2005-08-16 Gabor Kelemen <kelemeng@gnome.hu>

[beagle.git] / Util / Inotify.cs

//
// Inotify.cs
//
// Copyright (C) 2004 Novell, Inc.
//

//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//

// WARNING: This is not portable to Win32

using System;
using System.Collections;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;

using Mono.Posix;

namespace Beagle.Util {

        public class Inotify {

                public delegate void InotifyCallback (Watch watch, string path, string subitem, string srcpath, EventType type);

                /////////////////////////////////////////////////////////////////////////////////////

                [Flags]
                public enum EventType : uint {
                        Access         = 0x00000001, // File was accessed
                        Modify         = 0x00000002, // File was modified
                        Attrib         = 0x00000004, // File changed attributes
                        CloseWrite     = 0x00000008, // Writable file was closed
                        CloseNoWrite   = 0x00000010, // Non-writable file was close
                        Open           = 0x00000020, // File was opened
                        MovedFrom      = 0x00000040, // File was moved from X
                        MovedTo        = 0x00000080, // File was moved to Y
                        Create         = 0x00000100, // Subfile was created
                        Delete         = 0x00000200, // Subfile was deleted                     
                        DeleteSelf     = 0x00000400, // Self was deleted

                        Unmount        = 0x00002000, // Backing fs was unmounted
                        QueueOverflow  = 0x00004000, // Event queue overflowed
                        Ignored        = 0x00008000, // File is no longer being watched

                        IsDirectory    = 0x40000000, // Event is against a directory
                        OneShot        = 0x80000000, // Watch is one-shot

                        // For forward compatibility, define these explicitly
                        All            = (EventType.Access | EventType.Modify | EventType.Attrib |
                                          EventType.CloseWrite | EventType.CloseNoWrite | EventType.Open |
                                          EventType.MovedFrom | EventType.MovedTo | EventType.Create |
                                          EventType.Delete | EventType.DeleteSelf)
                }

                // Events that we want internally, even if the handlers do not
                static private EventType base_mask =  EventType.MovedFrom | EventType.MovedTo;

                /////////////////////////////////////////////////////////////////////////////////////

                static private Logger log;

                static public Logger Log { 
                        get { return log; }
                }

                /////////////////////////////////////////////////////////////////////////////////////

                [StructLayout (LayoutKind.Sequential)]
                private struct inotify_event {
                        public int       wd;
                        public EventType mask;
                        public uint      cookie;
                        public uint      len;
                }

                [DllImport ("libinotifyglue")]
                static extern int inotify_glue_init ();

                [DllImport ("libinotifyglue")]
                static extern int inotify_glue_watch (int fd, string filename, EventType mask);

                [DllImport ("libinotifyglue")]
                static extern int inotify_glue_ignore (int fd, int wd);

                [DllImport ("libinotifyglue")]
                static extern unsafe void inotify_snarf_events (int fd,
                                                                int timeout_seconds,
                                                                out int nr,
                                                                out IntPtr buffer);

                /////////////////////////////////////////////////////////////////////////////////////

                private class QueuedEvent {
                        public int       Wd;
                        public EventType Type;
                        public string    Filename;
                        public uint      Cookie;

                        public bool        Analyzed;
                        public bool        Dispatched;
                        public DateTime    HoldUntil;
                        public QueuedEvent PairedMove;

                        // Measured in milliseconds; 57ms is totally random
                        public const double DefaultHoldTime = 57;

                        public QueuedEvent ()
                        {
                                // Set a default HoldUntil time
                                HoldUntil = DateTime.Now.AddMilliseconds (DefaultHoldTime);
                        }

                        public void AddMilliseconds (double x)
                        {
                                HoldUntil = HoldUntil.AddMilliseconds (x);
                        }

                        public void PairWith (QueuedEvent other)
                        {
                                this.PairedMove = other;
                                other.PairedMove = this;
                                
                                if (this.HoldUntil < other.HoldUntil)
                                        this.HoldUntil = other.HoldUntil;
                                other.HoldUntil = this.HoldUntil;
                        }
                }

