+ − <?php
+ − /**
+ − * Class used internally by Diff to actually compute the diffs. This class is
+ − * implemented using native PHP code.
+ − *
+ − * The algorithm used here is mostly lifted from the perl module
+ − * Algorithm::Diff (version 1.06) by Ned Konz, which is available at:
+ − * http://www.perl.com/CPAN/authors/id/N/NE/NEDKONZ/Algorithm-Diff-1.06.zip
+ − *
+ − * More ideas are taken from:
+ − * http://www.ics.uci.edu/~eppstein/161/960229.html
+ − *
+ − * Some ideas (and a bit of code) are taken from analyze.c, of GNU
+ − * diffutils-2.7, which can be found at:
+ − * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
+ − *
+ − * Some ideas (subdivision by NCHUNKS > 2, and some optimizations) are from
+ − * Geoffrey T. Dairiki <dairiki@dairiki.org>. The original PHP version of this
+ − * code was written by him, and is used/adapted with his permission.
+ − *
+ − * $Horde: framework/Text_Diff/Diff/Engine/native.php,v 1.3 2006/01/06 15:56:52 jan Exp $
+ − *
+ − * @author Geoffrey T. Dairiki <dairiki@dairiki.org>
+ − * @package Text_Diff
+ − *
+ − * @access private
+ − */
+ − class Text_Diff_Engine_native {
+ −
+ − function diff($from_lines, $to_lines)
+ − {
+ − array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
+ − array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
+ −
+ − $n_from = count($from_lines);
+ − $n_to = count($to_lines);
+ −
+ − $this->xchanged = $this->ychanged = array();
+ − $this->xv = $this->yv = array();
+ − $this->xind = $this->yind = array();
+ − unset($this->seq);
+ − unset($this->in_seq);
+ − unset($this->lcs);
+ −
+ − // Skip leading common lines.
+ − for ($skip = 0; $skip < $n_from && $skip < $n_to; $skip++) {
+ − if ($from_lines[$skip] !== $to_lines[$skip]) {
+ − break;
+ − }
+ − $this->xchanged[$skip] = $this->ychanged[$skip] = false;
+ − }
+ −
+ − // Skip trailing common lines.
+ − $xi = $n_from; $yi = $n_to;
+ − for ($endskip = 0; --$xi > $skip && --$yi > $skip; $endskip++) {
+ − if ($from_lines[$xi] !== $to_lines[$yi]) {
+ − break;
+ − }
+ − $this->xchanged[$xi] = $this->ychanged[$yi] = false;
+ − }
+ −
+ − // Ignore lines which do not exist in both files.
+ − for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
+ − $xhash[$from_lines[$xi]] = 1;
+ − }
+ − for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
+ − $line = $to_lines[$yi];
+ − if (($this->ychanged[$yi] = empty($xhash[$line]))) {
+ − continue;
+ − }
+ − $yhash[$line] = 1;
+ − $this->yv[] = $line;
+ − $this->yind[] = $yi;
+ − }
+ − for ($xi = $skip; $xi < $n_from - $endskip; $xi++) {
+ − $line = $from_lines[$xi];
+ − if (($this->xchanged[$xi] = empty($yhash[$line]))) {
+ − continue;
+ − }
+ − $this->xv[] = $line;
+ − $this->xind[] = $xi;
+ − }
+ −
+ − // Find the LCS.
+ − $this->_compareseq(0, count($this->xv), 0, count($this->yv));
+ −
+ − // Merge edits when possible.
+ − $this->_shiftBoundaries($from_lines, $this->xchanged, $this->ychanged);
+ − $this->_shiftBoundaries($to_lines, $this->ychanged, $this->xchanged);
+ −
+ − // Compute the edit operations.
+ − $edits = array();
+ − $xi = $yi = 0;
+ − while ($xi < $n_from || $yi < $n_to) {
+ − assert($yi < $n_to || $this->xchanged[$xi]);
+ − assert($xi < $n_from || $this->ychanged[$yi]);
+ −
+ − // Skip matching "snake".
+ − $copy = array();
+ − while ($xi < $n_from && $yi < $n_to
+ − && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
+ − $copy[] = $from_lines[$xi++];
+ − ++$yi;
+ − }
+ − if ($copy) {
+ − $edits[] = &new Text_Diff_Op_copy($copy);
+ − }
+ −
+ − // Find deletes & adds.
