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_nsec;
 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                 static bool initialized;
 166
 167                 public int Connection
 168                 {
 169                         get { return conn; }
 170                 }
 171
 172                 public KqueueMonitor (FileSystemWatcher fsw)
 173                 {
 174                         this.fsw = fsw;
 175                         this.conn = -1;
 176                         if (!initialized){
 177                                 int t;
 178                                 initialized = true;
 179                                 var maxenv = Environment.GetEnvironmentVariable ("MONO_DARWIN_WATCHER_MAXFDS");
 180                                 if (maxenv != null && Int32.TryParse (maxenv, out t))
 181                                         maxFds = t;
 182                         }
 183                 }
 184
 185                 public void Dispose ()
 186                 {
 187                         CleanUp ();
 188                 }
 189
 190                 public void Start ()
 191                 {
 192                         lock (stateLock) {
 193                                 if (started)
 194                                         return;
 195
 196                                 conn = kqueue ();
 197
 198                                 if (conn == -1)
 199                                         throw new IOException (String.Format (
 200                                                 "kqueue() error at init, error code = '{0}'", Marshal.GetLastWin32Error ()));
 201
 202                                 thread = new Thread (() => DoMonitor ());
 203                                 thread.IsBackground = true;
 204                                 thread.Start ();
 205
 206                                 startedEvent.WaitOne ();
 207
 208                                 if (exc != null) {
 209                                         thread.Join ();
 210                                         CleanUp ();
 211                                         throw exc;
 212                                 }
 213
 214                                 started = true;
 215                         }
 216                 }
 217
 218                 public void Stop ()
 219                 {
 220                         lock (stateLock) {
 221                                 if (!started)
 222                                         return;
 223
 224                                 requestStop = true;
 225
 226                                 if (inDispatch)
 227                                         return;
 228                                 // This will break the wait in Monitor ()
 229                                 lock (connLock) {
 230                                         if (conn != -1)
 231                                                 close (conn);
 232                                         conn = -1;
 233                                 }
 234
 235                                 if (!thread.Join (2000))
 236                                         thread.Abort ();
 237
 238                                 requestStop = false;
 239                                 started = false;
 240
 241                                 if (exc != null)
 242                                         throw exc;
 243                         }
 244                 }
 245
 246                 void CleanUp ()
 247                 {
 248                         lock (connLock) {
 249                                 if (conn != -1)
 250                                         close (conn);
 251                                 conn = -1;
 252                         }
 253
 254                         foreach (int fd in fdsDict.Keys)
 255                                 close (fd);
 256
 257                         fdsDict.Clear ();
 258                         pathsDict.Clear ();
 259                 }
 260
 261                 void DoMonitor ()
 262                 {
 263                         try {
 264                                 Setup ();
 265                         } catch (Exception e) {
 266                                 exc = e;
 267                         } finally {
 268                                 startedEvent.Set ();
 269                         }
 270
 271                         if (exc != null) {
 272                                 fsw.DispatchErrorEvents (new ErrorEventArgs (exc));
 273                                 return;
 274                         }
 275
 276                         try {
 277                                 Monitor ();
 278                         } catch (Exception e) {
 279                                 exc = e;
 280                         } finally {
 281                                 CleanUp ();
 282                                 if (!requestStop) { // failure
 283                                         started = false;
 284                                         inDispatch = false;
 285                                         fsw.EnableRaisingEvents = false;
 286                                 }
 287                                 if (exc != null)
 288                                         fsw.DispatchErrorEvents (new ErrorEventArgs (exc));
 289                                 requestStop = false;
 290                         }
 291                 }
 292
 293                 void Setup ()
 294                 {
 295                         var initialFds = new List<int> ();
 296
 297                         // fsw.FullPath may end in '/', see https://bugzilla.xamarin.com/show_bug.cgi?id=5747
 298                         if (fsw.FullPath != "/" && fsw.FullPath.EndsWith ("/", StringComparison.Ordinal))
 299                                 fullPathNoLastSlash = fsw.FullPath.Substring (0, fsw.FullPath.Length - 1);
 300                         else
 301                                 fullPathNoLastSlash = fsw.FullPath;
 302
 303                         // GetFilenameFromFd() returns the *realpath* which can be different than fsw.FullPath because symlinks.
 304                         // If so, introduce a fixup step.
