How to convert integer to hex notation? - firebird

Question

Using: Firebird 2.5.3
In a stored procedure (PSQL), converting a number from hex notation to decimal notation is done easily:
DECLARE VARIABLE I INTEGER;
BEGIN
I = CAST('0x0FFFE' AS INTEGER); -- I will have the value 65534
How can the reverse be achieved? ie. Convert from decimal notation to hex notation?

Answer 1

Short of using a UDF (which would mean using an external library file), the solution is to write a stored procedure to accomplish this:
SET TERM ^^ ;
CREATE PROCEDURE INTTOHEX (
INPUTNUMBER BigInt)
returns (
OUTPUTNUMBER VarChar(8))
AS
DECLARE VARIABLE Q BigInt;
DECLARE VARIABLE R BigInt;
DECLARE VARIABLE T BigInt;
DECLARE VARIABLE H VARCHAR(1);
DECLARE VARIABLE S VARCHAR(6);
begin
/* Max input value allowed is: 4294967295 */
S = 'ABCDEF';
Q = 1;
OUTPUTNUMBER = '';
T = INPUTNUMBER;
WHILE (Q <> 0) DO
BEGIN
Q = T / 16;
R = MOD(T, 16);
T = Q;
IF (R > 9) THEN
H = SUBSTRING(S FROM (R-9) FOR 1);
ELSE
H = R;
OUTPUTNUMBER = H || OUTPUTNUMBER ;
END
SUSPEND;
end ^^
SET TERM ; ^^
You can call this stored procedure from standard SQL or another stored procedure like this:
For example:
SELECT OUTPUTNUMBER FROM INTTOHEX(65534);

Answer 2

just did a short firebird function,
could handle bigger number,
maybe could help someone
CREATE OR ALTER FUNCTION INT64TOHEX (
C BIGINT)
RETURNS VARCHAR(32)
AS
DECLARE VARIABLE IREM INTEGER;
DECLARE VARIABLE HEX VARCHAR(32);
BEGIN
IREM = MOD(C, 0XFF);
HEX = '';
WHILE (IREM > 0) DO
BEGIN
HEX = SUBSTRING('0123456789abcdef' FROM BIN_SHR(BIN_AND(C, 0XFF), 4) + 1 FOR 1) || SUBSTRING('0123456789abcdef' FROM BIN_AND(BIN_AND(C, 0XFF), 15) + 1 FOR 1) || HEX;
C = BIN_SHR(C, 8);
IREM = MOD(C, 0XFF);
END
RETURN TRIM(HEX);
END