mcs/class/System/System.IO/KeventWatcher.cs

   1 //
   2 // System.IO.KeventWatcher.cs: interface with osx kevent
   3 //
   4 // Authors:
   5 //      Geoff Norton (gnorton@customerdna.com)
   6 //      Cody Russell (cody@xamarin.com)
   7 //      Alexis Christoforides (lexas@xamarin.com)
   8 //
   9 // (c) 2004 Geoff Norton
  10 // Copyright 2014 Xamarin Inc
  11 //
  12 // Permission is hereby granted, free of charge, to any person obtaining
  13 // a copy of this software and associated documentation files (the
  14 // "Software"), to deal in the Software without restriction, including
  15 // without limitation the rights to use, copy, modify, merge, publish,
  16 // distribute, sublicense, and/or sell copies of the Software, and to
  17 // permit persons to whom the Software is furnished to do so, subject to
  18 // the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be
  21 // included in all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  30 //
  31
  32 using System;
  33 using System.Collections;
  34 using System.Collections.Generic;
  35 using System.ComponentModel;
  36 using System.Runtime.CompilerServices;
  37 using System.Runtime.InteropServices;
  38 using System.Text;
  39 using System.Threading;
  40 using System.Reflection;
  41
  42 namespace System.IO {
  43
  44         [Flags]
  45         enum EventFlags : ushort {
  46                 Add         = 0x0001,
  47                 Delete      = 0x0002,
  48                 Enable      = 0x0004,
  49                 Disable     = 0x0008,
  50                 OneShot     = 0x0010,
  51                 Clear       = 0x0020,
  52                 Receipt     = 0x0040,
  53                 Dispatch    = 0x0080,
  54
  55                 Flag0       = 0x1000,
  56                 Flag1       = 0x2000,
  57                 SystemFlags = unchecked (0xf000),
  58
  59                 // Return values.
  60                 EOF         = 0x8000,
  61                 Error       = 0x4000,
  62         }
  63
  64         enum EventFilter : short {
  65                 Read = -1,
  66                 Write = -2,
  67                 Aio = -3,
  68                 Vnode = -4,
  69                 Proc = -5,
  70                 Signal = -6,
  71                 Timer = -7,
  72                 MachPort = -8,
  73                 FS = -9,
  74                 User = -10,
  75                 VM = -11
  76         }
  77
  78         [Flags]
  79         enum FilterFlags : uint {
  80                 ReadPoll          = EventFlags.Flag0,
  81                 ReadOutOfBand     = EventFlags.Flag1,
  82                 ReadLowWaterMark  = 0x00000001,
  83
  84                 WriteLowWaterMark = ReadLowWaterMark,
  85
  86                 NoteTrigger       = 0x01000000,
  87                 NoteFFNop         = 0x00000000,
  88                 NoteFFAnd         = 0x40000000,
  89                 NoteFFOr          = 0x80000000,
  90                 NoteFFCopy        = 0xc0000000,
  91                 NoteFFCtrlMask    = 0xc0000000,
  92                 NoteFFlagsMask    = 0x00ffffff,
  93
  94                 VNodeDelete       = 0x00000001,
  95                 VNodeWrite        = 0x00000002,
  96                 VNodeExtend       = 0x00000004,
  97                 VNodeAttrib       = 0x00000008,
  98                 VNodeLink         = 0x00000010,
  99                 VNodeRename       = 0x00000020,
 100                 VNodeRevoke       = 0x00000040,
 101                 VNodeNone         = 0x00000080,
 102
 103                 ProcExit          = 0x80000000,
 104                 ProcFork          = 0x40000000,
 105                 ProcExec          = 0x20000000,
 106                 ProcReap          = 0x10000000,
 107                 ProcSignal        = 0x08000000,
 108                 ProcExitStatus    = 0x04000000,
 109                 ProcResourceEnd   = 0x02000000,
 110
 111                 // iOS only
 112                 ProcAppactive     = 0x00800000,
 113                 ProcAppBackground = 0x00400000,
 114                 ProcAppNonUI      = 0x00200000,
 115                 ProcAppInactive   = 0x00100000,
 116                 ProcAppAllStates  = 0x00f00000,
 117
 118                 // Masks
 119                 ProcPDataMask     = 0x000fffff,
 120                 ProcControlMask   = 0xfff00000,
 121
 122                 VMPressure        = 0x80000000,
 123                 VMPressureTerminate = 0x40000000,
 124                 VMPressureSuddenTerminate = 0x20000000,
 125                 VMError           = 0x10000000,
 126                 TimerSeconds      =    0x00000001,
 127                 TimerMicroSeconds =   0x00000002,
 128                 TimerNanoSeconds  =   0x00000004,
 129                 TimerAbsolute     =   0x00000008,
 130         }
 131
 132         [StructLayout(LayoutKind.Sequential)]
 133         struct kevent : IDisposable {
 134                 public UIntPtr ident;
 135                 public EventFilter filter;
