update kqueue when new directories are added

Utility/Kqueue.hs

@@ -100,7 +100,9 @@ removeSubDir dirmap dir = do
 		(toremove, rest) = M.partition (dirContains dir . dirName) dirmap
 
 foreign import ccall unsafe "libkqueue.h init_kqueue" c_init_kqueue
-	:: CInt -> Ptr Fd -> IO Fd
+	:: IO Fd
+foreign import ccall unsafe "libkqueue.h addfds_kqueue" c_addfds_kqueue
+	:: Fd -> CInt -> Ptr Fd -> IO ()
 foreign import ccall unsafe "libkqueue.h waitchange_kqueue" c_waitchange_kqueue
 	:: Fd -> IO Fd
 
@@ -108,9 +110,16 @@ foreign import ccall unsafe "libkqueue.h waitchange_kqueue" c_waitchange_kqueue
 initKqueue :: FilePath -> Pruner -> IO Kqueue
 initKqueue dir pruned = do
 	dirmap <- scanRecursive dir pruned
+	h <- c_init_kqueue
+	let kq = Kqueue h dirmap pruned
+	updateKqueue kq
+	return kq
+
+{- Updates a Kqueue, adding watches for its map. -}
+updateKqueue :: Kqueue -> IO ()
+updateKqueue (Kqueue h dirmap _) =
 	withArrayLen (M.keys dirmap) $ \fdcnt c_fds -> do
-		h <- c_init_kqueue (fromIntegral fdcnt) c_fds
+		c_addfds_kqueue h (fromIntegral fdcnt) c_fds
-		return $ Kqueue h dirmap pruned
 
 {- Stops a Kqueue. Note: Does not directly close the Fds in the dirmap,
  - so it can be reused.  -}
@@ -155,10 +164,16 @@ handleChange kq@(Kqueue h dirmap pruner) fd olddirinfo =
 
 			-- Update the cached dirinfo just looked up.
 			let newmap'' = M.insertWith' const fd newdirinfo newmap'
-			ret (newmap'', changes)
+
+			-- When new directories were added, need to update
+			-- the kqueue to watch them.
+			let kq' = Kqueue h newmap'' pruner
+			unless (null newdirinfos) $
+				updateKqueue kq'
+
+			return (kq', changes)
 		go Nothing = do
 			-- The directory has been moved or deleted, so
 			-- remove it from our map.
 			newmap <- removeSubDir dirmap (dirName olddirinfo)
-			ret (newmap, [])
+			return (Kqueue h newmap pruner, [])
-		ret (newmap, changes) = return $ (Kqueue h newmap pruner, changes)

Utility/libkqueue.c

@@ -18,11 +18,12 @@
  * 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,
+signed int helper(const int kq, const int fdcnt, const int *fdlist, int nodelay) {
-		struct timespec *timeout) {
 	int i, nev;
 	struct kevent evlist[1];
 	struct kevent chlist[fdcnt];
+	struct timespec avoiddelay = {0, 0};
+	struct timespec *timeout = nodelay ? &avoiddelay : NULL;
 	
 	for (i = 0; i < fdcnt; i++) {
 		EV_SET(&chlist[i], fdlist[i], EVFILT_VNODE,
@@ -43,30 +44,27 @@ signed int helper(const int kq, const int fdcnt, const int *fdlist,
 		return -1;
 }
 
-/* Initializes a kqueue, with a list of fds to watch for changes.
+/* Initializes a new, empty kqueue. */
- * Returns the kqueue's handle. */
 int init_kqueue(const int fdcnt, const int *fdlist) {
-	struct timespec nodelay = {0, 0};
 	int kq;
-
 	if ((kq = kqueue()) == -1) {
 		perror("kqueue");
 		exit(1);
 	}
-
-	/* Prime the pump with the list of fds, but don't wait for any
-	 * change events. */
-	helper(kq, fdcnt, fdlist, &nodelay);
-
 	return kq;
 }
 
+/* Adds fds to the set that should be watched. */
+void addfds_kqueue(const int kq, const int fdcnt, const int *fdlist) {
+	helper(kq, fdcnt, fdlist, 1);
+}
+
 /* Waits for a change event on a kqueue.
  *
  * Returns the fd that changed, or -1 on error.
  */
 signed int waitchange_kqueue(const int kq) {
-	return helper(kq, 0, NULL, NULL);
+	return helper(kq, 0, NULL, 0);
 }
 
 /*
@@ -74,7 +72,8 @@ main () {
 	int list[1];
 	int kq;
 	list[0]=open(".", O_RDONLY);
-	kq = init_kqueue(1, list);
+	kq = init_kqueue();
+	addfds_kqueue(kq, 1, list)
 	printf("change: %i\n", waitchange_kqueue(kq));
 }
 */