file_path_watcher_linux.cc revision cedac228d2dd51db4b79ea1e72c7f249408ee061 
1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/files/file_path_watcher.h"
6
7#include <errno.h>
8#include <string.h>
9#include <sys/inotify.h>
10#include <sys/ioctl.h>
11#include <sys/select.h>
12#include <unistd.h>
13
14#include <algorithm>
15#include <map>
16#include <set>
17#include <utility>
18#include <vector>
19
20#include "base/bind.h"
21#include "base/containers/hash_tables.h"
22#include "base/debug/trace_event.h"
23#include "base/file_util.h"
24#include "base/files/file_enumerator.h"
25#include "base/files/file_path.h"
26#include "base/lazy_instance.h"
27#include "base/location.h"
28#include "base/logging.h"
29#include "base/memory/scoped_ptr.h"
30#include "base/message_loop/message_loop.h"
31#include "base/message_loop/message_loop_proxy.h"
32#include "base/posix/eintr_wrapper.h"
33#include "base/synchronization/lock.h"
34#include "base/threading/thread.h"
35
36namespace base {
37
38namespace {
39
40class FilePathWatcherImpl;
41
42// Singleton to manage all inotify watches.
43// TODO(tony): It would be nice if this wasn't a singleton.
44// http://crbug.com/38174
45class InotifyReader {
46 public:
47  typedef int Watch;  // Watch descriptor used by AddWatch and RemoveWatch.
48  static const Watch kInvalidWatch = -1;
49
50  // Watch directory |path| for changes. |watcher| will be notified on each
51  // change. Returns kInvalidWatch on failure.
52  Watch AddWatch(const FilePath& path, FilePathWatcherImpl* watcher);
53
54  // Remove |watch| if it's valid.
55  void RemoveWatch(Watch watch, FilePathWatcherImpl* watcher);
56
57  // Callback for InotifyReaderTask.
58  void OnInotifyEvent(const inotify_event* event);
59
60 private:
61  friend struct DefaultLazyInstanceTraits<InotifyReader>;
62
63  typedef std::set<FilePathWatcherImpl*> WatcherSet;
64
65  InotifyReader();
66  ~InotifyReader();
67
68  // We keep track of which delegates want to be notified on which watches.
69  hash_map<Watch, WatcherSet> watchers_;
70
71  // Lock to protect watchers_.
72  Lock lock_;
73
74  // Separate thread on which we run blocking read for inotify events.
75  Thread thread_;
76
77  // File descriptor returned by inotify_init.
78  const int inotify_fd_;
79
80  // Use self-pipe trick to unblock select during shutdown.
81  int shutdown_pipe_[2];
82
83  // Flag set to true when startup was successful.
84  bool valid_;
85
86  DISALLOW_COPY_AND_ASSIGN(InotifyReader);
87};
88
89class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate,
90                            public MessageLoop::DestructionObserver {
91 public:
92  FilePathWatcherImpl();
93
94  // Called for each event coming from the watch. |fired_watch| identifies the
95  // watch that fired, |child| indicates what has changed, and is relative to
96  // the currently watched path for |fired_watch|.
97  //
98  // |created| is true if the object appears.
99  // |deleted| is true if the object disappears.
100  // |is_dir| is true if the object is a directory.
101  void OnFilePathChanged(InotifyReader::Watch fired_watch,
102                         const FilePath::StringType& child,
103                         bool created,
104                         bool deleted,
105                         bool is_dir);
106
107 protected:
108  virtual ~FilePathWatcherImpl() {}
109
110 private:
111  // Start watching |path| for changes and notify |delegate| on each change.
112  // Returns true if watch for |path| has been added successfully.
113  virtual bool Watch(const FilePath& path,
114                     bool recursive,
115                     const FilePathWatcher::Callback& callback) OVERRIDE;
116
117  // Cancel the watch. This unregisters the instance with InotifyReader.
118  virtual void Cancel() OVERRIDE;
119
120  // Cleans up and stops observing the message_loop() thread.
121  virtual void CancelOnMessageLoopThread() OVERRIDE;
122
123  // Deletion of the FilePathWatcher will call Cancel() to dispose of this
124  // object in the right thread. This also observes destruction of the required
125  // cleanup thread, in case it quits before Cancel() is called.
