Re: how to Initialise the contents of the table?

On 11/08/06, 蔷<Qiang Hu> <[email protected]> wrote:
> i saw this routine and i'm pulzzled about "table_entry = (struct
> tbModuleTable_entry
> *)netsnmp_extract_iterator_context(request);" it seems that
> table_entry get relevant datas from this
> netsnmp_extract_iterator_context;and how can i initial
> contents of table in iterator.

OK - take a step back.
There are three main areas involved in handling a table (regardless of
which helper you might use to do this):

  a)  Building a internal representation of the table
  b)  Choosing the appropriate row for a given request
  c)  Returning or updating the relevant columns from that row.

With most of the helpers, these three tasks tend to be handled separately.
In the case of the iterator helper:
  a)  is done via tbModuleTable_createEntry()
           (typically invoked from the init routine)
  b)  is handled by tbModuleTable_get_{first,next}_data_point
           (plus the main iterator helper)
  c)  is the responsibility of tbModuleTable_handler()


>i can't understand the iterator operation mechanism.

The get_{first,next} routines cycle through the rows of the table, in
whatever order is most natural, setting the index value(s) for each
row.  The main iterator handler keeps track of which row(s) are
relevant for this particular PDU.

Once this has been done, the iterator handler calls the
tbModuleTable_handler() routine, which extracts the relevant row for
each varbind ("request"), and works with the appropriate column from
it.

> i saw an exitent mib handler code of net-snmp which initials in
> this way as following:
>
>     iinfo->make_data_context = netSnmpHostsTable_context_convert_function;
>     iinfo->free_data_context = netSnmpHostsTable_data_free;
>     iinfo->free_loop_context_at_end = netSnmpHostsTable_loop_free;

No - I wouldn't use that particular example as a template.  It uses
the "iterator_access" framework, which is built upon the basic
iterator helper, but has a very different model.

> is there any examples mibs for how to modify the generater code by
> mib2c.iterate.conf?

Try looking at agent/nsCache.c
That uses the iterator helper, in a very similar way to your code.

Dave

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