 305                         int fd = open (fullPathNoLastSlash, O_EVTONLY, 0);
 306                         var resolvedFullPath = GetFilenameFromFd (fd);
 307                         close (fd);
 308
 309                         if (resolvedFullPath != fullPathNoLastSlash)
 310                                 fixupPath = resolvedFullPath;
 311                         else
 312                                 fixupPath = null;
 313
 314                         Scan (fullPathNoLastSlash, false, ref initialFds);
 315
 316                         var immediate_timeout = new timespec { tv_sec = (IntPtr)0, tv_nsec = (IntPtr)0 };
 317                         var eventBuffer = new kevent[0]; // we don't want to take any events from the queue at this point
 318                         var changes = CreateChangeList (ref initialFds);
 319
 320                         int numEvents;
 321                         int errno = 0;
 322                         do {
 323                                 numEvents = kevent (conn, changes, changes.Length, eventBuffer, eventBuffer.Length, ref immediate_timeout);
 324                                 if (numEvents == -1) {
 325                                         errno = Marshal.GetLastWin32Error ();
 326                                 }
 327                         } while (numEvents == -1 && errno == EINTR);
 328
 329                         if (numEvents == -1) {
 330                                 var errMsg = String.Format ("kevent() error at initial event registration, error code = '{0}'", errno);
 331                                 throw new IOException (errMsg);
 332                         }
 333                 }
 334
 335                 kevent[] CreateChangeList (ref List<int> FdList)
 336                 {
 337                         if (FdList.Count == 0)
 338                                 return emptyEventList;
 339
 340                         var changes = new List<kevent> ();
 341                         foreach (int fd in FdList) {
 342                                 var change = new kevent {
 343
 344                                         ident = (UIntPtr)fd,
 345                                         filter = EventFilter.Vnode,
 346                                         flags = EventFlags.Add | EventFlags.Enable | EventFlags.Clear,
 347                                         fflags = FilterFlags.VNodeDelete | FilterFlags.VNodeExtend |
 348                                                 FilterFlags.VNodeRename | FilterFlags.VNodeAttrib |
 349                                                 FilterFlags.VNodeLink | FilterFlags.VNodeRevoke |
 350                                                 FilterFlags.VNodeWrite,
 351                                         data = IntPtr.Zero,
 352                                         udata = IntPtr.Zero
 353                                 };
 354
 355                                 changes.Add (change);
 356                         }
 357                         FdList.Clear ();
 358
 359                         return changes.ToArray ();
 360                 }
 361
 362                 void Monitor ()
 363                 {
 364                         var eventBuffer = new kevent[32];
 365                         var newFds = new List<int> ();
 366                         List<PathData> removeQueue = new List<PathData> ();
 367                         List<string> rescanQueue = new List<string> ();
 368
 369                         int retries = 0;
 370
 371                         while (!requestStop) {
 372                                 var changes = CreateChangeList (ref newFds);
 373
 374                                 // We are calling an icall, so have to marshal manually
 375                                 // Marshal in
 376                                 int ksize = Marshal.SizeOf<kevent> ();
 377                                 var changesNative = Marshal.AllocHGlobal (ksize * changes.Length);
 378                                 for (int i = 0; i < changes.Length; ++i)
 379                                         Marshal.StructureToPtr (changes [i], changesNative + (i * ksize), false);
 380                                 var eventBufferNative = Marshal.AllocHGlobal (ksize * eventBuffer.Length);
 381
 382                                 int numEvents = kevent_notimeout (ref conn, changesNative, changes.Length, eventBufferNative, eventBuffer.Length);
 383
 384                                 // Marshal out
 385                                 Marshal.FreeHGlobal (changesNative);
 386                                 for (int i = 0; i < numEvents; ++i)
 387                                         eventBuffer [i] = Marshal.PtrToStructure<kevent> (eventBufferNative + (i * ksize));
 388                                 Marshal.FreeHGlobal (eventBufferNative);
 389
 390                                 if (numEvents == -1) {
 391                                         // Stop () signals us to stop by closing the connection
 392                                         if (requestStop)
 393                                                 break;
 394                                         int errno = Marshal.GetLastWin32Error ();
 395                                         if (errno != EINTR && ++retries == 3)
 396                                                 throw new IOException (String.Format (
 397                                                         "persistent kevent() error, error code = '{0}'", errno));
 398
 399                                         continue;
 400                                 }
 401                                 retries = 0;
 402
 403                                 for (var i = 0; i < numEvents; i++) {
 404                                         var kevt = eventBuffer [i];
 405
 406                                         if (!fdsDict.ContainsKey ((int)kevt.ident))
 407                                                 // The event is for a file that was removed
