/**
 *   Copyright (C) NAKAMURA Minoru <nminoru@nminoru.jp>
 *
 *   gcc -g -Wall -O0 -lrt timer_max_limit.c
 */
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <signal.h>
#include <time.h>
#include <assert.h>
#include <limits.h>
#include <errno.h>
#include <sched.h>

volatile int acc_sigusr1;

void handler(int signum, siginfo_t* info, void * p)
{
    acc_sigusr1++;
}

int main(int argc, char** argv)
{
    // タイマーに使うシグナル SIGUSR1 は通常ブロックするよ
    sigset_t  sigset;
    sigemptyset(&sigset);
    sigaddset(&sigset, SIGUSR1);
    sigprocmask(SIG_BLOCK, &sigset, NULL);

    // SIGUSR1 ハンドラの設定
    struct sigaction action;
    action.sa_flags = SA_SIGINFO;
    sigfillset(&action.sa_mask);
    action.sa_sigaction = handler;
    sigaction(SIGUSR1, &action, NULL);

    // イベント設定
    struct sigevent event;
    // event.sigev_notify  = SIGEV_NONE;
    event.sigev_notify  = SIGEV_SIGNAL;
    event.sigev_signo           = SIGUSR1;
    event.sigev_value.sival_int = 0xCAFEBABE;

    timer_t  timer;
    if (timer_create(CLOCK_REALTIME, &event, &timer)) {
        perror("timer_create");
        abort();
    }

    struct itimerspec spec, old_spec;
    spec.it_value.tv_sec     =  LONG_MAX;
    spec.it_value.tv_nsec    =  0;
    spec.it_interval.tv_sec  =  0;
    spec.it_interval.tv_nsec =  0;

    while(spec.it_value.tv_sec != 0) {
        if (timer_settime(timer, 0, &spec, NULL)) {
            if (errno == EINVAL) {
                spec.it_value.tv_sec /= 2;
                continue;
            }
            perror("timer_settime");
            abort();
        }

        if (timer_gettime(timer, &old_spec)) {
            perror("timer_gettime");
            abort();
        }

        acc_sigusr1 = 0;

        // SIGUSR1 を解除する。
        sigprocmask(SIG_UNBLOCK, &sigset, NULL);
        sched_yield(); // タイマーが来るかも知れないのを少し待つよ。
        sigprocmask(SIG_BLOCK, &sigset, NULL);

        printf("settime: %ld.%09ld\ngettime: %ld.%09ld%s\n\n",
               spec.it_value.tv_sec, spec.it_value.tv_nsec,
               old_spec.it_value.tv_sec, old_spec.it_value.tv_nsec,
               acc_sigusr1 ? " TIMER EXPIRED" : "");

        // タイマー解除
        struct itimerspec spec_clear;
        spec_clear.it_value.tv_sec     = 0;
        spec_clear.it_value.tv_nsec    = 0;
        spec_clear.it_interval.tv_sec  = 0;
        spec_clear.it_interval.tv_nsec = 0;
        
        timer_settime(timer, 0, &spec_clear, NULL);

        // 余分なシグナルを破棄
        sigprocmask(SIG_UNBLOCK, &sigset, NULL);
        sigprocmask(SIG_BLOCK, &sigset, NULL);

        spec.it_value.tv_sec /= 2;
    }

    return 0;
}