/*
 * from ftp://ftp.netbsd.org/pub/NetBSD/misc/gmcgarry/bench/syscallbench.tar.gz
 *
 * gcc -Wall -Werror -O3 -static -o ctx ctx.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>

#include <OS.h>

#define ITERATIONS      500000

static void
usage(void)
{
        printf("syscallbench [-h]\n");
        exit(1);
}

static int null_func(void)
{
        return 0;
}

static unsigned long test_func(int (*func)(void))
{
        struct timeval before, after;
        unsigned long elapsed;
        int i;

        gettimeofday(&before, NULL);
        for (i=0; i<ITERATIONS; i++) {
                func();
        }
        gettimeofday(&after, NULL);

        elapsed = 1000000 * (after.tv_sec - before.tv_sec);
        elapsed += after.tv_usec - before.tv_usec;
        return elapsed;
}

int
main(int argc, char *argv[])
{
        unsigned long overhead;
        unsigned long libcall;
        unsigned long syscall;
        
        if (argc > 1)
                usage();

        overhead = test_func(&null_func);
        libcall = test_func((void *)&getpid); // getpid is currently implemented as a library function returning the value of a global
        syscall = test_func((void *)&is_computer_on);

        printf("overhead time: %ld nanoseconds\n",
            (1000*(overhead))/ITERATIONS);

        printf("libcall time: %ld nanoseconds\n",
            (1000*(libcall-overhead))/ITERATIONS);

        printf("syscall time: %ld nanoseconds\n",
            (1000*(syscall-overhead))/ITERATIONS);

        return (0);
}