performance tweak

functions/mime.php

@@ -574,6 +574,7 @@ function decodeHeader ($string, $utfencode=true,$htmlsave=true) {
         $encoded = false;
         /* if encoded words are not separated by a linear-space-white we still catch them */
         $j = $i-1;
+	if ($chunk{0} === '=') { /* performance, saves an unnessecarry preg call */
         while ($match = preg_match('/^(.*)=\?([^?]*)\?(Q|B)\?([^?]*)\?=(.*)$/Ui',$chunk,$res)) {
             /* if the last chunk isn't an encoded string then put back the space, otherwise don't */
             if ($iLastMatch !== $j) {
@@ -615,6 +616,7 @@ function decodeHeader ($string, $utfencode=true,$htmlsave=true) {
             $chunk = $res[5];
             $encoded = true;
         }
+	}
         if (!$encoded) {
             if ($htmlsave) {
                 $ret .= ' ';