Writing UDFs for Firebird Embedded SQL Server

DECLARE EXTERNAL FUNCTION CreateParser
	BLOB
    RETURNS INTEGER BY VALUE
  ENTRY_POINT 'SampleUdf_CreateParser'  MODULE_NAME 'SampleUdf'
#
DECLARE EXTERNAL FUNCTION DestroyParser
	INTEGER
	RETURNS INTEGER BY VALUE
  ENTRY_POINT 'SampleUdf_DestroyParser'  MODULE_NAME 'SampleUdf'
#
DECLARE EXTERNAL FUNCTION GetName
	INTEGER
	RETURNS CSTRING(256)
  ENTRY_POINT 'SampleUdf_GetName'  MODULE_NAME 'SampleUdf'
#
DECLARE EXTERNAL FUNCTION GetFullPath
	INTEGER
	RETURNS CSTRING(256)
  ENTRY_POINT 'SampleUdf_GetFullPath'  MODULE_NAME 'SampleUdf'
#
DECLARE EXTERNAL FUNCTION GetCreationTime
	INTEGER
	RETURNS TIMESTAMP FREE_IT
  ENTRY_POINT 'SampleUdf_GetCreationTime'  MODULE_NAME 'SampleUdf'
#
DECLARE EXTERNAL FUNCTION GetAttributes
	INTEGER
	RETURNS INTEGER
  ENTRY_POINT 'SampleUdf_GetAttributes'  MODULE_NAME 'SampleUdf'
#
DECLARE EXTERNAL FUNCTION GetSize
	INTEGER
	RETURNS BIGINT
  ENTRY_POINT 'SampleUdf_GetSize'  MODULE_NAME 'SampleUdf'
#
CREATE TABLE RowDataTable (
	Id INTEGER NOT NULL PRIMARY KEY
  , Data BLOB
  )
#
CREATE TABLE FSTable
 (
	Id INTEGER NOT NULL PRIMARY KEY
  , FileName VARCHAR(256)
  , FullPath VARCHAR(256)
  , CreationTime TIMESTAMP 
  , Attributes INTEGER
  , FileSize BIGINT
  )
#
CREATE GENERATOR RowDataTable_Generator
#
CREATE GENERATOR FSTable_Generator
#
CREATE PROCEDURE AddRawData
(
  Data BLOB
)
RETURNS (newId INTEGER)
AS
BEGIN
    newId = GEN_ID(RowDataTable_Generator, 1);
    INSERT INTO RowDataTable (Id, Data) VALUES (:newId, :Data);
    SUSPEND;
END
#
CREATE PROCEDURE TransferData
RETURNS (counter INTEGER)
AS
DECLARE VARIABLE tmp INTEGER;
DECLARE VARIABLE parserPtr INTEGER;
DECLARE VARIABLE Data BLOB;
DECLARE VARIABLE FileName VARCHAR(256);
DECLARE VARIABLE FullPath VARCHAR(256);
DECLARE VARIABLE CreationTime TIMESTAMP;
DECLARE VARIABLE Attributes INTEGER;
DECLARE VARIABLE FileSize BIGINT;
BEGIN
	counter = 0;
	FOR SELECT Data FROM RowDataTable INTO :Data DO	BEGIN
		parserPtr = CreateParser(:Data);
		IF (parserPtr IS NOT NULL) THEN BEGIN
			FileName = GetName(:parserPtr);
			FullPath = GetFullPath(:parserPtr);
			CreationTime = GetCreationTime(:parserPtr);
			Attributes = GetAttributes(:parserPtr);
			FileSize = GetSize(:parserPtr);
			
			tmp = GEN_ID(FSTable_Generator, 1);
			INSERT INTO FSTable (Id, FileName, FullPath, CreationTime, Attributes, FileSize)
			VALUES (:tmp, :FileName, :FullPath, :CreationTime, :Attributes, :FileSize);
			counter = counter + 1;

			tmp = DestroyParser(:parserPtr);
		END
	END
	SUSPEND;
END