 408                                                 continue;
 409
 410                                         var pathData = fdsDict [(int)kevt.ident];
 411
 412                                         if ((kevt.flags & EventFlags.Error) == EventFlags.Error) {
 413                                                 var errMsg = String.Format ("kevent() error watching path '{0}', error code = '{1}'", pathData.Path, kevt.data);
 414                                                 fsw.DispatchErrorEvents (new ErrorEventArgs (new IOException (errMsg)));
 415                                                 continue;
 416                                         }
 417
 418                                         if ((kevt.fflags & FilterFlags.VNodeDelete) == FilterFlags.VNodeDelete || (kevt.fflags & FilterFlags.VNodeRevoke) == FilterFlags.VNodeRevoke) {
 419                                                 if (pathData.Path == fullPathNoLastSlash)
 420                                                         // The root path is deleted; exit silently
 421                                                         return;
 422
 423                                                 removeQueue.Add (pathData);
 424                                                 continue;
 425                                         }
 426
 427                                         if ((kevt.fflags & FilterFlags.VNodeRename) == FilterFlags.VNodeRename) {
 428                                                         UpdatePath (pathData);
 429                                         }
 430
 431                                         if ((kevt.fflags & FilterFlags.VNodeWrite) == FilterFlags.VNodeWrite) {
 432                                                 if (pathData.IsDirectory) //TODO: Check if dirs trigger Changed events on .NET
 433                                                         rescanQueue.Add (pathData.Path);
 434                                                 else
 435                                                         PostEvent (FileAction.Modified, pathData.Path);
 436                                         }
 437
 438                                         if ((kevt.fflags & FilterFlags.VNodeAttrib) == FilterFlags.VNodeAttrib || (kevt.fflags & FilterFlags.VNodeExtend) == FilterFlags.VNodeExtend)
 439                                                 PostEvent (FileAction.Modified, pathData.Path);
 440                                 }
 441
 442                                 removeQueue.ForEach (Remove);
 443                                 removeQueue.Clear ();
 444
 445                                 rescanQueue.ForEach (path => {
 446                                         Scan (path, true, ref newFds);
 447                                 });
 448                                 rescanQueue.Clear ();
 449                         }
 450                 }
 451
 452                 PathData Add (string path, bool postEvents, ref List<int> fds)
 453                 {
 454                         PathData pathData;
 455                         pathsDict.TryGetValue (path, out pathData);
 456
 457                         if (pathData != null)
 458                                 return pathData;
 459
 460                         if (fdsDict.Count >= maxFds)
 461                                 throw new IOException ("kqueue() FileSystemWatcher has reached the maximum number of files to watch.");
 462
 463                         var fd = open (path, O_EVTONLY, 0);
 464
 465                         if (fd == -1) {
 466                                 fsw.DispatchErrorEvents (new ErrorEventArgs (new IOException (String.Format (
 467                                         "open() error while attempting to process path '{0}', error code = '{1}'", path, Marshal.GetLastWin32Error ()))));
 468                                 return null;
 469                         }
 470
 471                         try {
 472                                 fds.Add (fd);
 473
 474                                 var attrs = File.GetAttributes (path);
 475
 476                                 pathData = new PathData {
 477                                         Path = path,
 478                                         Fd = fd,
 479                                         IsDirectory = (attrs & FileAttributes.Directory) == FileAttributes.Directory
 480                                 };
 481
 482                                 pathsDict.Add (path, pathData);
 483                                 fdsDict.Add (fd, pathData);
 484
 485                                 if (postEvents)
 486                                         PostEvent (FileAction.Added, path);
 487
 488                                 return pathData;
 489                         } catch (Exception e) {
 490                                 close (fd);
 491                                 fsw.DispatchErrorEvents (new ErrorEventArgs (e));
 492                                 return null;
 493                         }
 494
 495                 }
 496
 497                 void Remove (PathData pathData)
 498                 {
 499                         fdsDict.Remove (pathData.Fd);
 500                         pathsDict.Remove (pathData.Path);
 501                         close (pathData.Fd);
 502                         PostEvent (FileAction.Removed, pathData.Path);
 503                 }
 504
 505                 void RemoveTree (PathData pathData)
 506                 {
 507                         var toRemove = new List<PathData> ();
 508
 509                         toRemove.Add (pathData);
 510
 511                         if (pathData.IsDirectory) {
 512                                 var prefix = pathData.Path + Path.DirectorySeparatorChar;
 513                                 foreach (var path in pathsDict.Keys)
 514                                         if (path.StartsWith (prefix)) {
 515                                                 toRemove.Add (pathsDict [path]);
