more code cleanup

1 files changed, 864 insertions, 868 deletions

diff --git a/inc/DifferenceEngine.php b/inc/DifferenceEngine.php
index 760f1c39a..7b14e4463 100644
--- a/inc/DifferenceEngine.php
+++ b/inc/DifferenceEngine.php
@@ -10,75 +10,75 @@
 define('USE_ASSERTS', function_exists('assert'));
 
 class _DiffOp {
-  var $type;
-  var $orig;
-  var $closing;
+    var $type;
+    var $orig;
+    var $closing;
 
-  function reverse() {
-    trigger_error("pure virtual", E_USER_ERROR);
-  }
+    function reverse() {
+        trigger_error("pure virtual", E_USER_ERROR);
+    }
 
-  function norig() {
-    return $this->orig ? sizeof($this->orig) : 0;
-  }
+    function norig() {
+        return $this->orig ? count($this->orig) : 0;
+    }
 
-  function nclosing() {
-    return $this->closing ? sizeof($this->closing) : 0;
-  }
+    function nclosing() {
+        return $this->closing ? count($this->closing) : 0;
+    }
 }
 
 class _DiffOp_Copy extends _DiffOp {
-  var $type = 'copy';
-
-  function _DiffOp_Copy ($orig, $closing = false) {
-    if (!is_array($closing))
-      $closing = $orig;
-    $this->orig = $orig;
-    $this->closing = $closing;
-  }
-
-  function reverse() {
-    return new _DiffOp_Copy($this->closing, $this->orig);
-  }
+    var $type = 'copy';
+
+    function _DiffOp_Copy ($orig, $closing = false) {
+        if (!is_array($closing))
+            $closing = $orig;
+        $this->orig = $orig;
+        $this->closing = $closing;
+    }
+
+    function reverse() {
+        return new _DiffOp_Copy($this->closing, $this->orig);
+    }
 }
 
 class _DiffOp_Delete extends _DiffOp {
-  var $type = 'delete';
+    var $type = 'delete';
 
-  function _DiffOp_Delete ($lines) {
-    $this->orig = $lines;
-    $this->closing = false;
-  }
+    function _DiffOp_Delete ($lines) {
+        $this->orig = $lines;
+        $this->closing = false;
+    }
 
-  function reverse() {
-    return new _DiffOp_Add($this->orig);
-  }
+    function reverse() {
+        return new _DiffOp_Add($this->orig);
+    }
 }
 
 class _DiffOp_Add extends _DiffOp {
-  var $type = 'add';
+    var $type = 'add';
 
-  function _DiffOp_Add ($lines) {
-    $this->closing = $lines;
-    $this->orig = false;
-  }
+    function _DiffOp_Add ($lines) {
+        $this->closing = $lines;
+        $this->orig = false;
+    }
 
-  function reverse() {
-    return new _DiffOp_Delete($this->closing);
-  }
+    function reverse() {
+        return new _DiffOp_Delete($this->closing);
+    }
 }
 
 class _DiffOp_Change extends _DiffOp {
-  var $type = 'change';
+    var $type = 'change';
 
-  function _DiffOp_Change ($orig, $closing) {
-    $this->orig = $orig;
-    $this->closing = $closing;
-  }
+    function _DiffOp_Change ($orig, $closing) {
+        $this->orig = $orig;
+        $this->closing = $closing;
+    }
 
-  function reverse() {
-    return new _DiffOp_Change($this->closing, $this->orig);
-  }
+    function reverse() {
+        return new _DiffOp_Change($this->closing, $this->orig);
+    }
 }
 
 
@@ -102,577 +102,577 @@ class _DiffOp_Change extends _DiffOp {
  * @author Geoffrey T. Dairiki
  * @access private
  */
-class _DiffEngine
-{
-  function diff ($from_lines, $to_lines) {
-    $n_from = sizeof($from_lines);
-    $n_to = sizeof($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;
-    }
+class _DiffEngine {
+
+    function diff ($from_lines, $to_lines) {
+        $n_from = count($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[] = $xi;
-    }
+        // Ignore lines which do not exist in both files.
+        for ($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.
-    $this->_compareseq(0, sizeof($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 = array();
-    $xi = $yi = 0;
-    while ($xi < $n_from || $yi < $n_to) {
-      USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
-      USE_ASSERTS && 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)
-        $edits[] = new _DiffOp_Copy($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)
-        $edits[] = new _DiffOp_Change($delete, $add);
-      elseif ($delete)
-        $edits[] = new _DiffOp_Delete($delete);
-      elseif ($add)
-        $edits[] = new _DiffOp_Add($add);
-    }
-    return $edits;
-  }
-
-
-  /**
-   * Divide the Largest Common Subsequence (LCS) of the sequences
-   * [XOFF, XLIM) and [YOFF, YLIM) into NCHUNKS approximately equally
-   * sized segments.
-   *
-   * Returns (LCS, PTS).  LCS is the length of the LCS. PTS is an
-   * array of NCHUNKS+1 (X, Y) indexes giving the diving points between
-   * sub sequences.  The first sub-sequence is contained in [X0, X1),
-   * [Y0, Y1), the second in [X1, X2), [Y1, Y2) and so on.  Note
-   * that (X0, Y0) == (XOFF, YOFF) and
-   * (X[NCHUNKS], Y[NCHUNKS]) == (XLIM, YLIM).
-   *
-   * This function assumes that the first lines of the specified portions
-   * of the two files do not match, and likewise that the last lines do not
-   * match.  The caller must trim matching lines from the beginning and end
-   * of the portions it is going to specify.
-   */
-  function _diag ($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)
-    = array( $yoff, $ylim, $xoff, $xlim);
+        // Find the LCS.
+        $this->_compareseq(0, count($this->xv), 0, count($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 = array();
+        $xi = $yi = 0;
+        while ($xi < $n_from || $yi < $n_to) {
+            USE_ASSERTS && assert($yi < $n_to || $this->xchanged[$xi]);
+            USE_ASSERTS && 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)
+                $edits[] = new _DiffOp_Copy($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)
+                $edits[] = new _DiffOp_Change($delete, $add);
+            elseif ($delete)
+                $edits[] = new _DiffOp_Delete($delete);
+            elseif ($add)
+                $edits[] = new _DiffOp_Add($add);
+        }
+        return $edits;
     }
 
