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   1  <?php
   2  /**
   3   * Class used internally by Diff to actually compute the diffs.
   4   *
   5   * This class uses the xdiff PECL package (http://pecl.php.net/package/xdiff)
   6   * to compute the differences between the two input arrays.
   7   *
   8   * Copyright 2004-2010 The Horde Project (http://www.horde.org/)
   9   *
  10   * See the enclosed file COPYING for license information (LGPL). If you did
  11   * not receive this file, see http://opensource.org/licenses/lgpl-license.php.
  12   *
  13   * @author  Jon Parise <jon@horde.org>
  14   * @package Text_Diff
  15   */
  16  class Text_Diff_Engine_xdiff {
  17  
  18      /**
  19       */
  20      function diff($from_lines, $to_lines)
  21      {
  22          array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
  23          array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
  24  
  25          /* Convert the two input arrays into strings for xdiff processing. */
  26          $from_string = implode("\n", $from_lines);
  27          $to_string = implode("\n", $to_lines);
  28  
  29          /* Diff the two strings and convert the result to an array. */
  30          $diff = xdiff_string_diff($from_string, $to_string, count($to_lines));
  31          $diff = explode("\n", $diff);
  32  
  33          /* Walk through the diff one line at a time.  We build the $edits
  34           * array of diff operations by reading the first character of the
  35           * xdiff output (which is in the "unified diff" format).
  36           *
  37           * Note that we don't have enough information to detect "changed"
  38           * lines using this approach, so we can't add Text_Diff_Op_changed
  39           * instances to the $edits array.  The result is still perfectly
  40           * valid, albeit a little less descriptive and efficient. */
  41          $edits = array();
  42          foreach ($diff as $line) {
  43              if (!strlen($line)) {
  44                  continue;
  45              }
  46              switch ($line[0]) {
  47              case ' ':
  48                  $edits[] = new Text_Diff_Op_copy(array(substr($line, 1)));
  49                  break;
  50  
  51              case '+':
  52                  $edits[] = new Text_Diff_Op_add(array(substr($line, 1)));
  53                  break;
  54  
  55              case '-':
  56                  $edits[] = new Text_Diff_Op_delete(array(substr($line, 1)));
  57                  break;
  58              }
  59          }
  60  
  61          return $edits;
  62      }
  63  
  64  }