 136                 public EventFlags flags;
 137                 public FilterFlags fflags;
 138                 public IntPtr data;
 139                 public IntPtr udata;
 140
 141                 public void Dispose ()
 142                 {
 143                         if (udata != IntPtr.Zero)
 144                                 Marshal.FreeHGlobal (udata);
 145                 }
 146
 147
 148         }
 149
 150         [StructLayout(LayoutKind.Sequential)]
 151         struct timespec {
 152                 public IntPtr tv_sec;
 153                 public IntPtr tv_usec;
 154         }
 155
 156         class PathData
 157         {
 158                 public string Path;
 159                 public bool IsDirectory;
 160                 public int Fd;
 161         }
 162
 163         class KqueueMonitor : IDisposable
 164         {
 165                 public int Connection
 166                 {
 167                         get { return conn; }
 168                 }
 169
 170                 public KqueueMonitor (FileSystemWatcher fsw)
 171                 {
 172                         this.fsw = fsw;
 173                         this.conn = -1;
 174                 }
 175
 176                 public void Dispose ()
 177                 {
 178                         CleanUp ();
 179                 }
 180
 181                 public void Start ()
 182                 {
 183                         lock (stateLock) {
 184                                 if (started)
 185                                         return;
 186
 187                                 conn = kqueue ();
 188
 189                                 if (conn == -1)
 190                                         throw new IOException (String.Format (
 191                                                 "kqueue() error at init, error code = '{0}'", Marshal.GetLastWin32Error ()));
 192
 193                                 thread = new Thread (() => DoMonitor ());
 194                                 thread.IsBackground = true;
 195                                 thread.Start ();
 196
 197                                 startedEvent.WaitOne ();
 198
 199                                 if (exc != null) {
 200                                         thread.Join ();
 201                                         CleanUp ();
 202                                         throw exc;
 203                                 }
 204
 205                                 started = true;
 206                         }
 207                 }
 208
 209                 public void Stop ()
 210                 {
 211                         lock (stateLock) {
 212                                 if (!started)
 213                                         return;
 214
 215                                 requestStop = true;
 216
 217                                 if (inDispatch)
 218                                         return;
 219                                 // This will break the wait in Monitor ()
 220                                 lock (connLock) {
 221                                         if (conn != -1)
 222                                                 close (conn);
 223                                         conn = -1;
 224                                 }
 225
 226                                 if (!thread.Join (2000))
 227                                         thread.Abort ();
 228
 229                                 requestStop = false;
 230                                 started = false;
 231
 232                                 if (exc != null)
 233                                         throw exc;
 234                         }
 235                 }
 236
 237                 void CleanUp ()
 238                 {
 239                         lock (connLock) {
 240                                 if (conn != -1)
 241                                         close (conn);
 242                                 conn = -1;
 243                         }
 244
 245                         foreach (int fd in fdsDict.Keys)
 246                                 close (fd);
 247
 248                         fdsDict.Clear ();
 249                         pathsDict.Clear ();
 250                 }
 251
 252                 void DoMonitor ()
 253                 {
 254                         try {
 255                                 Setup ();
 256                         } catch (Exception e) {
 257                                 exc = e;
 258                         } finally {
 259                                 startedEvent.Set ();
 260                         }
 261
 262                         if (exc != null) {
 263                                 fsw.DispatchErrorEvents (new ErrorEventArgs (exc));
 264                                 return;
 265                         }
 266
 267                         try {
 268                                 Monitor ();
 269                         } catch (Exception e) {
