Ok to put() to tlm_fifo and call nb_can_get() in the same delta cycle?

[plafratt]

I am using a tlm_fifo. When I put() into it and then immediately call nb_can_get(), it is returning false. Is this an invalid use of the tlm_fifo to call put() and nb_can_get() in the same delta? Or, have I made a mistake somewhere?

[Eyck]

Neither is the case. Between putting an element into the fifo and the element becoming available is at least a delta cycle. And this is by design as in hardware it takes some time for values to propagate. sc_core::sc_fifo exposes the same behavior.

If you need immediate update you can use ordinary C++ containers like std::dequeue...

[plafratt]

Well, I'm not sure something like deque will provide what is needed, because I still need process notifications when an entry is written or read.

I think what I am not seeing is how to write into the fifo and then block the writer until the reader reads from it.  I can write something custom based on deque or something else (or look for another class in sc_core or tlm) to provide this, but wanted to be sure that tlm_fifo didn't provide this first.

[Eyck]

tlm_fifo provides a blocking read called get() as well as an event to use: ok_to_get(). To block the writer you can use ok_to_put() which is triggered when the fifo is read.

[plafratt]

Great, thank you. I was aware of ok_to_put(), but I think I had some confusion about how to use it in my situation. It looks like it should do what I need. Thanks!