Example: my_bit_or Definition

my_bit_or definition

The my_bit_or definition is somewhat simpler than the my_bit_xor example.

#include "extfnapiv4.h"
#include <stdlib.h>
#include <assert.h>


//  A simple (non-OLAP) aggregate UDF that ORs a set 
//  of unsigned integer arguments, and whenever asked
//  returns the resulting unsigned integer result.
//
//  The start function creates a little structure for
//  the running result, and the finish function then
//  deallocates it.
//
//  The aggregate usage restrictions for this aggregate UDF
//  only allow its use as a simple aggregate, so the
//  corresponding SQL declaration will look like:
//
//      CREATE AGGREGATE FUNCTION my_bit_or(IN arg1 UNSIGNED INT) 
//			RETURNS UNSIGNED INT
//                      ON EMPTY INPUT RETURNS NULL
//			OVER NOT ALLOWED
//			EXTERNAL NAME 'my_bit_or@libudfex'


typedef struct my_or_result {
  a_sql_uint32 _or_result;
  a_sql_uint32 _non_null_seen;
} my_or_result;



#if defined __cplusplus
extern "C" {
#endif 

static void my_or_start(a_v3_extfn_aggregate_context *cntxt)
{
}

static void my_or_finish(a_v3_extfn_aggregate_context *cntxt)
{
}

static void my_or_reset(a_v3_extfn_aggregate_context *cntxt)
{
  my_or_result *cptr = (my_or_result *)cntxt->_user_calculation_context;
  cptr->_or_result = 0;
  cptr->_non_null_seen = 0;
}


static void my_or_next_value(a_v3_extfn_aggregate_context *cntxt, 
                             void *arg_handle)
{
  an_extfn_value  arg;
  a_sql_uint32 arg1;

  my_or_result *cptr = (my_or_result *)cntxt->_user_calculation_context;

  //  Get the one argument, and add it to the total
  if (cntxt->get_value( arg_handle, 1, &arg ) && arg.data)
  {
      arg1 = *((a_sql_uint32 *)arg.data);
      cptr->_or_result |= arg1;
      cptr->_non_null_seen = 1; 
  }
}


static void my_or_evaluate(a_v3_extfn_aggregate_context *cntxt, 
                           void *arg_handle)
{
  an_extfn_value  outval;
  my_or_result *cptr = (my_or_result *)cntxt->_user_calculation_context;

  outval.type = DT_UNSINT;
  outval.piece_len = sizeof(a_sql_uint32);
  if (cptr->_non_null_seen)
  {
      outval.data = &cptr->_or_result;
  }
  else
  {
      // Return null if no values seen
      outval.data = 0; 
  }
  cntxt->set_value( arg_handle, &outval, 0 );
}



static a_v3_extfn_aggregate my_or_descriptor = 
{   
    &my_or_start, 
    &my_or_finish,
    &my_or_reset,
    &my_or_next_value,
    &my_or_evaluate,
    NULL, // drop_val_extfn
    NULL, // cume_eval,
    NULL, // next_subaggregate_extfn
    NULL, // drop_subaggregate_extfn
    NULL, // evaluate_superaggregate_extfn
    NULL, // reserved1_must_be_null
    NULL, // reserved2_must_be_null
    NULL, // reserved3_must_be_null
    NULL, // reserved4_must_be_null
    NULL, // reserved5_must_be_null
    0, // indicators
    ( short )sizeof( my_or_result ), // context size
    8, // context alignment
    0.0, //external_bytes_per_group 
    0.0, // external bytes per row
    0, // reserved6_must_be_null
    0, // reserved7_must_be_null
    0, // reserved8_must_be_null
    0, // reserved9_must_be_null
    0, // reserved10_must_be_null
    NULL // _for_server_internal_use
};


extern "C"
a_v3_extfn_aggregate *my_bit_or()
{
  return &my_or_descriptor;
}


#if defined __cplusplus
}
#endif