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