mp-wp_genesis 1 <?php
mp-wp_genesis 2 /**
mp-wp_genesis 3 * $Horde: framework/Text_Diff/Diff/Engine/native.php,v 1.10 2008/01/04 10:27:53 jan Exp $
mp-wp_genesis 4 *
mp-wp_genesis 5 * Class used internally by Text_Diff to actually compute the diffs. This
mp-wp_genesis 6 * class is implemented using native PHP code.
mp-wp_genesis 7 *
mp-wp_genesis 8 * The algorithm used here is mostly lifted from the perl module
mp-wp_genesis 9 * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
mp-wp_genesis 10 * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
mp-wp_genesis 11 *
mp-wp_genesis 12 * More ideas are taken from: http://www.ics.uci.edu/~eppstein/161/960229.html
mp-wp_genesis 13 *
mp-wp_genesis 14 * Some ideas (and a bit of code) are taken from analyze.c, of GNU
mp-wp_genesis 15 * diffutils-2.7, which can be found at:
mp-wp_genesis 16 * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
mp-wp_genesis 17 *
mp-wp_genesis 18 * Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
mp-wp_genesis 19 * Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
mp-wp_genesis 20 * code was written by him, and is used/adapted with his permission.
mp-wp_genesis 21 *
mp-wp_genesis 22 * Copyright 2004-2008 The Horde Project (http://www.horde.org/)
mp-wp_genesis 23 *
mp-wp_genesis 24 * See the enclosed file COPYING for license information (LGPL). If you did
mp-wp_genesis 25 * not receive this file, see http://opensource.org/licenses/lgpl-license.php.
mp-wp_genesis 26 *
mp-wp_genesis 27 * @author Geoffrey T. Dairiki <dairiki@dairiki.org>
mp-wp_genesis 28 * @package Text_Diff
mp-wp_genesis 29 */
mp-wp_genesis 30 class Text_Diff_Engine_native {
mp-wp_genesis 31
mp-wp_genesis 32 function diff($from_lines, $to_lines)
mp-wp_genesis 33 {
mp-wp_genesis 34 array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
mp-wp_genesis 35 array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
mp-wp_genesis 36
mp-wp_genesis 37 $n_from = count($from_lines);
mp-wp_genesis 38 $n_to = count($to_lines);
mp-wp_genesis 39
mp-wp_genesis 40 $this->xchanged = $this->ychanged = array();
mp-wp_genesis 41 $this->xv = $this->yv = array();
mp-wp_genesis 42 $this->xind = $this->yind = array();
mp-wp_genesis 43 unset($this->seq);
mp-wp_genesis 44 unset($this->in_seq);
mp-wp_genesis 45 unset($this->lcs);
mp-wp_genesis 46
mp-wp_genesis 47 // Skip leading common lines.
mp-wp_genesis 48 for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
mp-wp_genesis 49 if ($from_lines[$skip] !== $to_lines[$skip]) {
mp-wp_genesis 50 break;
mp-wp_genesis 51 }
mp-wp_genesis 52 $this->xchanged[$skip] = $this->ychanged[$skip] = false;
mp-wp_genesis 53 }
mp-wp_genesis 54
mp-wp_genesis 55 // Skip trailing common lines.
mp-wp_genesis 56 $xi = $n_from; $yi = $n_to;
mp-wp_genesis 57 for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
mp-wp_genesis 58 if ($from_lines[$xi] !== $to_lines[$yi]) {
mp-wp_genesis 59 break;
mp-wp_genesis 60 }
mp-wp_genesis 61 $this->xchanged[$xi] = $this->ychanged[$yi] = false;
mp-wp_genesis 62 }
mp-wp_genesis 63
mp-wp_genesis 64 // Ignore lines which do not exist in both files.
