@Override
public synchronized PathWatchKey register(Path path, Kind<?>[] kinds, Modifier[] modifiers)
throws IOException {
PathImpl pathImpl = checkAndCastToPathImpl(path);
int flags = makeFlagMask(kinds, modifiers);
// check that user only provided supported flags and modifiers
int supportedFlags =
(FLAG_FILTER_ENTRY_CREATE
| FLAG_FILTER_ENTRY_DELETE
| FLAG_FILTER_ENTRY_MODIFY
| FLAG_FILTER_KEY_INVALID);
if ((flags & ~supportedFlags) != 0)
throw new UnsupportedOperationException(
"The given watch event kind or modifier is not supported by this WatchService");
String pathname = pathImpl.getFile().getAbsolutePath();
PollingPathWatchKey key = null;
// request changeLock
BSD.write(closePipeWriteFd, new byte[1], 1);
synchronized (changeLock) {
if (kqueuefd == -1) throw new ClosedWatchServiceException();
{
Integer dirfdInteger = dirs.get(pathname);
if (dirfdInteger != null) key = keys.get(dirfdInteger);
}
if (key == null) {
// no directory file fd registered - we'll need to open
// one now
// create file descriptor and watch event first
boolean success = false;
int dirfd = -1;
try {
dirfd = BSD.open(pathname, BSD.O_RDONLY, 0);
if (dirfd == -1)
throw new IOException(
"error registering the path with the native OS: " + strerror(errno()));
kevent e = new kevent();
e.set_ident(dirfd);
e.set_filter(EVFILT_VNODE);
e.set_flags((short) (EV_ADD | EV_CLEAR));
e.set_fflags(NOTE_WRITE | NOTE_DELETE | NOTE_REVOKE);
int result = kevent(kqueuefd, new kevent[] {e}, null, null);
// do we need more specific error handling here?
if (result != 0)
throw new IOException(
"error registering the path with the native OS: " + strerror(errno()));
// create watch key and add it to the key and dirs maps
key = new PollingPathWatchKey(this, path, 0);
keys.put(dirfd, key);
dirs.put(pathname, dirfd);
} finally {
// if something went wrong, close descriptors
if (key == null) {
if (dirfd != -1) {
// if the descriptor has been added to the kqueue,
// it will be removed automatically when the descriptor
// closes.
BSD.close(dirfd);
}
}
}
}
if (key != null && key.getFlags() != flags) {
// check if modification flag has changed; moddiff will
// be +1 if the ENTRY_MODIFIED flag was added, -1 if
// it was removed (and 0 if it didn't change)
int moddiff = 0;
moddiff += (flags & FLAG_FILTER_ENTRY_MODIFY) != 0 ? +1 : 0;
moddiff += (key.getFlags() & FLAG_FILTER_ENTRY_MODIFY) != 0 ? -1 : 0;
numKeysRequiringPolling += moddiff;
key.setFlags(flags);
}
// retract request for change lock
BSD.read(closePipeReadFd, new byte[1], 1);
}
// first poll to capture initial state
key.poll();
return key;
}