 516                                         }
 517                         }
 518                         toRemove.ForEach (Remove);
 519                 }
 520
 521                 void UpdatePath (PathData pathData)
 522                 {
 523                         var newRoot = GetFilenameFromFd (pathData.Fd);
 524                         if (!newRoot.StartsWith (fullPathNoLastSlash)) { // moved outside of our watched path (so stop observing it)
 525                                 RemoveTree (pathData);
 526                                 return;
 527                         }
 528
 529                         var toRename = new List<PathData> ();
 530                         var oldRoot = pathData.Path;
 531
 532                         toRename.Add (pathData);
 533
 534                         if (pathData.IsDirectory) { // anything under the directory must have their paths updated
 535                                 var prefix = oldRoot + Path.DirectorySeparatorChar;
 536                                 foreach (var path in pathsDict.Keys)
 537                                         if (path.StartsWith (prefix))
 538                                                 toRename.Add (pathsDict [path]);
 539                         }
 540
 541                         foreach (var renaming in toRename) {
 542                                 var oldPath = renaming.Path;
 543                                 var newPath = newRoot + oldPath.Substring (oldRoot.Length);
 544
 545                                 renaming.Path = newPath;
 546                                 pathsDict.Remove (oldPath);
 547
 548                                 // destination may exist in our records from a Created event, take care of it
 549                                 if (pathsDict.ContainsKey (newPath)) {
 550                                         var conflict = pathsDict [newPath];
 551                                         if (GetFilenameFromFd (renaming.Fd) == GetFilenameFromFd (conflict.Fd))
 552                                                 Remove (conflict);
 553                                         else
 554                                                 UpdatePath (conflict);
 555                                 }
 556
 557                                 pathsDict.Add (newPath, renaming);
 558                         }
 559
 560                         PostEvent (FileAction.RenamedNewName, oldRoot, newRoot);
 561                 }
 562
 563                 void Scan (string path, bool postEvents, ref List<int> fds)
 564                 {
 565                         if (requestStop)
 566                                 return;
 567
 568                         var pathData = Add (path, postEvents, ref fds);
 569
 570                         if (pathData == null)
 571                                 return;
 572
 573                         if (!pathData.IsDirectory)
 574                                 return;
 575
 576                         var dirsToProcess = new List<string> ();
 577                         dirsToProcess.Add (path);
 578
 579                         while (dirsToProcess.Count > 0) {
 580                                 var tmp = dirsToProcess [0];
 581                                 dirsToProcess.RemoveAt (0);
 582
 583                                 var info = new DirectoryInfo (tmp);
 584                                 FileSystemInfo[] fsInfos = null;
 585                                 try {
 586                                         fsInfos = info.GetFileSystemInfos ();
 587
 588                                 } catch (IOException) {
 589                                         // this can happen if the directory has been deleted already.
 590                                         // that's okay, just keep processing the other dirs.
 591                                         fsInfos = new FileSystemInfo[0];
 592                                 }
 593
 594                                 foreach (var fsi in fsInfos) {
 595                                         if ((fsi.Attributes & FileAttributes.Directory) == FileAttributes.Directory && !fsw.IncludeSubdirectories)
 596                                                 continue;
 597
 598                                         if ((fsi.Attributes & FileAttributes.Directory) != FileAttributes.Directory && !fsw.Pattern.IsMatch (fsi.FullName))
 599                                                 continue;
 600
 601                                         var currentPathData = Add (fsi.FullName, postEvents, ref fds);
 602
 603                                         if (currentPathData != null && currentPathData.IsDirectory)
 604                                                 dirsToProcess.Add (fsi.FullName);
 605                                 }
 606                         }
 607                 }
 608
 609                 void PostEvent (FileAction action, string path, string newPath = null)
 610                 {
 611                         RenamedEventArgs renamed = null;
 612
 613                         if (requestStop || action == 0)
 614                                 return;
 615
 616                         // e.Name
 617                         string name = path.Substring (fullPathNoLastSlash.Length + 1);
 618
 619                         // only post events that match filter pattern. check both old and new paths for renames
 620                         if (!fsw.Pattern.IsMatch (path) && (newPath == null || !fsw.Pattern.IsMatch (newPath)))
 621                                 return;
 622
 623                         if (action == FileAction.RenamedNewName) {
 624                                 string newName = newPath.Substring (fullPathNoLastSlash.Length + 1);
 625                                 renamed = new RenamedEventArgs (WatcherChangeTypes.Renamed, fsw.Path, newName, name);
 626                         }
 627
 628                         fsw.DispatchEvents (action, name, ref renamed);
 629
