flesh out kqueue library

Have not tried to build this yet. But barring minor mistakes, I think it's
good.

Utility/libkqueue.c

@@ -5,18 +5,62 @@
  * Licensed under the GNU GPL version 3 or higher.
  */
 
-#include <errno.h>
 #include <stdio.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/event.h>
+#include <sys/time.h>
 
-/* Waits for a change event on one of the array of directory fds,
- * and returns the one that changed. */
-int waitchange(const int *fds) {
-//	if (kqueue(blah, &fds) != 0)
-//		return 0; /* errno is set */
-//	else
-		errno = 0;
+/* Initializes a kqueue, with a list of fds to watch for changes.
+ * Returns the kqueue's handle. */
+int init_kqueue(const int fdcnt, const int *fdlist) {
+	struct nodelay = {0, 0};
+	int kq;
 
-	printf("in waitchange!, %i %i\n", fds[0], fds[1]);
+	if ((kq = kqueue()) == -1) {
+		perror("kqueue");
+		exit(1);
+	}
 
-	return fds[0];
+	/* Prime the pump with the list of fds, but don't wait for any
+	 * change events. */
+	helper(kq, fdcnt, fdlist, &nodelay);
+
+	return kq;
+}
+
+/* Waits for a change event on a kqueue.
+ *
+ * Returns the fd that changed, or -1 on error.
+ */
+signed int waitchange_kqueue(const int kq) {
+	helper(kq, 0, NULL, NULL);
+}
+
+/* The specified fds are added to the set of fds being watched for changes.
+ * Fds passed to prior calls still take effect, so it's most efficient to
+ * not pass the same fds repeatedly.
+ */
+signed int helper(const int kq, const int fdcnt, const int *fdlist, cont struct *timeout) {
+	int i, nev;
+	struct kevent evlist[1];
+	struct kevent chlist[fdcnt];
+	
+	for (i = 0; i < fdcnt; i++) {
+		EV_SET(&chlist[i], fdlist[i], EVFILT_VNODE,
+			EV_ADD | EV_ENABLE | EV_CLEAR,
+			NOTE_WRITE,
+			1,
+			timeout);
+	}
+
+	nev = kevent(info->kq, info->chlist, info->cnt, info->evlist,
+			1, NULL);
+
+	if (nev == 1)
+		return evlist[0].ident;
+	else
+		return -1;
 }