[Discuss-gnuradio] How to get t (time) to calculate output = sin ( 2 * PI * freq * t ) ?

[Activecat]

Dear Sir,

I am building a custom block.  

How to know the time t, in seconds, of how long the flow graph has started?

Says, I build a block of analog_sig_source_f. 

Its work() function may involve a variable t (time) as below:

     for ( int i=0; i < noutput_items; i++ )  {

        out[i] = ampl * sin( 2 * PI * wave_freq * t )

     }

I know we there is a built-in Signal Source block, but I write this to illustrate what I need to do.

Regards,

activecat