Timer.cpp

// SPDX-FileCopyrightText: 2018 Lutz Freitag
// SPDX-License-Identifier: MIT
#include "Timer.h"

#include <cstring>
#include <time.h>

#include <stdexcept>
#include <cerrno>
#include <string>


namespace simplyfile {

namespace {
void normalize(struct timespec& time) {
    while (time.tv_nsec > 1000000000) {
        time.tv_nsec -= 1000000000;
        time.tv_sec += 1;
    }
    while (time.tv_nsec < -1000000000) {
        time.tv_nsec += 1000000000;
        time.tv_sec -= 1;
    }
}
}

Timer::Timer(int flags) 
    : FileDescriptor(::timerfd_create(CLOCK_MONOTONIC, flags))
{}

Timer::Timer(std::chrono::nanoseconds duration, bool oneShot, int flags)
    : FileDescriptor(::timerfd_create(CLOCK_MONOTONIC, flags))
{
    reset(duration, oneShot);
}
int Timer::getElapsed() const {
    uint64_t elapsed {0};
    ::read(*this, &elapsed, sizeof(elapsed));
    return elapsed;
}

void Timer::cancel() {
    struct itimerspec new_value{};
    if (timerfd_settime(*this, TFD_TIMER_ABSTIME, &new_value, NULL) == -1) {
        throw std::runtime_error("cannot cancel timer " + std::string(strerror(errno)));
    }
}

void Timer::reset(std::chrono::nanoseconds duration, bool oneShot) {
    cancel();
    struct itimerspec new_value {};
    struct timespec now;
    if (clock_gettime(CLOCK_MONOTONIC, &now) == -1) {
        throw std::runtime_error("cannot get the current time");
    }

    int64_t seconds     = std::chrono::duration_cast<std::chrono::seconds>(duration).count();
    int64_t nanoSeconds = std::chrono::duration_cast<std::chrono::nanoseconds>(duration - std::chrono::seconds(seconds)).count();

    new_value.it_value.tv_sec = now.tv_sec + seconds;
    new_value.it_value.tv_nsec = now.tv_nsec + nanoSeconds;
    normalize(new_value.it_value);

    if (not oneShot) {
        new_value.it_interval.tv_sec = seconds;
        new_value.it_interval.tv_nsec = nanoSeconds;
        normalize(new_value.it_interval);
    }

    if (timerfd_settime(*this, TFD_TIMER_ABSTIME, &new_value, NULL) == -1) {
        throw std::runtime_error("cannot set timeout for timerfd " + std::string(strerror(errno)));
    }
}


}