px4-firmware/Tools/tests-host/hrt.cpp

#include <sys/time.h>
#include <inttypes.h>
#include <drivers/drv_hrt.h>
#include <stdio.h>

hrt_abstime hrt_absolute_time() {
    struct timeval te; 
    gettimeofday(&te, NULL); // get current time
    hrt_abstime us = static_cast<uint64_t>(te.tv_sec) * 1e6 + te.tv_usec; // caculate us
    return us;
}

hrt_abstime hrt_elapsed_time(const volatile hrt_abstime *then) {
	// not thread safe
    return hrt_absolute_time() - *then;
}