126  virtual void WillDestroyCurrentMessageLoop() OVERRIDE;
127
128  // Inotify watches are installed for all directory components of |target_|. A
129  // WatchEntry instance holds the watch descriptor for a component and the
130  // subdirectory for that identifies the next component. If a symbolic link
131  // is being watched, the target of the link is also kept.
132  struct WatchEntry {
133    explicit WatchEntry(const FilePath::StringType& dirname)
134        : watch(InotifyReader::kInvalidWatch),
135          subdir(dirname) {}
136
137    InotifyReader::Watch watch;
138    FilePath::StringType subdir;
139    FilePath::StringType linkname;
140  };
141  typedef std::vector<WatchEntry> WatchVector;
142
143  // Reconfigure to watch for the most specific parent directory of |target_|
144  // that exists. Also calls UpdateRecursiveWatches() below.
145  void UpdateWatches();
146
147  // Reconfigure to recursively watch |target_| and all its sub-directories.
148  // - This is a no-op if the watch is not recursive.
149  // - If |target_| does not exist, then clear all the recursive watches.
150  // - Assuming |target_| exists, passing kInvalidWatch as |fired_watch| forces
151  //   addition of recursive watches for |target_|.
152  // - Otherwise, only the directory associated with |fired_watch| and its
153  //   sub-directories will be reconfigured.
154  void UpdateRecursiveWatches(InotifyReader::Watch fired_watch, bool is_dir);
155
156  // Enumerate recursively through |path| and add / update watches.
157  void UpdateRecursiveWatchesForPath(const FilePath& path);
158
159  // Do internal bookkeeping to update mappings between |watch| and its
160  // associated full path |path|.
161  void TrackWatchForRecursion(InotifyReader::Watch watch, const FilePath& path);
162
163  // Remove all the recursive watches.
164  void RemoveRecursiveWatches();
165
166  // |path| is a symlink to a non-existent target. Attempt to add a watch to
167  // the link target's parent directory. Returns true and update |watch_entry|
168  // on success.
169  bool AddWatchForBrokenSymlink(const FilePath& path, WatchEntry* watch_entry);
170
171  bool HasValidWatchVector() const;
172
173  // Callback to notify upon changes.
174  FilePathWatcher::Callback callback_;
175
176  // The file or directory we're supposed to watch.
177  FilePath target_;
178
179  bool recursive_;
180
181  // The vector of watches and next component names for all path components,
182  // starting at the root directory. The last entry corresponds to the watch for
183  // |target_| and always stores an empty next component name in |subdir|.
184  WatchVector watches_;
185
186  hash_map<InotifyReader::Watch, FilePath> recursive_paths_by_watch_;
187  std::map<FilePath, InotifyReader::Watch> recursive_watches_by_path_;
188
189  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl);
190};
191
192void InotifyReaderCallback(InotifyReader* reader, int inotify_fd,
193                           int shutdown_fd) {
194  // Make sure the file descriptors are good for use with select().
195  CHECK_LE(0, inotify_fd);
196  CHECK_GT(FD_SETSIZE, inotify_fd);
197  CHECK_LE(0, shutdown_fd);
198  CHECK_GT(FD_SETSIZE, shutdown_fd);
199
200  debug::TraceLog::GetInstance()->SetCurrentThreadBlocksMessageLoop();
201
202  while (true) {
203    fd_set rfds;
204    FD_ZERO(&rfds);
205    FD_SET(inotify_fd, &rfds);
206    FD_SET(shutdown_fd, &rfds);
207
208    // Wait until some inotify events are available.
209    int select_result =
210      HANDLE_EINTR(select(std::max(inotify_fd, shutdown_fd) + 1,
211                          &rfds, NULL, NULL, NULL));
212    if (select_result < 0) {
213      DPLOG(WARNING) << "select failed";
214      return;
215    }
216
217    if (FD_ISSET(shutdown_fd, &rfds))
218      return;
219
220    // Adjust buffer size to current event queue size.