mp-wp_genesis 65 for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
mp-wp_genesis 66 $xhash[$from_lines[$xi]] = 1;
mp-wp_genesis 67 }
mp-wp_genesis 68 for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
mp-wp_genesis 69 $line = $to_lines[$yi];
mp-wp_genesis 70 if (($this->ychanged[$yi] = empty($xhash[$line]))) {
mp-wp_genesis 71 continue;
mp-wp_genesis 72 }
mp-wp_genesis 73 $yhash[$line] = 1;
mp-wp_genesis 74 $this->yv[] = $line;
mp-wp_genesis 75 $this->yind[] = $yi;
mp-wp_genesis 76 }
mp-wp_genesis 77 for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
mp-wp_genesis 78 $line = $from_lines[$xi];
mp-wp_genesis 79 if (($this->xchanged[$xi] = empty($yhash[$line]))) {
mp-wp_genesis 80 continue;
mp-wp_genesis 81 }
mp-wp_genesis 82 $this->xv[] = $line;
mp-wp_genesis 83 $this->xind[] = $xi;
mp-wp_genesis 84 }
mp-wp_genesis 85
mp-wp_genesis 86 // Find the LCS.
mp-wp_genesis 87 $this->_compareseq(0, count($this->xv), 0, count($this->yv));
mp-wp_genesis 88
mp-wp_genesis 89 // Merge edits when possible.
mp-wp_genesis 90 $this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged);
mp-wp_genesis 91 $this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged);
mp-wp_genesis 92
mp-wp_genesis 93 // Compute the edit operations.
mp-wp_genesis 94 $edits = array();
mp-wp_genesis 95 $xi = $yi = 0;
mp-wp_genesis 96 while ($xi < $n_from || $yi < $n_to) {
mp-wp_genesis 97 assert($yi < $n_to || $this->xchanged[$xi]);
mp-wp_genesis 98 assert($xi < $n_from || $this->ychanged[$yi]);
mp-wp_genesis 99
mp-wp_genesis 100 // Skip matching "snake".
mp-wp_genesis 101 $copy = array();
mp-wp_genesis 102 while ($xi < $n_from && $yi < $n_to
mp-wp_genesis 103 && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
mp-wp_genesis 104 $copy[] = $from_lines[$xi++];
mp-wp_genesis 105 ++$yi;
mp-wp_genesis 106 }
mp-wp_genesis 107 if ($copy) {
mp-wp_genesis 108 $edits[] = &new Text_Diff_Op_copy($copy);
mp-wp_genesis 109 }
mp-wp_genesis 110
mp-wp_genesis 111 // Find deletes & adds.
mp-wp_genesis 112 $delete = array();
mp-wp_genesis 113 while ($xi < $n_from && $this->xchanged[$xi]) {
mp-wp_genesis 114 $delete[] = $from_lines[$xi++];
mp-wp_genesis 115 }
mp-wp_genesis 116
mp-wp_genesis 117 $add = array();
mp-wp_genesis 118 while ($yi < $n_to && $this->ychanged[$yi]) {
mp-wp_genesis 119 $add[] = $to_lines[$yi++];
mp-wp_genesis 120 }
mp-wp_genesis 121
mp-wp_genesis 122 if ($delete && $add) {
mp-wp_genesis 123 $edits[] = &new Text_Diff_Op_change($delete, $add);
mp-wp_genesis 124 } elseif ($delete) {
mp-wp_genesis 125 $edits[] = &new Text_Diff_Op_delete($delete);
mp-wp_genesis 126 } elseif ($add) {
mp-wp_genesis 127 $edits[] = &new Text_Diff_Op_add($add);
mp-wp_genesis 128 }
mp-wp_genesis 129 }
mp-wp_genesis 130
mp-wp_genesis 131 return $edits;
mp-wp_genesis 132 }
mp-wp_genesis 133
mp-wp_genesis 134 /**
mp-wp_genesis 135 * Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
mp-wp_genesis 136 * XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized
mp-wp_genesis 137 * segments.
mp-wp_genesis 138 *
mp-wp_genesis 139 * Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of
mp-wp_genesis 140 * NCHUNKS+1 (X, Y) indexes giving the diving points between sub
mp-wp_genesis 141 * sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1),
mp-wp_genesis 142 * the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) ==
mp-wp_genesis 143 * (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
mp-wp_genesis 144 *
mp-wp_genesis 145 * This function assumes that the first lines of the specified portions of
mp-wp_genesis 146 * the two files do not match, and likewise that the last lines do not
mp-wp_genesis 147 * match. The caller must trim matching lines from the beginning and end
mp-wp_genesis 148 * of the portions it is going to specify.