                /////////////////////////////////////////////////////////////////////////////////////

                static private int inotify_fd = -1;
                static private ArrayList event_queue = new ArrayList ();

                static Inotify ()
                {
                        log = Logger.Get ("Inotify");

                        if (Environment.GetEnvironmentVariable ("BEAGLE_DISABLE_INOTIFY") != null) {
                                Logger.Log.Debug ("BEAGLE_DISABLE_INOTIFY is set");
                                return;
                        }

                        if (Environment.GetEnvironmentVariable ("BEAGLE_INOTIFY_VERBOSE") != null)
                                Inotify.Verbose = true;

                        inotify_fd = inotify_glue_init ();
                        if (inotify_fd == -1)
                                Logger.Log.Warn ("Could not initialize inotify");
                }

                static public bool Enabled {
                        get { return inotify_fd >= 0; }
                }

                /////////////////////////////////////////////////////////////////////////////////////

                public interface Watch {
                        void Unsubscribe ();
                        void ChangeSubscription (EventType new_mask);
                }

                private class WatchInternal : Watch {
                        private InotifyCallback callback;
                        private EventType mask;
                        private WatchInfo watchinfo;
                        private bool is_subscribed;

                        public InotifyCallback Callback {
                                get { return callback; }
                        }

                        public EventType Mask {
                                get { return mask; }
                                set { mask = value; }
                        }

                        public WatchInternal (InotifyCallback callback, EventType mask, WatchInfo watchinfo)
                        {
                                this.callback = callback;
                                this.mask = mask;
                                this.watchinfo = watchinfo;
                                this.is_subscribed = true;
                        }

                        public void Unsubscribe ()
                        {
                                if (!this.is_subscribed)
                                        return;

                                Inotify.Unsubscribe (watchinfo, this);
                                this.is_subscribed = false;
                        }

                        public void ChangeSubscription (EventType mask)
                        {
                                if (! this.is_subscribed)
                                        return;

                                this.mask = mask;
                                CreateOrModifyWatch (this.watchinfo);
                        }

                }

                private class WatchInfo {
                        public int       Wd = -1;
                        public string    Path;
                        public bool      IsDirectory;
                        public EventType Mask;

                        public EventType FilterMask;
                        public EventType FilterSeen;

                        public ArrayList Children;
                        public WatchInfo Parent;

                        public ArrayList Subscribers;
                }

                static Hashtable watched_by_wd = new Hashtable ();
                static Hashtable watched_by_path = new Hashtable ();
                static WatchInfo last_watched = null;

                private class PendingMove {
                        public WatchInfo Watch;
                        public string    SrcName;
                        public DateTime  Time;
                        public uint      Cookie;

                        public PendingMove (WatchInfo watched, string srcname, DateTime time, uint cookie) {
                                Watch = watched;
                                SrcName = srcname;
                                Time = time;
                                Cookie = cookie;
                        }
                }

                static public int WatchCount {
                        get { return watched_by_wd.Count; }
                }

                static public bool IsWatching (string path)
                {
                        path = Path.GetFullPath (path);
                        return watched_by_path.Contains (path);
                }

                // Filter WatchInfo items when we do the Lookup.
                // We do the filtering here to avoid having to acquire
                // the watched_by_wd lock yet again.
                static private WatchInfo Lookup (int wd, EventType event_type)
                {
                        lock (watched_by_wd) {
                                WatchInfo watched;
                                if (last_watched != null && last_watched.Wd == wd)
                                        watched = last_watched;
                                else {
                                        watched = watched_by_wd [wd] as WatchInfo;
                                        if (watched != null)
                                                last_watched = watched;
                                }

                                if (watched != null && (watched.FilterMask & event_type) != 0) {
                                        watched.FilterSeen |= event_type;
                                        watched = null;
                                }

                                return watched;
                        }
                }

                // The caller has to handle all locking itself
                static private void Forget (WatchInfo watched)
                {
                        if (last_watched == watched)
                                last_watched = null;
                        if (watched.Parent != null)
                                watched.Parent.Children.Remove (watched);
                        watched_by_wd.Remove (watched.Wd);
                        watched_by_path.Remove (watched.Path);
                }

                static public Watch Subscribe (string path, InotifyCallback callback, EventType mask, EventType initial_filter)
                {
                        WatchInternal watch;
                        WatchInfo watched;
                        EventType mask_orig = mask;

