C Language Stored Procedure Returning No Data

We have a Java client that is using JDBC to communicate with the Postgres database. We have a stored procedure, foo, that is written in C which returns a byte array (bytea) to the Java client. This function takes in a couple of integers and based upon their values can return a byte array or no data. From a C stored procedure, how can I tell Postgres to pass on to the Java client that there is No Data? A zero length byte array or a null value is not the same as No Data.

Thanks for any help that you can give.

The stored procedure is defined as:

CREATE OR REPLACE FUNCTION foo(int8, int8)

RETURNS bytea AS 'foolib.so', 'foo'

LANGUAGE C STRICT;

The C function foo looks like:

PG_FUNCTION_INFO_V1(foo);

Datum foo ( PG_FUNCTION_ARGS)

{

int64 int1 = PG_GETARG_INT64(0);

int64 int2 = PG_GETARG_INT64(1);

bytea *data = NULL;

if ( int1 > 12345 ) {

/* Somehow indicate that there is no data */

/* Doing the following does not tell Java that there is no data; it gets a null value */

PG_RETURN_NULL();

}

/* Some processing */

PG_RETURN_BYTEA_P( data );

}