-  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($matches);
-    while (list ($junk, $y) = each($matches))
-      if (empty($this->in_seq[$y])) {
-      $k = $this->_lcs_pos($y);
-      USE_ASSERTS && assert($k > 0);
-      $ymids[$k] = $ymids[$k-1];
-      break;
-          }
-    while (list ($junk, $y) = each($matches)) {
-      if ($y > $this->seq[$k-1]) {
-      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;
-          }
-      else if (empty($this->in_seq[$y])) {
-      $k = $this->_lcs_pos($y);
-      USE_ASSERTS && assert($k > 0);
-      $ymids[$k] = $ymids[$k-1];
-          }
+
+    /**
+     * 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.
+     */
+    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)
+                = array( $yoff, $ylim, $xoff, $xlim);
         }
-      }
-    }
 
-  $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, $ylim);
+        if ($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($matches);
+                while (list ($junk, $y) = each($matches))
+                    if (empty($this->in_seq[$y])) {
+                        $k = $this->_lcs_pos($y);
+                        USE_ASSERTS && assert($k > 0);
+                        $ymids[$k] = $ymids[$k-1];
+                        break;
+                    }
+                while (list ($junk, $y) = each($matches)) {
+                    if ($y > $this->seq[$k-1]) {
+                        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;
+                    }
+                    else if (empty($this->in_seq[$y])) {
+                        $k = $this->_lcs_pos($y);
+                        USE_ASSERTS && assert($k > 0);
+                        $ymids[$k] = $ymids[$k-1];
+                    }
+                }
+            }
+        }
 
-  return array($this->lcs, $seps);
-  }
+        $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);
 
-  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 $this->lcs;
+        return array($this->lcs, $seps);
     }
 
-  $beg = 1;
-  while ($beg < $end) {
-    $mid = (int)(($beg + $end) / 2);
-    if ( $ypos > $this->seq[$mid] )
-    $beg = $mid + 1;
-    else
-    $end = $mid;
-    }
+    function _lcs_pos ($ypos) {
+        $end = $this->lcs;
+        if ($end == 0 || $ypos > $this->seq[$end]) {
+            $this->seq[++$this->lcs] = $ypos;
+            $this->in_seq[$ypos] = 1;
+            return $this->lcs;
+        }
 
-  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 $this->{x,y}changed[], by
-   * storing a 1 in the element for each line that is an insertion
-   * or deletion (ie. is not in the LCS).
-   *
-   * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
-   *
-   * Note that XLIM, YLIM are exclusive bounds.
-   * All line numbers are origin-0 and discarded lines are not counted.
-   */
-  function _compareseq ($xoff, $xlim, $yoff, $ylim) {
-  // Slide down the bottom initial diagonal.
-  while ($xoff < $xlim && $yoff < $ylim
-         && $this->xv[$xoff] == $this->yv[$yoff]) {
-    ++$xoff;
-    ++$yoff;
-    }
+        $beg = 1;
+        while ($beg < $end) {
+            $mid = (int)(($beg + $end) / 2);
+            if ( $ypos > $this->seq[$mid] )
+                $beg = $mid + 1;
+            else
+                $end = $mid;
+        }
 
-  // Slide up the top initial diagonal.
-  while ($xlim > $xoff && $ylim > $yoff
-         && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
-    --$xlim;
-    --$ylim;
-    }
+        USE_ASSERTS && assert($ypos != $this->seq[$end]);
 
-  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);
+        $this->in_seq[$this->seq[$end]] = false;
+        $this->seq[$end] = $ypos;
+        $this->in_seq[$ypos] = 1;
+        return $end;
     }
 
-  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 = $pt2;
-      }
-    }
-  }
-
-  /**
-   * Adjust inserts/deletes of identical lines to join changes
-   * as much as possible.
-   *
-   * We do something when a run of changed lines include a
-   * line at one end and has an excluded, identical line at the other.
-   * We are free to choose which identical line is included.
-   * `compareseq' usually chooses the one at the beginning,
-   * but usually it is cleaner to consider the following identical line
-   * to be the "change".
-   *
-   * This is extracted verbatim from analyze.c (GNU diffutils-2.7).
-   */
-  function _shift_boundaries ($lines, &$changed, $other_changed) {
-  $i = 0;
-  $j = 0;
-
-  USE_ASSERTS && assert('sizeof($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.
+    /**
+     * Find LCS of two sequences.
      *
-     * 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.
+     * The results are recorded in the vectors $this->{x,y}changed[], by
+     * storing a 1 in the element for each line that is an insertion
+     * or deletion (ie. is not in the LCS).
+     *
+     * The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
+     *
+     * Note that XLIM, YLIM are exclusive bounds.
+     * All line numbers are origin-0 and discarded lines are not counted.
      */
-    while ($j < $other_len && $other_changed[$j])
-    $j++;
-
-    while ($i < $len && ! $changed[$i]) {
-    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;
+    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;
+        }
 
