MX_Router::locate PHP Method

    public function locate($segments)
    {
        $this->located = 0;
        $ext = $this->config->item('controller_suffix') . EXT;
        /* use module route if available */
        if (isset($segments[0]) && ($routes = Modules::parse_routes($segments[0], implode('/', $segments)))) {
            $segments = $routes;
        }
        /* get the segments array elements */
        list($module, $directory, $controller) = array_pad($segments, 3, NULL);
        /* check modules */
        foreach (Modules::$locations as $location => $offset) {
            /* module exists? */
            if (is_dir($source = $location . $module . '/controllers/')) {
                $this->module = $module;
                $this->directory = $offset . $module . '/controllers/';
                /* module sub-controller exists? */
                if ($directory) {
                    /* module sub-directory exists? */
                    if (is_dir($source . $directory . '/')) {
                        $source .= $directory . '/';
                        $this->directory .= $directory . '/';
                        /* module sub-directory controller exists? */
                        if ($controller) {
                            if (is_file($source . ucfirst($controller) . $ext)) {
                                $this->located = 3;
                                return array_slice($segments, 2);
                            } else {
                                $this->located = -1;
                            }
                        }
                    } else {
                        if (is_file($source . ucfirst($directory) . $ext)) {
                            $this->located = 2;
                            return array_slice($segments, 1);
                        } else {
                            $this->located = -1;
                        }
                    }
                }
                /* module controller exists? */
                if (is_file($source . ucfirst($module) . $ext)) {
                    $this->located = 1;
                    return $segments;
                }
            }
        }
        if (!empty($this->directory)) {
            return;
        }
        /* application sub-directory controller exists? */
        if ($directory) {
            if (is_file(APPPATH . 'controllers/' . $module . '/' . ucfirst($directory) . $ext)) {
                $this->directory = $module . '/';
                return array_slice($segments, 1);
            }
            /* application sub-sub-directory controller exists? */
            if ($controller) {
                if (is_file(APPPATH . 'controllers/' . $module . '/' . $directory . '/' . ucfirst($controller) . $ext)) {
                    $this->directory = $module . '/' . $directory . '/';
                    return array_slice($segments, 2);
                }
            }
        }
        /* application controllers sub-directory exists? */
        if (is_dir(APPPATH . 'controllers/' . $module . '/')) {
            $this->directory = $module . '/';
            return array_slice($segments, 1);
        }
        /* application controller exists? */
        if (is_file(APPPATH . 'controllers/' . ucfirst($module) . $ext)) {
            return $segments;
        }
        $this->located = -1;
    }