#include <sys/event.h>
#include <sys/types.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

void test_event(int fd, int kq, const char *what, u_short flag)
{
    printf("  %s\n", what);
    struct kevent event, tevent;
    EV_SET(&event, fd, flag, EV_ADD | EV_CLEAR, 0, 0, NULL);

    int rc = kevent(kq, &event, 1, NULL, 0, NULL);
    if (rc == -1)
    {
        err(EXIT_FAILURE, "kevent (set)");
    }

    rc = kevent(kq, NULL, 0, &tevent, 1, NULL);
    if (rc == -1)
    {
        err(EXIT_FAILURE, "kevent (wait)");
    }
    else if (rc > 0)
    {
        if (tevent.flags & EV_ERROR)
        {
            err(EXIT_FAILURE, "kevent (flags)");
        }
        else
        {
            printf("    triggered\n");
        }
    }
}

void test(const char* path)
{
    printf("%s\n", path);
    int fd = open(path, O_RDONLY);
    if (fd == -1)
    {
        err(EXIT_FAILURE, "open failed: %s\n", path);
    }

    int kq = kqueue();
    if (kq == -1)
    {
        err(EXIT_FAILURE, "kqueue failed\n");
    }

    test_event(fd, kq, "read", EVFILT_READ);
    test_event(fd, kq, "write", EVFILT_WRITE);

    close(kq);
    close(fd);
}

int main()
{
    test("/dev/nullo");
    test("/dev/fullo");
    test("/dev/zeroo");

    return 0;
}