-    do {
-    /*
-     * Record the length of this run of changes, so that
-     * we can later determine whether the run has grown.
-     */
-    $runlength = $i - $start;
+        // Slide up the top initial diagonal.
+        while ($xlim > $xoff && $ylim > $yoff
+                && $this->xv[$xlim - 1] == $this->yv[$ylim - 1]) {
+            --$xlim;
+            --$ylim;
+        }
 
-    /*
-     * 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])
-      $start--;
-      USE_ASSERTS && assert('$j > 0');
-      while ($other_changed[--$j])
-      continue;
-      USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+        if ($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);
         }
 
-    /*
-     * 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])
-      $i++;
-
-      USE_ASSERTS && assert('$j < $other_len && ! $other_changed[$j]');
-      $j++;
-      if ($j < $other_len && $other_changed[$j]) {
-      $corresponding = $i;
-      while ($j < $other_len && $other_changed[$j])
-        $j++;
-          }
+        if ($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[$xoff++]] = 1;
         }
-      } while ($runlength != $i - $start);
+        else {
+            // Use the partitions to split this problem into subproblems.
+            reset($seps);
+            $pt1 = $seps[0];
+            while ($pt2 = next($seps)) {
+                $this->_compareseq ($pt1[0], $pt2[0], $pt1[1], $pt2[1]);
+                $pt1 = $pt2;
+            }
+        }
+    }
 
-    /*
-     * If possible, move the fully-merged run of changes
-     * back to a corresponding run in the other file.
+    /**
+     * 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).
      */
-    while ($corresponding < $i) {
-    $changed[--$start] = 1;
-    $changed[--$i] = 0;
-    USE_ASSERTS && assert('$j > 0');
-    while ($other_changed[--$j])
-      continue;
-    USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
-      }
+    function _shift_boundaries ($lines, &$changed, $other_changed) {
+        $i = 0;
+        $j = 0;
+
+        USE_ASSERTS && assert('count($lines) == count($changed)');
+        $len = count($lines);
+        $other_len = count($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]) {
+                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])
+                        $start--;
+                    USE_ASSERTS && assert('$j > 0');
+                    while ($other_changed[--$j])
+                        continue;
+                    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])
+                        $i++;
+
+                    USE_ASSERTS && assert('$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;
+                USE_ASSERTS && assert('$j > 0');
+                while ($other_changed[--$j])
+                    continue;
+                USE_ASSERTS && assert('$j >= 0 && !$other_changed[$j]');
+            }
+        }
     }
-  }
 }
 