                        if (!Path.IsPathRooted (path))
                                path = Path.GetFullPath (path);

                        bool is_directory = false;
                        if (Directory.Exists (path))
                                is_directory = true;
                        else if (! File.Exists (path))
                                throw new IOException (path);

                        lock (watched_by_wd) {
                                watched = watched_by_path [path] as WatchInfo;

                                if (watched == null) {
                                        // We need an entirely new WatchInfo object
                                        watched = new WatchInfo ();
                                        watched.Path = path;
                                        watched.IsDirectory = is_directory;
                                        watched.Subscribers = new ArrayList ();
                                        watched.Children = new ArrayList ();
                                        DirectoryInfo dir = new DirectoryInfo (path);
                                        watched.Parent = watched_by_path [dir.Parent.ToString ()] as WatchInfo;
                                        if (watched.Parent != null)
                                                watched.Parent.Children.Add (watched);
                                        watched_by_path [watched.Path] = watched;
                                }

                                watched.FilterMask = initial_filter;
                                watched.FilterSeen = 0;

                                watch = new WatchInternal (callback, mask_orig, watched);
                                watched.Subscribers.Add (watch);

                                CreateOrModifyWatch (watched);
                                watched_by_wd [watched.Wd] = watched;
                        }

                        return watch;
                }
                
                static public Watch Subscribe (string path, InotifyCallback callback, EventType mask)
                {
                        return Subscribe (path, callback, mask, 0);
                }

                static public EventType Filter (string path, EventType mask)
                {
                        EventType seen = 0;

                        path = Path.GetFullPath (path);

                        lock (watched_by_wd) {
                                WatchInfo watched;
                                watched = watched_by_path [path] as WatchInfo;

                                seen = watched.FilterSeen;
                                watched.FilterMask = mask;
                                watched.FilterSeen = 0;
                        }

                        return seen;
                }

                static private void Unsubscribe (WatchInfo watched, WatchInternal watch)
                {
                        watched.Subscribers.Remove (watch);

                        // Other subscribers might still be around                      
                        if (watched.Subscribers.Count > 0) {
                                // Minimize it
                                CreateOrModifyWatch (watched);
                                return;
                        }

                        int retval = inotify_glue_ignore (inotify_fd, watched.Wd);
                        if (retval < 0) {
                                string msg = String.Format ("Attempt to ignore {0} failed!", watched.Path);
                                throw new IOException (msg);
                        }

                        Forget (watched);
                        return;
                }

                // Ensure our watch exists, meets all the subscribers requirements,
                // and isn't matching any other events that we don't care about.
                static private void CreateOrModifyWatch (WatchInfo watched)
                {
                        EventType new_mask = base_mask;
                        foreach (WatchInternal watch in watched.Subscribers)
                                new_mask |= watch.Mask;

                        if (watched.Wd >= 0 && watched.Mask == new_mask)
                                return;

                        // We rely on the behaviour that watching the same inode twice won't result
                        // in the wd value changing.
                        // (no need to worry about watched_by_wd being polluted with stale watches)
                        
                        int wd = -1;
                        wd = inotify_glue_watch (inotify_fd, watched.Path, new_mask);
                        if (wd < 0) {
                                string msg = String.Format ("Attempt to watch {0} failed!", watched.Path);
                                throw new IOException (msg);
                        }
                        if (watched.Wd >= 0 && watched.Wd != wd) {
                                string msg = String.Format ("Watch handle changed unexpectedly!", watched.Path);        
                                throw new IOException (msg);
                        }

                        watched.Wd = wd;
                        watched.Mask = new_mask;
                }

                /////////////////////////////////////////////////////////////////////////////////////

                static Thread snarf_thread = null;
                static Thread dispatch_thread = null;
                static bool   running = false;

                static public void Start ()
                {
                        if (! Enabled)
                                return;

                        Logger.Log.Debug("Starting Inotify threads");

                        lock (event_queue) {
                                if (snarf_thread != null)
                                        return;

                                running = true;

