[Discuss-gnuradio] write a new block to split existing functionality

[Matt D]

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Hello everybody,

I want to create a block that displays some data made available by the
decoder block OP25..  OP25 was authored in the olden days before GRC.
 Then the program would display some traffic identification data on a
tab but now that OP25 has been adapted for GRC, this tab has been lost
and I want to bring it back.  So the task now is to split the existing
functionality into a separate block to make it GRC friendly.  Talking
about the C++ code in OP25 the author wrote:

we have “data_unit objects that can be asked to take a snapshot of
themselves creating a string describing their internal state that
obeys the Python text serialization format. When Python decodes the
pickle it gets a name/value map describing each of the fields.
Currently we have the snapshot_du_handler send the pickle as a message
and this may/may not be the appropriate mechanism for GRC.”

The fist question I have do we need a different message-passing
construct?

Second question is what kind of block needs to be written? I thought
maybe a sink, or probably better, a block with no inputs that just
waits on messages.  But I don't want to haul off doing this and find
out later it was the incorrect way to go.

Thanks a bunch
- -- 
Matt D
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