 /**
  * Class representing a 'diff' between two sequences of strings.
  */
-class Diff
-{
-  var $edits;
-
-  /**
-   * Constructor.
-   * Computes diff between sequences of strings.
-   *
-   * @param $from_lines array An array of strings.
-   *      (Typically these are lines from a file.)
-   * @param $to_lines array An array of strings.
-   */
-  function Diff($from_lines, $to_lines) {
-    $eng = new _DiffEngine;
-    $this->edits = $eng->diff($from_lines, $to_lines);
-    //$this->_check($from_lines, $to_lines);
-  }
-
-  /**
-   * Compute reversed Diff.
-   *
-   * SYNOPSIS:
-   *
-   *  $diff = new Diff($lines1, $lines2);
-   *  $rev = $diff->reverse();
-   * @return object A Diff object representing the inverse of the
-   *          original diff.
-   */
-  function reverse () {
-  $rev = $this;
-    $rev->edits = array();
-    foreach ($this->edits as $edit) {
-      $rev->edits[] = $edit->reverse();
+class Diff {
+
+    var $edits;
+
+    /**
+     * Constructor.
+     * Computes diff between sequences of strings.
+     *
+     * @param $from_lines array An array of strings.
+     *      (Typically these are lines from a file.)
+     * @param $to_lines array An array of strings.
+     */
+    function Diff($from_lines, $to_lines) {
+        $eng = new _DiffEngine;
+        $this->edits = $eng->diff($from_lines, $to_lines);
+        //$this->_check($from_lines, $to_lines);
     }
-  return $rev;
-  }
-
-  /**
-   * Check for empty diff.
-   *
-   * @return bool True iff two sequences were identical.
-   */
-  function isEmpty () {
-    foreach ($this->edits as $edit) {
-      if ($edit->type != 'copy')
-        return false;
+
+    /**
+     * Compute reversed Diff.
+     *
+     * SYNOPSIS:
+     *
+     *  $diff = new Diff($lines1, $lines2);
+     *  $rev = $diff->reverse();
+     * @return object A Diff object representing the inverse of the
+     *          original diff.
+     */
+    function reverse () {
+        $rev = $this;
+        $rev->edits = array();
+        foreach ($this->edits as $edit) {
+            $rev->edits[] = $edit->reverse();
+        }
+        return $rev;
     }
-    return true;
-  }
-
-  /**
-   * Compute the length of the Longest Common Subsequence (LCS).
-   *
-   * This is mostly for diagnostic purposed.
-   *
-   * @return int The length of the LCS.
-   */
-  function lcs () {
-  $lcs = 0;
-    foreach ($this->edits as $edit) {
-      if ($edit->type == 'copy')
-        $lcs += sizeof($edit->orig);
+
+    /**
+     * Check for empty diff.
+     *
+     * @return bool True iff two sequences were identical.
+     */
+    function isEmpty () {
+        foreach ($this->edits as $edit) {
+            if ($edit->type != 'copy')
+                return false;
+        }
+        return true;
     }
-  return $lcs;
-  }
-
-  /**
-   * Get the original set of lines.
-   *
-   * This reconstructs the $from_lines parameter passed to the
-   * constructor.
-   *
-   * @return array The original sequence of strings.
-   */
-  function orig() {
-    $lines = array();
-
-    foreach ($this->edits as $edit) {
-      if ($edit->orig)
-        array_splice($lines, sizeof($lines), 0, $edit->orig);
+
+    /**
+     * Compute the length of the Longest Common Subsequence (LCS).
+     *
+     * This is mostly for diagnostic purposed.
+     *
+     * @return int The length of the LCS.
+     */
+    function lcs () {
+        $lcs = 0;
+        foreach ($this->edits as $edit) {
+            if ($edit->type == 'copy')
+                $lcs += count($edit->orig);
+        }
+        return $lcs;
     }
-    return $lines;
-  }
-
-  /**
-   * Get the closing set of lines.
-   *
-   * This reconstructs the $to_lines parameter passed to the
-   * constructor.
-   *
-   * @return array The sequence of strings.
-   */
-  function closing() {
-    $lines = array();
-
-    foreach ($this->edits as $edit) {
-      if ($edit->closing)
-        array_splice($lines, sizeof($lines), 0, $edit->closing);
+
+    /**
+     * Get the original set of lines.
+     *
+     * This reconstructs the $from_lines parameter passed to the
+     * constructor.
+     *
+     * @return array The original sequence of strings.
+     */
+    function orig() {
+        $lines = array();
+
+        foreach ($this->edits as $edit) {
+            if ($edit->orig)
+                array_splice($lines, count($lines), 0, $edit->orig);
+        }
+        return $lines;
     }
-    return $lines;
-  }
-
-  /**
-   * Check a Diff for validity.
-   *
-   * This is here only for debugging purposes.
-   */
-  function _check ($from_lines, $to_lines) {
-    if (serialize($from_lines) != serialize($this->orig()))
-      trigger_error("Reconstructed original doesn't match", E_USER_ERROR);
-    if (serialize($to_lines) != serialize($this->closing()))
-      trigger_error("Reconstructed closing doesn't match", E_USER_ERROR);
-
-    $rev = $this->reverse();
-    if (serialize($to_lines) != serialize($rev->orig()))
-      trigger_error("Reversed original doesn't match", E_USER_ERROR);
-    if (serialize($from_lines) != serialize($rev->closing()))
-      trigger_error("Reversed closing doesn't match", E_USER_ERROR);
-
-
-    $prevtype = 'none';
-    foreach ($this->edits as $edit) {
-      if ( $prevtype == $edit->type )
-        trigger_error("Edit sequence is non-optimal", E_USER_ERROR);
-      $prevtype = $edit->type;
+
+    /**
+     * Get the closing set of lines.
+     *
+     * This reconstructs the $to_lines parameter passed to the
+     * constructor.
+     *
+     * @return array The sequence of strings.
+     */
+    function closing() {
+        $lines = array();
+
+        foreach ($this->edits as $edit) {
+            if ($edit->closing)
+                array_splice($lines, count($lines), 0, $edit->closing);
+        }
+        return $lines;
     }
 
-    $lcs = $this->lcs();
-    trigger_error("Diff okay: LCS = $lcs", E_USER_NOTICE);
-  }
+    /**
+     * Check a Diff for validity.
+     *
+     * This is here only for debugging purposes.
+     */
+    function _check ($from_lines, $to_lines) {
+        if (serialize($from_lines) != serialize($this->orig()))
+            trigger_error("Reconstructed original doesn't match", E_USER_ERROR);
+        if (serialize($to_lines) != serialize($this->closing()))
+            trigger_error("Reconstructed closing doesn't match", E_USER_ERROR);
+
+        $rev = $this->reverse();
+        if (serialize($to_lines) != serialize($rev->orig()))
+            trigger_error("Reversed original doesn't match", E_USER_ERROR);
+        if (serialize($from_lines) != serialize($rev->closing()))
+            trigger_error("Reversed closing doesn't match", E_USER_ERROR);
+
+        $prevtype = 'none';
+        foreach ($this->edits as $edit) {
+            if ( $prevtype == $edit->type )
+                trigger_error("Edit sequence is non-optimal", E_USER_ERROR);
+            $prevtype = $edit->type;
+        }
+
+        $lcs = $this->lcs();
+        trigger_error("Diff okay: LCS = $lcs", E_USER_NOTICE);
+    }
 }
 
 /**
  * FIXME: bad name.
  */
-class MappedDiff
-extends Diff
-{
-  /**
-   * Constructor.
-   *
-   * Computes diff between sequences of strings.
-   *
-   * This can be used to compute things like
-   * case-insensitve diffs, or diffs which ignore
-   * changes in white-space.
-   *
-   * @param $from_lines array An array of strings.
-   *  (Typically these are lines from a file.)
-   *
-   * @param $to_lines array An array of strings.
-   *
-   * @param $mapped_from_lines array This array should
-   *  have the same size number of elements as $from_lines.
-   *  The elements in $mapped_from_lines and
-   *  $mapped_to_lines are what is actually compared
-   *  when computing the diff.
-   *
-   * @param $mapped_to_lines array This array should
-   *  have the same number of elements as $to_lines.
-   */
-  function MappedDiff($from_lines, $to_lines,
+class MappedDiff extends Diff {
+    /**
+     * Constructor.
+     *
+     * Computes diff between sequences of strings.
+     *
+     * This can be used to compute things like
+     * case-insensitve diffs, or diffs which ignore
+     * changes in white-space.
+     *
+     * @param $from_lines array An array of strings.
+     *  (Typically these are lines from a file.)
+     *
+     * @param $to_lines array An array of strings.
+     *
+     * @param $mapped_from_lines array This array should
+     *  have the same size number of elements as $from_lines.
+     *  The elements in $mapped_from_lines and
+     *  $mapped_to_lines are what is actually compared
+     *  when computing the diff.
+     *
+     * @param $mapped_to_lines array This array should
+     *  have the same number of elements as $to_lines.
+     */
+    function MappedDiff($from_lines, $to_lines,
             $mapped_from_lines, $mapped_to_lines) {
 
