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