c++ - 使用 timer_create 传递用户数据

Question

我正在使用 timer_create 在 Linux 中创建一个计时器。回调原型(prototype)为:

static void TimerHandlerCB(int sig, siginfo_t *extra, void *cruft)

我如何传递用户数据，以便我可以在计时器到期后调用的回调中接收相同的数据。

这是我的示例代码:

int RegisterTimer(iDiffInTime)
{
    struct sigaction sa; 
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_SIGINFO;   /*call our handler*/
    sa.sa_sigaction = TimerHandlerCB;/*Event handler to be called after timer expires*/ 
    if(sigaction(SIGRTMAX, &sa, NULL) < 0)
    {
        perror("sigaction");
        return 1;
    }
    // Setup the timer
    sigevent sigev;
    timer_t timerid = 0;

    memset(&sigev, 0, sizeof(sigev));

    sigev.sigev_notify          = SIGEV_SIGNAL;
    sigev.sigev_signo           = SIGRTMAX;
    sigev.sigev_value.sival_ptr = &timerid;

    timer_t timerid;

    if (timer_create(CLOCK_REALTIME, &sigev, &timerid) == 0)
    {
        printf("Timer created\n");
        struct itimerspec itval, oitval;

        itval.it_value.tv_sec = iDiffInTime * 1000;
        itval.it_value.tv_nsec = 0;
        itval.it_interval.tv_sec = 0;
        itval.it_interval.tv_nsec = 0;

              //Populate handles required in TimerCallback
              Display_Handle hDisplay = ......//
              Buffer_Handle hBuf = .....//
        if (timer_settime(timerid, 0, &itval, &oitval) != 0)
        {
            perror("time_settime error!");
            return 1;
        }
    } 
    else 
    {
        perror("timer_create error!");
    }
    return 0
}

我在哪里传递 hDisplay 和 hBuf 以便我可以在 TimerHandlerCB 中接收它们？

Answer 1

你已经在做了:

sigev.sigev_value.sival_ptr = &timerid;

您可以在其中指定任何内容(指定 &timerid 通常用于区分多个计时器，但不是必需的)。现在在你的处理程序中:

static void timer_handler(int signo, siginfo_t *si, void *uc)
{
    /* si->si_value.sival_ptr */
}

引自 TLPI

When calling timer_create(), evp.sigev_value.sival_ptr is typically assigned the address of the timerid argument given in the same call. Alternatively, evp.sigev_value.sival_ptr may be assigned the address of a structure that contains the timerid given to timer_create()