Re: [Discuss-gnuradio] two inputs/outputs of different data types

[Eric Blossom]

On Wed, Apr 26, 2006 at 11:50:39AM -0400, Chuck Swiger wrote:
> How do you declare two inputs of different data types?
> 
> Several atsc blocks pass a stream of 'float' and also 'syminfo'
> (a struct of 4 ints).
> 
> >From what I can tell, gr_sync_block allows many inputs and outputs,
> but only of the same type(?).
> 
> gr_block::gr_block (const std::string &name,
>                     gr_io_signature_sptr input_signature,
>                     gr_io_signature_sptr output_signature)
> 
> where
> 
> gr_io_signature (int min_streams, int max_streams, size_t
> sizeof_stream_item)
> 
> tia
> --Chuck

Hi Chuck,

You're right.  FWIW, the underlying representation is designed to
support different types on each input or output stream, but the top
level constructor, gr_io_signature, doesn't implement an interface to it.

I'm pretty sure that sizeof(atsc::syminfo) is 4, which is the same as
sizeof(float).  This is true because the total width of the integer
bit fields in atsc::syminfo is <= 32.


Add 

  assert(sizeof(float) == sizeof(atsc::syminfo));

somewhere in work, and then cast away.  We lose clarity in the i/o
signature, but I'm pretty sure it'll work.  [ It worked before ;) ]


E.g.,

   int
   foo::work(...)
   {
     const float *in_sample = (const float *) input_items[0];
     const atsc::syminfo *in_tag = (const atsc::syminfo *) input_items[1];

     assert(sizeof(float) == sizeof(atsc::syminfo));

     ...
   }

Eric