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* Class used internally by Text_Diff to actually compute the diffs.
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* This class is implemented using native PHP code.
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* The algorithm used here is mostly lifted from the perl module
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* Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
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* http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
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* More ideas are taken from: http://www.ics.uci.edu/~eppstein/161/960229.html
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* Some ideas (and a bit of code) are taken from analyze.c, of GNU
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* diffutils-2.7, which can be found at:
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* ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
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* Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
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* Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
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* code was written by him, and is used/adapted with his permission.
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* Copyright 2004-2010 The Horde Project (http://www.horde.org/)
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* See the enclosed file COPYING for license information (LGPL). If you did
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* not receive this file, see http://opensource.org/licenses/lgpl-license.php.
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* @author Geoffrey T. Dairiki <dairiki@dairiki.org>
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class Text_Diff_Engine_native {
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function diff($from_lines, $to_lines)
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array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
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array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
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$n_from = count($from_lines);
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$n_to = count($to_lines);
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$this->xchanged = $this->ychanged = array();
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$this->xv = $this->yv = array();
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$this->xind = $this->yind = array();
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// Skip leading common lines.
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for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
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if ($from_lines[$skip] !== $to_lines[$skip]) {
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$this->xchanged[$skip] = $this->ychanged[$skip] = false;
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// Skip trailing common lines.
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$xi = $n_from; $yi = $n_to;
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for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
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if ($from_lines[$xi] !== $to_lines[$yi]) {
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$this->xchanged[$xi] = $this->ychanged[$yi] = false;
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// Ignore lines which do not exist in both files.
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for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
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$xhash[$from_lines[$xi]] = 1;
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for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
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$line = $to_lines[$yi];
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if (($this->ychanged[$yi] = empty($xhash[$line]))) {
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for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
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$line = $from_lines[$xi];
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if (($this->xchanged[$xi] = empty($yhash[$line]))) {
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$this->_compareseq(0, count($this->xv), 0, count($this->yv));
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// Merge edits when possible.
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$this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged);
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$this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged);
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// Compute the edit operations.
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while ($xi < $n_from || $yi < $n_to) {
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assert($yi < $n_to || $this->xchanged[$xi]);
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assert($xi < $n_from || $this->ychanged[$yi]);
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// Skip matching "snake".
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while ($xi < $n_from && $yi < $n_to
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&& !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
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$copy[] = $from_lines[$xi++];
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$edits[] = new Text_Diff_Op_copy($copy);
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// Find deletes & adds.
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while ($xi < $n_from && $this->xchanged[$xi]) {
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$delete[] = $from_lines[$xi++];
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while ($yi < $n_to && $this->ychanged[$yi]) {
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$add[] = $to_lines[$yi++];
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if ($delete && $add) {
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$edits[] = new Text_Diff_Op_change($delete, $add);
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$edits[] = new Text_Diff_Op_delete($delete);
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$edits[] = new Text_Diff_Op_add($add);
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* Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
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* XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized
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* Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of
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* NCHUNKS+1 (X, Y) indexes giving the diving points between sub
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* sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1),
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* the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) ==
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* (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
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* This function assumes that the first lines of the specified portions of
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* the two files do not match, and likewise that the last lines do not
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* match. The caller must trim matching lines from the beginning and end
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* of the portions it is going to specify.
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function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
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if ($xlim - $xoff > $ylim - $yoff) {
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/* Things seems faster (I'm not sure I understand why) when the
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* shortest sequence is in X. */
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list ($xoff, $xlim, $yoff, $ylim)
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= array($yoff, $ylim, $xoff, $xlim);
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for ($i = $ylim - 1; $i >= $yoff; $i--) {
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$ymatches[$this->xv[$i]][] = $i;
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for ($i = $ylim - 1; $i >= $yoff; $i--) {
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$ymatches[$this->yv[$i]][] = $i;
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$this->seq[0]= $yoff - 1;
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$this->in_seq = array();
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$numer = $xlim - $xoff + $nchunks - 1;
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for ($chunk = 0; $chunk < $nchunks; $chunk++) {
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for ($i = 0; $i <= $this->lcs; $i++) {
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$ymids[$i][$chunk - 1] = $this->seq[$i];
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$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $chunk) / $nchunks);
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for (; $x < $x1; $x++) {
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$line = $flip ? $this->yv[$x] : $this->xv[$x];
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if (empty($ymatches[$line])) {
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$matches = $ymatches[$line];
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while (list(, $y) = each($matches)) {
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if (empty($this->in_seq[$y])) {
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$k = $this->_lcsPos($y);
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$ymids[$k] = $ymids[$k - 1];
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while (list(, $y) = each($matches)) {
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if ($y > $this->seq[$k - 1]) {
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assert($y <= $this->seq[$k]);
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/* Optimization: this is a common case: next match is
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* just replacing previous match. */
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$this->in_seq[$this->seq[$k]] = false;
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$this->in_seq[$y] = 1;
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} elseif (empty($this->in_seq[$y])) {
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$k = $this->_lcsPos($y);
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$ymids[$k] = $ymids[$k - 1];
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$seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
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$ymid = $ymids[$this->lcs];
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for ($n = 0; $n < $nchunks - 1; $n++) {
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$x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
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$seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
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$seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
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return array($this->lcs, $seps);
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function _lcsPos($ypos)
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if ($end == 0 || $ypos > $this->seq[$end]) {
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$this->seq[++$this->lcs] = $ypos;
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$this->in_seq[$ypos] = 1;
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while ($beg < $end) {
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$mid = (int)(($beg + $end) / 2);
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if ($ypos > $this->seq[$mid]) {
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assert($ypos != $this->seq[$end]);
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$this->in_seq[$this->seq[$end]] = false;
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$this->seq[$end] = $ypos;
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$this->in_seq[$ypos] = 1;
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* Finds LCS of two sequences.
