Access fields from the appropriate threads in FilePathWatcherFSEvents.

base/files/file_path_watcher_fsevents.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
 #define BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
 
 #include <CoreServices/CoreServices.h>
 
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/files/file_path_watcher.h"
 
 namespace base {
 
 // Mac-specific file watcher implementation based on FSEvents.
 // There are trade-offs between the FSEvents implementation and a kqueue
 // implementation. The biggest issues are that FSEvents on 10.6 sometimes drops
 // events and kqueue does not trigger for modifications to a file in a watched
 // directory. See file_path_watcher_mac.cc for the code that decides when to
 // use which one.
 class FilePathWatcherFSEvents : public FilePathWatcher::PlatformDelegate {
  public:
   FilePathWatcherFSEvents();
 
-  // Called from the FSEvents callback whenever there is a change to the paths.
+  // FilePathWatcher::PlatformDelegate overrides.
+  bool Watch(const FilePath& path,
+             bool recursive,
+             const FilePathWatcher::Callback& callback) override;
+  void Cancel() override;
+
+ private:
+  static void FSEventsCallback(ConstFSEventStreamRef stream,
+                               void* event_watcher,
+                               size_t num_events,
+                               void* event_paths,
+                               const FSEventStreamEventFlags flags[],
+                               const FSEventStreamEventId event_ids[]);
+
+  ~FilePathWatcherFSEvents() override;
+
+  // Called from FSEventsCallback whenever there is a change to the paths.
   void OnFilePathsChanged(const std::vector<FilePath>& paths);
 
+  // Called on the message_loop() thread to dispatch path events. Can't access
+  // target_ and resolved_target_ directly as those are modified on the
+  // libdispatch thread.
+  void DispatchEvents(const std::vector<FilePath>& paths,
+                      const FilePath& target,
+                      const FilePath& resolved_target);
+
+  // Cleans up and stops the event stream.
+  void CancelOnMessageLoopThread() override;
+
   // (Re-)Initialize the event stream to start reporting events from
   // |start_event|.
   void UpdateEventStream(FSEventStreamEventId start_event);
 
   // Returns true if resolving the target path got a different result than
   // last time it was done.
   bool ResolveTargetPath();
 
-  // FilePathWatcher::PlatformDelegate overrides.
-  bool Watch(const FilePath& path,
-             bool recursive,
-             const FilePathWatcher::Callback& callback) override;
-  void Cancel() override;
-
- private:
-  ~FilePathWatcherFSEvents() override;
+  // Report an error watching the given target.
+  void ReportError(const FilePath& target);
 
   // Destroy the event stream.
   void DestroyEventStream();
 
   // Start watching the FSEventStream.
-  void StartEventStream(FSEventStreamEventId start_event);
-
-  // Cleans up and stops the event stream.
-  void CancelOnMessageLoopThread() override;
+  void StartEventStream(FSEventStreamEventId start_event, const FilePath& path);
 
   // Callback to notify upon changes.
+  // (Only accessed from the message_loop() thread.)
   FilePathWatcher::Callback callback_;
 
   // Target path to watch (passed to callback).
+  // (Only accessed from the libdispatch thread.)
   FilePath target_;
 
   // Target path with all symbolic links resolved.
+  // (Only accessed from the libdispatch thread.)
   FilePath resolved_target_;
 
   // Backend stream we receive event callbacks from (strong reference).
+  // (Only accessed from the libdispatch thread.)
   FSEventStreamRef fsevent_stream_;
 
   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherFSEvents);
 };
 
 }  // namespace base
 
 #endif  // BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_