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4.12 now.h: measuring time

The ‘now.h’ file provides some simple time measurement routines. It is not included in ‘nana.h’ so you must include this file separately.

It uses the ‘gettimeofday’ system call and has an accuracy of between 1us and 10ms depending on the operating system and hardware configuration.

See the IPM package if you require better measurement tools.1

— Function: double now ()

Returns the time in seconds since the beginning of time as defined by your system. If you call ‘now_reset’ the time will start again at 0.

— Function: double now_reset ()

Reset the times returned by ‘now’ to 0.

— Function: double now_delta (double *dp)

Returns the elapsed time between *dp and now(). It then sets *dp to now, thus giving a delta time between particular events. 

            t = now();
            for(;;) {
              ...; /* code that must finish in 50ms */
              I(now_delta(&t) <= 0.050);
            }

Footnotes

[1] In the fullness of time, we may integrate these routines in here.