805                                 array_splice( $lines, count( $lines ), 0, $edit->orig );
 806                         }
 807                 }
 808
 809                 return $lines;
 810         }
 811
 812         /**
 813          * Get the closing set of lines.
 814          *
 815          * This reconstructs the $to_lines parameter passed to the
 816          * constructor.
 817          *
 818          * @return string[] The sequence of strings.
 819          */
 820         public function closing() {
 821                 $lines = array();
 822
 823                 foreach ( $this->edits as $edit ) {
 824                         if ( $edit->closing ) {
 825                                 array_splice( $lines, count( $lines ), 0, $edit->closing );
 826                         }
 827                 }
 828
 829                 return $lines;
 830         }
 831 }
 832
 833 /**
 834  * @todo document, bad name.
 835  * @private
 836  * @ingroup DifferenceEngine
 837  */
 838 class MappedDiff extends Diff {
 839         /**
 840          * Constructor.
 841          *
 842          * Computes diff between sequences of strings.
 843          *
 844          * This can be used to compute things like
 845          * case-insensitve diffs, or diffs which ignore
 846          * changes in white-space.
 847          *
 848          * @param string[] $from_lines An array of strings.
 849          *   Typically these are lines from a file.
 850          * @param string[] $to_lines An array of strings.
 851          * @param string[] $mapped_from_lines This array should
 852          *   have the same size number of elements as $from_lines.
 853          *   The elements in $mapped_from_lines and
 854          *   $mapped_to_lines are what is actually compared
 855          *   when computing the diff.
 856          * @param string[] $mapped_to_lines This array should
 857          *   have the same number of elements as $to_lines.
 858          */
 859         public function __construct( $from_lines, $to_lines,
 860                 $mapped_from_lines, $mapped_to_lines ) {
 861                 wfProfileIn( __METHOD__ );
 862
 863                 assert( 'count( $from_lines ) == count( $mapped_from_lines )' );
 864                 assert( 'count( $to_lines ) == count( $mapped_to_lines )' );
 865
 866                 parent::__construct( $mapped_from_lines, $mapped_to_lines );
 867
 868                 $xi = $yi = 0;
 869                 $editCount = count( $this->edits );
 870                 for ( $i = 0; $i < $editCount; $i++ ) {
 871                         $orig = &$this->edits[$i]->orig;
 872                         if ( is_array( $orig ) ) {
 873                                 $orig = array_slice( $from_lines, $xi, count( $orig ) );
 874                                 $xi += count( $orig );
 875                         }
 876
 877                         $closing = &$this->edits[$i]->closing;
 878                         if ( is_array( $closing ) ) {
 879                                 $closing = array_slice( $to_lines, $yi, count( $closing ) );
 880                                 $yi += count( $closing );
 881                         }
 882                 }
 883                 wfProfileOut( __METHOD__ );
 884         }
 885 }
 886
 887 /**
 888  * Additions by Axel Boldt follow, partly taken from diff.php, phpwiki-1.3.3
 889  */
 890
 891 /**
 892  * @todo document
 893  * @private
 894  * @ingroup DifferenceEngine
 895  */
 896 class HWLDFWordAccumulator {
 897         public $insClass = ' class="diffchange diffchange-inline"';
 898         public $delClass = ' class="diffchange diffchange-inline"';
 899
 900         private $lines = array();
 901         private $line = '';
 902         private $group = '';
 903         private $tag = '';
 904
 905         /**
 906          * @param string $new_tag
 907          */
 908         private function flushGroup( $new_tag ) {
 909                 if ( $this->group !== '' ) {
 910                         if ( $this->tag == 'ins' ) {
 911                                 $this->line .= "<ins{$this->insClass}>" .
 912                                         htmlspecialchars( $this->group ) . '</ins>';
 913                         } elseif ( $this->tag == 'del' ) {
 914                                 $this->line .= "<del{$this->delClass}>" .
 915                                         htmlspecialchars( $this->group ) . '</del>';
 916                         } else {
 917                                 $this->line .= htmlspecialchars( $this->group );
 918                         }
 919                 }
 920                 $this->group = '';
 921                 $this->tag = $new_tag;
 922         }
 923
 924         /**
 925          * @param string $new_tag
 926          */
 927         private function flushLine( $new_tag ) {
 928                 $this->flushGroup( $new_tag );
 929                 if ( $this->line != '' ) {
 930                         array_push( $this->lines, $this->line );
 931                 } else {
 932                         # make empty lines visible by inserting an NBSP
 933                         array_push( $this->lines, '&#160;' );
 934                 }
 935                 $this->line = '';
 936         }
 937
 938         /**
 939          * @param string[] $words
 940          * @param string $tag
 941          */
 942         public function addWords( $words, $tag = '' ) {
 943                 if ( $tag != $this->tag ) {
 944                         $this->flushGroup( $tag );
 945                 }
 946
 947                 foreach ( $words as $word ) {
 948                         // new-line should only come as first char of word.
