system/modules/short_urls/dca/tl_short_urls.php
private function validate($name, $domain)
    {
        // check if a page exists
        if( !\Config::get('urlSuffix') && ( $objPages = \PageModel::findByAlias( $name ) ) !== null )
        {
            // check if short url has a domain
            if( $domain > 0 )
            {
                $valid = true;
                while( $objPages->next() )
                {
                    // load page details
                    $objPages->current()->loadDetails();

                    // if one of the found pages is within the same domain, do not allow it
                    if( $objPages->rootId == $domain )
                    {
                        $valid = false;
                        break;
                    }
                }

                if( $valid )
                    return;         
            }

            // otherwise throw exception
            throw new Exception(sprintf($GLOBALS['TL_LANG']['tl_short_urls']['pageExists'], $name));
        }
    }
private function validate($name, $domain)
    {
        // check if a page exists
        if( !\Config::get('urlSuffix') && ( $objPages = \PageModel::findByAlias( $name ) ) !== null )
        {
            // check if short url has a domain
            if( $domain > 0 )
            {
                $valid = true;
                while( $objPages->next() )
                {
                    // load page details
                    $objPages->current()->loadDetails();

                    // if one of the found pages is within the same domain, do not allow it
                    if( $objPages->rootId == $domain )
                    {
                        $valid = false;
                        break;
                    }
                }

                if( $valid )
                    return;         
            }

            // otherwise throw exception
            throw new Exception(sprintf($GLOBALS['TL_LANG']['tl_short_urls']['pageExists'], $name));
        }
    }
Validate the name of a short url
@param  string $name
@param  string $domain
@return void