mp-wp_genesis 149 */
mp-wp_genesis 150 function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
mp-wp_genesis 151 {
mp-wp_genesis 152 $flip = false;
mp-wp_genesis 153
mp-wp_genesis 154 if ($xlim - $xoff > $ylim - $yoff) {
mp-wp_genesis 155 /* Things seems faster (I'm not sure I understand why) when the
mp-wp_genesis 156 * shortest sequence is in X. */
mp-wp_genesis 157 $flip = true;
mp-wp_genesis 158 list ($xoff, $xlim, $yoff, $ylim)
mp-wp_genesis 159 = array($yoff, $ylim, $xoff, $xlim);
mp-wp_genesis 160 }
mp-wp_genesis 161
mp-wp_genesis 162 if ($flip) {
mp-wp_genesis 163 for ($i = $ylim - 1; $i >= $yoff; $i--) {
mp-wp_genesis 164 $ymatches[$this->xv[$i]][] = $i;
mp-wp_genesis 165 }
mp-wp_genesis 166 } else {
mp-wp_genesis 167 for ($i = $ylim - 1; $i >= $yoff; $i--) {
mp-wp_genesis 168 $ymatches[$this->yv[$i]][] = $i;
mp-wp_genesis 169 }
mp-wp_genesis 170 }
mp-wp_genesis 171
mp-wp_genesis 172 $this->lcs = 0;
mp-wp_genesis 173 $this->seq[0]= $yoff - 1;
mp-wp_genesis 174 $this->in_seq = array();
mp-wp_genesis 175 $ymids[0] = array();
mp-wp_genesis 176
mp-wp_genesis 177 $numer = $xlim - $xoff + $nchunks - 1;
mp-wp_genesis 178 $x = $xoff;
mp-wp_genesis 179 for ($chunk = 0; $chunk < $nchunks; $chunk++) {
mp-wp_genesis 180 if ($chunk > 0) {
mp-wp_genesis 181 for ($i = 0; $i <= $this->lcs; $i++) {
mp-wp_genesis 182 $ymids[$i][$chunk - 1] = $this->seq[$i];
mp-wp_genesis 183 }
mp-wp_genesis 184 }
mp-wp_genesis 185
mp-wp_genesis 186 $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $chunk) / $nchunks);
mp-wp_genesis 187 for (; $x < $x1; $x++) {
mp-wp_genesis 188 $line = $flip ? $this->yv[$x] : $this->xv[$x];
mp-wp_genesis 189 if (empty($ymatches[$line])) {
mp-wp_genesis 190 continue;
mp-wp_genesis 191 }
mp-wp_genesis 192 $matches = $ymatches[$line];
mp-wp_genesis 193 reset($matches);
mp-wp_genesis 194 while (list(, $y) = each($matches)) {
mp-wp_genesis 195 if (empty($this->in_seq[$y])) {
mp-wp_genesis 196 $k = $this->_lcsPos($y);
mp-wp_genesis 197 assert($k > 0);
mp-wp_genesis 198 $ymids[$k] = $ymids[$k - 1];
mp-wp_genesis 199 break;
mp-wp_genesis 200 }
mp-wp_genesis 201 }
mp-wp_genesis 202 while (list(, $y) = each($matches)) {
mp-wp_genesis 203 if ($y > $this->seq[$k - 1]) {
mp-wp_genesis 204 assert($y <= $this->seq[$k]);
mp-wp_genesis 205 /* Optimization: this is a common case: next match is
mp-wp_genesis 206 * just replacing previous match. */
mp-wp_genesis 207 $this->in_seq[$this->seq[$k]] = false;
