Wikka Mod 013

Type: Feature Addition

Credit:

Jason Tourtelotte


Added "Page History" link in footer.php to make this addition easily accessible.



handlers/page/history.php

<div class="page">
<?php
if ($this->HasAccess("read")) {
    // load revisions for this page
    if ($pages = $this->LoadRevisions($this->tag))
    {
        if ($user = $this->GetUser())
        {
            $max = $user["revisioncount"];
        }
        else
        {
            $max = 20;
        }

        $c = 0;
        foreach ($pages as $page)
        {
            $c++;
            if (($c <= $max) || !$max)
            {

                $pageB = $this->LoadPageById($page["id"]);
                $bodyB = explode("\n", $pageB["body"]);

                if ($pageA)
                {
                    // show by default. We'll do security checks next.
                    $allowed = 1;

                    // check if the loaded pages are actually revisions of the current page! (fixes #0000046)
                    //print_r($pageA); print_r($this->page); exit;
                    if (($pageA['tag'] != $this->page['tag']) || ($pageB['tag'] != $this->page['tag'])) {
                        $allowed = 0;
                    }
                    // show if we're still allowed to see the diff
                    if ($allowed) {

                        // prepare bodies
                        $bodyA = explode("\n", $pageA["body"]);
                        // $bodyB = explode("\n", $pageB["body"]);

                        $added = array_diff($bodyA, $bodyB);
                        $deleted = array_diff($bodyB, $bodyA);
                       
                        if ($c == 2) {
                            $output .= "<strong>Most recent edit on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br />\n";
                        }
                        else {
                           $output .= "<strong>Edited on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span><br />\n";
                        }                  
   
                        if ($added)
                        {
                            // remove blank lines
                            $output .= "<br />\n<strong>Additions:</strong><br />\n";
                            $output .= "<div class=\"additions\">".$this->Format(implode("\n", $added))."</div>";
                        }

                        if ($deleted)
                        {
                            $output .= "<br />\n<strong>Deletions:</strong><br />\n";
                            $output .= "<div class=\"deletions\">".$this->Format(implode("\n", $deleted))."</div>";
                        }

                        if (!$added && !$deleted)
                        {
                            $output .= "<br />\nNo differences.";
                        }
                        $output .= "<br />\n<HR><br />\n";
                    }
                }
                else {
                    // $output .= "<DIV class=\"revisioninfo\">Current page:</div>".$this->Format($pageB["body"])."<br />\n<HR><br />\n";
                }   
                $pageA = $this->LoadPageById($page["id"]);
            $EditedByUser = $this->Format($page["user"]);
            }
        }
    $output .= "<strong>Oldest known version of this page was edited on <a href=\"".$this->href("", "", "time=".urlencode($pageB["time"]))."\">".$pageB["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br />\n";
    $output .= "<DIV class=\"revisioninfo\">Page view:</div>".$this->Format(implode("\n", $bodyB));
    }
    print($output);

} else {
    print("<em>You aren't allowed to read this page.</em>");
}
?>
</div>



handlers/page/history2.php

<div class="page">
<?php
if ($this->HasAccess("read")) {
    // load revisions for this page
    if ($pages = $this->LoadRevisions($this->tag))
    {
        if ($user = $this->GetUser())
        {
            $max = $user["revisioncount"];
        }
        else
        {
            $max = 20;
        }

        $c = 0;
        foreach ($pages as $page)
        {
            $c++;
            if (($c <= $max) || !$max)
            {

                $pageA = $this->LoadPageById($page["id"]);
                $bodyB = explode("\n", $pageB["body"]);
       
                if ($pageB)
                {
                    // show by default. We'll do security checks next.
                    $allowed = 1;

                    // check if the loaded pages are actually revisions of the current page! (fixes #0000046)
                    //print_r($pageA); print_r($this->page); exit;
                    if (($pageA['tag'] != $this->page['tag']) || ($pageB['tag'] != $this->page['tag'])) {
                        $allowed = 0;
                    }
                    // show if we're still allowed to see the diff
                    if ($allowed) {


        // extract text from bodies
        $textA = $pageA["body"];
        $textB = $pageB["body"];
   
        $sideA = new Side($textA);
        $sideB = new Side($textB);
   
        $bodyA='';
        $sideA->split_file_into_words($bodyA);
   
        $bodyB='';
        $sideB->split_file_into_words($bodyB);
   
        // diff on these two file
        $diff = new Diff(split("\n",$bodyA),split("\n",$bodyB));
   
        // format output
        $fmt = new DiffFormatter();
   
        $sideO = new Side($fmt->format($diff));
   
        $resync_left=0;
        $resync_right=0;
   
        $count_total_right=$sideB->getposition() ;
   
        $sideA->init();
        $sideB->init();
   
