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wp-includes/Text/Diff/Engine/xdiff.php

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+<?php
+/**
+ * Class used internally by Diff to actually compute the diffs.
+ *
+ * This class uses the xdiff PECL package (http://pecl.php.net/package/xdiff)
+ * to compute the differences between the two input arrays.
+ *
+ * Copyright 2004-2010 The Horde Project (http://www.horde.org/)
+ *
+ * See the enclosed file COPYING for license information (LGPL). If you did
+ * not receive this file, see https://opensource.org/license/lgpl-2-1/.
+ *
+ * @author  Jon Parise <jon@horde.org>
+ * @package Text_Diff
+ */
+class Text_Diff_Engine_xdiff {
+
+    /**
+     */
+    function diff($from_lines, $to_lines)
+    {
+        array_walk($from_lines, array('Text_Diff', 'trimNewlines'));
+        array_walk($to_lines, array('Text_Diff', 'trimNewlines'));
+
+        /* Convert the two input arrays into strings for xdiff processing. */
+        $from_string = implode("\n", $from_lines);
+        $to_string = implode("\n", $to_lines);
+
+        /* Diff the two strings and convert the result to an array. */
+        $diff = xdiff_string_diff($from_string, $to_string, count($to_lines));
+        $diff = explode("\n", $diff);
+
+        /* Walk through the diff one line at a time.  We build the $edits
+         * array of diff operations by reading the first character of the
+         * xdiff output (which is in the "unified diff" format).
+         *
+         * Note that we don't have enough information to detect "changed"
+         * lines using this approach, so we can't add Text_Diff_Op_changed
+         * instances to the $edits array.  The result is still perfectly
+         * valid, albeit a little less descriptive and efficient. */
+        $edits = array();
+        foreach ($diff as $line) {
+            if (!strlen($line)) {
+                continue;
+            }
+            switch ($line[0]) {
+            case ' ':
+                $edits[] = new Text_Diff_Op_copy(array(substr($line, 1)));
+                break;
+
+            case '+':
+                $edits[] = new Text_Diff_Op_add(array(substr($line, 1)));
+                break;
+
+            case '-':
+                $edits[] = new Text_Diff_Op_delete(array(substr($line, 1)));
+                break;
+            }
+        }
+
+        return $edits;
+    }
+
+}