Informix DataBlade API Programmer's Manual DataBlade API Function Descriptions

The mi_fp_returnisnull() accessor function determines whether the return value of a user-defined function is an SQL NULL from its associated MI_FPARAM structure.

mi_boolean mi_fp_returnisnull(fparam_ptr, ret_pos)

MI_FPARAM *fparam_ptr;

mi_integer ret_pos;

fparam_ptr	is a pointer to the associated MI_FPARAM structure.
ret_pos	is the index position into the null-return array for the return value to check for a NULL value. For user-defined functions, the only valid value is 0.

Valid in Client LIBMI Application?	Valid in User-Defined Routine?
Yes	Yes

The mi_fp_returnisnull() function determines whether the routine return value at position ret_pos in the MI_FPARAM structure that fparam_ptr references contains the SQL NULL value. The MI_FPARAM structure stores information about whether function return values are NULL in the zero-based null-return array. To obtain information about the nth return value, use a ret_pos value of n-1. For example, the following call to mi_fp_returnisnull() determines whether the first return value of the my_func() user-defined function, with which fparam1 is associated is NULL:

mi_integer my_func(...., fparam1)
	

	MI_FPARAM *fparam1;
{
	if ( mi_fp_returnisnull(fparam1, 0) == MI_TRUE )

		/* code to handle NULL return value */


Important: C user-defined functions always have only one return value. 

See the descriptions of the following functions: mi_fp_argisnull(), mi_fp_retlen(), mi_fp_retprec(), mi_fp_retscale(), mi_fp_rettype(), mi_fp_setargisnull(), and mi_fp_setreturnisnull().