        $output='';


                      if ($c == 2) {
                            echo "<strong>Most recent edit on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br /><br />\n";
                        }
                        else {
                            // $output .= "<strong>Comparing <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> to <a href=\"".$this->href("", "", "time=".urlencode($pageB["time"]))."\">".$pageB["time"]."</a></strong><br />\n";
                          echo "<strong>Edited on <a href=\"".$this->href("", "", "time=".urlencode($pageA["time"]))."\">".$pageA["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span><br /><br />\n";
                    }                  
 
   
          while (1) {
               
              $sideO->skip_line();
              if ($sideO->isend()) {
              break;
              }
   
              if ($sideO->decode_directive_line()) {
            $argument=$sideO->getargument();
            $letter=$sideO->getdirective();
              switch ($letter) {
                case 'a':
                  $resync_left = $argument[0];
                  $resync_right = $argument[2] - 1;
                  break;
   
                case 'd':
                  $resync_left = $argument[0] - 1;
                  $resync_right = $argument[2];
                  break;
   
                case 'c':
                  $resync_left = $argument[0] - 1;
                  $resync_right = $argument[2] - 1;
                  break;
   
                }
   
                $sideA->skip_until_ordinal($resync_left);
                $sideB->copy_until_ordinal($resync_right,$output);
     
    // deleted word
   
                if (($letter=='d') || ($letter=='c')) {
                  $sideA->copy_whitespace($output);
                  $output .="++";
                  $sideA->copy_word($output);
                  $sideA->copy_until_ordinal($argument[1],$output);
                  $output .="++";
                }
   
    // inserted word
                if ($letter == 'a' || $letter == 'c') {
                $sideB->copy_whitespace($output);
                $output .="+&pound;&pound;";
                $sideB->copy_word($output);
                $sideB->copy_until_ordinal($argument[3],$output);
                $output .="+&pound;&pound;";
                }
   
          }
   
        }
   
          $sideB->copy_until_ordinal($count_total_right,$output);
          $sideB->copy_whitespace($output);
          $out=$this->Format($output);
          echo $out;
          echo "<BR><BR>";
          echo "<HR>";
       

                    }
                }
                else {
                    // $output .= "<DIV class=\"revisioninfo\">Current page:</div>".$this->Format($pageB["body"])."<br />\n<HR><br />\n";
                }   
                $pageB = $this->LoadPageById($page["id"]);
        $EditedByUser = $this->Format($page["user"]);
          }
        }
   $bodyE = explode("\n", $pageB["body"]);
   $end_output .= "<strong>Oldest known version of this page was edited on <a href=\"".$this->href("", "", "time=".urlencode($pageB["time"]))."\">".$pageB["time"]."</a> by ".$EditedByUser."</strong> <span style=\"color:#888;font-size:smaller;\">[".$page["note"]."]</span></strong><br /><br />\n";
    $end_output .= $this->Format(implode("\n", $bodyE));
    }
    print($end_output);

} else {
    print("<em>You aren't allowed to read this page.</em>");
}


    // Side : a string for wdiff
   
    class Side {
        var $position;
        var $cursor;
        var $content;
        var $character;
        var $directive;
        var $argument;
        var $length;

        function Side($content) {
           $this->content=$content;
           $this->position=0;
           $this->cursor=0;
           $this->directive='';
           $this->argument=array();
           $this->length=strlen($this->content);
           $this->character=substr($this->content,0,1);
           
        }

        function getposition() {
           return $this->position;
        }

        function getcharacter() {
           return $this->character;
        }

        function getdirective() {
           return $this->directive;
        }

        function getargument() {
           return $this->argument;
        }

        function nextchar() {
           $this->cursor++;
           $this->character=substr($this->content,$this->cursor,1);
        }

        function copy_until_ordinal($ordinal,&$out)  {
           while ($this->position < $ordinal) {
          $this->copy_whitespace($out);
          $this->copy_word($out);
           }
        }

        function skip_until_ordinal($ordinal) {
           while ($this->position < $ordinal) {
          $this->skip_whitespace();
          $this->skip_word();
           }
        }

        function split_file_into_words (&$out) {
           while (!$this->isend()) {
         $this->skip_whitespace();
         if ($this->isend()) {
           break;
         }
         $this->copy_word($out);
         $out .="\n";
           }
        }
       
        function init() {
           $this->position=0;
           $this->cursor=0;
           $this->directive='';
           $this->argument=array();
           $this->character=substr($this->content,0,1);
        }   

        function isspace($char) {
           if (ereg('[[:space:]]',$char)) {
          return true;
           }
           else {
          return false;
           }
        }

        function isdigit($char) {
           if (ereg('[[:digit:]]',$char)) {
          return true;
           }
           else {
          return false;
           }
        }

        function isend() {
           if (($this->cursor)>=($this->length)) {
          return true;
           }
           else {
          return false;
           }
        }



        function copy_whitespace(&$out)  {
         while (!$this->isend() && $this->isspace($this->character)) {
            $out .=$this->character;
            $this->nextchar();
         }
        }