+ − $delete = array();
+ − while ($xi < $n_from && $this->xchanged[$xi]) {
+ − $delete[] = $from_lines[$xi++];
+ − }
+ −
+ − $add = array();
+ − while ($yi < $n_to && $this->ychanged[$yi]) {
+ − $add[] = $to_lines[$yi++];
+ − }
+ −
+ − if ($delete && $add) {
+ − $edits[] = &new Text_Diff_Op_change($delete, $add);
+ − } elseif ($delete) {
+ − $edits[] = &new Text_Diff_Op_delete($delete);
+ − } elseif ($add) {
+ − $edits[] = &new Text_Diff_Op_add($add);
+ − }
+ − }
+ −
+ − return $edits;
+ − }
+ −
+ − /**
+ − * Divides the Largest Common Subsequence (LCS) of the sequences (XOFF,
+ − * XLIM) and (YOFF, YLIM) into NCHUNKS approximately equally sized
+ − * segments.
+ − *
+ − * Returns (LCS, PTS). LCS is the length of the LCS. PTS is an array of
+ − * NCHUNKS+1 (X, Y) indexes giving the diving points between sub
+ − * sequences. The first sub-sequence is contained in (X0, X1), (Y0, Y1),
+ − * the second in (X1, X2), (Y1, Y2) and so on. Note that (X0, Y0) ==
+ − * (XOFF, YOFF) and (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
+ − *
+ − * This function assumes that the first lines of the specified portions of
+ − * the two files do not match, and likewise that the last lines do not
+ − * match. The caller must trim matching lines from the beginning and end
+ − * of the portions it is going to specify.
+ − */
+ − function _diag ($xoff, $xlim, $yoff, $ylim, $nchunks)
+ − {
+ − $flip = false;
+ −
+ − if ($xlim - $xoff > $ylim - $yoff) {
+ − /* Things seems faster (I'm not sure I understand why) when the
+ − * shortest sequence is in X. */
+ − $flip = true;
+ − list ($xoff, $xlim, $yoff, $ylim)
+ − = array($yoff, $ylim, $xoff, $xlim);
+ − }
+ −
+ − if ($flip) {
+ − for ($i = $ylim - 1; $i >= $yoff; $i--) {
+ − $ymatches[$this->xv[$i]][] = $i;
+ − }
+ − } else {
+ − for ($i = $ylim - 1; $i >= $yoff; $i--) {
+ − $ymatches[$this->yv[$i]][] = $i;
+ − }
+ − }
+ −
+ − $this->lcs = 0;
+ − $this->seq[0]= $yoff - 1;
+ − $this->in_seq = array();
+ − $ymids[0] = array();
+ −
+ − $numer = $xlim - $xoff + $nchunks - 1;
+ − $x = $xoff;
+ − for ($chunk = 0; $chunk < $nchunks; $chunk++) {
+ − if ($chunk > 0) {
+ − for ($i = 0; $i <= $this->lcs; $i++) {
+ − $ymids[$i][$chunk - 1] = $this->seq[$i];
+ − }
+ − }
+ −
+ − $x1 = $xoff + (int)(($numer + ($xlim-$xoff)*$chunk) / $nchunks);
+ − for (; $x < $x1; $x++) {
+ − $line = $flip ? $this->yv[$x] : $this->xv[$x];
+ − if (empty($ymatches[$line])) {
+ − continue;
+ − }
+ − $matches = $ymatches[$line];
+ − foreach ($matches as $y) {
+ − if (empty($this->in_seq[$y])) {
+ − $k = $this->_lcsPos($y);
+ − assert($k > 0);
+ − $ymids[$k] = $ymids[$k - 1];
+ − break;
+ − }
+ − }
+ −
+ − while (list($junk, $y) = each($matches)) {
+ − if ($y > $this->seq[$k - 1]) {
+ − assert($y < $this->seq[$k]);
+ − /* Optimization: this is a common case: next match is
+ − * just replacing previous match. */
+ − $this->in_seq[$this->seq[$k]] = false;
+ − $this->seq[$k] = $y;
+ − $this->in_seq[$y] = 1;