 630                         if (fsw.Waiting) {
 631                                 lock (fsw) {
 632                                         fsw.Waiting = false;
 633                                         System.Threading.Monitor.PulseAll (fsw);
 634                                 }
 635                         }
 636                 }
 637
 638                 private string GetFilenameFromFd (int fd)
 639                 {
 640                         var sb = new StringBuilder (__DARWIN_MAXPATHLEN);
 641
 642                         if (fcntl (fd, F_GETPATH, sb) != -1) {
 643                                 if (fixupPath != null)
 644                                         sb.Replace (fixupPath, fullPathNoLastSlash, 0, fixupPath.Length); // see Setup()
 645
 646                                 return sb.ToString ();
 647                         } else {
 648                                 fsw.DispatchErrorEvents (new ErrorEventArgs (new IOException (String.Format (
 649                                         "fcntl() error while attempting to get path for fd '{0}', error code = '{1}'", fd, Marshal.GetLastWin32Error ()))));
 650                                 return String.Empty;
 651                         }
 652                 }
 653
 654                 const int O_EVTONLY = 0x8000;
 655                 const int F_GETPATH = 50;
 656                 const int __DARWIN_MAXPATHLEN = 1024;
 657                 const int EINTR = 4;
 658                 static readonly kevent[] emptyEventList = new System.IO.kevent[0];
 659                 int maxFds = Int32.MaxValue;
 660
 661                 FileSystemWatcher fsw;
 662                 int conn;
 663                 Thread thread;
 664                 volatile bool requestStop = false;
 665                 AutoResetEvent startedEvent = new AutoResetEvent (false);
 666                 bool started = false;
 667                 bool inDispatch = false;
 668                 Exception exc = null;
 669                 object stateLock = new object ();
 670                 object connLock = new object ();
 671
 672                 readonly Dictionary<string, PathData> pathsDict = new Dictionary<string, PathData> ();
 673                 readonly Dictionary<int, PathData> fdsDict = new Dictionary<int, PathData> ();
 674                 string fixupPath = null;
 675                 string fullPathNoLastSlash = null;
 676
 677                 [DllImport ("libc", CharSet=CharSet.Auto, SetLastError=true)]
 678                 static extern int fcntl (int file_names_by_descriptor, int cmd, StringBuilder sb);
 679
 680                 [DllImport ("libc", SetLastError=true)]
 681                 extern static int open (string path, int flags, int mode_t);
 682
 683                 [DllImport ("libc")]
 684                 extern static int close (int fd);
 685
 686                 [DllImport ("libc", SetLastError=true)]
 687                 extern static int kqueue ();
 688
 689                 [DllImport ("libc", SetLastError=true)]
 690                 extern static int kevent (int kq, [In]kevent[] ev, int nchanges, [Out]kevent[] evtlist, int nevents, [In] ref timespec time);
 691
 692                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 693                 extern static int kevent_notimeout (ref int kq, IntPtr ev, int nchanges, IntPtr evtlist, int nevents);
 694         }
 695
 696         class KeventWatcher : IFileWatcher
 697         {
 698                 static bool failed;
 699                 static KeventWatcher instance;
 700                 static Hashtable watches;  // <FileSystemWatcher, KqueueMonitor>
 701
 702                 private KeventWatcher ()
 703                 {
 704                 }
 705
 706                 // Locked by caller
 707                 public static bool GetInstance (out IFileWatcher watcher)
 708                 {
 709                         if (failed == true) {
 710                                 watcher = null;
 711                                 return false;
 712                         }
 713
 714                         if (instance != null) {
 715                                 watcher = instance;
 716                                 return true;
 717                         }
 718
 719                         watches = Hashtable.Synchronized (new Hashtable ());
 720                         var conn = kqueue();
 721                         if (conn == -1) {
 722                                 failed = true;
 723                                 watcher = null;
 724                                 return false;
 725                         }
 726                         close (conn);
 727
 728                         instance = new KeventWatcher ();
 729                         watcher = instance;
 730                         return true;
 731                 }
 732
 733                 public void StartDispatching (FileSystemWatcher fsw)
 734                 {
 735                         KqueueMonitor monitor;
 736
 737                         if (watches.ContainsKey (fsw)) {
 738                                 monitor = (KqueueMonitor)watches [fsw];
 739                         } else {
 740                                 monitor = new KqueueMonitor (fsw);
 741                                 watches.Add (fsw, monitor);
 742                         }
 743
 744                         monitor.Start ();
 745                 }
 746
 747                 public void StopDispatching (FileSystemWatcher fsw)
 748                 {
 749                         KqueueMonitor monitor = (KqueueMonitor)watches [fsw];
 750                         if (monitor == null)
 751                                 return;
 752
 753                         monitor.Stop ();
 754                 }
 755
 756                 [DllImport ("libc")]
 757                 extern static int close (int fd);
 758
 759                 [DllImport ("libc")]
 760                 extern static int kqueue ();
 761         }
 762 }
 763