        function skip_whitespace()  {
         while (!$this->isend() && $this->isspace($this->character)) {
            $this->nextchar();
         }
        }

        function skip_line()  {
          while (!$this->isend() && !$this->isdigit($this->character)) {
          while (!$this->isend() && $this->character!="\n")
          $this->nextchar();
          if($this->character=="\n")
              $this->nextchar();
           }
         }



         function copy_word(&$out) {
         while (!$this->isend() && !($this->isspace($this->character))) {
            $out.=$this->character;
            $this->nextchar();
         }
         $this->position++;
         }

         function skip_word() {

         while (!$this->isend() && !($this->isspace($this->character))) {
            $this->nextchar();
         }
         $this->position++;
         }


     function decode_directive_line() {

      $value=0;                
      $state=0;                
      $error=0;              

      while (!$error && $state < 4) {
          if ($this->isdigit($this->character)) {
          $value = 0;
          while($this->isdigit($this->character)) {
              $value = 10 * $value + $this->character - '0';
              $this->nextchar();
          }
          }
          else if ($state != 1 && $state != 3)
          $error = 1;

          /* Assign the proper value.  */

          $this->argument[$state] = $value;

          /* Skip the following character.  */

          switch ($state) {
        case 0:
        case 2:
          if ($this->character == ',')
             $this->nextchar();
          break;

        case 1:
          if ($this->character == 'a' || $this->character == 'd' || $this->character == 'c') {
              $this->directive = $this->character;
              $this->nextchar();
            }
          else
            $error = 1;
          break;

          case 3:
          if ($this->character != "\n")
            $error = 1;
            break;
          }
         $state++;
          }

      /* Complete reading of the line and return success value.  */

      while ((!$this->isend()) && ($this->character != "\n")) {
          $this->nextchar();
      }
      if ($this->character == "\n")
          $this->nextchar();

      return !$error;
    }



    }

    // difflib
    //
    // A PHP diff engine for phpwiki.
    //
    // Copyright (C) 2000, 2001 Geoffrey T. Dairiki <dairiki@dairiki.org>
    // You may copy this code freely under the conditions of the GPL.
    //


    // PHP3 does not have assert()
    define('USE_ASSERTS', function_exists('assert'));

    class _DiffOp {
        var $type;
        var $orig;
        var $final;
       

        function norig() {
        return $this->orig ? sizeof($this->orig) : 0;
        }

        function nfinal() {
        return $this->final ? sizeof($this->final) : 0;
        }
    }

    class _DiffOp_Copy extends _DiffOp {
        var $type = 'copy';
       
        function _DiffOp_Copy ($orig, $final = false) {
        if (!is_array($final))
            $final = $orig;
        $this->orig = $orig;
        $this->final = $final;
        }

    }

    class _DiffOp_Delete extends _DiffOp {
        var $type = 'delete';
       
        function _DiffOp_Delete ($lines) {
        $this->orig = $lines;
        $this->final = false;
        }

    }

    class _DiffOp_Add extends _DiffOp {
        var $type = 'add';
       
        function _DiffOp_Add ($lines) {
        $this->final = $lines;
        $this->orig = false;
        }

    }

    class _DiffOp_Change extends _DiffOp {
        var $type = 'change';
       
        function _DiffOp_Change ($orig, $final) {
        $this->orig = $orig;
        $this->final = $final;
        }

    }
       
         
    /**
     * 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 are (and a bit of code) are from 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
     *
     * Finally, some ideas (subdivision by NCHUNKS > 2, and some optimizations)
     * are my own.
     *
     * @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;
        }
       
        // 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);
        }

        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];
                }
            }
            }
        }

        $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 _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;
        }

        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;
        }

        // 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).
         */

        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.
             *
             * 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);
        }

    }

           

    /**
     * A class to format Diffs
     *
     * This class formats the diff in classic diff format.
     * It is intended that this class be customized via inheritance,
     * to obtain fancier outputs.
     */

    class DiffFormatter
    {

        /**
         * Format a diff.
         *
         * @param $diff object A Diff object.
         * @return string The formatted output.
         */

        function format($diff) {

        $xi = $yi = 1;
        $block = false;
        $context = array();

        $this->_start_diff();

        foreach ($diff->edits as $edit) {
            if ($edit->type == 'copy') {
            if (is_array($block)) {
                if (sizeof($edit->orig) <= 0) {
                $block[] = $edit;
                }
                else{
                $this->_block($x0, + $xi - $x0,
                          $y0, + $yi - $y0,
                          $block);
                $block = false;
                }
            }
            }
            else {
            if (! is_array($block)) {
                $x0 = $xi;
                $y0 = $yi;
                $block = array();
            }
            $block[] = $edit;
            }

            if ($edit->orig)
            $xi += sizeof($edit->orig);
            if ($edit->final)
            $yi += sizeof($edit->final);
        }

        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));
        }

        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."\n";
        }

    }
   
?>
</div>
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