 270                                 exc = e;
 271                         } finally {
 272                                 CleanUp ();
 273                                 if (!requestStop) { // failure
 274                                         started = false;
 275                                         inDispatch = false;
 276                                         fsw.EnableRaisingEvents = false;
 277                                 }
 278                                 if (exc != null)
 279                                         fsw.DispatchErrorEvents (new ErrorEventArgs (exc));
 280                                 requestStop = false;
 281                         }
 282                 }
 283
 284                 void Setup ()
 285                 {
 286                         var initialFds = new List<int> ();
 287
 288                         // fsw.FullPath may end in '/', see https://bugzilla.xamarin.com/show_bug.cgi?id=5747
 289                         if (fsw.FullPath != "/" && fsw.FullPath.EndsWith ("/", StringComparison.Ordinal))
 290                                 fullPathNoLastSlash = fsw.FullPath.Substring (0, fsw.FullPath.Length - 1);
 291                         else
 292                                 fullPathNoLastSlash = fsw.FullPath;
 293
 294                         // GetFilenameFromFd() returns the *realpath* which can be different than fsw.FullPath because symlinks.
 295                         // If so, introduce a fixup step.
 296                         int fd = open (fullPathNoLastSlash, O_EVTONLY, 0);
 297                         var resolvedFullPath = GetFilenameFromFd (fd);
 298                         close (fd);
 299
 300                         if (resolvedFullPath != fullPathNoLastSlash)
 301                                 fixupPath = resolvedFullPath;
 302                         else
 303                                 fixupPath = null;
 304
 305                         Scan (fullPathNoLastSlash, false, ref initialFds);
 306
 307                         var immediate_timeout = new timespec { tv_sec = (IntPtr)0, tv_usec = (IntPtr)0 };
 308                         var eventBuffer = new kevent[0]; // we don't want to take any events from the queue at this point
 309                         var changes = CreateChangeList (ref initialFds);
 310
 311                         int numEvents = kevent (conn, changes, changes.Length, eventBuffer, eventBuffer.Length, ref immediate_timeout);
 312
 313                         if (numEvents == -1) {
 314                                 var errMsg = String.Format ("kevent() error at initial event registration, error code = '{0}'", Marshal.GetLastWin32Error ());
 315                                 throw new IOException (errMsg);
 316                         }
 317                 }
 318
 319                 kevent[] CreateChangeList (ref List<int> FdList)
 320                 {
 321                         if (FdList.Count == 0)
 322                                 return emptyEventList;
 323
 324                         var changes = new List<kevent> ();
 325                         foreach (int fd in FdList) {
 326                                 var change = new kevent {
 327
 328                                         ident = (UIntPtr)fd,
 329                                         filter = EventFilter.Vnode,
 330                                         flags = EventFlags.Add | EventFlags.Enable | EventFlags.Clear,
 331                                         fflags = FilterFlags.VNodeDelete | FilterFlags.VNodeExtend |
 332                                                 FilterFlags.VNodeRename | FilterFlags.VNodeAttrib |
 333                                                 FilterFlags.VNodeLink | FilterFlags.VNodeRevoke |
 334                                                 FilterFlags.VNodeWrite,
 335                                         data = IntPtr.Zero,
 336                                         udata = IntPtr.Zero
 337                                 };
 338
 339                                 changes.Add (change);
 340                         }
 341                         FdList.Clear ();
 342
 343                         return changes.ToArray ();
 344                 }
 345
 346                 void Monitor ()
 347                 {
 348                         var eventBuffer = new kevent[32];
 349                         var newFds = new List<int> ();
 350                         List<PathData> removeQueue = new List<PathData> ();
 351                         List<string> rescanQueue = new List<string> ();
 352
 353                         int retries = 0;
 354
 355                         while (!requestStop) {
 356                                 var changes = CreateChangeList (ref newFds);
 357
 358                                 // We are calling an icall, so have to marshal manually
 359                                 // Marshal in
 360                                 int ksize = Marshal.SizeOf<kevent> ();
