public static function get_pathname_hash($contextid, $component, $filearea, $itemid, $filepath, $filename) {
        return sha1("/$contextid/$component/$filearea/$itemid".$filepath.$filename);
    }
public static function get_pathname_hash($contextid, $component, $filearea, $itemid, $filepath, $filename) {
        return sha1("/$contextid/$component/$filearea/$itemid".$filepath.$filename);
    }
public static function get_pathname_hash ( $ contextid , $ component , $ filearea , $ itemid , $ filepath , $ filename ) { return sha1 ( "/$contextid/$component/$filearea/$itemid" . $ filepath . $ filename ) ; }
Calculates sha1 hash of unique full path name information.

This hash is a unique file identifier - it is used to improve
performance and overcome db index size limits.

@param int $contextid context ID
@param string $component component
@param string $filearea file area
@param int $itemid item ID
@param string $filepath file path
@param string $filename file name
@return string sha1 hash
Calculates sha1 hash of unique full path name information .