#define _BSD_VISIBILE
#include <sys/param.h>
#include <sys/time.h>
#include <err.h>
#include <assert.h>
#include <stdio.h>
#include <time.h>

static inline int64_t
mynow(void)
{
        int x;
        struct timespec tp;

        x = clock_gettime(CLOCK_VIRTUAL, &tp);
        assert(x == 0);

        return (tstosbt(tp));
}

int
main(int argc, char **argv)
{
        size_t iterations = 1, i;
        int64_t a, b, t;
        size_t sz;
        unsigned sec, usec;

        for (t = 0; t < mstosbt(100); iterations *= 2) {
                a = mynow();
                for (i = 0; i < iterations; i++) {
                        int retry = 10;
                        unsigned long rndval;

                        __asm __volatile(
                            "1:\n\t"
                            "rdrand %1\n\t"
                            "jc 2f\n\t"
                            "dec %0\n\t"
                            "jne 1b\n\t"
                            "2:"
                            : "+r" (retry), "=r" (rndval) : : "cc");
                        if (retry == 0)
                                errx(1, "failed 10 times");
                }
                b = mynow();
                t = b - a;
        }

        sz = sizeof(unsigned long);
        sec = t >> 32;
        usec = sbttous(t & 0xffffffff);

        printf("%zu iterations of %zu bytes each took %u.%06u seconds.ms, or\n",
            iterations, sz, sec, usec);

        double x = (double)sz * iterations / (sec + (((double)usec) / 1000000));
        printf("%.3f B/s %.3f kB/s %.3f MiB/s\n", x, x/1024, x/1024/1024);
}