Referencing pointer host variables in C programs

If you use the DB2® coprocessor, you can reference any declared pointer host variables in your SQL statements.

Procedure

To reference pointer host variables in C and C++ programs:

Specify the pointer host variable exactly as it was declared. The only exception is when you reference pointers to nul-terminated character arrays. In this case, you do not have to include the parentheses that were part of the declaration.
Examples of scalar pointer host variable references:
Table 1. Example references to scalar pointer host variables
Declaration Description Reference 
short *hvshortp;
hvshortp is a pointer host variable that points to two bytes of storage. 
EXEC SQL set:*hvshortp=123; 
double *hvdoubp;
 hvdoubp is a pointer host variable that points to eight bytes of storage. 
EXEC SQL set:*hvdoubp=456;
 
char (*hvcharpn) [20];
 hvcharpn is a pointer host variable that points to a nul-terminated character array of up to 20 bytes. 
EXEC SQL set:
*hvcharpn='nul_terminated';
Example of a bounded character pointer host variable reference: Suppose that your program declares the following bounded character pointer host variable: 
struct {
  unsigned long len;
  char * data;
  } hvbcharp;
The following example references this bounded character pointer host variable: Start of change
hvcharp.len = dynlen;  a 
hvcharp.data = (char *) malloc (hvcharp.len);  b 
EXEC SQL set :hvcharp = 'data buffer with length';  c 
End of change
Note:
a
dynlen can be either a compile time constant or a variable with a value that is assigned at run time.
b
Storage is dynamically allocated for hvcharp.data.
c
The SQL statement references the name of the structure, not an element within the structure.
Examples of array pointer host variable references:
Table 2. Example references to array pointer host variables
Declaration Description Reference 
short * hvarrpl[6]
 hvarrp1 is an array of 6 pointers that point to two bytes of storage each. 
EXEC SQL set:*hvarrpl[n]=123; 
double * hvarrp2[3]
 hvarrp2 is an array of 3 pointers that point to 8 bytes of storage each. 
EXEC SQL set:*hvarrp2[n]=456;
 
struct {
   unsigned long len;
   char * data; }
hvbarrp3[5];
 hvbarrp3 is an array of 5 bounded character pointers. 
EXEC SQL set :hvarrp3[n] = 
'data buffer with length'
Example of a structure array host variable reference: Suppose that your program declares the following pointer to the structure tbl_struct: 
struct tbl_struct *ptr_tbl_struct =
 (struct tbl_struct *) malloc (sizeof (struct tbl_struct) * n);
To reference this data is SQL statements, use the pointer as shown in the following example. Assume that tbl_sel_cur is a declared cursor. 
for (L_col_cnt = 0; L_col_cnt < n; L_con_cnt++)
{ ...
  EXEC SQL FETCH tbl_sel_cur INTO :ptr_tbl_struct [L_col_cnt]
  ...
}