Making a port optional

[dilawar]

https://www.doulos.com/knowhow/systemc/new_standard suggests to do the following.

sc_port<i_f, 1, SC_ZERO_OR_MORE_BOUND> opt_port;

I am trying to replace some of my `sc_out` and `sc_in` with optional ports. I would like to replace them with `sc_out_opt` and `sc_in_opt` class in headers of my modules.

What is the best way to derive these classes such that my code-base works with minimal changes to code?

1. Should I derive them from `sc_port<i_f, 1, SC_ZERO_OR_MORE_BOUND>` or `sc_in` and `sc_out` classes?

2. Can I force a port policy on `sc_in` and `sc_out` in module constructor?

Any other suggestions?

[maehne]

If you don't use the member functions added that were added for convenience to `sc_in`, `sc_out`, and `sc_inout` to, e.g., call `read()`, `write()`, and the event member functions via the `.` operator than via the corresponding member function in the interface accessed via the `->` operator, you might be able to avoid entirely the derivation of new port classes. Instead, you could simply use a template alias, which was introduced with C++'11:

template<typename T>
using sc_in_opt = sc_core::sc_port<sc_signal_in_if<T>, 1, SC_ZERO_OR_MORE_BOUND>;
template<typename T>
using sc_inout_opt = sc_core::sc_port<sc_signal_inout_if<T>, 1, SC_ZERO_OR_MORE_BOUND>;
template<typename T>
using sc_out_opt = sc_core::sc_port<sc_signal_inout_if<T>, 1, SC_ZERO_OR_MORE_BOUND>;

If you want to also provide all member functions of `sc_in`, `sc_out`, and `sc_inout`, you will have to derive from the `sc_port` class and implement the full interface as defined in IEEE Std 1666-2011. 

[dilawar]

Thank you maehne. I'll use the `sc_port` solution. It clearly marks my intention in declaration.

cheers,

    Dilawar