mp-wp_genesis 208 $this->seq[$k] = $y;
mp-wp_genesis 209 $this->in_seq[$y] = 1;
mp-wp_genesis 210 } elseif (empty($this->in_seq[$y])) {
mp-wp_genesis 211 $k = $this->_lcsPos($y);
mp-wp_genesis 212 assert($k > 0);
mp-wp_genesis 213 $ymids[$k] = $ymids[$k - 1];
mp-wp_genesis 214 }
mp-wp_genesis 215 }
mp-wp_genesis 216 }
mp-wp_genesis 217 }
mp-wp_genesis 218
mp-wp_genesis 219 $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
mp-wp_genesis 220 $ymid = $ymids[$this->lcs];
mp-wp_genesis 221 for ($n = 0; $n < $nchunks - 1; $n++) {
mp-wp_genesis 222 $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
mp-wp_genesis 223 $y1 = $ymid[$n] + 1;
mp-wp_genesis 224 $seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
mp-wp_genesis 225 }
mp-wp_genesis 226 $seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
mp-wp_genesis 227
mp-wp_genesis 228 return array($this->lcs, $seps);
mp-wp_genesis 229 }
mp-wp_genesis 230
mp-wp_genesis 231 function _lcsPos($ypos)
mp-wp_genesis 232 {
mp-wp_genesis 233 $end = $this->lcs;
mp-wp_genesis 234 if ($end == 0 || $ypos > $this->seq[$end]) {
mp-wp_genesis 235 $this->seq[++$this->lcs] = $ypos;
mp-wp_genesis 236 $this->in_seq[$ypos] = 1;
mp-wp_genesis 237 return $this->lcs;
mp-wp_genesis 238 }
mp-wp_genesis 239
mp-wp_genesis 240 $beg = 1;
mp-wp_genesis 241 while ($beg < $end) {
mp-wp_genesis 242 $mid = (int)(($beg + $end) / 2);
mp-wp_genesis 243 if ($ypos > $this->seq[$mid]) {
mp-wp_genesis 244 $beg = $mid + 1;
mp-wp_genesis 245 } else {
mp-wp_genesis 246 $end = $mid;
mp-wp_genesis 247 }
mp-wp_genesis 248 }
mp-wp_genesis 249
mp-wp_genesis 250 assert($ypos != $this->seq[$end]);
mp-wp_genesis 251
mp-wp_genesis 252 $this->in_seq[$this->seq[$end]] = false;
mp-wp_genesis 253 $this->seq[$end] = $ypos;
mp-wp_genesis 254 $this->in_seq[$ypos] = 1;
mp-wp_genesis 255 return $end;
mp-wp_genesis 256 }
mp-wp_genesis 257
mp-wp_genesis 258 /**
mp-wp_genesis 259 * Finds LCS of two sequences.
mp-wp_genesis 260 *
mp-wp_genesis 261 * The results are recorded in the vectors $this->{x,y}changed[], by
mp-wp_genesis 262 * storing a 1 in the element for each line that is an insertion or
mp-wp_genesis 263 * deletion (ie. is not in the LCS).
mp-wp_genesis 264 *
mp-wp_genesis 265 * The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
mp-wp_genesis 266 *
mp-wp_genesis 267 * Note that XLIM, YLIM are exclusive bounds. All line numbers are
mp-wp_genesis 268 * origin-0 and discarded lines are not counted.