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* The results are recorded in the vectors $this->{x,y}changed[], by
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* storing a 1 in the element for each line that is an insertion or
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* deletion (ie. is not in the LCS).
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* The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
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* Note that XLIM, YLIM are exclusive bounds. All line numbers are
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* origin-0 and discarded lines are not counted.
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function _compareseq ($xoff, $xlim, $yoff, $ylim)
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/* Slide down the bottom initial diagonal. */
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while ($xoff < $xlim && $yoff < $ylim
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&& $this->xv[$xoff] == $this->yv[$yoff]) {
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/* Slide up the top initial diagonal. */
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while ($xlim > $xoff && $ylim > $yoff
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&& $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
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if ($xoff == $xlim || $yoff == $ylim) {
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/* This is ad hoc but seems to work well. $nchunks =
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* sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks =
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* max(2,min(8,(int)$nchunks)); */
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$nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
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= $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
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/* X and Y sequences have no common subsequence: mark all
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while ($yoff < $ylim) {
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$this->ychanged[$this->yind[$yoff++]] = 1;
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while ($xoff < $xlim) {
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$this->xchanged[$this->xind[$xoff++]] = 1;
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/* Use the partitions to split this problem into subproblems. */
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while ($pt2 = next($seps)) {
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$this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
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* Adjusts inserts/deletes of identical lines to join changes as much as
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* We do something when a run of changed lines include a line at one end
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* and has an excluded, identical line at the other. We are free to
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* choose which identical line is included. `compareseq' usually chooses
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* the one at the beginning, but usually it is cleaner to consider the
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* following identical line to be the "change".
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* This is extracted verbatim from analyze.c (GNU diffutils-2.7).
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function _shiftBoundaries($lines, &$changed, $other_changed)
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assert('count($lines) == count($changed)');
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$len = count($lines);
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$other_len = count($other_changed);
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/* Scan forward to find the beginning of another run of
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* changes. Also keep track of the corresponding point in the
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* Throughout this code, $i and $j are adjusted together so that
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* the first $i elements of $changed and the first $j elements of
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* $other_changed both contain the same number of zeros (unchanged
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* Furthermore, $j is always kept so that $j == $other_len or
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* $other_changed[$j] == false. */
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while ($j < $other_len && $other_changed[$j]) {
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while ($i < $len && ! $changed[$i]) {
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assert('$j < $other_len && ! $other_changed[$j]');
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while ($j < $other_len && $other_changed[$j]) {
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/* Find the end of this run of changes. */
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while (++$i < $len && $changed[$i]) {
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/* Record the length of this run of changes, so that we can
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* later determine whether the run has grown. */
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$runlength = $i - $start;
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/* Move the changed region back, so long as the previous
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* unchanged line matches the last changed one. This merges
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* with previous changed regions. */
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while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
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$changed[--$start] = 1;
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$changed[--$i] = false;
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while ($start > 0 && $changed[$start - 1]) {
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while ($other_changed[--$j]) {
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assert('$j >= 0 && !$other_changed[$j]');
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/* Set CORRESPONDING to the end of the changed run, at the
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* last point where it corresponds to a changed run in the
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* other file. CORRESPONDING == LEN means no such point has
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$corresponding = $j < $other_len ? $i : $len;
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/* Move the changed region forward, so long as the first
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* changed line matches the following unchanged one. This
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* merges with following changed regions. Do this second, so
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* that if there are no merges, the changed region is moved
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* forward as far as possible. */
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while ($i < $len && $lines[$start] == $lines[$i]) {
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$changed[$start++] = false;
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while ($i < $len && $changed[$i]) {
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assert('$j < $other_len && ! $other_changed[$j]');
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if ($j < $other_len && $other_changed[$j]) {
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while ($j < $other_len && $other_changed[$j]) {
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} while ($runlength != $i - $start);
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/* If possible, move the fully-merged run of changes back to a
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* corresponding run in the other file. */
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while ($corresponding < $i) {
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$changed[--$start] = 1;
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while ($other_changed[--$j]) {
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assert('$j >= 0 && !$other_changed[$j]');
added
removed
wp-includes/Text/Diff/Engine/native.php
