Re: [Discuss-gnuradio] Stream to PDU - Guaranteed to not lump tags?

[Michael Dickens]

Hi Dave - The tagged stream -> PDU block will look at for the provided tag 
string at the current 0 offset & if found then that's what the PDU data size 
(in items) will be [this is actually handled in the "tagged_stream_block" 
parent class]. If there are interim tags (within the output PDU size in items), 
then they are just added as meta-data to the PDU. Each PDU is created 
independent of the other PDUs, and just 1 created per call to "work". Not sure 
if this is what you were looking to have answered; if not, please clarity. 
Cheers! - MLD

On Wed, Jan 10, 2018, at 11:30 AM, Dave NotTelling wrote:
> The wording of the title likely needs work, but the basic idea is this:
> 
>  * Suppose that I have a ZMQ message source that has arbitrarily sized 
> vectors of some consistent type
>  * I convert that over to a tagged stream, do some operations on it, then 
> convert it back to a PDU
>  * Assume for a second that several of the offsets in the tagged stream are 
> very small (only say 10 samples each) and back to back
>  * Is there a guarantee that each of the 10 sample offsets will result in a 
> single PDU?
>
>Looking at the source of tagged_stream_to_pdu it seems that there is no check 
>that multiple tag offsets arrived in a single call to work.  Or is that 
>something that cannot happen?  Having a contract that no more than one offset 
>can arrive at a single call to work would be really nice, but I imagine that 
>doing so could cause some pretty serious performance issues.