mp-wp_genesis 269 */
mp-wp_genesis 270 function _compareseq ($xoff, $xlim, $yoff, $ylim)
mp-wp_genesis 271 {
mp-wp_genesis 272 /* Slide down the bottom initial diagonal. */
mp-wp_genesis 273 while ($xoff < $xlim && $yoff < $ylim
mp-wp_genesis 274 && $this->xv[$xoff] == $this->yv[$yoff]) {
mp-wp_genesis 275 ++$xoff;
mp-wp_genesis 276 ++$yoff;
mp-wp_genesis 277 }
mp-wp_genesis 278
mp-wp_genesis 279 /* Slide up the top initial diagonal. */
mp-wp_genesis 280 while ($xlim > $xoff && $ylim > $yoff
mp-wp_genesis 281 && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
mp-wp_genesis 282 --$xlim;
mp-wp_genesis 283 --$ylim;
mp-wp_genesis 284 }
mp-wp_genesis 285
mp-wp_genesis 286 if ($xoff == $xlim || $yoff == $ylim) {
mp-wp_genesis 287 $lcs = 0;
mp-wp_genesis 288 } else {
mp-wp_genesis 289 /* This is ad hoc but seems to work well. $nchunks =
mp-wp_genesis 290 * sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks =
mp-wp_genesis 291 * max(2,min(8,(int)$nchunks)); */
mp-wp_genesis 292 $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
mp-wp_genesis 293 list($lcs, $seps)
mp-wp_genesis 294 = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
mp-wp_genesis 295 }
mp-wp_genesis 296
mp-wp_genesis 297 if ($lcs == 0) {
mp-wp_genesis 298 /* X and Y sequences have no common subsequence: mark all
mp-wp_genesis 299 * changed. */
mp-wp_genesis 300 while ($yoff < $ylim) {
mp-wp_genesis 301 $this->ychanged[$this->yind[$yoff++]] = 1;
mp-wp_genesis 302 }
mp-wp_genesis 303 while ($xoff < $xlim) {
mp-wp_genesis 304 $this->xchanged[$this->xind[$xoff++]] = 1;
mp-wp_genesis 305 }
mp-wp_genesis 306 } else {
mp-wp_genesis 307 /* Use the partitions to split this problem into subproblems. */
mp-wp_genesis 308 reset($seps);
mp-wp_genesis 309 $pt1 = $seps[0];
mp-wp_genesis 310 while ($pt2 = next($seps)) {
mp-wp_genesis 311 $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
mp-wp_genesis 312 $pt1 = $pt2;
mp-wp_genesis 313 }
mp-wp_genesis 314 }
mp-wp_genesis 315 }
mp-wp_genesis 316
mp-wp_genesis 317 /**
mp-wp_genesis 318 * Adjusts inserts/deletes of identical lines to join changes as much as
mp-wp_genesis 319 * possible.
mp-wp_genesis 320 *
mp-wp_genesis 321 * We do something when a run of changed lines include a line at one end
mp-wp_genesis 322 * and has an excluded, identical line at the other. We are free to
mp-wp_genesis 323 * choose which identical line is included. `compareseq' usually chooses
mp-wp_genesis 324 * the one at the beginning, but usually it is cleaner to consider the
mp-wp_genesis 325 * following identical line to be the "change".
mp-wp_genesis 326 *
mp-wp_genesis 327 * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
mp-wp_genesis 328 */
mp-wp_genesis 329 function _shiftBoundaries($lines, &$changed, $other_changed)
mp-wp_genesis 330 {
mp-wp_genesis 331 $i = 0;
mp-wp_genesis 332 $j = 0;
mp-wp_genesis 333
mp-wp_genesis 334 assert('count($lines) == count($changed)');
mp-wp_genesis 335 $len = count($lines);
mp-wp_genesis 336 $other_len = count($other_changed);
mp-wp_genesis 337
mp-wp_genesis 338 while (1) {
mp-wp_genesis 339 /* Scan forward to find the beginning of another run of
mp-wp_genesis 340 * changes. Also keep track of the corresponding point in the
mp-wp_genesis 341 * other file.
mp-wp_genesis 342 *
mp-wp_genesis 343 * Throughout this code, $i and $j are adjusted together so that
mp-wp_genesis 344 * the first $i elements of $changed and the first $j elements of
mp-wp_genesis 345 * $other_changed both contain the same number of zeros (unchanged
mp-wp_genesis 346 * lines).