221    int buffer_size;
222    int ioctl_result = HANDLE_EINTR(ioctl(inotify_fd, FIONREAD,
223                                          &buffer_size));
224
225    if (ioctl_result != 0) {
226      DPLOG(WARNING) << "ioctl failed";
227      return;
228    }
229
230    std::vector<char> buffer(buffer_size);
231
232    ssize_t bytes_read = HANDLE_EINTR(read(inotify_fd, &buffer[0],
233                                           buffer_size));
234
235    if (bytes_read < 0) {
236      DPLOG(WARNING) << "read from inotify fd failed";
237      return;
238    }
239
240    ssize_t i = 0;
241    while (i < bytes_read) {
242      inotify_event* event = reinterpret_cast<inotify_event*>(&buffer[i]);
243      size_t event_size = sizeof(inotify_event) + event->len;
244      DCHECK(i + event_size <= static_cast<size_t>(bytes_read));
245      reader->OnInotifyEvent(event);
246      i += event_size;
247    }
248  }
249}
250
251static LazyInstance<InotifyReader>::Leaky g_inotify_reader =
252    LAZY_INSTANCE_INITIALIZER;
253
254InotifyReader::InotifyReader()
255    : thread_("inotify_reader"),
256      inotify_fd_(inotify_init()),
257      valid_(false) {
258  if (inotify_fd_ < 0)
259    PLOG(ERROR) << "inotify_init() failed";
260
261  shutdown_pipe_[0] = -1;
262  shutdown_pipe_[1] = -1;
263  if (inotify_fd_ >= 0 && pipe(shutdown_pipe_) == 0 && thread_.Start()) {
264    thread_.message_loop()->PostTask(
265        FROM_HERE,
266        Bind(&InotifyReaderCallback, this, inotify_fd_, shutdown_pipe_[0]));
267    valid_ = true;
268  }
269}
270
271InotifyReader::~InotifyReader() {
272  if (valid_) {
273    // Write to the self-pipe so that the select call in InotifyReaderTask
274    // returns.
275    ssize_t ret = HANDLE_EINTR(write(shutdown_pipe_[1], "", 1));
276    DPCHECK(ret > 0);
277    DCHECK_EQ(ret, 1);
278    thread_.Stop();
279  }
280  if (inotify_fd_ >= 0)
281    close(inotify_fd_);
282  if (shutdown_pipe_[0] >= 0)
283    close(shutdown_pipe_[0]);
284  if (shutdown_pipe_[1] >= 0)
285    close(shutdown_pipe_[1]);
286}
287
288InotifyReader::Watch InotifyReader::AddWatch(
289    const FilePath& path, FilePathWatcherImpl* watcher) {
290  if (!valid_)
291    return kInvalidWatch;
292
293  AutoLock auto_lock(lock_);
294
295  Watch watch = inotify_add_watch(inotify_fd_, path.value().c_str(),
296                                  IN_ATTRIB | IN_CREATE | IN_DELETE |
297                                  IN_CLOSE_WRITE | IN_MOVE |
298                                  IN_ONLYDIR);
299
300  if (watch == kInvalidWatch)
301    return kInvalidWatch;
302
303  watchers_[watch].insert(watcher);
304
305  return watch;
306}
307
308void InotifyReader::RemoveWatch(Watch watch, FilePathWatcherImpl* watcher) {
309  if (!valid_ || (watch == kInvalidWatch))
310    return;
311
312  AutoLock auto_lock(lock_);
313
314  watchers_[watch].erase(watcher);
315
316  if (watchers_[watch].empty()) {
317    watchers_.erase(watch);
318    inotify_rm_watch(inotify_fd_, watch);
319  }
320}
321
322void InotifyReader::OnInotifyEvent(const inotify_event* event) {
323  if (event->mask & IN_IGNORED)
324    return;
325
326  FilePath::StringType child(event->len ? event->name : FILE_PATH_LITERAL(""));
327  AutoLock auto_lock(lock_);
328
329  for (WatcherSet::iterator watcher = watchers_[event->wd].begin();
330       watcher != watchers_[event->wd].end();
331       ++watcher) {
332    (*watcher)->OnFilePathChanged(event->wd,
333                                  child,
334                                  event->mask & (IN_CREATE | IN_MOVED_TO),
335                                  event->mask & (IN_DELETE | IN_MOVED_FROM),
336                                  event->mask & IN_ISDIR);
337  }
338}
339
340FilePathWatcherImpl::FilePathWatcherImpl()
341    : recursive_(false) {
342}
343
344void FilePathWatcherImpl::OnFilePathChanged(InotifyReader::Watch fired_watch,
345                                            const FilePath::StringType& child,
346                                            bool created,
347                                            bool deleted,
348                                            bool is_dir) {
349  if (!message_loop()->BelongsToCurrentThread()) {
350    // Switch to message_loop() to access |watches_| safely.
