UDF Library Placement

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Earlier versions of InterBase had few requirements about the placement of UDF libraries. For security reasons, current versions of InterBase have the following requirements for the placement of UDF libraries:

• On any platform, the module can be referenced with no path name if it is in <<InterBase_home>>/UDF or <<InterBase_home>>/intl.
• If the library in a directory other than <InterBase_home>/UDF or <<InterBase_home>>/intl, you must specify its location in InterBase configuration file (ibconfig) using the EXTERNAL_FUNCTION_DIRECTORY parameter. Give the complete pathname to the library, including a drive letter in the case of a Windows server.

When either of the above conditions is met, InterBase finds the library. You do not need to specify a path in the declaration.

Note: The library must reside on the same machine as the InterBase server.

To specify a location for UDF libraries in ibconfig, enter a line such as the following:

Windows:

EXTERNAL_FUNCTION_DIRECTORY "C:\<InterBase_home>\Mylibraries"

Unix:

EXTERNAL_FUNCTION_DIRECTORY "/usr/interbase/Mylibraries"

Note that it is no longer sufficient to include a complete path name for the module in the DECLARE EXTERNAL FUNCTION statement. You must list the path in the EXTERNAL_FUNCTION_DIRECTORY parameter of the InterBase configuration file if the library is not located in <InterBase_home>/UDF or <InterBase_home>/intl.

Important: For security reasons, InterBase strongly recommends that you place your compiled libraries in directories that are dedicated to InterBase libraries. Placing InterBase libraries in directories such as C:\WINNT\system32 or /usr/lib permits access to all libraries in those directories and is a serious security hole.

Example: The following statement declares the TOPS() UDF to a database:

DECLARE EXTERNAL FUNCTION TOPS
CHAR(256), INTEGER, BLOB
RETURNS INTEGER BY VALUE
ENTRY_POINT 'TE1' MODULE_NAME 'TM1';

This example does not need the FREE_IT keyword because only cstrings, CHAR, and VARCHAR return types require memory allocation. The module must be in InterBase UDF directory or in a directory that is named in the configuration file.

Example: The following isql script declares UDFs, ABS() and TRIM(), to the employee.gdb database:

CONNECT 'employee.gdb';
DECLARE EXTERNAL FUNCTION ABS
DOUBLE PRECISION
RETURNS DOUBLE PRECISION BY VALUE
ENTRY_POINT 'fn_abs' MODULE_NAME 'ib_udf';
DECLARE EXTERNAL FUNCTION TRIM
SMALLINT, CSTRING(256), SMALLINT
RETURNS CSTRING(256) FREE_IT
ENTRY_POINT 'fn_trim' MODULE_NAME 'ib_udf';
COMMIT;

Note that no extension is supplied for the module name. This creates a portable module. Windows machines add a dll extension automatically.