Модуль 5. Лекция 18 - Школа системного моделирования

#define _GNU_SOURCE
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>
#include <sys/timerfd.h>
#include <time.h>
#include <errno.h>

#include "piCtl.h"

static void do_step(void)
{
    static bool OverrunFlag = false;

    if (OverrunFlag) {
        /* model step overrun – skip this tick */
        return;
    }

    OverrunFlag = true;
    piCtl_step();
    OverrunFlag = false;
}

int main(void)
{
    int tfd;
    struct itimerspec ts;
    uint64_t expirations;
    FILE * fd;
    
    piCtl_init();
    fd = fopen("output.csv","wt");

    /* Create timerfd (monotonic clock = no jumps on NTP) */
    tfd = timerfd_create(CLOCK_MONOTONIC, 0);
    if (tfd == -1) {
        perror("timerfd_create");
        return 1;
    }

    /* 1 ms period */
    ts.it_interval.tv_sec  = 0;
    ts.it_interval.tv_nsec = 1 * 1000 * 1000;  /* 1 ms */

    /* start after 1 ms */
    ts.it_value = ts.it_interval;

    if (timerfd_settime(tfd, 0, &ts, NULL) == -1) {
        perror("timerfd_settime");
        return 1;
    }

    /* Main loop driven by timer */
    while (1) {
        ssize_t s = read(tfd, &expirations, sizeof(expirations));
        if (s != sizeof(expirations)) {
            perror("read(timerfd)");
            break;
        }

        /*
         * expirations > 1 means we missed ticks
         * (model slower than real-time)
         */
        while (expirations--) {
            do_step();
        }
    }

    piCtl_term();
    close(tfd);
    return 0;
}