Re: HEX String to INTEGER conversion

To help myself with an interim solution I came up with the following procedure to convert a HEX string to BIGINT:

CREATE PROCEDURE hex2int (IN i_hex VARCHAR, OUT o_result BIGINT)  
LANGUAGE SQLSCRIPT  
SQL SECURITY INVOKER AS
  pos INTEGER := 1;
  hex_len INTEGER;
  current_digit CHAR;
  current_val INTEGER;
  result BIGINT := 0;
BEGIN
  DECLARE hex2int CONDITION FOR SQL_ERROR_CODE 10001;
  DECLARE EXIT HANDLER FOR hex2int RESIGNAL;
  hex_len := LENGTH(:i_hex);
  WHILE pos <= hex_len DO
       result := result * 16;
       current_digit := SUBSTR(:i_hex, pos, 1);
       -- format checking
       IF NOT ((current_digit >= 'A' and current_digit <= 'F') or
              (current_digit >= '0' and current_digit <= '9')) THEN
          SIGNAL hex2int SET MESSAGE_TEXT = 
                'Invalid hex cipher: ' || current_digit || ' at position ' || pos;
       END IF;
       current_val := MOD(to_number(to_binary(current_digit)),30);
       IF current_val >= 11 THEN
            result := result + current_val - 1;
       ELSE
            result := result + current_val;
       END IF;
       pos := pos + 1;
  END WHILE;
  o_result := result;
END;

Test Call:

CALL hex2int('FF', ?);

Any hints to express this typconversion directly without using a stored procedure?