351    message_loop()->PostTask(
352        FROM_HERE,
353        Bind(&FilePathWatcherImpl::OnFilePathChanged, this,
354             fired_watch, child, created, deleted, is_dir));
355    return;
356  }
357
358  // Check to see if CancelOnMessageLoopThread() has already been called.
359  // May happen when code flow reaches here from the PostTask() above.
360  if (watches_.empty()) {
361    DCHECK(target_.empty());
362    return;
363  }
364
365  DCHECK(MessageLoopForIO::current());
366  DCHECK(HasValidWatchVector());
367
368  // Used below to avoid multiple recursive updates.
369  bool did_update = false;
370
371  // Find the entry in |watches_| that corresponds to |fired_watch|.
372  for (size_t i = 0; i < watches_.size(); ++i) {
373    const WatchEntry& watch_entry = watches_[i];
374    if (fired_watch != watch_entry.watch)
375      continue;
376
377    // Check whether a path component of |target_| changed.
378    bool change_on_target_path =
379        child.empty() ||
380        (child == watch_entry.linkname) ||
381        (child == watch_entry.subdir);
382
383    // Check if the change references |target_| or a direct child of |target_|.
384    bool is_watch_for_target = watch_entry.subdir.empty();
385    bool target_changed =
386        (is_watch_for_target && (child == watch_entry.linkname)) ||
387        (is_watch_for_target && watch_entry.linkname.empty()) ||
388        (watch_entry.subdir == child && watches_[i + 1].subdir.empty());
389
390    // Update watches if a directory component of the |target_| path
391    // (dis)appears. Note that we don't add the additional restriction of
392    // checking the event mask to see if it is for a directory here as changes
393    // to symlinks on the target path will not have IN_ISDIR set in the event
394    // masks. As a result we may sometimes call UpdateWatches() unnecessarily.
395    if (change_on_target_path && (created || deleted) && !did_update) {
396      UpdateWatches();
397      did_update = true;
398    }
399
400    // Report the following events:
401    //  - The target or a direct child of the target got changed (in case the
402    //    watched path refers to a directory).
403    //  - One of the parent directories got moved or deleted, since the target
404    //    disappears in this case.
405    //  - One of the parent directories appears. The event corresponding to
406    //    the target appearing might have been missed in this case, so recheck.
407    if (target_changed ||
408        (change_on_target_path && deleted) ||
409        (change_on_target_path && created && PathExists(target_))) {
410      if (!did_update) {
411        UpdateRecursiveWatches(fired_watch, is_dir);
412        did_update = true;
413      }
414      callback_.Run(target_, false /* error */);
415      return;
416    }
417  }
418
419  if (ContainsKey(recursive_paths_by_watch_, fired_watch)) {
420    if (!did_update)
421      UpdateRecursiveWatches(fired_watch, is_dir);
422    callback_.Run(target_, false /* error */);
423  }
424}
425
426bool FilePathWatcherImpl::Watch(const FilePath& path,
427                                bool recursive,
428                                const FilePathWatcher::Callback& callback) {
429  DCHECK(target_.empty());
430  DCHECK(MessageLoopForIO::current());
431
432  set_message_loop(MessageLoopProxy::current().get());
433  callback_ = callback;
434  target_ = path;
435  recursive_ = recursive;
436  MessageLoop::current()->AddDestructionObserver(this);
437
438  std::vector<FilePath::StringType> comps;
439  target_.GetComponents(&comps);
440  DCHECK(!comps.empty());
441  for (size_t i = 1; i < comps.size(); ++i)
442    watches_.push_back(WatchEntry(comps[i]));
443  watches_.push_back(WatchEntry(FilePath::StringType()));
444  UpdateWatches();
445  return true;
446}
447
448void FilePathWatcherImpl::Cancel() {
449  if (callback_.is_null()) {
450    // Watch was never called, or the message_loop() thread is already gone.