-    assert(sizeof($from_lines) == sizeof($mapped_from_lines));
-    assert(sizeof($to_lines) == sizeof($mapped_to_lines));
+        assert(count($from_lines) == count($mapped_from_lines));
+        assert(count($to_lines) == count($mapped_to_lines));
 
-    $this->Diff($mapped_from_lines, $mapped_to_lines);
+        $this->Diff($mapped_from_lines, $mapped_to_lines);
 
-    $xi = $yi = 0;
-    for ($i = 0; $i < sizeof($this->edits); $i++) {
-      $orig = &$this->edits[$i]->orig;
-      if (is_array($orig)) {
-        $orig = array_slice($from_lines, $xi, sizeof($orig));
-        $xi += sizeof($orig);
-      }
+        $xi = $yi = 0;
+        $ecnt = count($this->edits);
+        for ($i = 0; $i < $ecnt; $i++) {
+            $orig = &$this->edits[$i]->orig;
+            if (is_array($orig)) {
+                $orig = array_slice($from_lines, $xi, count($orig));
+                $xi += count($orig);
+            }
 
-      $closing = &$this->edits[$i]->closing;
-      if (is_array($closing)) {
-        $closing = array_slice($to_lines, $yi, sizeof($closing));
-        $yi += sizeof($closing);
-      }
+            $closing = &$this->edits[$i]->closing;
+            if (is_array($closing)) {
+                $closing = array_slice($to_lines, $yi, count($closing));
+                $yi += count($closing);
+            }
+        }
     }
-  }
 }
 
 /**
@@ -682,150 +682,149 @@ extends Diff
  * It is intended that this class be customized via inheritance,
  * to obtain fancier outputs.
  */
-class DiffFormatter
-{
-  /**
-   * Number of leading context "lines" to preserve.
-   *
-   * This should be left at zero for this class, but subclasses
-   * may want to set this to other values.
-   */
-  var $leading_context_lines = 0;
-
-  /**
-   * Number of trailing context "lines" to preserve.
-   *
-   * This should be left at zero for this class, but subclasses
-   * may want to set this to other values.
-   */
-  var $trailing_context_lines = 0;
-
-  /**
-   * Format a diff.
-   *
-   * @param $diff object A Diff object.
-   * @return string The formatted output.
-   */
-  function format($diff) {
-
-    $xi = $yi = 1;
-    $block = false;
-    $context = array();
-
-    $nlead = $this->leading_context_lines;
-    $ntrail = $this->trailing_context_lines;
-
-    $this->_start_diff();
-
-    foreach ($diff->edits as $edit) {
-      if ($edit->type == 'copy') {
-        if (is_array($block)) {
-          if (sizeof($edit->orig) <= $nlead + $ntrail) {
-            $block[] = $edit;
-          }
-          else{
-            if ($ntrail) {
-              $context = array_slice($edit->orig, 0, $ntrail);
-              $block[] = new _DiffOp_Copy($context);
+class DiffFormatter {
+    /**
+     * Number of leading context "lines" to preserve.
+     *
+     * This should be left at zero for this class, but subclasses
+     * may want to set this to other values.
+     */
+    var $leading_context_lines = 0;
+
+    /**
+     * Number of trailing context "lines" to preserve.
+     *
+     * This should be left at zero for this class, but subclasses
+     * may want to set this to other values.
+     */
+    var $trailing_context_lines = 0;
+
+    /**
+     * Format a diff.
+     *
+     * @param $diff object A Diff object.
+     * @return string The formatted output.
+     */
+    function format($diff) {
+
+        $xi = $yi = 1;
+        $block = false;
+        $context = array();
+
+        $nlead = $this->leading_context_lines;
+        $ntrail = $this->trailing_context_lines;
+
+        $this->_start_diff();
+
+        foreach ($diff->edits as $edit) {
+            if ($edit->type == 'copy') {
+                if (is_array($block)) {
+                    if (count($edit->orig) <= $nlead + $ntrail) {
+                        $block[] = $edit;
+                    }
+                    else{
+                        if ($ntrail) {
+                            $context = array_slice($edit->orig, 0, $ntrail);
+                            $block[] = new _DiffOp_Copy($context);
+                        }
+                        $this->_block($x0, $ntrail + $xi - $x0,
+                                $y0, $ntrail + $yi - $y0,
+                                $block);
+                        $block = false;
+                    }
+                }
+                $context = $edit->orig;
             }
-            $this->_block($x0, $ntrail + $xi - $x0,
-                    $y0, $ntrail + $yi - $y0,
-                    $block);
-            $block = false;
-          }
+            else {
+                if (! is_array($block)) {
+                    $context = array_slice($context, count($context) - $nlead);
+                    $x0 = $xi - count($context);
+                    $y0 = $yi - count($context);
+                    $block = array();
+                    if ($context)
+                        $block[] = new _DiffOp_Copy($context);
+                }
+                $block[] = $edit;
+            }
+
+            if ($edit->orig)
+                $xi += count($edit->orig);
+            if ($edit->closing)
+                $yi += count($edit->closing);
         }
-        $context = $edit->orig;
-      }
-      else {
-        if (! is_array($block)) {
-          $context = array_slice($context, sizeof($context) - $nlead);
-          $x0 = $xi - sizeof($context);
-          $y0 = $yi - sizeof($context);
-          $block = array();
-          if ($context)
-            $block[] = new _DiffOp_Copy($context);
+
+        if (is_array($block))
+            $this->_block($x0, $xi - $x0,
+                    $y0, $yi - $y0,
+                    $block);
+
+        return $this->_end_diff();
+    }
+
+    function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
+        $this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
+        foreach ($edits as $edit) {
+            if ($edit->type == 'copy')
+                $this->_context($edit->orig);
+            elseif ($edit->type == 'add')
+                $this->_added($edit->closing);
+            elseif ($edit->type == 'delete')
+                $this->_deleted($edit->orig);
+            elseif ($edit->type == 'change')
+                $this->_changed($edit->orig, $edit->closing);
+            else
+                trigger_error("Unknown edit type", E_USER_ERROR);
         }
-        $block[] = $edit;
-      }
+        $this->_end_block();
+    }
+
+    function _start_diff() {
+        ob_start();
+    }
+
+    function _end_diff() {
+        $val = ob_get_contents();
+        ob_end_clean();
+        return $val;
+    }
+
+    function _block_header($xbeg, $xlen, $ybeg, $ylen) {
+        if ($xlen > 1)
+            $xbeg .= "," . ($xbeg + $xlen - 1);
+        if ($ylen > 1)
+            $ybeg .= "," . ($ybeg + $ylen - 1);
+
+        return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
+    }
+
+    function _start_block($header) {
+        echo $header;
+    }
+
+    function _end_block() {
+    }
+
+    function _lines($lines, $prefix = ' ') {
+        foreach ($lines as $line)
+            echo "$prefix $line\n";
+    }
+
+    function _context($lines) {
+        $this->_lines($lines);
+    }
 
