[Discuss-gnuradio] Inherited block

Sir,

I want to inherit generic_encoder in my convolutional encoder block to use the functions 

{{

int get_input_size();             ............ (1)

int get_output_size();           .............(2)

}}

and from gr::block I want to use 

{{

int fixed_rate_ninput_to_noutput (int ninput);                  ..........................(3)

int fixed_rate_noutput_to_ninput (int noutput);               ..........................(4)

}}

to setup ninput_items and noutput_items. Can you provide a detailed description of these functions ?

What files will I need to edit other than header and implementation header and .cc files to implement this inherited block ?

Also I am heaving a little misconception about call of function (3). Should I need to call this function or it will call itself?