451    set_cancelled();
452    return;
453  }
454
455  // Switch to the message_loop() if necessary so we can access |watches_|.
456  if (!message_loop()->BelongsToCurrentThread()) {
457    message_loop()->PostTask(FROM_HERE,
458                             Bind(&FilePathWatcher::CancelWatch,
459                                  make_scoped_refptr(this)));
460  } else {
461    CancelOnMessageLoopThread();
462  }
463}
464
465void FilePathWatcherImpl::CancelOnMessageLoopThread() {
466  set_cancelled();
467
468  if (!callback_.is_null()) {
469    MessageLoop::current()->RemoveDestructionObserver(this);
470    callback_.Reset();
471  }
472
473  for (size_t i = 0; i < watches_.size(); ++i)
474    g_inotify_reader.Get().RemoveWatch(watches_[i].watch, this);
475  watches_.clear();
476  target_.clear();
477
478  if (recursive_)
479    RemoveRecursiveWatches();
480}
481
482void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() {
483  CancelOnMessageLoopThread();
484}
485
486void FilePathWatcherImpl::UpdateWatches() {
487  // Ensure this runs on the message_loop() exclusively in order to avoid
488  // concurrency issues.
489  DCHECK(message_loop()->BelongsToCurrentThread());
490  DCHECK(HasValidWatchVector());
491
492  // Walk the list of watches and update them as we go.
493  FilePath path(FILE_PATH_LITERAL("/"));
494  bool path_valid = true;
495  for (size_t i = 0; i < watches_.size(); ++i) {
496    WatchEntry& watch_entry = watches_[i];
497    InotifyReader::Watch old_watch = watch_entry.watch;
498    watch_entry.watch = InotifyReader::kInvalidWatch;
499    watch_entry.linkname.clear();
500    if (path_valid) {
501      watch_entry.watch = g_inotify_reader.Get().AddWatch(path, this);
502      if (watch_entry.watch == InotifyReader::kInvalidWatch) {
503        if (IsLink(path)) {
504          path_valid = AddWatchForBrokenSymlink(path, &watch_entry);
505        } else {
506          path_valid = false;
507        }
508      }
509    }
510    if (old_watch != watch_entry.watch)
511      g_inotify_reader.Get().RemoveWatch(old_watch, this);
512    path = path.Append(watch_entry.subdir);
513  }
514
515  UpdateRecursiveWatches(InotifyReader::kInvalidWatch,
516                         false /* is directory? */);
517}
518
519void FilePathWatcherImpl::UpdateRecursiveWatches(
520    InotifyReader::Watch fired_watch,
521    bool is_dir) {
522  if (!recursive_)
523    return;
524
525  if (!DirectoryExists(target_)) {
526    RemoveRecursiveWatches();
527    return;
528  }
529
530  // Check to see if this is a forced update or if some component of |target_|
531  // has changed. For these cases, redo the watches for |target_| and below.
532  if (!ContainsKey(recursive_paths_by_watch_, fired_watch)) {
533    UpdateRecursiveWatchesForPath(target_);
534    return;
535  }
536
537  // Underneath |target_|, only directory changes trigger watch updates.
538  if (!is_dir)
539    return;
540
541  const FilePath& changed_dir = recursive_paths_by_watch_[fired_watch];
542
543  std::map<FilePath, InotifyReader::Watch>::iterator start_it =
544      recursive_watches_by_path_.lower_bound(changed_dir);
545  std::map<FilePath, InotifyReader::Watch>::iterator end_it = start_it;
546  for (; end_it != recursive_watches_by_path_.end(); ++end_it) {
547    const FilePath& cur_path = end_it->first;
548    if (!changed_dir.IsParent(cur_path))
549      break;
550    if (!DirectoryExists(cur_path))
551      g_inotify_reader.Get().RemoveWatch(end_it->second, this);
552  }
553  recursive_watches_by_path_.erase(start_it, end_it);
554  UpdateRecursiveWatchesForPath(changed_dir);
555}
556
557void FilePathWatcherImpl::UpdateRecursiveWatchesForPath(const FilePath& path) {
558  DCHECK(recursive_);
559  DCHECK(!path.empty());
560  DCHECK(DirectoryExists(path));
561
562  // Note: SHOW_SYM_LINKS exposes symlinks as symlinks, so they are ignored
563  // rather than followed. Following symlinks can easily lead to the undesirable
564  // situation where the entire file system is being watched.