-      if ($edit->orig)
-        $xi += sizeof($edit->orig);
-      if ($edit->closing)
-        $yi += sizeof($edit->closing);
+    function _added($lines) {
+        $this->_lines($lines, ">");
+    }
+    function _deleted($lines) {
+        $this->_lines($lines, "<");
     }
 
-    if (is_array($block))
-      $this->_block($x0, $xi - $x0,
-              $y0, $yi - $y0,
-              $block);
-
-    return $this->_end_diff();
-  }
-
-  function _block($xbeg, $xlen, $ybeg, $ylen, &$edits) {
-    $this->_start_block($this->_block_header($xbeg, $xlen, $ybeg, $ylen));
-    foreach ($edits as $edit) {
-      if ($edit->type == 'copy')
-        $this->_context($edit->orig);
-      elseif ($edit->type == 'add')
-        $this->_added($edit->closing);
-      elseif ($edit->type == 'delete')
-        $this->_deleted($edit->orig);
-      elseif ($edit->type == 'change')
-        $this->_changed($edit->orig, $edit->closing);
-      else
-        trigger_error("Unknown edit type", E_USER_ERROR);
+    function _changed($orig, $closing) {
+        $this->_deleted($orig);
+        echo "---\n";
+        $this->_added($closing);
     }
-    $this->_end_block();
-  }
-
-  function _start_diff() {
-    ob_start();
-  }
-
-  function _end_diff() {
-    $val = ob_get_contents();
-    ob_end_clean();
-    return $val;
-  }
-
-  function _block_header($xbeg, $xlen, $ybeg, $ylen) {
-    if ($xlen > 1)
-      $xbeg .= "," . ($xbeg + $xlen - 1);
-    if ($ylen > 1)
-      $ybeg .= "," . ($ybeg + $ylen - 1);
-
-    return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;
-  }
-
-  function _start_block($header) {
-    echo $header;
-  }
-
-  function _end_block() {
-  }
-
-  function _lines($lines, $prefix = ' ') {
-    foreach ($lines as $line)
-      echo "$prefix $line\n";
-  }
-
-  function _context($lines) {
-    $this->_lines($lines);
-  }
-
-  function _added($lines) {
-    $this->_lines($lines, ">");
-  }
-  function _deleted($lines) {
-    $this->_lines($lines, "<");
-  }
-
-  function _changed($orig, $closing) {
-    $this->_deleted($orig);
-    echo "---\n";
-    $this->_added($closing);
-  }
 }
 
 
@@ -837,100 +836,97 @@ class DiffFormatter
 define('NBSP', "\xC2\xA0");     // utf-8 non-breaking space.
 
