note

timerfd对应的时钟到期后，对应内部数据(uint64)计数加1

timerfd支持read方法，poll方法

code

#include <sys/timerfd.h>
#include <poll.h>
#include <thread>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

void timerfd_test1(void)
{ 
    class timer {
public:
    struct callback {
        void* (*fun)(void*);
        void* arg;
    };
    timer() {
        this->fd = -1;
        this->cb = nullptr;
    }
    ~timer() {
        if (this->fd > 0) {

        }
    }
    int init(long interval) {
        int ret = -1;
        ret = timerfd_create(CLOCK_REALTIME, 0);
        if (ret == -1) {
            return -1;
        }
        this->fd = ret;

        this->interval = interval;

        return 0;
    }
    int start(void) {
        if (!cb) {
            return -1;
        }
        if (fd < 0) {
            return -1;
        }

        struct itimerspec tim;
        struct timespec now;
        int ret = -1;

        ret = clock_gettime(CLOCK_REALTIME, &now);
        if (ret == -1) {
            return -1;
        }

        tim.it_interval.tv_sec = interval;
        tim.it_interval.tv_nsec = 0;
        tim.it_value.tv_nsec = now.tv_nsec;
        tim.it_value.tv_sec = now.tv_sec;

        ret = timerfd_settime(this->fd, TFD_TIMER_ABSTIME, &tim, nullptr);
        if (ret == -1) {
            return -1;
        }

        this->running = true;

        std::thread t(&timer::routine, this, this); // 第一个this因为非静态成员函数做线程，第二个this为参数
        t.detach();

        return 0;
    }
    int stop(void) {
        running = false;
        return 0;
    }
    int setcb(callback* cbIn) {
        if (!cbIn) {
            return -1;
        }
        if (cbIn->fun == nullptr) {
            return -1;
        }
        if (cbIn->arg == nullptr) {
            return -1;
        }
        if (this->cb) {
            return -1;
        }
        this->cb = cbIn;
        return 0;
    }
protected:
private:
    int fd;
    long interval;
    bool running;
    callback* cb;
    void routine(void* arg) {
        if (arg == nullptr) {
            return;
        }
        
        timer* me = static_cast<timer*>(arg);
        int ret = -1;
        struct pollfd fds;
        uint64_t cnt = 0;
        ssize_t n = 0;

        fds.fd = me->fd;
        fds.events = POLLIN;
        fds.revents = 0;

        while (me->running) {
            ret = poll(&fds, 1, 0);
            if (ret == -1) {
                fprintf(stderr, "poll error,%s\n", strerror(errno));
                continue;
            }
            if (ret == 0) {
                // fprintf(stdout, "poll return no event\n");
                continue;
            }
            if ((ret == 1) && (fds.revents == POLLIN)) {
                // fprintf(stdout, "poll return read event\n");
                n = read(fds.fd, &cnt, sizeof(uint64_t));
                if (n < 0) {
                    fprintf(stderr, "read error,%s\n", strerror(errno));
                    continue;
                }
                if (n != sizeof(uint64_t)) {
                    fprintf(stdout, "read return not uint64_t\n");
                    continue;
                }
                for (uint64_t i = 0; i < cnt; ++i) {
                    (me->cb->fun)(me->cb->arg);
                }
            }
        }
    }
    };

    timer t;
    timer::callback cb;
    auto f = [](void*arg) -> void* {
        fprintf(stdout, "%s calleb,arg:%s\n", __FUNCTION__, (char*)arg);
        return nullptr;
    };
    cb.fun = f;
    cb.arg = (void*)"hello";

    t.setcb(&cb);
    t.init(1);
    t.start();
    std::this_thread::sleep_for(std::chrono::milliseconds(10000));
    t.stop();
    std::this_thread::sleep_for(std::chrono::milliseconds(10000));
    fprintf(stdout, "%s returning...\n", __FUNCTION__);
}

test