#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <sys/uio.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <assert.h>

int main(int argc, char *argv[])
{
  struct kevent kev;
  char *filename;
  char buf[128];
  int c;
  int fd = -1;
  int kq = -1;

  if(argc != 2)
    {
      fprintf(stderr, "usage: kqfile <file>\n");
      goto err;
    }

  filename = argv[1];

  /* open the file specified */
  if((fd = open(filename, O_RDONLY)) == -1)
    {
      fprintf(stderr, "could not open %s\n", filename);
      goto err;
    }

  /* allocate a kqueue */
  if((kq = kqueue()) == -1)
    {
      fprintf(stderr, "could not allocate a kqueue\n");
      goto err;
    }

  /* register the opened file with the kqueue for read events */
  EV_SET(&kev, fd, EVFILT_READ, EV_ADD, 0, 0, NULL);
  if(kevent(kq, &kev, 1, NULL, 0, NULL) == -1)
    {
      fprintf(stderr, "could not register fd %d with kq\n", fd);
      goto err;
    }

  while((c = kevent(kq, NULL, 0, &kev, 1, NULL)) != -1)
    {
      assert(c == 1);
      assert(kev.ident == fd);

      fprintf(stdout,
	      "ident %d filter 0x%04x flags 0x%04x fflags 0x%04x data %d\n",
	      kev.ident, kev.filter, kev.flags, kev.fflags, kev.data);

      if((c = read(fd, buf, sizeof(buf))) == 0)
	{
	  fprintf(stdout, "EOF!\n");
	  break;
	}

      fprintf(stdout, "read %d bytes\n", c);
    }

 err:
  if(fd != -1) close(fd);
  if(kq != -1) close(kq);
  return -1;
}