 361                                 var changesNative = Marshal.AllocHGlobal (ksize * changes.Length);
 362                                 for (int i = 0; i < changes.Length; ++i)
 363                                         Marshal.StructureToPtr (changes [i], changesNative + (i * ksize), false);
 364                                 var eventBufferNative = Marshal.AllocHGlobal (ksize * eventBuffer.Length);
 365
 366                                 int numEvents = kevent_notimeout (ref conn, changesNative, changes.Length, eventBufferNative, eventBuffer.Length);
 367
 368                                 // Marshal out
 369                                 Marshal.FreeHGlobal (changesNative);
 370                                 for (int i = 0; i < numEvents; ++i)
 371                                         eventBuffer [i] = Marshal.PtrToStructure<kevent> (eventBufferNative + (i * ksize));
 372                                 Marshal.FreeHGlobal (eventBufferNative);
 373
 374                                 if (numEvents == -1) {
 375                                         // Stop () signals us to stop by closing the connection
 376                                         if (requestStop)
 377                                                 break;
 378                                         if (++retries == 3)
 379                                                 throw new IOException (String.Format (
 380                                                         "persistent kevent() error, error code = '{0}'", Marshal.GetLastWin32Error ()));
 381
 382                                         continue;
 383                                 }
 384                                 retries = 0;
 385
 386                                 for (var i = 0; i < numEvents; i++) {
 387                                         var kevt = eventBuffer [i];
 388
 389                                         if (!fdsDict.ContainsKey ((int)kevt.ident))
 390                                                 // The event is for a file that was removed
 391                                                 continue;
 392
 393                                         var pathData = fdsDict [(int)kevt.ident];
 394
 395                                         if ((kevt.flags & EventFlags.Error) == EventFlags.Error) {
 396                                                 var errMsg = String.Format ("kevent() error watching path '{0}', error code = '{1}'", pathData.Path, kevt.data);
 397                                                 fsw.DispatchErrorEvents (new ErrorEventArgs (new IOException (errMsg)));
 398                                                 continue;
 399                                         }
 400
 401                                         if ((kevt.fflags & FilterFlags.VNodeDelete) == FilterFlags.VNodeDelete || (kevt.fflags & FilterFlags.VNodeRevoke) == FilterFlags.VNodeRevoke) {
 402                                                 if (pathData.Path == fullPathNoLastSlash)
 403                                                         // The root path is deleted; exit silently
 404                                                         return;
 405
 406                                                 removeQueue.Add (pathData);
 407                                                 continue;
 408                                         }
 409
 410                                         if ((kevt.fflags & FilterFlags.VNodeRename) == FilterFlags.VNodeRename) {
 411                                                         UpdatePath (pathData);
 412                                         }
 413
 414                                         if ((kevt.fflags & FilterFlags.VNodeWrite) == FilterFlags.VNodeWrite) {
 415                                                 if (pathData.IsDirectory) //TODO: Check if dirs trigger Changed events on .NET
 416                                                         rescanQueue.Add (pathData.Path);
 417                                                 else
 418                                                         PostEvent (FileAction.Modified, pathData.Path);
 419                                         }
 420
 421                                         if ((kevt.fflags & FilterFlags.VNodeAttrib) == FilterFlags.VNodeAttrib || (kevt.fflags & FilterFlags.VNodeExtend) == FilterFlags.VNodeExtend)
 422                                                 PostEvent (FileAction.Modified, pathData.Path);
 423                                 }
 424
 425                                 removeQueue.ForEach (Remove);
 426                                 removeQueue.Clear ();
 427
 428                                 rescanQueue.ForEach (path => {
 429                                         Scan (path, true, ref newFds);
 430                                 });
 431                                 rescanQueue.Clear ();
 432                         }
 433                 }
 434
 435                 PathData Add (string path, bool postEvents, ref List<int> fds)
