--- /dev/null
+<?php
+/**
+ * $Horde: framework/Text_Diff/Diff/Engine/native.php,v 1.10 2008/01/04 10:27:53 jan Exp $
+ *
+ * Class used internally by Text_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.
+ *
+ * Copyright 2004-2008 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file COPYING for license information (LGPL). If you did
+ * not receive this file, see http://opensource.org/licenses/lgpl-license.php.
+ *
+ * @author Geoffrey T. Dairiki <dairiki@dairiki.org>
+ * @package Text_Diff
+ */
+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];
+ reset($matches);
+ while (list(, $y) = each($matches)) {
+ if (empty($this->in_seq[$y])) {
+ $k = $this->_lcsPos($y);
+ assert($k > 0);
+ $ymids[$k] = $ymids[$k - 1];
+ break;
+ }
+ }
+ while (list(, $y) = each($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]');
+ }
+ }
+ }
+
+}
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