565  FileEnumerator enumerator(
566      path,
567      true /* recursive enumeration */,
568      FileEnumerator::DIRECTORIES | FileEnumerator::SHOW_SYM_LINKS);
569  for (FilePath current = enumerator.Next();
570       !current.empty();
571       current = enumerator.Next()) {
572    DCHECK(enumerator.GetInfo().IsDirectory());
573
574    if (!ContainsKey(recursive_watches_by_path_, current)) {
575      // Add new watches.
576      InotifyReader::Watch watch =
577          g_inotify_reader.Get().AddWatch(current, this);
578      TrackWatchForRecursion(watch, current);
579    } else {
580      // Update existing watches.
581      InotifyReader::Watch old_watch = recursive_watches_by_path_[current];
582      DCHECK_NE(InotifyReader::kInvalidWatch, old_watch);
583      InotifyReader::Watch watch =
584          g_inotify_reader.Get().AddWatch(current, this);
585      if (watch != old_watch) {
586        g_inotify_reader.Get().RemoveWatch(old_watch, this);
587        recursive_paths_by_watch_.erase(old_watch);
588        recursive_watches_by_path_.erase(current);
589        TrackWatchForRecursion(watch, current);
590      }
591    }
592  }
593}
594
595void FilePathWatcherImpl::TrackWatchForRecursion(InotifyReader::Watch watch,
596                                                 const FilePath& path) {
597  DCHECK(recursive_);
598  DCHECK(!path.empty());
599  DCHECK(target_.IsParent(path));
600
601  if (watch == InotifyReader::kInvalidWatch)
602    return;
603
604  DCHECK(!ContainsKey(recursive_paths_by_watch_, watch));
605  DCHECK(!ContainsKey(recursive_watches_by_path_, path));
606  recursive_paths_by_watch_[watch] = path;
607  recursive_watches_by_path_[path] = watch;
608}
609
610void FilePathWatcherImpl::RemoveRecursiveWatches() {
611  if (!recursive_)
612    return;
613
614  for (hash_map<InotifyReader::Watch, FilePath>::const_iterator it =
615           recursive_paths_by_watch_.begin();
616       it != recursive_paths_by_watch_.end();
617       ++it) {
618    g_inotify_reader.Get().RemoveWatch(it->first, this);
619  }
620  recursive_paths_by_watch_.clear();
621  recursive_watches_by_path_.clear();
622}
623
624bool FilePathWatcherImpl::AddWatchForBrokenSymlink(const FilePath& path,
625                                                   WatchEntry* watch_entry) {
626  DCHECK_EQ(InotifyReader::kInvalidWatch, watch_entry->watch);
627  FilePath link;
628  if (!ReadSymbolicLink(path, &link))
629    return false;
630
631  if (!link.IsAbsolute())
632    link = path.DirName().Append(link);
633
634  // Try watching symlink target directory. If the link target is "/", then we
635  // shouldn't get here in normal situations and if we do, we'd watch "/" for
636  // changes to a component "/" which is harmless so no special treatment of
637  // this case is required.
638  InotifyReader::Watch watch =
639      g_inotify_reader.Get().AddWatch(link.DirName(), this);
640  if (watch == InotifyReader::kInvalidWatch) {
641    // TODO(craig) Symlinks only work if the parent directory for the target
642    // exist. Ideally we should make sure we've watched all the components of
643    // the symlink path for changes. See crbug.com/91561 for details.
644    DPLOG(WARNING) << "Watch failed for "  << link.DirName().value();
645    return false;
646  }
647  watch_entry->watch = watch;
648  watch_entry->linkname = link.BaseName().value();
649  return true;
650}
651
652bool FilePathWatcherImpl::HasValidWatchVector() const {
653  if (watches_.empty())
654    return false;
655  for (size_t i = 0; i < watches_.size() - 1; ++i) {
656    if (watches_[i].subdir.empty())
657      return false;
658  }
659  return watches_[watches_.size() - 1].subdir.empty();
660}
661
662}  // namespace
663
664FilePathWatcher::FilePathWatcher() {
665  impl_ = new FilePathWatcherImpl();
666}
667
668}  // namespace base
669