 436                 {
 437                         PathData pathData;
 438                         pathsDict.TryGetValue (path, out pathData);
 439
 440                         if (pathData != null)
 441                                 return pathData;
 442
 443                         if (fdsDict.Count >= maxFds)
 444                                 throw new IOException ("kqueue() FileSystemWatcher has reached the maximum number of files to watch.");
 445
 446                         var fd = open (path, O_EVTONLY, 0);
 447
 448                         if (fd == -1) {
 449                                 fsw.DispatchErrorEvents (new ErrorEventArgs (new IOException (String.Format (
 450                                         "open() error while attempting to process path '{0}', error code = '{1}'", path, Marshal.GetLastWin32Error ()))));
 451                                 return null;
 452                         }
 453
 454                         try {
 455                                 fds.Add (fd);
 456
 457                                 var attrs = File.GetAttributes (path);
 458
 459                                 pathData = new PathData {
 460                                         Path = path,
 461                                         Fd = fd,
 462                                         IsDirectory = (attrs & FileAttributes.Directory) == FileAttributes.Directory
 463                                 };
 464
 465                                 pathsDict.Add (path, pathData);
 466                                 fdsDict.Add (fd, pathData);
 467
 468                                 if (postEvents)
 469                                         PostEvent (FileAction.Added, path);
 470
 471                                 return pathData;
 472                         } catch (Exception e) {
 473                                 close (fd);
 474                                 fsw.DispatchErrorEvents (new ErrorEventArgs (e));
 475                                 return null;
 476                         }
 477
 478                 }
 479
 480                 void Remove (PathData pathData)
 481                 {
 482                         fdsDict.Remove (pathData.Fd);
 483                         pathsDict.Remove (pathData.Path);
 484                         close (pathData.Fd);
 485                         PostEvent (FileAction.Removed, pathData.Path);
 486                 }
 487
 488                 void RemoveTree (PathData pathData)
 489                 {
 490                         var toRemove = new List<PathData> ();
 491
 492                         toRemove.Add (pathData);
 493
 494                         if (pathData.IsDirectory) {
 495                                 var prefix = pathData.Path + Path.DirectorySeparatorChar;
 496                                 foreach (var path in pathsDict.Keys)
 497                                         if (path.StartsWith (prefix)) {
 498                                                 toRemove.Add (pathsDict [path]);
 499                                         }
 500                         }
 501                         toRemove.ForEach (Remove);
 502                 }
 503
 504                 void UpdatePath (PathData pathData)
 505                 {
 506                         var newRoot = GetFilenameFromFd (pathData.Fd);
 507                         if (!newRoot.StartsWith (fullPathNoLastSlash)) { // moved outside of our watched path (so stop observing it)
 508                                 RemoveTree (pathData);
 509                                 return;
 510                         }
 511
 512                         var toRename = new List<PathData> ();
 513                         var oldRoot = pathData.Path;
 514
 515                         toRename.Add (pathData);
 516
 517                         if (pathData.IsDirectory) { // anything under the directory must have their paths updated
 518                                 var prefix = oldRoot + Path.DirectorySeparatorChar;
 519                                 foreach (var path in pathsDict.Keys)
 520                                         if (path.StartsWith (prefix))
 521                                                 toRename.Add (pathsDict [path]);
 522                         }
 523
 524                         foreach (var renaming in toRename) {
 525                                 var oldPath = renaming.Path;
 526                                 var newPath = newRoot + oldPath.Substring (oldRoot.Length);
 527
 528                                 renaming.Path = newPath;
 529                                 pathsDict.Remove (oldPath);
 530
 531                                 // destination may exist in our records from a Created event, take care of it
 532                                 if (pathsDict.ContainsKey (newPath)) {
 533                                         var conflict = pathsDict [newPath];