                                snarf_thread = new Thread (new ThreadStart (SnarfWorker));
                                snarf_thread.Start ();

                                dispatch_thread = new Thread (new ThreadStart (DispatchWorker));
                                dispatch_thread.Start ();
                        }
                }

                static public void Stop ()
                {
                        if (! Enabled)
                                return;

                        lock (event_queue) {
                                running = false;
                                Monitor.Pulse (event_queue);
                        }
                }

                static unsafe void SnarfWorker ()
                {
                        Encoding filename_encoding = Encoding.UTF8;
                        int event_size = Marshal.SizeOf (typeof (inotify_event));
                        
                        while (running) {

                                // We get much better performance if we wait a tiny bit
                                // between reads in order to let events build up.
                                // FIXME: We need to be smarter here to avoid queue overflows.
                                Thread.Sleep (15);

                                IntPtr buffer;
                                int nr;

                                // Will block while waiting for events, but with a 1s timeout.
                                inotify_snarf_events (inotify_fd, 
                                                      1, 
                                                      out nr,
                                                      out buffer);

                                if (!running)
                                        break;

                                if (nr == 0)
                                        continue;

                                ArrayList new_events = new ArrayList ();

                                bool saw_overflow = false;
                                while (nr > 0) {

                                        // Read the low-level event struct from the buffer.
                                        inotify_event raw_event;
                                        raw_event = (inotify_event) Marshal.PtrToStructure (buffer, typeof (inotify_event));
                                        buffer = (IntPtr) ((long) buffer + event_size);

                                        if ((raw_event.mask & EventType.QueueOverflow) != 0)
                                                saw_overflow = true;

                                        // Now we convert our low-level event struct into a nicer object.
                                        QueuedEvent qe = new QueuedEvent ();
                                        qe.Wd = raw_event.wd;
                                        qe.Type = raw_event.mask;
                                        qe.Cookie = raw_event.cookie;

                                        // Extract the filename payload (if any) from the buffer.
                                        byte [] filename_bytes = new byte[raw_event.len];
                                        Marshal.Copy (buffer, filename_bytes, 0, (int) raw_event.len);
                                        buffer = (IntPtr) ((long) buffer + raw_event.len);
                                        int n_chars = 0;
                                        while (n_chars < filename_bytes.Length && filename_bytes [n_chars] != 0)
                                                ++n_chars;
                                        qe.Filename = "";
                                        if (n_chars > 0)
                                                qe.Filename = filename_encoding.GetString (filename_bytes, 0, n_chars);

                                        new_events.Add (qe);
                                        nr -= event_size + (int) raw_event.len;
                                }

                                if (saw_overflow)
                                        Logger.Log.Warn ("Inotify queue overflow!");

                                lock (event_queue) {
                                        event_queue.AddRange (new_events);
                                        Monitor.Pulse (event_queue);
                                }
                        }
                }


                static public bool Verbose = false;

                // Update the watched_by_path hash and the path stored inside the watch
                // in response to a move event.
                static private void MoveWatch (WatchInfo watch, string name)            
                {
                        watched_by_path.Remove (watch.Path);
                        watch.Path = name;
                        watched_by_path [watch.Path] = watch;

                        if (Verbose)
                                Console.WriteLine ("*** inotify: Moved Watch to {0}", watch.Path);
                }

                // A directory we are watching has moved.  We need to fix up its path, and the path of
                // all of its subdirectories, their subdirectories, and so on.
                static private void HandleMove (string srcpath, string dstpath)
                {
                        WatchInfo start = watched_by_path [srcpath] as WatchInfo;       // not the same as src!
                        if (start == null) {
                                Console.WriteLine ("Lookup failed for {0}", srcpath);
                                return;
                        }

                        // Queue our starting point, then walk its subdirectories, invoking MoveWatch() on
                        // each, repeating for their subdirectories.  The relationship between start, child
                        // and dstpath is fickle and important.
                        Queue queue = new Queue();
                        queue.Enqueue (start);
                        do {
                                WatchInfo target = queue.Dequeue () as WatchInfo;
                                for (int i = 0; i < target.Children.Count; i++) {
                                        WatchInfo child = target.Children[i] as WatchInfo;
                                        string name = Path.Combine (dstpath, child.Path.Substring (start.Path.Length + 1));
                                        MoveWatch (child, name);
                                        queue.Enqueue (child);
                                }
                        } while (queue.Count > 0);