mp-wp_genesis 347 *
mp-wp_genesis 348 * Furthermore, $j is always kept so that $j == $other_len or
mp-wp_genesis 349 * $other_changed[$j] == false. */
mp-wp_genesis 350 while ($j < $other_len && $other_changed[$j]) {
mp-wp_genesis 351 $j++;
mp-wp_genesis 352 }
mp-wp_genesis 353
mp-wp_genesis 354 while ($i < $len && ! $changed[$i]) {
mp-wp_genesis 355 assert('$j < $other_len && ! $other_changed[$j]');
mp-wp_genesis 356 $i++; $j++;
mp-wp_genesis 357 while ($j < $other_len && $other_changed[$j]) {
mp-wp_genesis 358 $j++;
mp-wp_genesis 359 }
mp-wp_genesis 360 }
mp-wp_genesis 361
mp-wp_genesis 362 if ($i == $len) {
mp-wp_genesis 363 break;
mp-wp_genesis 364 }
mp-wp_genesis 365
mp-wp_genesis 366 $start = $i;
mp-wp_genesis 367
mp-wp_genesis 368 /* Find the end of this run of changes. */
mp-wp_genesis 369 while (++$i < $len && $changed[$i]) {
mp-wp_genesis 370 continue;
mp-wp_genesis 371 }
mp-wp_genesis 372
mp-wp_genesis 373 do {
mp-wp_genesis 374 /* Record the length of this run of changes, so that we can
mp-wp_genesis 375 * later determine whether the run has grown. */
mp-wp_genesis 376 $runlength = $i - $start;
mp-wp_genesis 377
mp-wp_genesis 378 /* Move the changed region back, so long as the previous
mp-wp_genesis 379 * unchanged line matches the last changed one. This merges
mp-wp_genesis 380 * with previous changed regions. */
mp-wp_genesis 381 while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
mp-wp_genesis 382 $changed[--$start] = 1;
mp-wp_genesis 383 $changed[--$i] = false;
mp-wp_genesis 384 while ($start > 0 && $changed[$start - 1]) {
mp-wp_genesis 385 $start--;
mp-wp_genesis 386 }
mp-wp_genesis 387 assert('$j > 0');
mp-wp_genesis 388 while ($other_changed[--$j]) {
mp-wp_genesis 389 continue;
mp-wp_genesis 390 }
mp-wp_genesis 391 assert('$j >= 0 && !$other_changed[$j]');
mp-wp_genesis 392 }
mp-wp_genesis 393
mp-wp_genesis 394 /* Set CORRESPONDING to the end of the changed run, at the
mp-wp_genesis 395 * last point where it corresponds to a changed run in the
mp-wp_genesis 396 * other file. CORRESPONDING == LEN means no such point has
mp-wp_genesis 397 * been found. */
mp-wp_genesis 398 $corresponding = $j < $other_len ? $i : $len;
mp-wp_genesis 399
mp-wp_genesis 400 /* Move the changed region forward, so long as the first
mp-wp_genesis 401 * changed line matches the following unchanged one. This
mp-wp_genesis 402 * merges with following changed regions. Do this second, so
mp-wp_genesis 403 * that if there are no merges, the changed region is moved
mp-wp_genesis 404 * forward as far as possible. */
mp-wp_genesis 405 while ($i < $len && $lines[$start] == $lines[$i]) {
mp-wp_genesis 406 $changed[$start++] = false;
mp-wp_genesis 407 $changed[$i++] = 1;
mp-wp_genesis 408 while ($i < $len && $changed[$i]) {
mp-wp_genesis 409 $i++;
mp-wp_genesis 410 }
mp-wp_genesis 411
mp-wp_genesis 412 assert('$j < $other_len && ! $other_changed[$j]');
mp-wp_genesis 413 $j++;
mp-wp_genesis 414 if ($j < $other_len && $other_changed[$j]) {
mp-wp_genesis 415 $corresponding = $i;
mp-wp_genesis 416 while ($j < $other_len && $other_changed[$j]) {
mp-wp_genesis 417 $j++;
mp-wp_genesis 418 }
mp-wp_genesis 419 }
mp-wp_genesis 420 }
mp-wp_genesis 421 } while ($runlength != $i - $start);
mp-wp_genesis 422
mp-wp_genesis 423 /* If possible, move the fully-merged run of changes back to a
mp-wp_genesis 424 * corresponding run in the other file. */
mp-wp_genesis 425 while ($corresponding < $i) {
mp-wp_genesis 426 $changed[--$start] = 1;
mp-wp_genesis 427 $changed[--$i] = 0;
mp-wp_genesis 428 assert('$j > 0');
mp-wp_genesis 429 while ($other_changed[--$j]) {
mp-wp_genesis 430 continue;
mp-wp_genesis 431 }
mp-wp_genesis 432 assert('$j >= 0 && !$other_changed[$j]');
mp-wp_genesis 433 }
mp-wp_genesis 434 }
mp-wp_genesis 435 }
mp-wp_genesis 436
mp-wp_genesis 437 }