 534                                         if (GetFilenameFromFd (renaming.Fd) == GetFilenameFromFd (conflict.Fd))
 535                                                 Remove (conflict);
 536                                         else
 537                                                 UpdatePath (conflict);
 538                                 }
 539
 540                                 pathsDict.Add (newPath, renaming);
 541                         }
 542
 543                         PostEvent (FileAction.RenamedNewName, oldRoot, newRoot);
 544                 }
 545
 546                 void Scan (string path, bool postEvents, ref List<int> fds)
 547                 {
 548                         if (requestStop)
 549                                 return;
 550
 551                         var pathData = Add (path, postEvents, ref fds);
 552
 553                         if (pathData == null)
 554                                 return;
 555
 556                         if (!pathData.IsDirectory)
 557                                 return;
 558
 559                         var dirsToProcess = new List<string> ();
 560                         dirsToProcess.Add (path);
 561
 562                         while (dirsToProcess.Count > 0) {
 563                                 var tmp = dirsToProcess [0];
 564                                 dirsToProcess.RemoveAt (0);
 565
 566                                 var info = new DirectoryInfo (tmp);
 567                                 FileSystemInfo[] fsInfos = null;
 568                                 try {
 569                                         fsInfos = info.GetFileSystemInfos ();
 570
 571                                 } catch (IOException) {
 572                                         // this can happen if the directory has been deleted already.
 573                                         // that's okay, just keep processing the other dirs.
 574                                         fsInfos = new FileSystemInfo[0];
 575                                 }
 576
 577                                 foreach (var fsi in fsInfos) {
 578                                         if ((fsi.Attributes & FileAttributes.Directory) == FileAttributes.Directory && !fsw.IncludeSubdirectories)
 579                                                 continue;
 580
 581                                         if ((fsi.Attributes & FileAttributes.Directory) != FileAttributes.Directory && !fsw.Pattern.IsMatch (fsi.FullName))
 582                                                 continue;
 583
 584                                         var currentPathData = Add (fsi.FullName, postEvents, ref fds);
 585
 586                                         if (currentPathData != null && currentPathData.IsDirectory)
 587                                                 dirsToProcess.Add (fsi.FullName);
 588                                 }
 589                         }
 590                 }
 591
 592                 void PostEvent (FileAction action, string path, string newPath = null)
 593                 {
 594                         RenamedEventArgs renamed = null;
 595
 596                         if (requestStop || action == 0)
 597                                 return;
 598
 599                         // e.Name
 600                         string name = path.Substring (fullPathNoLastSlash.Length + 1);
 601
 602                         // only post events that match filter pattern. check both old and new paths for renames
 603                         if (!fsw.Pattern.IsMatch (path) && (newPath == null || !fsw.Pattern.IsMatch (newPath)))
 604                                 return;
 605
 606                         if (action == FileAction.RenamedNewName) {
 607                                 string newName = newPath.Substring (fullPathNoLastSlash.Length + 1);
 608                                 renamed = new RenamedEventArgs (WatcherChangeTypes.Renamed, fsw.Path, newName, name);
 609                         }
 610
 611                         fsw.DispatchEvents (action, name, ref renamed);
 612
 613                         if (fsw.Waiting) {
 614                                 lock (fsw) {
 615                                         fsw.Waiting = false;
 616                                         System.Threading.Monitor.PulseAll (fsw);
 617                                 }
 618                         }
 619                 }
 620
 621                 private string GetFilenameFromFd (int fd)
 622                 {
 623                         var sb = new StringBuilder (__DARWIN_MAXPATHLEN);
 624
 625                         if (fcntl (fd, F_GETPATH, sb) != -1) {
 626                                 if (fixupPath != null)
 627                                         sb.Replace (fixupPath, fullPathNoLastSlash, 0, fixupPath.Length); // see Setup()
 628
 629                                 return sb.ToString ();
 630                         } else {
