timer.c

/*
 * Copyright (c) 2018, Kontron Europe GmbH
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/timerfd.h>

#include <glib.h>


#ifndef TIMEVAL_TO_TIMESPEC
#define TIMEVAL_TO_TIMESPEC(tv, ts) {          \
        (ts)->tv_sec = (tv)->tv_sec;           \
        (ts)->tv_nsec = (tv)->tv_usec * 1000;  \
}
#endif

#ifndef TIMESPEC_TO_TIMEVAL
#define TIMESPEC_TO_TIMEVAL(tv, ts) {          \
        (tv)->tv_sec = (ts)->tv_sec;           \
        (tv)->tv_usec = (ts)->tv_nsec / 1000;  \
}
#endif

#define NSEC_PER_SEC 1000000000
void timespec_diff(const struct timespec *a, const struct timespec *b,
                   struct timespec *result)
{
    gint64 diff;
    diff = NSEC_PER_SEC * (gint64)((gint64) b->tv_sec - (gint64) a->tv_sec);;
    diff += ((gint64) b->tv_nsec - (gint64) a->tv_nsec);
    result->tv_sec = diff / NSEC_PER_SEC;
    result->tv_nsec = diff % NSEC_PER_SEC;
}


#define TIME_BEFORE_NS 300000

static int get_timeval_to_next_slice(struct timespec *now, struct timespec *next,
        struct timespec *interval)
{
    gint64 interval_ns = interval->tv_nsec;

    if ((now->tv_nsec + interval_ns) >= 1000000000) {
        next->tv_sec = now->tv_sec + 1;
        next->tv_nsec = 0;

    } else {
        next->tv_sec = now->tv_sec;
        next->tv_nsec =
            ((now->tv_nsec / interval_ns) + 1) * interval_ns;
    }

    return 0;
}

void wait_for_next_timeslice(struct timespec *interval, gint offset_usec,
        struct timespec *next, struct timespec *t0)
{
    int rc;
    struct timespec ts_now;
    struct timespec ts_target;

    if (clock_gettime(CLOCK_REALTIME, &ts_now)) {
        perror("clock_gettime");
    }

    /* calculate wanted target time */
    get_timeval_to_next_slice(&ts_now, &ts_target, interval);

    if (t0 != NULL) {
        memcpy(t0, &ts_target, sizeof(struct timespec));
    }

    ts_target.tv_nsec += (offset_usec * 1000);
    if (next != NULL) {
        memcpy(next, &ts_target, sizeof(struct timespec));
    }

    rc = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &ts_target, NULL);
    if (rc != 0) {
        if (rc != EINTR) {
            perror("clock_nanosleep failed");
        }
    }

    return;
}

char *timespec_to_iso_string(struct timespec *time)
{
    GString *iso_string;
    struct tm t;
    guint32 nsec;
    char buf[32];

    if (time != NULL) {
        nsec = time->tv_nsec;
        if (gmtime_r(&(time->tv_sec), &t) == NULL)
            return NULL;
    } else {
        time_t sec = 0;
        nsec = 0;
        if (gmtime_r(&sec, &t) == NULL)
            return NULL;
    }

    strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%S", &t);
    iso_string = g_string_new_len(buf, strlen(buf));
    g_string_append_printf(iso_string, ".%09d", nsec);

    return g_string_free(iso_string, FALSE);
}