diff --git a/inc/inc.Utils.php b/inc/inc.Utils.php
index 69780e777..edb100c0f 100644
--- a/inc/inc.Utils.php
+++ b/inc/inc.Utils.php
@@ -367,6 +367,34 @@ function utf8_basename($path, $suffix='') { /* {{{ */
 	return $file;
 } /* }}} */
 
+/**
+ * Return a valid file name
+ *
+ * This function returns a valid file name for the given document content
+ * or an arbitrary string. If a document content is given the name of
+ * the document will be used. The extension of the file name will be
+ * either taken from the document name or the original file. If the two
+ * differ the extension from the original file name will be used.
+ *
+ * @param object|string $content document content or an arbitrary string
+ * @return string valid file name
+ */
+function getFilenameByDocname($content) { /* {{{ */
+	if(is_string) {
+		$filename = $content;
+	} else {
+		$document = $content->getDocument();
+		$ext = pathinfo($document->getName(), PATHINFO_EXTENSION);
+		$oext = pathinfo($content->getOriginalFileName(), PATHINFO_EXTENSION);
+		if($ext == $oext)
+			$filename = $document->getName();
+		else {
+			$filename = $document->getName().'.'.$oext;
+		}
+	}
+	return mb_ereg_replace("([^\w\s\d\-_~,;\[\]\(\).])", '', $filename);
+} /* }}} */
+
 function getLogger($prefix='') { /* {{{ */
 	global $settings;