UDF example: my_plus definition

The definition for the my_plus example.

my_plus definition

Because this UDF needs no initialization or shutdown function, those values within the descriptor structure are set to 0. The descriptor function name matches the EXTERNAL NAME used in the declaration. The evaluate method does not check the data type for arguments, because they are declared as INT.

#include "extfnapiv3.h"
#include <stdlib.h>


//  A simple deterministic scalar UDF that just adds
//  two integer arguments and then returns the result.
//
//  Corresponding SQL declaration:
//
//	CREATE FUNCTION my_plus(IN arg1 INT, IN arg2 INT) 
//			                               RETURNS INT
//			                               DETERMINISTIC
//                                  IGNORE NULL VALUES
//			                               EXTERNAL NAME 'my_plus@libudfex'
//
#if defined __cplusplus
extern "C" {
#endif

static void my_plus_evaluate(a_v3_extfn_scalar_context *cntxt, 
                      void *arg_handle)
{
  an_extfn_value  arg;
  an_extfn_value  outval;
  a_sql_int32 arg1, arg2, result;

  //  Get first argument
  (void) cntxt->get_value( arg_handle, 1, &arg );
  if (arg.data == NULL)
  {
      return;
  }
  arg1 = *((a_sql_int32 *)arg.data);

  //  Get second argument
  (void) cntxt->get_value( arg_handle, 2, &arg );
  if (arg.data == NULL)
  {
      return;
  }
  arg2 = *((a_sql_int32 *)arg.data);

  //  Set the result value
  outval.type = DT_INT;
  outval.piece_len = sizeof(a_sql_int32);
  result = arg1 + arg2;
  outval.data = &result;
  cntxt->set_value( arg_handle, &outval, 0 );
}


static a_v3_extfn_scalar my_plus_descriptor = { 
	0, 
	0, 
	&my_plus_evaluate,
	0,			// Reserved - initialize to NULL
	0,			// Reserved - initialize to NULL
	0,			// Reserved - initialize to NULL
	0,			// Reserved - initialize to NULL
	0,			// Reserved - initialize to NULL
        NULL                    // _for_server_internal_use
};


a_v3_extfn_scalar *my_plus()
{
  return &my_plus_descriptor;
}

#if defined __cplusplus
}
#endif