private function _gen_hash($query = '')
{
    // Check if we have a salt value set in our config file
    if ( $this->config->item('hash_salt') === FALSE )
    {
        show_error('A hashing salt value must be set.');
    }

    // If we passed in an array, we need to build it into a string
    if( is_array($query) )
    {
        $query = $this->_build_query($query);
    }

    // If our query has the &hashValue in it still (from beanstream's response), get rid of it
    if( strpos($query, '&hashValue=') !== FALSE )
    {
        $query = substr($query, 0, strpos($query, '&hashValue='));
    }

    // Add the salt onto our query
    $string = $query.$this->config->item('hash_salt');

    return sha1($string);
}


private function _build_query($data = array())
{
    $query = '';

    foreach ( $data as $k => $v )
    {
        $v = ( $k == 'trnAmount' ) ? $v : $this->_bs_encode($v);

        $query .= '&' . $k . '=' . $v;
    }

    // substr used to get rid of the leading "&"
    return substr($query, 1);
}


// Encodes spaces into a "+" and all other non-alphanumerics into their hex values
private function _bs_encode($str = '')
{
    return preg_replace_callback(
        '([^A-Za-z0-9])',
        create_function(
            '$non_alphanum',
            '
            $c = $non_alphanum[0];
            return ( $c == " " ) ? "+" : "%".strtoupper(bin2hex($c));
            '
        ),
        $str
    );
}