On Mon, Sep 21, 2015 at 7:38 PM, Tom Rondeau <t...@trondeau.com> wrote:
> On Mon, Sep 21, 2015 at 6:40 AM, bob wole <bnw...@gmail.com> wrote:
>
>> I am studying the code of correlate_access_code_bb_impl.cc for
>> understanding its working. I see that the block is derive from "block"
>> class of gr as written in correlate_access_code_bb_ts.h file
>>
>>
>> class DIGITAL_API correlate_access_code_bb_ts : virtual public block
>>
>>
>> I read earlier that blocks derived from "block"/"gr::block" should
>> implement forecast() method, but I did not see any implementation of
>> forecast() in code of correlate_access_code_bb_impl.cc.
>>
>> Can somebody please tell me why ?
>>
>> --
>> Bob
>>
>
>
> First, you have a misunderstanding of the header/source relationship.
> There are a number of correlate* blocks in GNU Radio (and an unwritten plan
> to organize them better in the future). The correlate_access_code_bb is one
> block, and this is a gr::sync_block. The correlate_access_code_bb_ts is
> another block, and this one is a gr::block.
>
> If you look at the code for block.cc, you'll see it implements a forecast
> function already:
>
> void
> block::forecast(int noutput_items, gr_vector_int &ninput_items_required)
> {
> unsigned ninputs = ninput_items_required.size ();
> for(unsigned i = 0; i < ninputs; i++)
> ninput_items_required[i] = noutput_items + history() - 1;
> }
>
>
> That means that any block that derives from gr::block gets this behavior,
> which tells the scheduler that given noutput_items, the block needs this
> many input items to produce that output amount. This is a satisfactory
> condition for many blocks, so no, you don't /have/ to overload forecast in
> your derived block if this condition meets your block's behavior.
>
> Tom
>
>
Hi Tom,
Sorry, actually there were typos in my email. I was talking about the block
"correlate_access_code_bb_ts" all the time instead of
"correlate_access_code_bb". Thanks for clearing things and being helpful as
always.
--
Bob
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