 631                                 fsw.DispatchErrorEvents (new ErrorEventArgs (new IOException (String.Format (
 632                                         "fcntl() error while attempting to get path for fd '{0}', error code = '{1}'", fd, Marshal.GetLastWin32Error ()))));
 633                                 return String.Empty;
 634                         }
 635                 }
 636
 637                 const int O_EVTONLY = 0x8000;
 638                 const int F_GETPATH = 50;
 639                 const int __DARWIN_MAXPATHLEN = 1024;
 640                 static readonly kevent[] emptyEventList = new System.IO.kevent[0];
 641                 const int maxFds = 200;
 642
 643                 FileSystemWatcher fsw;
 644                 int conn;
 645                 Thread thread;
 646                 volatile bool requestStop = false;
 647                 AutoResetEvent startedEvent = new AutoResetEvent (false);
 648                 bool started = false;
 649                 bool inDispatch = false;
 650                 Exception exc = null;
 651                 object stateLock = new object ();
 652                 object connLock = new object ();
 653
 654                 readonly Dictionary<string, PathData> pathsDict = new Dictionary<string, PathData> ();
 655                 readonly Dictionary<int, PathData> fdsDict = new Dictionary<int, PathData> ();
 656                 string fixupPath = null;
 657                 string fullPathNoLastSlash = null;
 658
 659                 [DllImport ("libc", EntryPoint="fcntl", CharSet=CharSet.Auto, SetLastError=true)]
 660                 static extern int fcntl (int file_names_by_descriptor, int cmd, StringBuilder sb);
 661
 662                 [DllImport ("libc")]
 663                 extern static int open (string path, int flags, int mode_t);
 664
 665                 [DllImport ("libc")]
 666                 extern static int close (int fd);
 667
 668                 [DllImport ("libc")]
 669                 extern static int kqueue ();
 670
 671                 [DllImport ("libc")]
 672                 extern static int kevent (int kq, [In]kevent[] ev, int nchanges, [Out]kevent[] evtlist, int nevents, [In] ref timespec time);
 673
 674                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 675                 extern static int kevent_notimeout (ref int kq, IntPtr ev, int nchanges, IntPtr evtlist, int nevents);
 676         }
 677
 678         class KeventWatcher : IFileWatcher
 679         {
 680                 static bool failed;
 681                 static KeventWatcher instance;
 682                 static Hashtable watches;  // <FileSystemWatcher, KqueueMonitor>
 683
 684                 private KeventWatcher ()
 685                 {
 686                 }
 687
 688                 // Locked by caller
 689                 public static bool GetInstance (out IFileWatcher watcher)
 690                 {
 691                         if (failed == true) {
 692                                 watcher = null;
 693                                 return false;
 694                         }
 695
 696                         if (instance != null) {
 697                                 watcher = instance;
 698                                 return true;
 699                         }
 700
 701                         watches = Hashtable.Synchronized (new Hashtable ());
 702                         var conn = kqueue();
 703                         if (conn == -1) {
 704                                 failed = true;
 705                                 watcher = null;
 706                                 return false;
 707                         }
 708                         close (conn);
 709
 710                         instance = new KeventWatcher ();
 711                         watcher = instance;
 712                         return true;
 713                 }
 714
 715                 public void StartDispatching (FileSystemWatcher fsw)
 716                 {
 717                         KqueueMonitor monitor;
 718
 719                         if (watches.ContainsKey (fsw)) {
 720                                 monitor = (KqueueMonitor)watches [fsw];
 721                         } else {
 722                                 monitor = new KqueueMonitor (fsw);
 723                                 watches.Add (fsw, monitor);
 724                         }
 725
 726                         monitor.Start ();
 727                 }
 728
 729                 public void StopDispatching (FileSystemWatcher fsw)
 730                 {
 731                         KqueueMonitor monitor = (KqueueMonitor)watches [fsw];
 732                         if (monitor == null)
 733                                 return;
 734
 735                         monitor.Stop ();
 736                 }
 737
 738                 [DllImport ("libc")]
 739                 extern static int close (int fd);
 740
 741                 [DllImport ("libc")]
 742                 extern static int kqueue ();
 743         }
 744 }
 745