 class _HWLDF_WordAccumulator {
-  function _HWLDF_WordAccumulator () {
-    $this->_lines = array();
-    $this->_line = '';
-    $this->_group = '';
-    $this->_tag = '';
-  }
-
-  function _flushGroup ($new_tag) {
-    if ($this->_group !== '') {
-    if ($this->_tag == 'mark')
-      $this->_line .= '<strong>'.$this->_group.'</strong>';
-    else
-    $this->_line .= $this->_group;
-  }
-    $this->_group = '';
-    $this->_tag = $new_tag;
-  }
-
-  function _flushLine ($new_tag) {
-    $this->_flushGroup($new_tag);
-    if ($this->_line != '')
-      $this->_lines[] = $this->_line;
-    $this->_line = '';
-  }
-
-  function addWords ($words, $tag = '') {
-    if ($tag != $this->_tag)
-      $this->_flushGroup($tag);
-
-    foreach ($words as $word) {
-      // new-line should only come as first char of word.
-      if ($word == '')
-        continue;
-      if ($word[0] == "\n") {
-        $this->_group .= NBSP;
-        $this->_flushLine($tag);
-        $word = substr($word, 1);
-      }
-      assert(!strstr($word, "\n"));
-      $this->_group .= $word;
+    function _HWLDF_WordAccumulator () {
+        $this->_lines = array();
+        $this->_line = '';
+        $this->_group = '';
+        $this->_tag = '';
     }
-  }
-
-  function getLines() {
-    $this->_flushLine('~done');
-    return $this->_lines;
-  }
-}
 
-class WordLevelDiff extends MappedDiff
-{
-  function WordLevelDiff ($orig_lines, $closing_lines) {
-    list ($orig_words, $orig_stripped) = $this->_split($orig_lines);
-    list ($closing_words, $closing_stripped) = $this->_split($closing_lines);
+    function _flushGroup ($new_tag) {
+        if ($this->_group !== '') {
+            if ($this->_tag == 'mark')
+                $this->_line .= '<strong>'.$this->_group.'</strong>';
+            else
+                $this->_line .= $this->_group;
+        }
+        $this->_group = '';
+        $this->_tag = $new_tag;
+    }
 
+    function _flushLine ($new_tag) {
+        $this->_flushGroup($new_tag);
+        if ($this->_line != '')
+            $this->_lines[] = $this->_line;
+        $this->_line = '';
+    }
 
-    $this->MappedDiff($orig_words, $closing_words,
-              $orig_stripped, $closing_stripped);
-  }
+    function addWords ($words, $tag = '') {
+        if ($tag != $this->_tag)
+            $this->_flushGroup($tag);
+
+        foreach ($words as $word) {
+            // new-line should only come as first char of word.
+            if ($word == '')
+                continue;
+            if ($word[0] == "\n") {
+                $this->_group .= NBSP;
+                $this->_flushLine($tag);
+                $word = substr($word, 1);
+            }
+            assert(!strstr($word, "\n"));
+            $this->_group .= $word;
+        }
+    }
 
-  function _split($lines) {
-    // FIXME: fix POSIX char class.
-#    if (!preg_match_all('/ ( [^\S\n]+ | [[:alnum:]]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
-    if (!preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
-              implode("\n", $lines),
-              $m)) {
-      return array(array(''), array(''));
+    function getLines() {
+        $this->_flushLine('~done');
+        return $this->_lines;
     }
-    return array($m[0], $m[1]);
-  }
+}
+
+class WordLevelDiff extends MappedDiff {
 
-  function orig () {
-    $orig = new _HWLDF_WordAccumulator;
+    function WordLevelDiff ($orig_lines, $closing_lines) {
+        list ($orig_words, $orig_stripped) = $this->_split($orig_lines);
+        list ($closing_words, $closing_stripped) = $this->_split($closing_lines);
 
-    foreach ($this->edits as $edit) {
-      if ($edit->type == 'copy')
-        $orig->addWords($edit->orig);
-      elseif ($edit->orig)
-        $orig->addWords($edit->orig, 'mark');
+        $this->MappedDiff($orig_words, $closing_words,
+                $orig_stripped, $closing_stripped);
     }
-    return $orig->getLines();
-  }
 
-  function closing () {
-    $closing = new _HWLDF_WordAccumulator;
+    function _split($lines) {
+            if (!preg_match_all('/ ( [^\S\n]+ | [0-9_A-Za-z\x80-\xff]+ | . ) (?: (?!< \n) [^\S\n])? /xs',
+                    implode("\n", $lines),
+                    $m)) {
+            return array(array(''), array(''));
+            }
+            return array($m[0], $m[1]);
+            }
+
+            function orig () {
+            $orig = new _HWLDF_WordAccumulator;
 
-    foreach ($this->edits as $edit) {
-      if ($edit->type == 'copy')
-        $closing->addWords($edit->closing);
-      elseif ($edit->closing)
-        $closing->addWords($edit->closing, 'mark');
-    }
-    return $closing->getLines();
-  }
+            foreach ($this->edits as $edit) {
+            if ($edit->type == 'copy')
+            $orig->addWords($edit->orig);
+            elseif ($edit->orig)
+            $orig->addWords($edit->orig, 'mark');
+            }
+            return $orig->getLines();
+            }
+
+            function closing () {
+                $closing = new _HWLDF_WordAccumulator;
+
+                foreach ($this->edits as $edit) {
+                    if ($edit->type == 'copy')
+                        $closing->addWords($edit->closing);
+                    elseif ($edit->closing)
+                        $closing->addWords($edit->closing, 'mark');
+                }
+                return $closing->getLines();
+            }
 }
 
