Stored procedure to generate UUID32 in Firebird 2.5+

gistfile1.sql

CREATE OR ALTER PROCEDURE GEN_UUID32 RETURNS (RESULT CHAR(32))
AS 
  DECLARE VARIABLE UUID36 CHAR(36);
BEGIN 
  SELECT
    UUID_TO_CHAR(GEN_UUID())
  FROM RDB$DATABASE
  INTO :UUID36;

  SELECT
    SUBSTRING(:UUID36 FROM 1 FOR 8) ||
    SUBSTRING(:UUID36 FROM 10 FOR 4) ||
    SUBSTRING(:UUID36 FROM 15 FOR 4) ||
    SUBSTRING(:UUID36 FROM 20 FOR 4) ||
    SUBSTRING(:UUID36 FROM 25)
  FROM RDB$DATABASE
  INTO :RESULT;

  SUSPEND;
END