+ − } elseif (empty($this->in_seq[$y])) {
+ − $k = $this->_lcsPos($y);
+ − assert($k > 0);
+ − $ymids[$k] = $ymids[$k - 1];
+ − }
+ − }
+ − }
+ − }
+ −
+ − $seps[] = $flip ? array($yoff, $xoff) : array($xoff, $yoff);
+ − $ymid = $ymids[$this->lcs];
+ − for ($n = 0; $n < $nchunks - 1; $n++) {
+ − $x1 = $xoff + (int)(($numer + ($xlim - $xoff) * $n) / $nchunks);
+ − $y1 = $ymid[$n] + 1;
+ − $seps[] = $flip ? array($y1, $x1) : array($x1, $y1);
+ − }
+ − $seps[] = $flip ? array($ylim, $xlim) : array($xlim, $ylim);
+ −
+ − return array($this->lcs, $seps);
+ − }
+ −
+ − function _lcsPos($ypos)
+ − {
+ − $end = $this->lcs;
+ − if ($end == 0 || $ypos > $this->seq[$end]) {
+ − $this->seq[++$this->lcs] = $ypos;
+ − $this->in_seq[$ypos] = 1;
+ − return $this->lcs;
+ − }
+ −
+ − $beg = 1;
+ − while ($beg < $end) {
+ − $mid = (int)(($beg + $end) / 2);
+ − if ($ypos > $this->seq[$mid]) {
+ − $beg = $mid + 1;
+ − } else {
+ − $end = $mid;
+ − }
+ − }
+ −
+ − assert($ypos != $this->seq[$end]);
+ −
+ − $this->in_seq[$this->seq[$end]] = false;
+ − $this->seq[$end] = $ypos;
+ − $this->in_seq[$ypos] = 1;
+ − return $end;
+ − }
+ −
+ − /**
+ − * Finds LCS of two sequences.
+ − *
+ − * The results are recorded in the vectors $this->{x,y}changed[], by
+ − * storing a 1 in the element for each line that is an insertion or
+ − * deletion (ie. is not in the LCS).
+ − *
+ − * The subsequence of file 0 is (XOFF, XLIM) and likewise for file 1.
+ − *
+ − * Note that XLIM, YLIM are exclusive bounds. All line numbers are
+ − * origin-0 and discarded lines are not counted.
+ − */
+ − function _compareseq ($xoff, $xlim, $yoff, $ylim)
+ − {
+ − /* Slide down the bottom initial diagonal. */
+ − while ($xoff < $xlim && $yoff < $ylim
+ − && $this->xv[$xoff] == $this->yv[$yoff]) {
+ − ++$xoff;
+ − ++$yoff;
+ − }
+ −
+ − /* Slide up the top initial diagonal. */
+ − while ($xlim > $xoff && $ylim > $yoff
+ − && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
+ − --$xlim;
+ − --$ylim;
+ − }
+ −
+ − if ($xoff == $xlim || $yoff == $ylim) {
+ − $lcs = 0;
+ − } else {
+ − /* This is ad hoc but seems to work well. $nchunks =
+ − * sqrt(min($xlim - $xoff, $ylim - $yoff) / 2.5); $nchunks =
+ − * max(2,min(8,(int)$nchunks)); */
+ − $nchunks = min(7, $xlim - $xoff, $ylim - $yoff) + 1;
+ − list($lcs, $seps)
+ − = $this->_diag($xoff, $xlim, $yoff, $ylim, $nchunks);
+ − }
+ −
+ − if ($lcs == 0) {
+ − /* X and Y sequences have no common subsequence: mark all
+ − * changed. */
+ − while ($yoff < $ylim) {
+ − $this->ychanged[$this->yind[$yoff++]] = 1;
+ − }
+ − while ($xoff < $xlim) {
+ − $this->xchanged[$this->xind[$xoff++]] = 1;
+ − }
+ − } else {
+ − /* Use the partitions to split this problem into subproblems. */
+ − reset($seps);
+ − $pt1 = $seps[0];
+ − while ($pt2 = next($seps)) {
+ − $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
+ − $pt1 = $pt2;
+ − }
+ − }
+ − }
+ −
+ − /**
+ − * Adjusts inserts/deletes of identical lines to join changes as much as
+ − * possible.
