Re: [Discuss-gnuradio] Work function template for vector I/O

[Martin Braun]

On 11.02.2014 09:57, Randall Poe wrote:
> I'm sure this must exist somewhere but I've been unable to find it among
> the tutorials and mailing lists.
> I've got the basics of writing blocks down. I've successfully created a
> C++ block with float input and output streams, and gotten it to load
> into GRC.
> Now I'd like to do something more interesting with vector I/O, probably
> complex vectors. It's my understanding that each input or output item
> can be an entire vector<float>, correct? and that consuming or
> generating one item means consuming or generating that entire array?
> Does anyone have a source example? I'm uncertain about things like what
> the cast of input_items and output_items should look like. Also the
> memory allocation. Do I create a new vector for each output item and
> trust that GRC will destroy it somewhere downstream? I'm talking about
> vectors that may potentially contain megabytes, so I want to make sure I
> do the memory management right.

Randall,

a couple of things:

* There's tons of examples, check out any block with a _vcc suffix. 
Short answer, you just set the item size (e.g. sizeof(gr_complex) * vlen).
* Cast: const gr_complex *input_items = (const gr_complex *) input_items[0];
* This will *not* generate a std::vector, but a regular C-style array. 
You don't need to destroy it, the buffers get allocated automatically.
* You don't have unlimited space in buffers between blocks. If you're 
streaming massive amounts, you might want to use tags to declare item 
boundaries.

MB