                        // Ultimately, fixup the original watch, too
                        MoveWatch (start, dstpath);
                }

                static private void SendEvent (WatchInfo watched, string filename, string srcpath, EventType mask)
                {
                        // Does the watch care about this event?
                        if ((watched.Mask & mask) == 0)
                                return;

                        bool isDirectory = false;
                        if ((mask & EventType.IsDirectory) != 0)
                                isDirectory = true;

                        if (Verbose) {
                                Console.WriteLine ("*** inotify: {0} {1} {2} {3} {4} {5}",
                                                   mask, watched.Wd, watched.Path,
                                                   filename != "" ? filename : "\"\"",
                                                   isDirectory == true ? "(directory)" : "(file)",
                                                   srcpath != null ? "(from " + srcpath + ")" : "");
                        }

                        if (watched.Subscribers == null)
                                return;

                        foreach (WatchInternal watch in watched.Subscribers)
                                try {
                                        if (watch.Callback != null && (watch.Mask & mask) != 0)
                                                watch.Callback (watch, watched.Path, filename, srcpath, mask);
                                } catch (Exception e) {
                                        Logger.Log.Error ("Caught exception executing Inotify callbacks");
                                        Logger.Log.Error (e); 
                                }
                }

                ////////////////////////////////////////////////////////////////////////////////////////////////////

                // Dispatch-time operations on the event queue
               
                static Hashtable pending_move_cookies = new Hashtable ();

                // Clean up the queue, removing dispatched objects.
                // We assume that the called holds the event_queue lock.
                static void CleanQueue_Unlocked ()
                {
                        int first_undispatched = 0;
                        while (first_undispatched < event_queue.Count) {
                                QueuedEvent qe = event_queue [first_undispatched] as QueuedEvent;
                                if (! qe.Dispatched)
                                        break;
                                
                                if (qe.Cookie != 0)
                                        pending_move_cookies.Remove (qe.Cookie);
                                
                                ++first_undispatched;
                        }

                        if (first_undispatched > 0)
                                event_queue.RemoveRange (0, first_undispatched);

                }

                // Apply high-level processing to the queue.  Pair moves,
                // coalesce events, etc.
                // We assume that the caller holds the event_queue lock.
                static void AnalyzeQueue_Unlocked ()
                {
                        int first_unanalyzed = event_queue.Count;
                        while (first_unanalyzed > 0) {
                                --first_unanalyzed;
                                QueuedEvent qe = event_queue [first_unanalyzed] as QueuedEvent;
                                if (qe.Analyzed) {
                                        ++first_unanalyzed;
                                        break;
                                }
                        }
                        if (first_unanalyzed == event_queue.Count)
                                return;

                        // Walk across the unanalyzed events...
                        for (int i = first_unanalyzed; i < event_queue.Count; ++i) {
                                QueuedEvent qe = event_queue [i] as QueuedEvent;

                                // Pair off the MovedFrom and MovedTo events.
                                if (qe.Cookie != 0) {
                                        if ((qe.Type & EventType.MovedFrom) != 0) {
                                                pending_move_cookies [qe.Cookie] = qe;
                                                // This increases the MovedFrom's HoldUntil time,
                                                // giving us more time for the matching MovedTo to
                                                // show up.
                                                // (512 ms is totally arbitrary)
                                                qe.AddMilliseconds (512); 
                                        } else if ((qe.Type & EventType.MovedTo) != 0) {
                                                QueuedEvent paired_move = pending_move_cookies [qe.Cookie] as QueuedEvent;
                                                if (paired_move != null) {
                                                        paired_move.Dispatched = true;
                                                        qe.PairedMove = paired_move;
                                                }
                                        }
                                }

                                qe.Analyzed = true;
                        }
                }

                static void DispatchWorker ()
                {
                        while (running) {
                                QueuedEvent next_event = null;

                                // Until we find something we want to dispatch, we will stay
                                // inside the following block of code.
                                lock (event_queue) {

