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- <?php
- namespace Drupal\Component\Diff\Engine;
- use Drupal\Component\Utility\Unicode;
- /**
- * Class used internally by Diff to actually compute the diffs.
- *
- * 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 from analyze.c, from GNU
- * diffutils-2.7, which can be found at:
- * ftp://gnudist.gnu.org/pub/gnu/diffutils/diffutils-2.7.tar.gz
- *
- * closingly, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
- * are my own.
- *
- * Line length limits for robustness added by Tim Starling, 2005-08-31
- *
- * @author Geoffrey T. Dairiki, Tim Starling
- * @private
- * @subpackage DifferenceEngine
- */
- class DiffEngine {
- const USE_ASSERTS = FALSE;
- const MAX_XREF_LENGTH = 10000;
- public function diff($from_lines, $to_lines) {
- $n_from = sizeof($from_lines);
- $n_to = sizeof($to_lines);
- $this->xchanged = $this->ychanged = [];
- $this->xv = $this->yv = [];
- $this->xind = $this->yind = [];
- unset($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++) {
- $xhash[$this->_line_hash($from_lines[$xi])] = 1;
- }
- for ($yi = $skip; $yi < $n_to - $endskip; $yi++) {
- $line = $to_lines[$yi];
- if ($this->ychanged[$yi] = empty($xhash[$this->_line_hash($line)])) {
- continue;
- }
- $yhash[$this->_line_hash($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($yhash[$this->_line_hash($line)])) {
- continue;
- }
- $this->xv[] = $line;
- $this->xind[] = $xi;
- }
- // Find the LCS.
- $this->_compareseq(0, sizeof($this->xv), 0, sizeof($this->yv));
- // Merge edits when possible
- $this->_shift_boundaries($from_lines, $this->xchanged, $this->ychanged);
- $this->_shift_boundaries($to_lines, $this->ychanged, $this->xchanged);
- // Compute the edit operations.
- $edits = [];
- $xi = $yi = 0;
- while ($xi < $n_from || $yi < $n_to) {
- $this::USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
- $this::USE_ASSERTS && assert($xi < $n_from || $this->ychanged[$yi]);
- // Skip matching "snake".
- $copy = [];
- while ( $xi < $n_from && $yi < $n_to && !$this->xchanged[$xi] && !$this->ychanged[$yi]) {
- $copy[] = $from_lines[$xi++];
- ++$yi;
- }
- if ($copy) {
- $edits[] = new DiffOpCopy($copy);
- }
- // Find deletes & adds.
- $delete = [];
- while ($xi < $n_from && $this->xchanged[$xi]) {
- $delete[] = $from_lines[$xi++];
- }
- $add = [];
- while ($yi < $n_to && $this->ychanged[$yi]) {
- $add[] = $to_lines[$yi++];
- }
- if ($delete && $add) {
- $edits[] = new DiffOpChange($delete, $add);
- }
- elseif ($delete) {
- $edits[] = new DiffOpDelete($delete);
- }
- elseif ($add) {
- $edits[] = new DiffOpAdd($add);
- }
- }
- return $edits;
- }
- /**
- * Returns the whole line if it's small enough, or the MD5 hash otherwise.
- */
- protected function _line_hash($line) {
- if (Unicode::strlen($line) > $this::MAX_XREF_LENGTH) {
- return md5($line);
- }
- else {
- return $line;
- }
- }
- /**
- * Divide the Largest Common Subsequence (LCS) of the sequences
- * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
- * sized segments.
- *
- * Returns (LCS, PTS). LCS is the length of the LCS. PTS is an
- * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
- * sub sequences. The first sub-sequence is contained in [X0, X1),
- * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on. Note
- * that (X0, Y0) == (XOFF, YOFF) and
- * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
- *
- * This function assumes that the first lines of the specified portions
- * of the two files do not match, and likewise that the last lines do not
- * match. The caller must trim matching lines from the beginning and end
- * of the portions it is going to specify.
- */
- protected function _diag($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 in X.
- $flip = TRUE;
- list($xoff, $xlim, $yoff, $ylim) = [$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 = [];
- $ymids[0] = [];
- $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($matches);
- while (list ($junk, $y) = each($matches)) {
- if (empty($this->in_seq[$y])) {
- $k = $this->_lcs_pos($y);
- $this::USE_ASSERTS && assert($k > 0);
- $ymids[$k] = $ymids[$k - 1];
- break;
- }
- }
- while (list ($junk, $y) = each($matches)) {
- if ($y > $this->seq[$k - 1]) {
- $this::USE_ASSERTS && assert($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 = $this->_lcs_pos($y);
- $this::USE_ASSERTS && assert($k > 0);
- $ymids[$k] = $ymids[$k - 1];
- }
- }
- }
- }
- $seps[] = $flip ? [$yoff, $xoff] : [$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[] = $flip ? [$y1, $x1] : [$x1, $y1];
- }
- $seps[] = $flip ? [$ylim, $xlim] : [$xlim, $ylim];
- return [$this->lcs, $seps];
- }
- protected function _lcs_pos($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;
- }
- }
- $this::USE_ASSERTS && assert($ypos != $this->seq[$end]);
- $this->in_seq[$this->seq[$end]] = FALSE;
- $this->seq[$end] = $ypos;
- $this->in_seq[$ypos] = 1;
- return $end;
- }
- /**
- * Find LCS of two sequences.
- *
- * The results are recorded in the vectors $this->{x,y}changed[], by
- * storing a 1 in the element for each line that is an insertion
- * or deletion (ie. is not in the LCS).
- *
- * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
- *
- * Note that XLIM, YLIM are exclusive bounds.
- * All line numbers are origin-0 and discarded lines are not counted.
- */
- protected function _compareseq($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 = $pt2;
- }
- }
- }
- /**
- * Adjust inserts/deletes of identical lines to join changes
- * as much as possible.
- *
- * We do something when a run of changed lines include a
- * line at one end and has an excluded, identical line at the other.
- * We are free to choose which identical line is included.
- * `compareseq' usually chooses the one at the beginning,
- * but usually it is cleaner to consider the following identical line
- * to be the "change".
- *
- * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
- */
- protected function _shift_boundaries($lines, &$changed, $other_changed) {
- $i = 0;
- $j = 0;
- $this::USE_ASSERTS && assert('sizeof($lines) == sizeof($changed)');
- $len = sizeof($lines);
- $other_len = sizeof($other_changed);
- while (1) {
- /*
- * Scan forwards to find 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]) {
- $this::USE_ASSERTS && assert('$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--;
- }
- $this::USE_ASSERTS && assert('$j > 0');
- while ($other_changed[--$j]) {
- continue;
- }
- $this::USE_ASSERTS && assert('$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++;
- }
- $this::USE_ASSERTS && assert('$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;
- $this::USE_ASSERTS && assert('$j > 0');
- while ($other_changed[--$j]) {
- continue;
- }
- $this::USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
- }
- }
- }
- }
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