+ − *
+ − * We do something when a run of changed lines include a line at one end
+ − * and has an excluded, identical line at the other. We are free to
+ − * choose which identical line is included. `compareseq' usually chooses
+ − * the one at the beginning, but usually it is cleaner to consider the
+ − * following identical line to be the "change".
+ − *
+ − * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
+ − */
+ − function _shiftBoundaries($lines, &$changed, $other_changed)
+ − {
+ − $i = 0;
+ − $j = 0;
+ −
+ − assert('count($lines) == count($changed)');
+ − $len = count($lines);
+ − $other_len = count($other_changed);
+ −
+ − while (1) {
+ − /* Scan forward to find the beginning of another run of
+ − * changes. Also keep track of the corresponding point in the
+ − * other file.
+ − *
+ − * Throughout this code, $i and $j are adjusted together so that
+ − * the first $i elements of $changed and the first $j elements of
+ − * $other_changed both contain the same number of zeros (unchanged
+ − * lines).
+ − *
+ − * Furthermore, $j is always kept so that $j == $other_len or
+ − * $other_changed[$j] == false. */
+ − while ($j < $other_len && $other_changed[$j]) {
+ − $j++;
+ − }
+ −
+ − while ($i < $len && ! $changed[$i]) {
+ − assert('$j < $other_len && ! $other_changed[$j]');
+ − $i++; $j++;
+ − while ($j < $other_len && $other_changed[$j]) {
+ − $j++;
+ − }
+ − }
+ −
+ − if ($i == $len) {
+ − break;
+ − }
+ −
+ − $start = $i;
+ −
+ − /* Find the end of this run of changes. */
+ − while (++$i < $len && $changed[$i]) {
+ − continue;
+ − }
+ −
+ − do {
+ − /* Record the length of this run of changes, so that we can
+ − * later determine whether the run has grown. */
+ − $runlength = $i - $start;
+ −
+ − /* Move the changed region back, so long as the previous
+ − * unchanged line matches the last changed one. This merges
+ − * with previous changed regions. */
+ − while ($start > 0 && $lines[$start - 1] == $lines[$i - 1]) {
+ − $changed[--$start] = 1;
+ − $changed[--$i] = false;
+ − while ($start > 0 && $changed[$start - 1]) {
+ − $start--;
+ − }
+ − assert('$j > 0');
+ − while ($other_changed[--$j]) {
+ − continue;
+ − }
+ − assert('$j >= 0 && !$other_changed[$j]');
+ − }
+ −
+ − /* Set CORRESPONDING to the end of the changed run, at the
+ − * last point where it corresponds to a changed run in the
+ − * other file. CORRESPONDING == LEN means no such point has
+ − * been found. */
+ − $corresponding = $j < $other_len ? $i : $len;
+ −
+ − /* Move the changed region forward, so long as the first
+ − * changed line matches the following unchanged one. This
+ − * merges with following changed regions. Do this second, so
+ − * that if there are no merges, the changed region is moved
+ − * forward as far as possible. */
+ − while ($i < $len && $lines[$start] == $lines[$i]) {
+ − $changed[$start++] = false;
+ − $changed[$i++] = 1;
+ − while ($i < $len && $changed[$i]) {
+ − $i++;
+ − }
+ −
+ − assert('$j < $other_len && ! $other_changed[$j]');
+ − $j++;
+ − if ($j < $other_len && $other_changed[$j]) {
+ − $corresponding = $i;
+ − while ($j < $other_len && $other_changed[$j]) {
+ − $j++;
+ − }
+ − }
+ − }
+ − } while ($runlength != $i - $start);
+ −
+ − /* If possible, move the fully-merged run of changes back to a
+ − * corresponding run in the other file. */
+ − while ($corresponding < $i) {
+ − $changed[--$start] = 1;
+ − $changed[--$i] = 0;
+ − assert('$j > 0');
+ − while ($other_changed[--$j]) {
+ − continue;
+ − }
+ − assert('$j >= 0 && !$other_changed[$j]');
+ − }
+ − }
+ − }
+ −
+ − }