diff core/lib/Drupal/Component/Diff/Engine/DiffEngine.php @ 0:4c8ae668cc8c

Initial import (non-working)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/lib/Drupal/Component/Diff/Engine/DiffEngine.php	Wed Nov 29 16:09:58 2017 +0000
@@ -0,0 +1,456 @@
+<?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]');
+      }
+    }
+  }
+
+}