Re: Retrieving table from external data (row identification?)

It's solved... :)

The correct procedure in my case, is to allocate data context in
get_next_data_point(...)

so, a skeleton of the _access.c

xxx_get_first_data_point()
{
  my_loop_info * loopctx;
  loopctx = SNMP_ALLOC_MEMORY(my_loop_info);
  ...
  //obtain number of rows and/or any other info useful for looping
  ...

  my_loop_context = *loopctx;
  return xxx_get_next_data()
{

xxx_get_next_data_point()
{
  int iter;
  my_loop_info *loopctx;
  my_data_info *datactx;

  loopctx = *my_loop_ctx;
  datactx = SNMP_ALLOC_MEMORY(my_data_info); //<--- CAUTION! function
free_data_context must be allocated in iinfo to free this

  while (/*condition obtained from loopctx variables*/)
  {
      iter++;
      datactx->A = get_A_value(iter);
      datactx->B = get_B_value(iter);

  }
  /* no more rows */
  *loopctx= NULL;
  return NULL;
}


Dave, thanks for give me some pointers... literally :P


On Thu, Jul 3, 2008 at 1:27 PM, Victor Palacio <
[email protected]> wrote:

>
>
> On Thu, Jul 3, 2008 at 11:13 AM, Dave Shield <[email protected]>
> wrote:
>
>> 2008/7/3 Victor Palacio <[email protected]>:
>> >
>> > I'm trying to use table iterator from code skeleton generated with
>> > mib2c.iterate.conf.
>> >
>> > When I use snmptable on the agent,  get_first_data_point function is
>> > executed every time one column is consulted, so I suppose I must load
>> > data for consulted row in data context.
>> >
>> >  The problem is... How can I identify which row (index) is consulted
>>
>> You don't - that's the job of the iterator helper.
>>
>> You provide the get_{first,next}_data_point functions, which
>> walk through the table in whatever order is most convenient.
>>
>> The iterator helper will identify the row(s) which are required for
>> the current request.  It then calls your handler routine, passing
>> the data structure for that row, as suppied via the 'data_context'
>> parameter of the two get_{first,next} routines.
>>
>>
>> Dave
>>
>
>
>
> --
> Thanks for your answer, Dave... but I still have problems with this.
>
> My problem is that all rows are using the last data context, so I get same
> information for all rows, although then number of rows is correct.
>
> In _get_first_data_point, I ...
>
> 1)Create Loop and Data context,
> 2)set number of rows in loop context and,
> 3)call get_next_data_point
>
> In get_next_data_point, I assume that I can use same data_context. Perhaps
> must I allocate new data context in get_next_data_point?
>
> Regards,
>
> CODE:
>
> myTable_get_next_data_point(void **my_loop_context, void **my_data_context,
>                          netsnmp_variable_list *put_index_data,
>                          netsnmp_iterator_info *mydata)
> {
>
>     netsnmp_variable_list *vptr;
>
>     my_loop_info *loopctx = *my_loop_context;
>     my_data_info *datactx = *my_data_context;
>
>     if (!loopctx){
>       return NULL;
>     }
>
>
>     while (iter < loopctx->MAX_ROWS){
>         iter++;
>
>         /* OBTAIN VALUES A and B FOR ITER */
>         //...
>
>         datactx->index = iter;
>         datactx->A = A;
>         datactx->B = B;
>
>         vptr = put_index_data;
>         snmp_set_var_value(vptr, (u_char *) & datactx->index,
>                            sizeof(datactx->index));
>
>         *my_loop_context = loopctx;
>         *my_data_context = datactx;
>
>         return put_index_data;
>
>     }
>
>     /* we're out of data */
>     *my_loop_context = NULL;
>
>     return NULL;
> }
>
> ********************
> Victor M. Palacio
> ********************




-- 
********************
Victor M. Palacio
********************

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