 /**
@@ -938,8 +934,8 @@ class WordLevelDiff extends MappedDiff
  *
  * This class formats the diff in classic "unified diff" format.
  */
-class UnifiedDiffFormatter extends DiffFormatter
-{
+class UnifiedDiffFormatter extends DiffFormatter {
+
     function UnifiedDiffFormatter($context_lines = 4) {
         $this->leading_context_lines = $context_lines;
         $this->trailing_context_lines = $context_lines;
@@ -969,12 +965,12 @@ class UnifiedDiffFormatter extends DiffFormatter
  *  Wikipedia Table style diff formatter.
  *
  */
-class TableDiffFormatter extends DiffFormatter
-{
-  function TableDiffFormatter() {
-    $this->leading_context_lines = 2;
-    $this->trailing_context_lines = 2;
-  }
+class TableDiffFormatter extends DiffFormatter {
+
+    function TableDiffFormatter() {
+        $this->leading_context_lines = 2;
+        $this->trailing_context_lines = 2;
+    }
 
     function format($diff) {
         // Preserve whitespaces by converting some to non-breaking spaces.
@@ -985,83 +981,83 @@ class TableDiffFormatter extends DiffFormatter
         return $val;
     }
 
-  function _pre($text){
-    $text = htmlspecialchars($text);
-    return $text;
-  }
-
-  function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
-    global $lang;
-    $l1 = $lang['line'].' '.$xbeg;
-    $l2 = $lang['line'].' '.$ybeg;
-    $r = '<tr><td class="diff-blockheader" colspan="2">'.$l1.":</td>\n" .
-      '<td class="diff-blockheader" colspan="2">'.$l2.":</td></tr>\n";
-    return $r;
-  }
-
-  function _start_block( $header ) {
-    print( $header );
-  }
-
-  function _end_block() {
-  }
-
-  function _lines( $lines, $prefix=' ', $color="white" ) {
-  }
-
-  function addedLine( $line ) {
-    return '<td>+</td><td class="diff-addedline">' .
-      $line.'</td>';
-
-  }
-
-  function deletedLine( $line ) {
-    return '<td>-</td><td class="diff-deletedline">' .
-      $line.'</td>';
-  }
-
-  function emptyLine() {
-    return '<td colspan="2">&nbsp;</td>';
-  }
-
-  function contextLine( $line ) {
-    return '<td> </td><td class="diff-context">'.$line.'</td>';
-  }
-
-  function _added($lines) {
-    foreach ($lines as $line) {
-      print( '<tr>' . $this->emptyLine() .
-        $this->addedLine( $line ) . "</tr>\n" );
+    function _pre($text){
+        $text = htmlspecialchars($text);
+        return $text;
+    }
+
+    function _block_header( $xbeg, $xlen, $ybeg, $ylen ) {
+        global $lang;
+        $l1 = $lang['line'].' '.$xbeg;
+        $l2 = $lang['line'].' '.$ybeg;
+        $r = '<tr><td class="diff-blockheader" colspan="2">'.$l1.":</td>\n" .
+            '<td class="diff-blockheader" colspan="2">'.$l2.":</td></tr>\n";
+        return $r;
+    }
+
+    function _start_block( $header ) {
+        print( $header );
+    }
+
+    function _end_block() {
+    }
+
+    function _lines( $lines, $prefix=' ', $color="white" ) {
+    }
+
+    function addedLine( $line ) {
+        return '<td>+</td><td class="diff-addedline">' .
+            $line.'</td>';
+
+    }
+
+    function deletedLine( $line ) {
+        return '<td>-</td><td class="diff-deletedline">' .
+            $line.'</td>';
     }
-  }
 
-  function _deleted($lines) {
-    foreach ($lines as $line) {
-      print( '<tr>' . $this->deletedLine( $line ) .
-        $this->emptyLine() . "</tr>\n" );
+    function emptyLine() {
+        return '<td colspan="2">&nbsp;</td>';
     }
-  }
 
-  function _context( $lines ) {
-    foreach ($lines as $line) {
-      print( '<tr>' . $this->contextLine( $line ) .
-        $this->contextLine( $line ) . "</tr>\n" );
+    function contextLine( $line ) {
+        return '<td> </td><td class="diff-context">'.$line.'</td>';
     }
-  }
 
-  function _changed( $orig, $closing ) {
-    $diff = new WordLevelDiff( $orig, $closing );
-    $del = $diff->orig();
-    $add = $diff->closing();
+    function _added($lines) {
+        foreach ($lines as $line) {
+            print( '<tr>' . $this->emptyLine() .
+                    $this->addedLine( $line ) . "</tr>\n" );
+        }
+    }
+
+    function _deleted($lines) {
+        foreach ($lines as $line) {
+            print( '<tr>' . $this->deletedLine( $line ) .
+                    $this->emptyLine() . "</tr>\n" );
+        }
+    }
+
+    function _context( $lines ) {
+        foreach ($lines as $line) {
+            print( '<tr>' . $this->contextLine( $line ) .
+                    $this->contextLine( $line ) . "</tr>\n" );
+        }
+    }
+
+    function _changed( $orig, $closing ) {
+        $diff = new WordLevelDiff( $orig, $closing );
+        $del = $diff->orig();
+        $add = $diff->closing();
 
-    while ( $line = array_shift( $del ) ) {
-      $aline = array_shift( $add );
-      print( '<tr>' . $this->deletedLine( $line ) .
-        $this->addedLine( $aline ) . "</tr>\n" );
+        while ( $line = array_shift( $del ) ) {
+            $aline = array_shift( $add );
+            print( '<tr>' . $this->deletedLine( $line ) .
+                    $this->addedLine( $aline ) . "</tr>\n" );
+        }
+        $this->_added( $add ); # If any leftovers
     }
-    $this->_added( $add ); # If any leftovers
-  }
 }
 
 
-//Setup VIM: ex: et ts=2 enc=utf-8 :
+//Setup VIM: ex: et ts=4 enc=utf-8 :