 949                         if ( $word == '' ) {
 950                                 continue;
 951                         }
 952                         if ( $word[0] == "\n" ) {
 953                                 $this->flushLine( $tag );
 954                                 $word = substr( $word, 1 );
 955                         }
 956                         assert( '!strstr( $word, "\n" )' );
 957                         $this->group .= $word;
 958                 }
 959         }
 960
 961         /**
 962          * @return string[]
 963          */
 964         public function getLines() {
 965                 $this->flushLine( '~done' );
 966
 967                 return $this->lines;
 968         }
 969 }
 970
 971 /**
 972  * @todo document
 973  * @private
 974  * @ingroup DifferenceEngine
 975  */
 976 class WordLevelDiff extends MappedDiff {
 977         const MAX_LINE_LENGTH = 10000;
 978
 979         /**
 980          * @param string[] $orig_lines
 981          * @param string[] $closing_lines
 982          */
 983         public function __construct( $orig_lines, $closing_lines ) {
 984                 wfProfileIn( __METHOD__ );
 985
 986                 list( $orig_words, $orig_stripped ) = $this->split( $orig_lines );
 987                 list( $closing_words, $closing_stripped ) = $this->split( $closing_lines );
 988
 989                 parent::__construct( $orig_words, $closing_words,
 990                         $orig_stripped, $closing_stripped );
 991                 wfProfileOut( __METHOD__ );
 992         }
 993
 994         /**
 995          * @param string[] $lines
 996          *
 997          * @return array[]
 998          */
 999         private function split( $lines ) {
1000                 wfProfileIn( __METHOD__ );
1001
1002                 $words = array();
1003                 $stripped = array();
1004                 $first = true;
1005                 foreach ( $lines as $line ) {
1006                         # If the line is too long, just pretend the entire line is one big word
1007                         # This prevents resource exhaustion problems
1008                         if ( $first ) {
1009                                 $first = false;
1010                         } else {
1011                                 $words[] = "\n";
1012                                 $stripped[] = "\n";
1013                         }
1014                         if ( strlen( $line ) > self::MAX_LINE_LENGTH ) {
1015                                 $words[] = $line;
1016                                 $stripped[] = $line;
1017                         } else {
1018                                 $m = array();
1019                                 if ( preg_match_all( '/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
1020                                         $line, $m )
1021                                 ) {
1022                                         foreach ( $m[0] as $word ) {
1023                                                 $words[] = $word;
1024                                         }
1025                                         foreach ( $m[1] as $stripped_word ) {
1026                                                 $stripped[] = $stripped_word;
1027                                         }
1028                                 }
1029                         }
1030                 }
1031                 wfProfileOut( __METHOD__ );
1032
1033                 return array( $words, $stripped );
1034         }
1035
1036         /**
1037          * @return string[]
1038          */
1039         public function orig() {
1040                 wfProfileIn( __METHOD__ );
1041                 $orig = new HWLDFWordAccumulator;
1042
1043                 foreach ( $this->edits as $edit ) {
1044                         if ( $edit->type == 'copy' ) {
1045                                 $orig->addWords( $edit->orig );
1046                         } elseif ( $edit->orig ) {
1047                                 $orig->addWords( $edit->orig, 'del' );
1048                         }
1049                 }
1050                 $lines = $orig->getLines();
1051                 wfProfileOut( __METHOD__ );
1052
1053                 return $lines;
1054         }
1055
1056         /**
1057          * @return string[]
1058          */
1059         public function closing() {
1060                 wfProfileIn( __METHOD__ );
1061                 $closing = new HWLDFWordAccumulator;
1062
1063                 foreach ( $this->edits as $edit ) {
1064                         if ( $edit->type == 'copy' ) {
1065                                 $closing->addWords( $edit->closing );
1066                         } elseif ( $edit->closing ) {
1067                                 $closing->addWords( $edit->closing, 'ins' );
1068                         }
1069                 }
1070                 $lines = $closing->getLines();
1071                 wfProfileOut( __METHOD__ );
1072
1073                 return $lines;
1074         }
1075
1076 }