                                        while (running) {
                                                CleanQueue_Unlocked ();

                                                AnalyzeQueue_Unlocked ();

                                                // Now look for an event to dispatch.
                                                DateTime min_hold_until = DateTime.MaxValue;
                                                DateTime now = DateTime.Now;
                                                foreach (QueuedEvent qe in event_queue) {
                                                        if (qe.Dispatched)
                                                                continue;
                                                        if (qe.HoldUntil <= now) {
                                                                next_event = qe;
                                                                break;
                                                        }
                                                        if (qe.HoldUntil < min_hold_until)
                                                                min_hold_until = qe.HoldUntil;
                                                }

                                                // If we found an event, break out of this block
                                                // and dispatch it.
                                                if (next_event != null)
                                                        break;
                                                
                                                // If we didn't find an event to dispatch, we can sleep
                                                // (1) until the next hold-until time
                                                // (2) until the lock pulses (which means something changed, so
                                                //     we need to check that we are still running, new events
                                                //     are on the queue, etc.)
                                                // and then we go back up and try to find something to dispatch
                                                // all over again.
                                                if (min_hold_until == DateTime.MaxValue)
                                                        Monitor.Wait (event_queue);
                                                else
                                                        Monitor.Wait (event_queue, min_hold_until - now);
                                        }
                                }

                                // If "running" gets set to false, we might get a null next_event as the above
                                // loop terminates
                                if (next_event == null)
                                        return;

                                // Now we have an event, so we release the event_queue lock and do
                                // the actual dispatch.
                                
                                // Before we get any further, mark it
                                next_event.Dispatched = true;

                                WatchInfo watched;
                                watched = Lookup (next_event.Wd, next_event.Type);
                                if (watched == null)
                                        continue;

                                string srcpath = null;

                                // If this event is a paired MoveTo, there is extra work to do.
                                if ((next_event.Type & EventType.MovedTo) != 0 && next_event.PairedMove != null) {
                                        WatchInfo paired_watched;
                                        paired_watched = Lookup (next_event.PairedMove.Wd, next_event.PairedMove.Type);

                                        if (paired_watched != null) {
                                                // Set the source path accordingly.
                                                srcpath = Path.Combine (paired_watched.Path, next_event.PairedMove.Filename);
                                                
                                                // Handle the internal rename of the directory.
                                                string dstpath = Path.Combine (watched.Path, next_event.Filename);

                                                //if (Directory.Exists (dstpath))
                                                HandleMove (srcpath, dstpath);
                                        }
                                }

                                SendEvent (watched, next_event.Filename, srcpath, next_event.Type);

                                // If a directory we are watching gets ignored, we need
                                // to remove it from the watchedByFoo hashes.
                                if ((next_event.Type & EventType.Ignored) != 0) {
                                        lock (watched_by_wd)
                                                Forget (watched);
                                }
                        }
                }

                /////////////////////////////////////////////////////////////////////////////////

#if INOTIFY_TEST
                static void Main (string [] args)
                {
                        Queue to_watch = new Queue ();
                        bool recursive = false;

                        foreach (string arg in args) {
                                if (arg == "-r" || arg == "--recursive")
                                        recursive = true;
                                else {
                                        // Our hashes work without a trailing path delimiter
                                        string path = arg.TrimEnd ('/');
                                        to_watch.Enqueue (path);
                                }
                        }

                        while (to_watch.Count > 0) {
                                string path = (string) to_watch.Dequeue ();

                                Console.WriteLine ("Watching {0}", path);
                                Inotify.Subscribe (path, null, Inotify.EventType.All);

                                if (recursive) {
                                        foreach (string subdir in DirectoryWalker.GetDirectories (path))
                                                to_watch.Enqueue (subdir);
                                }
                        }

                        Inotify.Start ();
                        Inotify.Verbose = true;

                        while (Inotify.Enabled && Inotify.WatchCount > 0)
                                Thread.Sleep (1000);

                        if (Inotify.WatchCount == 0)
                                Console.WriteLine ("Nothing being watched.");

                        // Kill the event-reading thread so that we exit
                        Inotify.Stop ();
                }
#endif

        }
}