1  /* kqueue interface, C mini-library
 2   *
 3   * Copyright 2012 Joey Hess <id@joeyh.name>
 4   *
 5   * License: BSD-2-clause
 6   */
 7  
 8  #include <stdio.h>
 9  #include <dirent.h>
10  #include <fcntl.h>
11  #include <stdlib.h>
12  #include <unistd.h>
13  #include <sys/types.h>
14  #include <sys/event.h>
15  #include <sys/time.h>
16  #include <errno.h>
17  
18  /* The specified fds are added to the set of fds being watched for changes.
19   * Fds passed to prior calls still take effect, so it's most efficient to
20   * not pass the same fds repeatedly.
21   *
22   * Returns the fd that changed, or -1 on error.
23   */
24  signed int helper(const int kq, const int fdcnt, const int *fdlist, int nodelay) {
25  	int i, nev;
26  	struct kevent evlist[1];
27  	struct kevent chlist[fdcnt];
28  	struct timespec avoiddelay = {0, 0};
29  	struct timespec *timeout = nodelay ? &avoiddelay : NULL;
30  	
31  	for (i = 0; i < fdcnt; i++) {
32  		EV_SET(&chlist[i], fdlist[i], EVFILT_VNODE,
33  			EV_ADD | EV_ENABLE | EV_CLEAR,
34  			NOTE_WRITE,
35  			0, 0);
36  	}
37  
38  	nev = kevent(kq, chlist, fdcnt, evlist, 1, timeout);
39  	if (nev == 1)
40  		return evlist[0].ident;
41  	else
42  		return -1;
43  }
44  
45  /* Initializes a new, empty kqueue. */
46  int init_kqueue() {
47  	int kq;
48  	if ((kq = kqueue()) == -1) {
49  		perror("kqueue");
50  		exit(1);
51  	}
52  	return kq;
53  }
54  
55  /* Adds fds to the set that should be watched. */
56  void addfds_kqueue(const int kq, const int fdcnt, const int *fdlist) {
57  	helper(kq, fdcnt, fdlist, 1);
58  }
59  
60  /* Waits for a change event on a kqueue. */
61  signed int waitchange_kqueue(const int kq) {
62  	return helper(kq, 0, NULL, 0);
63  }
64  
65  /*
66  main () {
67  	int list[1];
68  	int kq;
69  	list[0]=open(".", O_RDONLY);
70  	kq = init_kqueue();
71  	addfds_kqueue(kq, 1, list)
72  	printf("change: %i\n", waitchange_kqueue(kq));
73  }
74  */